International Rice Research Newsletter Vol.13 No.5

Guidelines for contributors

Categories of research reported GERMPLASM IMPROVEMENT

CROP AND RESOURCE MANAGEMENT

Criteria for IRRN research reports

SOCIOECONOMIC AND ENVIRONMENTAL IMPACT

EDUCATION AND COMMUNICATION

IRRN GUIDELINES The International Rice Research Newsletter objective is:

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genetic resources genetics breeding methods yield potential grain quality and nutritional value disease resistance insect resistance drought tolerance excess water tolerance adverse temperature tolerance adverse soils tolerance integrated germplasm improvement seed technology research techniques data management and computer

modeling

soils and soil characterization soil microbiology and biological N

physiology and plant nutrition crop management soil fertility and fertilizer management disease management insect management weed management managing other pests integrated pest management water management farm machinery environmental analysis postharvest technology farming systems research methodology data management and computer

fertilizer

modeling

environment production livelihood

training and technology transfer

communication research information storage and retrieval

research

CONTENTS GERMPLASM ENVIRONVEMENT Genetic resources

4 Characteristics of Oryza indandamanica Ellis, a newly discovered

4 Taxonomic key for identifying the 22 species in the genus Oryza 5 Efficiency of wide compatibility gene

6 Sensitivity of upland rice genotypes to gamma radiation

7 Heritability of primary root length 7 Rice panicle characteristics 8 Flowering behavior of photoperiod-sensitive rice germplasm of

9 Grain yield and duration of ratoon rice varieties 9 Hybrid rice in rainfed environments

10 Modified method for apparent amylose content (AC) of milled rice 10 Grain characteristics of traditional Basmati varieties of northwest

wild species

Breeding methods

Yield potential

Bangladesh

Grain quality and nutritional value

India Disease resistance

11 Varietal ranking of blast (Bl) severity in Korean farmers' fields 12 Varietal reaction to tungro (RTV) with change in leafhopper

13 Resistance to bacterial leaf streak (BLS) in hybrid rice and parental

13 Sieve tube number in tungro (RTV)-infected rice plants 13 Simplification of sampling method for assessing bacterial blight

14 Susceptibility of bacterial blight (BB) differential varieties of IRRI,

“virulence”

lines

(BB) severity

Japan, and Korea in Nepal Insect resistance

14 Use of tissue culture to evaluate rice resistance to lepidopterous

15 Improved sources of plant resistance to yellow stem borer (YSB)

16 High virulence of new brown planthopper (BPH) populations in the

pests

Scirpophaga incertulas Walker in rice

Mekong Delta, Vietnam Drought tolerance

16 Rice sensitivity to water deficit at different growth stages 17 A low-cost rapid screening technique for seminal root elongation

17 Performance of rice breeding lines under medium deepwater Excess water tolerance

conditions Adverse temperature tolerance

18 Spikelet sterility in three rice cultivars 18 Hybrid rice responses to high temperature at flowering

19 Modified screening method for salt tolerance 19 Rice yield responses in a saline soil in Sri Lanka

20 Nepal releases nine rice varieties 21 Evaluation of African Upland Rice Advanced Trial (AURAT) at

Adverse soils tolerance

Integrated germplasm improvement

Ibadan, Nigeria Data management and computer modeling

21 Models for panicle growth simulation

CROP AND RESOURCE MANAGEMENT Soils and soil characterization

21 Effect of soil type on draft force needed to plow soils of South Sulawesi, Indonesia

Soil microbiology and biological N fertilizer 22 Growth and K uptake of Azolla pinnata under different salt levels 23 Herbicide-azolla integration for weed control in transplanted

IR60 rice Physiology and plant nutrition

protein content of rice

potential

23 Effect of N forms on leaf nitrate reductase activity, yield, and

24 Root and shoot growth of Oryza sativa L. as affected by redox

Crop management 24 Effect of irrigation, and seedling age and number on rice yield 24 Rice response to N rates and delayed planting

25 Effect of N source and application time on rice 25 Estimation of pH, ammonium N, and nitrate N of floodwater with

integrated N management of lowland rice 26 Efficiency of modified urea granules in transplanted rice 27 Leucaena as green leaf manure for lowland rice 27 Fertilizer requirement of rice - rice - green manure cropping system 27 Effect of rice plants on fertilizer N losses in flooded soil 28 Organic and inorganic N effect on rice 28 Effect of plant spacing on N release of sulfur-coated urea (SCU) in

29 Effect of azolla and other fertilizers on rice yields 29 Effects of seedling age and zinc application on yield of rice

30 A new sheath disease of rice in India caused by Monographella

30 Improved method of purifying rice tungro spherical virus (RTSV)

31 Severe outbreak of green leafhopper (GLH) in Cuddapah District,

31 Parasitoids of leaffolder (LF) pupae from Haryana, India 31 An expert system for insecticide control of brown planthopper

32 Effect of neem on yeast-like symbionts (YLS) harbored by brown

33 A new tarsonemid mite, Ogmotarsonemus sp. (Tarsonemidae:

33 Neem for control of rice thrips 34 Infection of brown planthopper (BPH) with insect fungi in the

34 Effect of Dimilin (R) and Dipel (R) on leaffolder (LF) larvae

Soil fertility and fertilizer management

wetland rice

Disease management

albescens

Insect management

Andhra Pradesh, India

(BPH)

planthopper (BPH)

Acari), on rice in Tamil Nadu, India

laboratory

Weed management 35 Weed control in direct seeded rice under puddled condition 35 Unrecorded weed hosts for rice blast (Bl) pathogen Pyricularia

36 Weed flora in rice in Bhubaneswar (Orissa, India) 36 Integrated weed and water management in transplanted rice

37 A crab trap for a deepwater rice (DWR) pest

37 Performance of rice-based cropping systems in river floodplains 38 Rice cultivation practices in a Negrito foraging society in

38 Cassava varieties for 5-mo summer rice fallow in Kerala

oryzae Cav. in India

Managing other pests

Farming systems

northeastern Luzon, Philippines

Data management and computer modeling 38 Modeling feeding rates of rice leaffolder (LF) Cnaphalocrocis

medinalis on different plant stages

ANNOUNCEMENTS 39 Irrigation symposium planned 39 Origin of Cultivated Rice 40 Rice lexicography published 40 New IRRI publications

ERRATUM

The IRGC is receiving more and more requests for seeds of wild species of

Oryza, from both rice scientists and biotech workers using rice as an experimental material. Recent revisions in the taxonomy and nomenclature of the 20 wild species and 2 cultigens (cultivated species) in the genus necessitate a revised taxonomic key to identify newly collected materials or to

reevaluate previous identification. A working key prepared earlier has

been revised and updated to assist biologists using the wild species as novel sources of resistance to diseases and insects and tolerance for eco-edaphic stresses.

O. indandamanica averages 10 tillers/plant with shoot fresh weight of 3.8 g and root fresh weight of 0.8 g. Basal internode diameter averages 1.2 cm. Leaf area per plant averages 0.24 m 2

and leaves respond to moisture stress by rolling. Unbranched panicles bear an average of 8 awnless spikelets, which shed pollen having 4-5% sterility. The grains are nonglutinous. This species is diploid with a chromosome number of 2n = 24. To determine the characteristics presented in the table, 10 plants were randomly selected from the original habitat.

O. indandamanica is morphologically similar to Oryza meyeriana (Zoll. & Mor.) Baill. var. meyeriana (Backer s.n.) and Oryza meyeriana var. granulata (Watt) Duistermaat with which this species should be compared.

A new wild species, O. indandamanica has been discovered in Rutland (11.50°N, 92.25°E), Andaman Islands, India. The perennial, herbaceous species was growing on a rocky slope over light loam soil, on a stream bank. Average annual rainfall is 3,000 mm, spread unevenly over 8 mo of the year. Temperature ranges from 27 to 32 °C, with 60-80% relative humidity.

GERMPLASM IMPROVEMENT Genetic resources

Characteristics of Oryza indandamanica Ellis, a newly discovered wild species

T. V. R. S. Sharma, N. D. Majumder, T. Ram, and A. B. Mandal, Central Agricultural Research Institute for A & N Islands, Port Blair 744101, India

Morphoagronomic characteristics of Oryza indandamanica Ellis.

Character Observation

Coleoptile length: mesocotyl 2.59

Primary leaf length: 8.59

Primary leaf length: coleoptile 3.31

Leaves (no.) on main culm 4 Leaf thickness (cm) 0.0125 Length of flag leaf (cm) 4.53 Width of flag leaf (cm) 0.50 Tiller angle (°) 45 Average internode no. 7

length

mesocotyl length

length

Average internode length (cm) 5.36

Grain density (grains/cm) 1.98 Proteinous layer in grain Peripheral (not Scent

Lemma and palea surface Glabrous Percent filled grains/panicle 75

uniform) Nonscented

Taxonomic key for identifying the 22 species in the genus Oryza T. T. Chang, International Rice Germplasm Center (IRGC), IRRI

A working key to the valid species of Oryza (modified after Roschevicz, 1931; Chatterjee, 1948; Tateoka, 1963; Bardenas and Chang, 1966; Tateoka, 1965; Sharma and Shastry, 1965; Ng et al., 1981). A-1 Sterile lemmas present

B-1 Sterile lemmas linear or linear lanceolate C-1 Ligule of lower leaves 14-45 mm long, tips acute

D-1 Annual; leaf blades narrow; no rhizomes; spikelets persistent, 3-14 mm long, 2-5 mm wide; Asian origin; cultivated; diploid ....... sativa D-2 Annual; semi-erect to decumbent growth; without rhizomes; basal internodes spongy; spikelets oblong and deciduous; short anthers;

Asian origin; diploid ...................................................................................................................................................................................... nivara D-3 Annual, some perennial; erect to semi-erect growth; without rhizomes; tightly adpressed short secondary rachises resulting in more

compact panicle; stiff, erect, ascending panicle branches; Australian origin; diploid ................................................................... meridionalis El Perennial; erect habit; branched, spreading rhizomes; long anthers fill entire spikelet; elliptic pollen; African origin;

diploid ................................................................................................................................................................................. longistaminata E2 Perennial; prostrate or floating habit; weak rhizomes; long anthers; adventitious roots and extravaginal branching at higher

nodes; long internodes; lax panicles; long, slender, deciduous spikelets; Asian origin; diploid ........................................... rufipogon E3 Perennial; semierect habit; stoloniferous culms; long awns and long spikelets; American origin; diploid ................ glumaepatula

C-2 Ligule of lower leaves shorter than 6 mm, tip round or truncate D-4 Sterile lemmas almost equal in length and similar in structure to lemma and palea; ligule with a fringe of hairs at the apex; leaves

D-5 Sterile lemmas considerably shorter than the lemma and palea broad; American origin; perennial; tetraploid ................................................................................................................................... grandiglumis

E-4 Annual; plants erect; leaves glabrous to slightly scabrid; panicles more or less compact; lemma and palea perfectly or almost perfectly glabrous; sometimes hispid; spikelets usually awnless or short-awned; main panicle axis without secondary or tertiary branches; spikelet length between 7-9 mm; spikelet width 2.9-3.6 mm; tip of sterile lemmas acute; African origin; cultivated; diploid glaberrima

spikelets 7.8-11.0 mm long, 2.8-3.4 mm wide, always awned (10 cm or longer); awns bristled; sterile lemmas 2.1-5.0 mm long, acuminate at tip; African origin; diploid ........................................................................................................................................ barthii a

............................................................................................................................................................................................... E5 Annual; plants erect to spreading panicles open, main axis with secondary or rarely tertiary branches; lemma and palea hispid;

4 IRRN 13:5 (October 1988)

schlechteri

Efficiency of wide compatibility gene

D. Senadhira, R. M. Herrera, and J. P. Roxas, Plant Breeding Department, IRRI

In breeding for tolerance for low temperature and problem soils, we use varieties having the wide compatibility gene to combine agronomic traits of japonica and indica varieties.

In the 1987 wet season, we used 3 varieties with the wide compatibility gene (BPI-176 [indica], N22 [aus], and Moroberekan [japonica]) to make 66 single crosses involving a range of indicas and japonicas, and one tongil (indica/japonica hybrid). Hybrid seeds were planted in the IRRI F 1 nursery in 1988 dry season.

E-6 Perennial; main axis of panicle slightly woolly pubescent at the base of primary branches, the rest smooth and glabrous; axis increasingly hispid-scabrid toward the tip; awns less than 5 cm long; sterile lemmas linear or linear lanceolate; rhizomatous; Australian origin; diploid ....................................................................................................................................... australiensis

F-1 Perennial; plant not rhizomatous; leaves broad E-7 Ligule with a fringe of hairs at the apex

G-1 Width of leaves less than 5 cm; spikelets less than 7 mm long; American origin; tetraploid .................. latifolia G-2 Width of leaves more than 5 cm; spikelets more than 7 mm long; American origin; tetraploid .................... alta

E-8 Ligule without fringe of hairs at the apex, leaves less than 2 cm broad F-2 Width of spikelets less than 2 mm

G-3 Panicle branches not spreading; length of spikelets 4.5-6.0 mm, width 15 - 2.0 mm; culm base slender, hard and not spongy; ligule less than 3.5 mm, never split, hard , flexuous with fine bristles; sterile lemmas acuminate and narrowly triangular; African origin; perennial; diploid ................................................................................ eichingeri

G-4 Length of spikelets 3.7 - 4.7 mm; width usually less than 2 mm; panicle small with spreading branches; awned (2 cm or less) or awnless; Asian origin; perennial; tetraploid ..................................................................................... minuta

G-5 Length of spikelets more than 5 mm; width 2.0-2.5 mm; culm base soft and spongy, ligule longer than 3.0 mm, soft, and split when dried; straight or flexuous with rigid bristles; panicle loose with spreading branches; sterile lemmas acute and triangular; African origin; perennial; tetraploid punctata

cm, or awnless; occasionally rhizomatous; Asian origin; perennial; diploid ............................................................................. cinalis

F-3 Width of spikelet more than 2 mm

E-9 Ligule glabrous or hairy; length of spikelets less than 5 mm, width almost always more than 2 mm; awns often shorter than 2

A-2 Sterile lemmas subulate or setaceous B-2 Surface of sterile lemmas and palea granulate; sterile lemmas minute, long, tapered from base; usually awnless

C-3 Spikelets oblong to elliptic oblong, shorter than 7 mm; Asian origin; perennial; diploid ......................................................................... granulata C-4 Spikelets narrowly oblong to lanceolate, longer than 7 mm; Asian origin; perennial; diploid .............................................................. meyeriana

C-5 Lemma ciliate along keel, without wing; leaves herbaceous B-3 Surface of lemma and palea not granulate; awned; spikelets 8-17 mm long

D-6 Awns 6-15 mm long; sterile lemmas shorter than lemma; Asian origin; perennial; tetraploid ........................................................... ridleyi D-7 Awns 16-36 mm tong; sterile lemmas as long as or longer than lemma; New Guinean origin; perennial; tetraploid .......... longiglumis

B-4 Surface of lemma almost smooth with fine longitudinally dotted stippled surface C-6 Spikelets linear, 1-2 mm wide; awns 6-17 mm long; sterile lemmas always much shorter than lemma; African origin; annual;

A-3 Spikelets 15 - 1.75 mm long; nodes hairy; New Guinean origin diploid .............................................................................................................................................................................................................. brachyantha

NOTES 1. Excluded from the key are taxa of doubtful validity or names of uncertain application: O. abromeitiana, O. collina, O. fatua, O. malampuzhaensis, O.

2. Removed from the genus Oryza are taxa formerly known as ‘O. angustifolia’, ‘O. perrieri’, and ‘O. tisseranti’ - to the genus Leersia; ‘O. coarctata’ (renamed

3. For specimens of uncertain morphological identity, a determination of somatic chromosome numbers from young root-tips will be helpful in certain

4. Annual and perennial growth habits are rather difficult to distinguish when the plants are grown under tropical conditions; the term “annual” refers to a

perennis, O. perennis subsp. cubensis, O. schweinfurthiana, O. stapfii, O. ubanghensis, and O. indandamanica.

as Porteresia coarctata ); and ‘O. subulata’ (to the genus Rhynchoryza ).

cases.

primary seed-propagated form while “perennial“ refers to a taxon adapted to vegetative propagation by underground plant parts.

a Formerly known as O. breviligulata, includes the weed race O. stapfii.

Spikelet fertility of hybrids between ordinary varieties (female parent) and those with the wide compatibility gene (male parent). IRRI, 1988 dry season.

Spikelet fertility (%) Female parent

BPI-76 N22

ARC6000 83.0 96.9 91.0 China 1039 90.7 86.2 87.4 IR4630-22-2-5-1-3 91.9 66.6 70.1

IR44670-168-2-3-1 96.5 84.2 72.4

Moroberekan

Indica

IR9884-54-3-1E-P1 84.4 72.3 86.0 IR31868-64-2-3-3-3 79.4 36.6 75.3 IR32843-92-2-2-3 95.0 79.4 71.6

Barkat

Nona Bokra SR26B

Japonica Akihikari

Sasanishiki Ta-mao-tao Tatsumi mochi

95.5 92.3

31.8 76.9

43.3 81.0 30.3 59.3 23.6 69.8 33.1 59.6 78.8 53.2

84.4 72.3

97.0 90.9 95.5 89.6 86.7

Milyang 54 92.1 40.8 93.0 Mean 74.0 66.3 84.2 SD 26.7 19.3 9.4

Tongil

IRRN 13:5 (October 1988) 5

.........................................................................................................................................

.................................................................................

At maturity, 10 main panicles were Fertility was normal in all crosses with programs because of its poor randomly harvested to determine Moroberekan. performance under lowland conditions. spikelet fertility for each cross (see Thus, the efficacy of the wide Acceptable varieties with efficient wide table). BPI-76 showed normal fertility compatibility gene varies from variety to adaptability gene need to be isolated or with indicas, the tongil, and one variety. Although the gene of developed. japonica. Fertility with N22 was highly Moroberekan was very effective, it may variable among japonicas or indicas. not be the best to use in breeding

Breeding methods

Sensitivity of upland rice genotypes to gamma radiation

H. C. Pathak and M. S. Patel, Gujarat Agricultural University, Derol, Panchmahals, Gujarat, India

We irradiated 3 genotypes of upland rice—Sathi 34-36, a local high-yielding, late, and tall genotype; IET2473, dwarf, mid-early, and coarse-grained; and Culture 102-5, semidwarf with medium duration and long, fine grain—with 5, 10, 15, and 20 kR doses of gamma rays. The experiment, with 2 replications, measured germination percentage, and root and shoot length at 10 d after planting.

Germination percentage was not appreciably reduced by gamma radiation. Root lengths were progressively reduced from 0 kR (7.14 cm) to 20 kR (3.82 cm) (see figure). Of the 3 genotypes, Culture 102- 5 had longest roots at 0 kR and shortest at 20 kR. Gamma radiation did not reduce shoot lengths except in Culture

Analysis of variance confirmed that 102-5.

radiation effects on root and shoot lengths varied significantly among varieties. The root length of Culture 102-5 was reduced 0.30 cm for every kR unit increase in radiation, compared to an average of 0.09 cm/ kR unit for the 2 other varieties. Radiation reduced shoot

Effect of gamma ray doses on root and shoot lengths of 3 upland rice genotypes. Gujarat, India, 1987.

length of Culture 102-5, increased those kR as the criteria for measuring of Sathi 34-36, but had no effect on sensitivity. those of IET2473. Culture 102-5 was clearly the most

We used rate of reduction in all three sensitive among the varieties tested. seedling characters per unit increase of

The International Rice Research Newsletter is published to expedite communication among scientists concerned with rice research and the development of improved technology for rice and rice-based farming systems. Readers are encouraged to write authors at their published addresses to discuss the research and obtain more details.


Yield potential repeated selection in advanced generations of the best 5% of the

expected. The primary root length showed a moderately high heritability in

population. each cross (82.4 to 52.3%), although the Heritability of primary root The F 2 lines provide a prediction of estimated numbers of effective factors

length the genetic advance, or improvement were low (see table).

N. G. Hajra, S. G. Hajra, RRII, North Eastern Research Complex, P.O. Kunjaban, Tripura 799006; and P. Bairagi, Botany Department, Burdwan University, Burdwan 713104, India

In rice, as in most cereals, root systems show high variability because the genes controlling them come under environmental influences. We crossed 11 varieties having good and poor root systems and obtained 7 cross- combinations. Seedlings were grown in test tubes with White’s medium. Primary root length was recorded at 28 d and different parameters estimated to indicate the nature and degree of improvement by hybridization in F 2 generation. CH1040/ NC918 and CH47/CH63 were relatively stable, with low response to environment. The five other crosses were highly responsive to environmental fluctuations, requiring

Genetic parameters of primary root length in 7 rice crosses.

Larkoch/ CH10/ CH1040/ CH47/ CH988/ Badkalamkati Boak/ Parameter a NC918 NC918 NC918 CH63 CHI7 65/CH4 NC918

Mean (cm) P 1 8.73 10.80 9.13 11.13 10.93 18.03 15.07

P 2 18.80 18.80 18.80 20.73 17.27

F 1 14.80 13.70 13.60 19.30 19.00 18.68 F 2 15.80 14.00 12.30 16.20 20.01

VP 1 VP 2

VF 2 25.83 12.27 9.04 11.43 18.73

18.43 18.80

(P 1 + P 2 ) /2 13.77 14.80 13.97 15.93 14.10 18.33 16.53 16.10

22.03 19.47

Variance 3.86 4.29 3.38 3.64 5.26 5.59 4.46 5.23 5.23 5.23 6.00 5.86 5.54 5.23

VE 14.08 12.38

VG 21.28 7.51 4.74 6.60 13.17 9.07 7.54 GA 8.63 4.42 3.25 4.02 6.27 4.98 4.41

Heritability h 2 (%) 82.4 6.20 52.39 57.78 10.30 64.41 60.88 Estimated effective factors K 0.59 1 1.07 1 2.46 2 1.74 2 0.38 0 0 0.23 = 0

4.54 4.76 4.30 4.82 5.56 5.01 4.34

VE = environmental-variance, VF 2 = variation of F 2 population, P 1 and P 2 = av root length of a VG = genetic variance, GA = genetic advance, VP 1 and VP 2 = variation of first and second parents,

parent one and two, F 1 and F 2 = av primary root length of F 1 and F 2 hybrids.

Rice panicle characteristics density (HD) grains, having specific gravity >1.20, are found mostly on

S. Mallik A. M. Aguilar, and B. S. Vergara, primary branches of rice panicles. Plant Physiology Department, IRRI Increasing the percentage of HD grains

by decreasing the number of secondary We studied panicle characteristics of 10 branches can increase rice yield IR varieties, 16 O. glaberrima potential. The number of HD grains accessions, and 16 lines from a cross may also improve with better delivery involving upland rice parents. High system of the assimilates, such as more

vascular bundles, and bigger culms or thicker culms.

The glaberrimas had comparatively more primary branches and more spikelets on primary branches than did IR and upland entries (Table 1). They also had fewer secondary branches-the location of most low density grains- and fewer spikelets on them.

Table 1. Range and mean of 10 panicle characters in 3 types of rice varieties. IRRI, 1988.

Range Mean Character

IR varieties O. glaberrima Upland IR varieties O. glaberrima Upland

1. Primary branches (no.) (Pbr) 7 - 16.3 8 - 16.3 7.7- 14.7 10.3 ± 0.7 13.1 ± 0.7 12.1 ± 0.5 2. Spikelets on Pbr (no.) (SPbr) 37 -124 51 -139 38.3- 91.3 60.2 ± 7.5 99.3 ± 7.0 70.6 ± 3.7 3. Secondary branches (no.) (Sbr) 18.8- 34.8 2.2- 27.7 5.7- 39 26.7 ± 2.0 12.8 ± 1.9 27 ± 2.8 4. Spikelets on Sbr (no.) (SSbr) 60.3-117 4.7- 59.7 12.3-130.7 87.3 ± 6.4 33.2 ± 5.6 85 ± 9.6 5. Total spikelets (no.) (TSP) 100 -241 91 -199 51 -208 147.5 ± 12.2 132.4 ± 7.2 155.5 ± 12.7 6. Inner vascular bundle (no.) (IVB) 14 - 25.5 13.7- 18.7 9 - 22.7 19.9 ± 1.1 15.8 ± 0.4 16.0 ± 0.9 7. Outer vascular bundle (no.) (OVB) 16.8- 30.5 17.3- 36 13.7- 34.5 21 ± 1.2 34.1 ± 9.3 24.8 ± 1.7 8. Culm diameter (mm) (CD) 2.1- 3.2 1.6- 2.6 1.3- 3 2.3 ± 0.1 2 ± 0.1 2.4 ± 0.1 9. Air space (mm) (Asp) 1.5- 2.4 0.8- 1.8 0.6- 2.1 1.7 ± 0.1 1.2 ± 0.1 1.5 ± 0.1

10. Culm thickness a (mm) (Cth) 0.3- 0.4 0.3- 0.5 0.3- 0.6 0.3 ± 0.01 0.4 ± 0.01 0.4 ± 0.02

a Cth = (CD – ASp)/2.


~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The three types differed little in total spikelet number, indicating that panicles with more primary branches and fewer secondary branches can be obtained without reducing total spikelets per panicle. IR varieties had more inner vascular bundles from just below the neck node and glaberrimas had more outer vascular bundles. Culm diameter and air space did not vary widely, but culms were thinner in IR varieties.

Correlation coefficients (Table 2) among characters show that primary

branch number was significantly correlated with number of spikelets on primary branch, total spikelets, and inner vascular bundle. In upland lines, culm thickness was correlated with all characters except number of inner vascular bundle. Culm thickness might prove to be a useful overall measure of desirable traits.

Breeding programs should transfer useful traits of glaberrimas and upland lines into IR varieties to increase the number of HD grains.

Table 2. Phenotypic interrelationship between different panicle characters in 3 types of rice varieties. a

IRRI, 1988. 1 2 3

Pbr SPbr Sbr a b c a b c a b c

2.SPbr 3.Sbr 4.SSbr 5.TSP 6.IVB 7.OVB 8.CD 9.ASp

10.Cth

.97**

.59

.65*

.93**

.80**

.95**

.89**

.85**

.60

.96** –.46 –.46

.56*

.60* –.02

.11

.15 –.80**

.98**

.77**

.77**

.86**

.91**

.83**

.89**

.88**

.61*

.49

.55

.90**

.69*

.93**

.85**

.77**

.74*

–.34 .8 1** –.36 .80** .94** .99** .99** .68** .89** .79** .45 .98** .62* .87** .67* .04 .54** .05 .79** .61 –.19 .73** .24 .87** .68* .38 .83** .27 .85** .72* .34 .73**

–.05 .58* .02 .12 .82** 4 5 6

SSbr TSP IVB a b c a b c a b c

2.SPbr 3.Sbr 4.SSbr 5.TSP .86** .44 .98** 6.IVB .79** .02 .54* .83* .61* .66** 7.OVB .68* –.21 .71** .93** –.12 .76** .82** –.29 .74** 8.CD .71* .37 .83** .89** .52* .88** .80** .53* .80** 9.ASp .75* .31 .74** .86** .51* .81** .81** .62* .83**

10.Cth .20 .15 .82** .56 .06 .79** .43 –.15 .41

Flowering behavior of photoperiodsensitive rice germplasm of Bangladesh

Md. E. Haque, A. Baset, Z. Zeenat, and N. M. Miah, Plant Breeding Division, Bangladesh Rice Research Institute (BRRI), P.O. BRRI, Gazipur, Bangladesh

Most traditional transplanted aman rice varieties of Bangladesh are photoperiod- sensitive; however, sensitivity varies with variety and location.

Nearly 1,050 photoperiod-sensitive germplasm were grown in 1987 transplanted aman season in the BRRI experimental field (latitude 24°N) to observe flowering behavior. Materials were seeded on 20 Jul and transplanted on 22 Aug.

Varieties flowered from 15 Oct to 25 Nov (see figure). More varieties (395) flowered 1-5 Nov, synchronized with the strongly photoperiod-sensitive local variety Nizersail. Varieties flowering before 1 Nov could be moderately sensitive or have a long critical photoperiod. Those flowering later could be very strongly sensitive to photoperiod or have a short critical photoperiod. Another group of weakly photoperiod-sensitive varieties in Bangladesh flowering from late Sep to mid-Oct is not included here.

7 8 9 OVB CD ASP

a b c a b c a b c 2.SPbr 3.Sbr 4.SSbr 5.TSP 6.IVB 7.OVB 8.CD .94** –.12 .75** 9.ASp .90** –.07 .68** .97** .89** .97**

10.Cth .63 –.12 .71** .53 .30 .71** .36 –.15 .53* a a = IR varieties, b = O. glaberrima, c = upland lines. *, ** = significant at 5% and 1% levels of probability, respectively.

The International Hybrid Rice Newsletter is published for researchers in hybrid rice development and technology. Its content focuses on discussions of current issues; it does not publish research reports. For more information, write Dr. S. S. Virmani, Hybrid Rice Newsletter editor, IRRI, P. O. Box 933, Manila, Philippines.

Distribution of varieties by date of flowering. BRRI, Bangladesh, 1987.


Flowering on 1-10 Nov indicates that this reason, most Bangladesh introduced photoperiod-sensitive most varieties have critical photoperiod photoperiod-sensitive varieties flower varieties flower later than Bangladesh longer (12-12.5 h) than those of Thai, too early if planted in Thailand and in varieties because their critical Burmese, and Vietnamese varieties. For similar latitudes. On the other hand, the photoperiod is shorter.

Grain yield and duration of ratoon rice varieties

A. Palchamy and S. Purushothaman, Agricultural College and Research Institute (ACRI), Tamil Nadu Agricultural University, Madurai 625104, India

To evaluate ratoon performance, we measured grain yield and duration of 10 short- and medium-duration rice varieties during 1984-85 at ACRI.

The main as well as ratoon crop received 100-22-41.5 kg NPK/ ha. Immediately after rice harvest, ratoon’ stubbles were cleaned. Irrigation was given from day 3 onwards. All P and K plus half of N was applied 7 d after cutting. The balance of N was applied in 2 splits on day 25 (maximum tillering) and day 35 (panicle initiation).

Ratoon crop yields varied from 0.43 to 2.20 t/ha (see table). Bhavani’s high

Grain yield and duration of ratoon rice. Madurai, India, 1984-85.

Yield (t/ha) Crop duration (d)

Variety Main planted Ratoon Ratoon yield

planted crop yield (%)

crop compared with Planted crop Ratoon

Bhavani 2.5 2.2 86.6 128 78 Ponni 1.7 0.4 27.2 138 88 Puduvai Ponni 2.4 0.8 31.5 138 66 IR20 3.0 0.9 30.7 128 77 ACM8 0.8 0.7 80.0 120 67 ACM9 3.6 1.2 34.6 104 81 ACMl0 2.9 1.6 54.3 104 81 CO43 2.6 0.7 25.9 135 69 CO44 2.0 0.9 46.6 120 81 MDU2 2.6 0.5 17.9 138 77

LSD (P=0.05) 0.5

a Yellowing disease reduced yields.

yield of 2.2 t/ha was 86.6% of main crop ratoon crop. Analysis showed no yield. Ratoon crop durations varied significant correlation between ratoon from 69 to 81 d. Bhavani’s field duration crop grain yield and duration. was 128 d in the main crop and 78 d in

Hybrid rice in rainfed environments

O. S. Namuco, K. T. Ingram, and M. A. Maguling, Agronomy Department; and S. S. Virmani, Plant Breeding Department, IRRI

Two hybrids (IR46830A/IR9761-19-1R and IR54752A/IR46R) and their parents were dry seeded (75 kg/ ha) and grown under strictly rainfed conditions in lowland and upland fields of IRRI in 1987 wet season. IR46, one of the parents, was the check variety. Urea (90 kg N/ha) was topdressed on 17 Sep. Water deficit occurred 45 to 60 d after seeding (DAS) with a maximum stress of 69 kPa soil moisture tension at 20 cm soil depth and 5 kPa at 60 cm.

The table shows the performance of the F 1 hybrids and their parents under rainfed conditions. Hybrid IR46830A/IR9761-19-1R yielded

Yield and yield components of 2 F 1 hybrid rices and their parents under rainfed environments. IRRI, 1987.

Entry yield Grain Panicles

weight (t/ha)

100-grain Filled Harvest (no./m 2 ) grains index

(g) (%)

Lowland site IR46830A/IR9761-19-1R (F 1 ) 3.2 1118 1.90 62.62 0.30 IR9761-19-1 0.7 788 1.28 57.05 0.18

2.4 986 1.78 62.19 0.30 2.2 716 2.13 56.67 0.20 2.3 926 2.03 72.09 0.28 1.7 574 2.30 62.73 0.20

LSD (0.05) 0.4 320 0.20 22.50 0.06

IR46830A/IR9761-19-1R (F 1 ) 1.0 970 1.93 64.28 0.30 IR9761-19-1 0.6 794 1.73 42.75 0.30

0.5 910 1.65 46.60 0.23 0.8 522 2.15 69.80 0.20 0.6 492 1.90 69.20 0.23 0.8 490 2.20 62.50 0.25

LSD (0.05) 0.3 220 0.18 14.66 0.08

IR46830 IR54752A/IR46R (F 1 ) IR46 IR54752

Upland site

IR46830 IR54752A/IR46R (F 1 ) IR46 IR54752

highest with 105% midparent heterosis exhibited only 7% and 8% midparent for the lowland trial and 78% for the heterosis in the 2 trials and yielded as upland trial. Hybrid IR54752A/IR46R, much as did IR46.


The high yield of IR46830A/IR9761- 19-1R was attributed to a high number of panicles. It showed midparent heterosis for all characters at both sites.

Results indicate that hybrids developed specifically for irrigated lowland can be grown under rainfed conditions and still exhibit heterosis

even when subjected to water deficit. Results further suggest that hybrid rices can be developed for rainfed environments.

Grain quality and nutritional value

Modified method for apparent amylose content (AC) of milled rice

C. M. Perez and B. O. Juliano, Cereal Chemistry Department, IRRI

Colorimetric amylose assay based on amylose standard alone overestimates AC of milled rice because of amylopectin-iodine complex interference at acid pH. Addition of amylopectin (waxy rice starch, 0.6% amylose) to amylose in the standard mixture lowers amylose values, particularly for high- amylose rice. These values are probably closer to true AC since the potato amylose standard is only 80% pure.

Amylose values, however, are expressed on milled rice basis of about 90% starch. Recently, starches of high- amylose indica rices were shown to have the same true AC (about 18%) as low- amylose japonica rices. The increased iodine-blue color was due mainly to

Apparent AC of defatted milled rice flour in pH 4.5-4.8 acetate buffer based on amylose standard and amylose-amylopectin standard with starch content calculated to 90% and 70% of milled rice. a IRRI, 1988.

Apparent AC (%) based on

Variety name Amy1ose Amylose + alone amylopectin to

90% 70% starch starch

IR29

IR24 IR64 IR8

IR2071-137-5

Mean

8.2 16.2 19.9 28.2 32.2 20.9

0.6 9.2

13.2 22.0 26.2 14.2

1.9 10.6 14.6 23.4 27.6 15.6

a Standard: amylose 0-30 mg/100 ml; amylose: amylopectin 0-30: 90-60 mg/100 ml for 90% starch or 0-30: 90-40 mg/100 ml for 70% starch with defatted milled rice standards at 100 mg/ 100 ml.


high-iodine binding amylopectin; thus. apparent AC of high-amylose rice starches is 25-26%. High-amylose rice amylopectin has iodine complexing properties different from waxy rice amylopectin, while waxy and low- amylose rice amylopectins are similar in branching properties.

Because classification of milled rice AC into low (10-20%), intermediate (20- 25%), and high (>25%) is well accepted and documented, we propose maintaining such classification but calling it apparent AC.

These values can be obtained for defatted rice flour in the amylose- amylopectin standard method by

adjusting starch level (amylose + amylopectin) from 90% to 70% of the milled rice weight. Adding a constant correction factor, 1.4%, to all amylose values based on the 90% starch standard maintains the above classification scheme (see table). With this method, calibration is at pH 4.5-4.8 in acetate buffer, reducing errors inherent in the Williams procedure at alkaline pH. Excess iodine characterizes the acid pH procedure as reflected in the greenish amylose-iodine solution. Defatting with refluxing 95% ethanol gives more accurate apparent amylose values than using undefatted samples, because fat contents of samples are not necessarily identical at similar milling conditions.

The detailed procedure is available upon request.

Grain characteristics of traditional Basmati varieties of northwest India

V. P. Singh, E. A. Siddiq, F. U. Zaman, and A. R. Sadananda, Genetics Division, Indian Agricultural Research Institute, New Delhi 110012, India

We collected 23 traditional Basmati varieties from northwest India and

studied their grain characteristics (see table).

We divided varieties into two groups. Varieties of group A—HBC-5 (Havana Basmati collection), HBC-85, Pakistani Basmati (Amritsar), Basmati Kota, and Karnal local—have a growth duration of 145-150 d, and are phenotypically similar to Karnal local, which fetches the highest prices in the domestic and export markets.

Grain characteristics of Basmati varieties, India.

Group A (n = 5) Group B (n = 18)

Range Mean SEM Range Mean SEM Character

Milled rice length (mm) Brown rice (% of rough rice) Total milled rice

Head rice (% of rough rice) Milled rice breadth (mm) Length-to-breadth ratio Length of cooked grain (mm) Elongation ratio Alkali spreading value Amylose content (%)

(% of rough rice)

1.00 - 7.35 78.20 - 79.40 65.30 - 67.70

32.20 - 42.50 1.74 - 1.78 4.02 - 4.13

13.90 - 15.00 1.89 - 2.12 3.80 - 5.00

21.00 - 23.00

1.20 78.74 66.72

38.14 1.76 4.08

14.55 2.02 4.28

22.00

0.062 0.235 0.533

1.873 0.008 0.018 0.198 0.042 0.224 0.316

6.17 - 6.87 78.60 - 80.50 65.80 - 68.80

25.10 - 58.50 1.69 - 1.89 3.15 - 3.84

12.20 - 14.00 1.89 - 2.19 3.00 - 4.00

21.00 - 23.50

6.5 1 79.80 67.31

47.24 1.81 3.56

13.26 2.04 3.46

21.86

0.041 0.128 0.198

1.846 0.013 0.037 0.127 0.021 0.087 0.212

Varieties of 135-140 d duration represent group B. HBC-30,40,45,46, 85,98 and 136; Mohabawali, Kanwali, Chanderbani 1 and 11, Niranjanpur, and Ramgarh (named after the villages of Dehra-Dun Valley) are phenotypically similar to Basmati 370 whereas Hansraj and N-10B resemble Type-3. Among these cultures, only Basmati 370 and Type-3 have been officially released for

Disease resistance

Varietal ranking of blast (Bl) severity in Korean farmers' fields

S. W. Ahn, C. H. Kim, and N. K. Park, IRRI; and H. C. Choi and S. Y. Cho, CES, Rural Development Administration, Korea

Varietal reactions to rice Bl in farmers' fields and their relative ranking help determine resistance level, virulence frequency, disease pressure, and their interactions. Such rankings can guide cultural management.

To develop a varietal ranking in Korea, we used an indirect method without taking a comprehensive disease survey. We compared 56 varieties released in Korea: 26 of Tongil type (Korean indica) and 30 of japonica type. Most of the 51 varieties released before 1984 were grown in a considerable area. Cultivation area and duration of varieties vary widely, often highly influenced by Bl. Criteria for comparisons were the relative degree of maximum leaf or panicle Bl incidence and severity, yield losses due to Bl, and chemical requirement. Varieties were classified into 9 groups (Table l), and common features of five odd-numbered ranking groups were described (Table 2). Ranking groups 2,4, 6, and 8 reflect severity levels between those of the odd- numbered groups described. To minimize subjectivity, five evaluators rated each variety several times until they unanimously agreed.

Varieties scored 1 or 2, such as Taebaeg and Cheongcheong, were

cultivation and seed production.

(see table) appear to be in growth duration, milled rice length, length-to- breadth ratio, head rice recovery, and alkali spreading value. Difference in head rice recovery could possibly be due to postharvest handling and mechanical factors, but the lower mean value

Major differences in groups A and B (38.14%) in group A as compared to group B (47.24%) suggests higher vulnerability of longer grains to breakage.

Farmers grow Basmati 370, Type-3, and Karnal local under different names, warranting study of key diagnostic characteristics to establish their identities.

Table 1. Relative ranking of Korean varieties based on B1 severity in farmers' field. Korea, 1988.

Rank Tongil type Japonica type

1 Taebaeg (79), Chupung (79)

3 Cheongcheong (79), Samgang (182) 4 Palgwang (78), Milyang 42 (78)

5 Gaya (82), Weonpung (83), Shinseonchd (82),

2

Milyang 30 (77)

Baegyang (82), Shinwang (82) Seomjin (82), Nonglim Na 1 (67)

Seolag (79), Sobaeg (82), Boggwang (81), Dobong (79), Sangpung (81), Kwanak (79), Yeongdeog (85), Dongiin (81), Daecheong (84),

6 Seogwang (79), Hangangchal (79) Nongbaeg (69), Odae (82),

7

8

9

Baegunchal (79), Pungsan (81), Nampung (81) Saetbeol (77), Geumgang (77)

Milyang 23 (76), Sujeong (81), Yeongpung (82), Nopung (77), Tongil (71), Yushin (75), Hwanggeum (76), Chilseong (84)

Bonggwang (74) Chiag (81), Gwangmyeong (84), Namyang (83) Daechang (81), Yeomyeong (77), Jinheung (62), Palgeum (67). Chugwang (81) Seonam (82), Giho (83), Cheonma (84), Jiniu (79), Nagdong (75), Samnam (81), Chucheone (70)

a Total planting area of underlined varieties is more than 5,000 ha for Tongil type, and more than 10,000 ha for japonica type as of 1986. Figures in parentheses indicate year the variety was released.

planted in more than 10,000 ha each until 1984, but their levels of quantitative (partial or field) resistance are not known because compatible isolates were either absent or extremely low in frequency. Variety Samgang was cultivated in more than 130,000 ha from 1984 to 1987, yet no severe Bl outbreak was observed. Several varieties scoring 4 or 5, such as Seomjin, Milyang 42, and Milyang 30, have high levels of quantitative resistance. They occasionally may require one or two chemical applications. Varieties that scored 6 frequently need four applications, two for leaf Bl and two for

Table 2. Common features of Korean varieties in each ranking group of Bl severity in farmers’ fields. Korea, 1988.

Rank Common features

1 Extremely low incidence and severity. 3 Low incidence with minor damage.

5 Bl is common. Low to moderate Chemical application seldom necessary.

severity, without severe yield loss. Three or fewer chemical applications sufficient.

severity. Four or five application needed.

Extensive chemical application required, with control less than anticipated.

7 Moderate lo high incidence and

9 Severe Bl and significant yield loss.


panicle Bl. Varieties scored higher than 6 are vulnerable to Bl and damage could be high. Cultivation of many cultivars in rank 9 was discontinued because of severe outbreak of Bl. Yet several late-

maturing varieties with good grain quality favored by Koreans are widely grown in the southern plain of Korea with intensive applications of chemicals for Bl control. On these varieties, panicle

Bl is less severe than leaf Bl. The ranking can be applied to other

varieties when no historical quantitative disease data are available.

Varietal reaction to tungro (RTV) with change in leafhopper "virulence"

G. Dahal, V. M. Aguiero, R. C. Cabunagan, and H. Hibino, IRRI

Green leafhopper (GLH) Nephotettix virescens populations were periodically collected at Koronadal, South Cotabato; Maligaya, Nueva Ecija; and Los Baños (IRRI Experimental Farm), Laguna, in the Philippines in 1986-88 and reared on TN1 plants in cages in an insect-proof greenhouse. First or second generation adults that had fed on RTV-infected plants were allowed to feed 1 d on test seedlings. GLH feeding behavior was monitored by the color reaction of honeydew excreted by GLH on bromocresol-treated filter paper disks: blue color (basic reaction) indicates phloem feeding and brown or orange color (acidic reaction) indicates xylem feeding. At 3 wk after the feeding, seedlings were indexed by latex serology for the presence of rice tungro bacilliform (RTBV) and spherical (RTSV) viruses.

GLH populations collected thrice at Koronadal had similar transmission efficiency and feeding behavior on each test cultivar. GLH populations collected thrice at Maligaya were also similar. All these populations transmitted RTBV and RTSV together (RTBV + RTSV) at high efficiency and fed mainly from both phloem and xylem on IR54.

Six populations collected at Los Baños varied in their transmission efficiencies and feeding behavior, especially on IR54. Populations collected prior to Apr 1987 transmitted mostly RTBV alone and fed mainly from xylem on IR54. Populations collected after Aug 1987 efficiently transmitted RTBV + RTSV, and fed predominantly' from both phloem and


Area of acidic and basic honeydew spots (a), percentage of area of basic honeydew spots (b) excreted by 6 GLH collections from IRRI farm, Los Baños, Philippines, Aug 1986-Jan 1988, during a 22-h inoculation feeding, and transmission of RTBV and RTSV to 6 rice cultivars (c). IRRI, 1988.

RTBV and RTSV incidencea in 14 rice cultivars in demonstration plots at IRRI, 1986 and 1988 DS. b

1986 dry season 1988 dry season

Plants Plants (%) with Plants Plants (%) with Cultivar tested

(no.) RTBV+ RTBV RTSV (no.) RTBV+ RTBV RTSV tested

RTSV RTSV

IR8 IR22 IR26 IR30 IR36 IR42 IR54 IR58 IR64 Gam Pai 30-12-15 Sigadis Peta TN1

36 36 36 36 36 36 36 50 c

90 d

–

90 d

36

87 0 0

67 70

1 0 0 0

50 2

83

– – 11 59 41

7 12

3 0 6 1

22 12 13

– 2 0 0

15 10 19

9 12

9 7 7 2

36

36 36 36 36 56 36 70 34 34 36

–

–

56

0 0

11 61 71 3

66 80 38 78

–

–

14

31 25 0 0

11 0 4

15 9 8

–

–

19

0 0

75 36 16 33 23

0 24

6

–

– a Plants were indexed by latex serology. b Dashes indicate not tested. c Tested in 1985 WS. d Tested in 1985 DS.

xylem on IR54 and IR64 (see figure). Additional measurements Jan-Feb 1988 confirmed this. The shift in feeding

behavior on IR54 and IR64 of the Los Baños population from predominant xylem feeding to phloem and xylem

feeding could be the major reason for the shift in virus transmission efficiency.

At Los Baños, RTV incidence in IR54, IR64, and some other cultivars having Gam Pai 30-12-15 in their parentage was very low before the 1986

Resistance to bacterial leaf streak (BLS) in hybrid rice and parental lines

Li Ren-Hua, Hunan Hybrid Rice Research Center, Changsha, Hunan, China; and E. Medalla, Plant Pathology Department, IRRI

Five rice hybrids from IRRI and their male sterile (A) and restorer (R) lines were evaluated against two isolates of BLS in the greenhouse. Pregerminated seeds were grown in plastic trays, three rows in a tray, one for each F 1 , A, and R lines.

Isolates 93 and 335 of Xanthomonas campestris pv. oryzicola were used to spray-inoculate the test plants at 21 and 30 d after sowing (DAS). The bacterial suspension was adjusted to l09 cells/ml. Scoring was done 10 and 15 d after inoculation (DAI) using the Standard evaluation system for rice (SES), based on leaf area infection.

Sieve tube number in tungro (RTV)-infected rice plants

B. Srinivasulu and R. Jeyarajan, Plant Pathology Department, Tamil Nadu Agricultural University, Coimbatore, India

To study the effect of RTV infection on phloem tissues, we collected leaves from healthy and RTV-infected rice plants. Cross sections of leaves of the same age were dipped in a saturated solution of phloroglucinol in 18% hydrochloric acid. The phloem cells per microscopic field were counted.

in infected leaves. However, the mean number of sieve tubes was 123 in healthy leaves, compared to 73 in diseased leaves. We conclude that RTV reduced sieve tubes 41%.

We found no necrosis of phloem cells

wet season (WS) and very high from 1988. These results indicate the 1987 dry season (DS) onward. RTBV + breakdown of IR54 and IR64 resistance RTSV incidence on IR54 and IR64 was to RTV in Los Baños in 1987 DS was very low in 1986, but very high in 1988 due to a shift in GLH virulence. RTBV (see table). Gam Pai 30-12-15 also had + RTSV incidence on IR36 was high in high incidence of RTBV + RTSV in 1986, but low in 1988 (see table).

Reactions of different A and R lines and F 1 to BLS. IRRI, 1988.

Hybrid

Reaction a

Isolate 93 Isolate 335

A R F 1 A R F 1

IR46830A/IR50 7.2 4.0

IR46830A/IR9761-19-1 8.0 4.6

IR54752A/IR54 8.8 3.8

IR54752A/IR19392-211-1 8.7 3.1

Zhonshan 97A/Milyang 54 8.4 6.2

4.9 3.7 8.9 5.3 7.5 2.4

8.7 4.8

0

7.7 4.4

8.5 6.3 7.9 3.2

8.9 4.3 2.1 2.0

2.5 2.2 6 .0 3.7 5.2 6.1 7.4 6.5 3.4 0.3 5.0 3.7 3.1 1.8 5.2 6.0 3.7 7.5 0

3.8 5.1

4.9 6.8 2.5 5.7 2.0 6.3 0.0 2.7

a Scores are averages at 10 DAI on plants inoculated at 21 DAS (fist row in each set), and 30 DAS (second row). 0-3 = resistant, 3.1-4.9 = moderately resistant, 5-9 = susceptible.

Of the five hybrids, Zhonshan The two parental lines with moderate 97A/ Milyang 54 was resistant to the resistance produced rice hybrids with two isolates in both inoculation stages moderate resistance. The R line (see table). IR46830A and IR54752A contributed resistance in F 1 for the A became moderately resistant when line-susceptible and R line-resistant inoculated with isolate 93 at 30 DAS. combination.

Simplification of sampling method for assessing

Severity was assessed 5 times at 49 d after transplanting (DT), 55 DT, 62 DT, 69 DT, and 76 DT, on 8 hills per plot.

bacterial blight (BB) severity Leaf area damage on each of the top

N. Nilpanit, W. Sirisantana, and S. Disthaporn, Division of Plant Pathology Microbiology, K. Soontrajarn, Rice Research Institute, Department of Agriculture, Bangkhen, Bangkok 10900,

and

three leaves of each tiller (LADl, LAD2, and LAD3) as well as whole hill damage (VLAD) were visually assessed and expressed in percent. The average leaf area damage of leaves 1-3 (ALAD)

Thailand and disease incidence for each leaf

This study attempted to simplify methods to assess BB ( Xanthomonas campestris pv. oryzae ) severity. Rice variety RD9 was transplanted into 5 × 5 m2 plots at Pathum Thani Rice Research Center, Thailand, during DS 1987. Disease was induced by inoculation in several levels on border rows of seven treatments with two replications each.

position (IL1, IL2, IL3, and ILT) were calculated.

At maximum tillering (49 DT) and booting (55 DT) severity on the third leaf (LAD3) was highly correlated with average severity on the whole hill (ALAD) (see table). At flowering (62 DT), close correlations between average severity on a hill and severity on second or third leaves (LAD2 and LAD3) were found. At milk (69 DT) and dough


stages (76 DT), close correlations between average severity on a hill and the flag leaf (LAD1) or second leaf (LAD2) were observed. At all growth stages, incidence on all upper three leaves (ILT) was closely related to average severity on these leaves (ALAD).

Results suggest that BB severity can be assessed on one of the upper three leaves instead of on all three. The method could be further simplified by counting infected leaves, rather than by estimating leaf damage.

Susceptibility of bacterial blight (BB) differential varieties of IRRI, Japan, and Korea in Nepal

P. B. Karki, D. N. Sah, and D. N. Manandhar, Agriculture Station, Parwanipur, Nepal

BB caused by Xanthomonas campestris pv. oryzae (Xco) is a major rice disease in the terai and inner terai regions (main rice-growing area) of Nepal. Recently, this disease was observed also in the warm river basins of the hill regions. The numerous pathogenic races of Xco in Nepal hinder efforts to breed resistant varieties. To identify pathogenic variability of Xco, IRRI and Japanese varieties were tested as possible differentials at Parwanipur, Janakpur, and Kankai from 1979 to 1987.

Twenty-one-day-old seedlings of differential varieties were transplanted in 3 rows, each 5 m long. Each hill had 1 seedling and spacing was 20 × 20 cm. The plots were fertilized with NPK at 120-30-30 kg/ha. Plants were clip- inoculated at maximum tillering. The disease was scored 21 d after inoculation according to the IRRI Standard evaluation system for rice.

All IRRI varieties and Japanese differentials except DV85 in the 1979 test at Kankai were found susceptible to Nepalese isolates. The differential varieties have these resistance genes: Java 14, Xa-1 and Xa-3; Kogyoku, Xa-1 and Xa-kg; Nigeria 5, Xa-1 and Xa-2; Tetep, Xa-1 and Xa-2; IR20, Xa-4; IR1545-339-2-2, xa-5; DV85, xa-5 and


Xa-7 Kuntlan, Xa-6; and CAS209, Xa- 10. During 1979 tests, Korean differentials Milyang 23, Yushin, Suweon 281, and Tongil with resistance genes from Kinmaze, Kogyoku, Kogyoku, and Rantai-emas groups, respectively, were also nonfunctional against Parwanipur and Kankai isolates.

Thus, IRRI, Japanese, and Korean resistant varieties cannot be used as differentials to identify pathogenic races of Xco in Nepal. Therefore, national programs should develop their own differentials, possibly using local popular varieties, to monitor pathogenic variability of Xco.

Insect resistance

Use of tissue culture to evaluate rice resistance to lepidopterous pests

P. Caballero, D. H. Shin, Z. R. Khan, R. C. Saxena, B. O. Juliano, and F. J. Zapata, IRRI

Larval development was evaluated on plant tissues cultured from rice genotypes varying in levels of insect resistance. Murashige and Skoog (MS) and Linsmaier and Skoog (LS) media were used to induce and develop callus. Each liter of MS medium was supplemented with 2 mg 2, 4-D, 1 mg BAP, and 30 g sucrose (MS3); and each

liter of LS medium, with 1 mg 2,4-D and 30 g sucrose. Oryza ridleyi and Rexoro calli were obtained on LS medium; Chianan 2, Yabami Montakhab 47, and IR5865-26-1 calli were obtained on MS3 medium.

In a no-choice bioassay, about 200 mg of callus were placed in a 5-cm- diameter Gelman 7242 petri dish (see figure). Rexoro and O. ridleyi were susceptible and resistant checks, respectively. Due to limitations in available callus, Chianan 2 was bioassayed only against Scirpophaga incertulas, Yabami Montakhab 47 against Chilo suppressalis, and Ptb 10 and IR5685-26-1 against Cnaphalocrocis medinalis. Insect egg masses were surface sterilized and incubated at 28 ºC until eggs hatched. Callus in each petri

Lepidopterous pests reared on rice plant calli: a) C. medinalis larvae feeding on Ptb 10 callus; b) S. incertulas larva feeding on resistant O. ridleyi callus; c) growth of C. medinalis larvae on calli of O. ridleyi (c1), IR5865-26-1 (c2), Ptb 10 (c3), and Rexoro (c4); and d) growth of C. suppressalis larvae on calli of O. ridleyi (d1), Yabami Montakhab 47 (d2), and Rexoro (d3). IRRI, 1987-88.

dish was infested with 3 neonate larvae and incubated at 26 °C, at 12 h light/12 h darkness photoperiod. Each treatment was replicated five times.

normally on susceptible Rexoro. After 20 d of infestation, neonate S. incertulas larvae developed to 5th instar on Rexoro callus and to 3d on Chianan 2, but failed to survive on O. ridleyi. At 15 d after infestation, C. suppressalis neonate developed to 5th instar on Rexoro, to 4th on Yabami Montakhab 47, and to 2d on O. ridleyi. At 17 d after infestation, C. medinalis neonate larvae developed to 5th instar on Rexoro and Ptb 10 calli, to 4th on IR5865-26-1, and to 2d on O. ridleyi callus.

Results verify the use of tissue culture to investigate rice resistance to insect pests. Further work could provide plant breeders with sensitive screening tools to develop rice germplasm with better sustainable levels of insect resistance.

In all cases, larvae developed

Improved sources of plant resistance to yellow stem borer (YSB) Scirpophaga incertulas Walker in rice

P. S. P. Rao and G. Padhi, Central Rice Research Institute, Cuttack 753006, India

Dependable sources of resistance to YSB have not been available. For example, Ratna and Sashyashree, said to have moderate field resistance to YSB, have not been resistant to heavy infestation. Since 1980, we have worked to identify better donors of resistance.

In kharif 1980 and 1986, YSB broke out at heading stage in 121 late (140 d and above) cultures and varieties in 5 experiments and seed multiplication plots, resulting in whiteheads (up to 45.7%). In kharif 1982,1983, 1985, and 1986 and rabi 1983 and 1987, 6 planned experiments involving 352 entries (including national and international YSB screening sets, named varieties of IRRI, and repeats from earlier years) were field tested. Test plants (minimum of 4 and maximum of 16 per entry) were implanted with 24 healthy, laboratory- laid 4-d-old egg masses of YSB per hill

YSB infestation in selected test entries in different screening trials under outbreak conditions or egg mass implantation in growing plants in the field. Cuttack, India, 1980-87.

Trial Season and year Details of entries Entry

1

2

3

4

5

6

7

8

9

10

11

Kharif 1980

Kharif 1980

Kharif 1980

Kharif 1980

Kharif 1982

Rabi 1983

Kharif 1983

Kharif 1985

Rabi 1986

Kharif 1986

Rabi 1987

30 late varieties a

51 late cultures a

(replicated)

10 late cultures a

(replicated)

10 late cultures a

(replicated) 25 entries of IRTP YSB screening set + 11 others (replicated) b

20 entries b

80 breeding lines b

+ 25 others

60 entries of stem borer set (DRR) + 20 others b

30 released IR varieties + 20 other entries b

20 varieties on farm a

36 entries of stem borer screening, kharif 1986 (DRR) + 30 IR varieties + 15 others b

Infestation (%)

Mahsuri 5.2 CR1010 45.7

CR301-3066 nil Mahsuri 2.2

Jagannath 42.3

CR260-30 nil CR1016 27.4

CR259-398-326-155 2.5

CR260-30 0.3 CR1018 21.6 IR9828-23-1 5.5 Ratna 22.8 W1263 9.2 CO 18 7.9 W1253 4.1 IR15723-45-3-2-2-2 4.8 CR317-166 8.0 IR29 19.2

Deadhearts Whiteheads W1263 11.7 19.1 IR15723-45-3-2-2-2 16.1 11.6 IR9828-23-1 13.7 8.1 W1253 16.6 NF GEB24 52.6 NF IR29 35.9 32.4

Infestation (%)

CR260-151-81-2-710 9.7 CR260-167-247-179 10.0 CR260-30 17.4 IR9828-23-1 25.0 IR15723-45-3-2-2-2 28.0 W1253 7.6 Sashyashree 77.3

RP2199-7-10-8-3 5.9 W1253 6.0

W1263 10.2 IR9828-23-1 4.3

RP2069-39-3-1-4 39.5 IR20 19.2 IR58 IR24

18.9 47.5

CR1018 28.6 CR260-100-11 2.3 CR260-30 3.2

IR5 50.0

IET9405 (OR437) 4.9

W1253 9.3

W1263 3.3

RP2199-3-3-1-6 8.8

IR15723-45-3-2-2-2 4.0

IR9828-23-1 10.5

a YSB outbreak in field at heading. b YSB egg mass implantation in growing plants in field.

between 35 and 70 d after planting, and CR260-30 (trial 4), W1253 (5), W1263 borer infestation was evaluated at 20- (5), IR9828-23-1 (5), IR15723-45-3-2-2-2 25 d after implantation. (5), and Mahsuri (2) proved consistently

adequate YSB pressure on the 473 promising donors for use in YSB entries (see table). resistance breeding programs.

Borer incidence in all 11 trials showed resistant to YSB. They are the most


High virulence of new brown planthopper (BPH) populations in the Mekong Delta, Vietnam

Nguyen Van Huynh, Plant Protection Department, Faculty of Agriculture, University of Can Tho; and Han Thi Nhung, Southern Plant Protection Center, Vietnam

Since BPH biotype 2 occurred in the Mekong Delta in 1977 (IRRN 6/ 1977), it has been controlled by integrated pest management using resistant varieties.

However, in late 1986 and early 1987, two populations were detected. They were collected, mass-reared, and tested in the screenhouse with the differential set for BPH biotype by the seedling nursery method (see table).

Giang Province in 1986 wet season shows moderate damage on varieties carrying the resistant gene bph 2 (ASD7 and IR46) and even on varieties with Bph I gene (IR26). The population from

The population collected from Tien

Drought tolerance

Rice sensitivity to water deficit at different growth stages

K. T. Ingram and E. B. Yambao, Agronomy Department, IRRI

In the IRRI greenhouse, we measured sensitivity of rice in various growth stages to water deficit of several durations.

One IR64 plant per pot was grown in pots 55 cm high, 20 cm internal diameter and containing about 16 kg of Maahas clay soil under aerobic conditions. Control pots were watered daily to replenish all water lost by evapotranspiration. In water deficit treatments, water was withheld for 5, 10, or 15 d beginning at 10, 25, 40, 55, 70, 85, and 100 d after seeding (DAS). At the end of each stress period, plants were fully rewatered. During stress, the soil was covered with polyethylene and


Reactions of the differential varieties for BPH biotypes to 2 BPH populations collected in the Mekong Delta, Vietnam, 1986-87.

Reaction to BPH populations a

Differential variety Resistant gene Tien Giang An Giang

a b a b

Taichung Native 1 Susceptible check IR26

9 Bph 1 – – 5 7

Mudgo Bph 1 2 ASD7

5 Bph 2 3 5 5 9

NN3A bph 2 – – 7 9 NN6A bph 2 – – 7 9 IR13240-10-1 bph 2 – – 7 9 IR46 bph 2 + minor 4 6 Rathu Heenati Bph 3 1 2 0 1 Ptb 33 Bph 3 + bph 4 1 2 1 1 Balamawee bph 4 1 2 – –

a Damage was rated 1 to 9 twice: a = when all plants of TN1 were dead, and b = 7 d after the first scoring.

– 9 –

– –

– –

An Giang Province collected on moderately attacked. IR13240-10-1 in early 1987 shows higher These results indicate new damage on the currently cultivated populations of a new biotype are varieties carrying bph 2 gene with becoming strong enough to damage damage scores from 5 to 7. The varieties resistant varieties widely cultivated in with Bph 3 and bph 4 genes were not the area. This demands intensive damaged, but IR26 with Bph I was surveillance.

aluminum to minimize evaporation. Daily transpiration was estimated by weighing pots, and stress intensity was estimated as the cumulative difference between transpiration in control and stress treatments, (Tc - Ts).

During vegetative growth, water deficit had no effect on grain yield (see table). During the reproductive phase, water deficit of 5 or 10 d reduced yields by 25 to 45% and water deficit of 15 d reduced yields up to 88%. These results confirm previous findings that rice yields are reduced most when drought occurs during reproductive stage.

total with greatest Tc from 55 to 70 DAS. In other words, maximum yield reduction coincided with maximum

Control plants transpired about 50 kg

leaf area, Ts was also less than Tc after rewatering. If true, then the errant point should fall much closer to the regression.

If rice sensitivity to water deficit changed with growth stage, then we would expect to have different regressions between (Tc-Ts) and yield at different growth stages. Since yield data from stresses at all growth stages fall on the same regression

Grain yield of IR64 in response to water deficit at different growth stages and durations. IRRI, 1988.

Stress onset Grain yield a (g/plant) at in days stress duration of

seeding 5 d 10 d 15 d after

Tc. Grain yield was highly correlated 10 45 a-f 51 a-c 55 a

with (Tc - Ts), even with data from all 25 52 ab 49 a-e 50 a-d 40 40 d-g 41 c-g 16 i

growth stages combined (see figure). 55 40 c-g 31 gh 7 j The greatest deviation from the 70 37 fg 36 fg 26 h

regression line is for 15d stress at 85 41 a-f 39 e-g 42 b-f

panicle initiation. We computed (Tc-Ts) only during the stress

period. Possibly because of reductions in Control (no stress) grain yield was 54 g/plant.

100 40 c-g 39 e-g –

nificantly different at P<0.05 by DMRT. a Yields followed by the same letter are not sig-

Relationship between summation of daily difference between transpiration of control and stressed plants, and grain yield. IRRI, 1988.

line, differences in grain yield with drought at different growth stages can be entirely accounted for by differences in S (Tc - Ts).

Though IR64 was most susceptible to yield reduction by drought at flowering, it was not most sensitive to water deficit then. Rather, stress developed fastest and plants were most severely stressed at flowering because rapid growth then used water fastest. It appears that S (Tc-Ts) alone, with no factor to scale for growth stage, can be used as a drought stress index to compare results of screening trials in different locations and years.

A low-cost rapid screening technique for seminal root elongation

P. Gomathinuyagam and S. Natarajan, Agricultural Research Station, Paramakudi; and M. Subramanian and M. Nagarajan, Agricultural College and Research Institute, Madurai, India

Deep roots offer resistance to drought. To identify deep-rooted rice genotypes, we developed a new method of growing seedlings in solution culture. This technique fosters seminal root growth in young seedlings by hindering adventitious root growth: 1. With nylon net, cover tightly the

mouth of a tall measuring cylinder or

glass jar, preferably 30 cm high, 8 cm diameter (see figure).

2. Fill the jar to its brim with water. 3. Place 25 uniform pregerminated seeds

over the nylon net so they touch the water.

4. Radicles enter the water in 24 h. 5. Daily, drain the water level to arrest

adventitious root growth so only tips of long radicles touch the water by 1 mm. (To drain water from jar, use a small rubber tube 2 mm in diameter.) The seedlings with short or malformed radicles will dry up.

6. Thereafter, drain the water every 24 h, continuing to allow root tips to touch the water.

7. Seven days after germination, take out the seedlings and compare lengths of seminal roots. Deep-rooted Pregerminated seeds grown for 1 wk in a tall glass genotypes will develop longer seminal cylinder, mouth covered with nylon net.

roots. The advantages of this technique greatly from deep-rooted genotypes,

1. Root elongation provides valid data 3. Where a greenhouse is not available, for drought resistance. this simple technique can supplement

2. Shallow-rooted genotypes vary field data.

follow: allowing quick visual screening.

Excess water tolerance

Performance of rice breeding In rainfed lowland rice-growing areas lines under medium with impeded drainage, water may deepwater conditions stagnate at depths above 25 cm for

much of the growing season. Field M. M. Amante and D. J. Mackill, Plant experiments were conducted under Breeding Department, IRRI medium deep conditions at IRRI 1983-

Yields of promising rainfed lowland rices and check cultivars grown under medium deepwater conditions (25-50 cm water depth). IRRI, 1983-85.

Duration a Height a Lodging a Yield (t/ha) Designation

(d) (cm) score Grand mean yield (t/ha) 1983 1984 1985

IR13149-71-3-2-3 127 123 3.2 2.7 2.9 4.4 IR24705-11-3-2-3-3 137 123 2.8

3.3

IR26760-27-1-3-2-1 141 131 1.9 3.0 4.5 3.2

4.3 2.1 2.6 4.2 IR26760-76-2-1-2-3 133

3.0 128

IR19382-42-3-3-2 136 3.5

134 2.0 2.5 4.3

2.3 2.9

IR9217-58-2-2 2.4 2.3 4.0

126 127 3.3 2.6 2.5 3.3 2.8 2.9

120 119 5.3 2.4 2.0 2.7 129

2.4 113

132 2.7 1.9 1.8 3.2 2.3

152 7.0 0.6 1.4 1.3 1.1

IR54 IR42 Mahsuri

LSD (0.05) 0.8 0.6 0.9

a Duration, height, and lodging score (SES scale) are means from the 3 yr.


In the phytotron, spikelets treated with a constant day temperature of 27, 29, 31, 33, 35, 37, and 39 °C for 6 consecutive hours from 0800 to 1400 h had sterility percentages of 10.0, 11.5, 7.7, 9.2, 15.8, 26.4, and 74.3%, respectively. Thus the percentage of sterility increased as temperature increased beyond 35 °C, a correlation significant at 1% level.

Sustaining the high temperature progressively increased sterility. Sterility was 15.5, 26.6, and 28.8% when the spikelets were treated at 35 °C for 2, 4, and 6 h, respectively.

Spikelet sterility induced by natural climatic high temperature was observed during flowering in fields in southeastern Sichuan, China. Results (see table)

We studied hybrid rice responses to high temperature at flowering in the phytotron and under natural climatic conditions in southeastern Sichuan, China. Panicles of hybrids Shan You 2 and Ai You 2 that emerged 50-60% at the same growth stage were observed. Before temperature treatments, spikelets that had undergone anthesis were cut. After treatment, unbloomed spikelets were cut.

Hybrid rice responses to high temperature at flowering

V. D. Naidu and P. S. Reddy, Andhra Pradesh Agricultural University, Agricultural Research Station (ARS), Nellore 524004, A.P., India

observed for sterility in the field. IR20 recorded 4.3%; Rasi, 28.8%; and IR50, 15.2% sterility (see table). The suspected cause of the high sterility in IR50 is high temperature from panicle initiation to flowering. The higher temperatures might have affected meiosis, resulting in sterility.

and palea in florets were twisted. Most florets were aborted (see figure).

IR20 in rabi 1983, and Rasi and IR50 in late rabi 1984-85 and 1985-86 were

Spikelet deformity was observed in three rice cultivars at ARS farm in rabi 1983 (Oct-Mar), late rabi 1984-85 (Feb-Jun), and rabi 1985-86. Sterility ranged from 4 to 29%. When panicles were opened at booting, the androecium and gynoecium were already aborted and the lemma

85 wet seasons relating yield to agronomic traits of rainfed lowland breeding lines. Water depth was maintained at 25 to 50 cm from 3 wk after transplanting to maturity. We tested 75 entries in 1983, 73 in 1984, and 64 in 1985. They included check cultivars and advanced breeding lines, with entry changes each year.

Grain yields were low in 1983 and 1984 (0.6-3.0 t/ha), but were as high as 4.9 t/ha in 1985. They did not correlate well with agronomic traits. In 1984, a

subset of 25 entries was grown under shallow (5 cm) water depth. Grain yield for medium deepwater and shallow conditions correlated positively ( r = 0.66), indicating that yield potential at both water depths was related. Tillering did not correlate with yield nor differ between depths. Plant heights averaged 138 cm over all entries under medium deep conditions, compared to 131 cm under shallow conditions. Average lodging score by Standard evaluation

system for rice (SES) was 5.5 in medium deepwater and 2.6 in shallow water.

Twenty-one breeding lines were included in all years’ trials. Correlations between years were low. Several breeding lines performed better than check cultivars (see table).

In selecting lines for medium deep conditions, it is important to conduct yield trials over several years and select for intermediate plant height and lodging resistance.

Adverse temperature tolerance

Spikelet sterility in three rice cultivars

Spikelet sterility in 3 rice cultivars and weather parameters during panicle initiation to flowering. ARS, Nellore, India, 1983-86.

Weather parameter a

Cultivar affected affected spikelets sterility Maximum Minimum Relative (%) (%) (no./panicle) (%) temp temp humidity

(° C) (°C) (%) IR20 100 100 134.5 4.3 28.9 21.1 85.1 IR50 100 90 76.5 28.8 38.1 26.9 71.8 Rasi 100 100 66.4 15.2 37.0 26.0 70.3

Hills Panicles Total Spikelet

a Rainfall was nil during the trials.

Tan Zhonghe, Lan Taiyuan, and Fang Wen, Sichuan Academy of Agricultural Sciences; and Ren Chang Fu, Southwestern Agricultural University, China

Characteristics of sterile spikelets under high temperature at panicle initiation.


Percentage of spikelet sterility induced by high temperature under natural climatic condition in southeastern Sichuan, China.

Daily mean Daily maximum Sterility (%)

Spikelets or panicles Method temperature temperature

(° C) (°C) observed (no.)

Spikelet 27.9 ± 1.02 32.4 ± 1.75 7.24 ± 1.64 11,984 treatment 31.27 ± 1.12 36.35 ± 1.11 10.85 ± 2.05 7,719 Panicle 27.2 ± 1.10 31.35 ± 2.39 14.87 ± 2.84 200 treatment 30.87 ± 0.06 35.27 ± 0.25 21.93 ± 1.36 150

indicate that daily mean temperatures spikelets at meiosis, 778 at pollen grain 30 °C or lower and daily maximum development stage, and 1,320 at temperatures 35 °C or lower flowering, using 35 °C for 4 h in the significantly affected spikelet sterility. phytotron. This induced 4.1% sterility at

to high temperature, we treated 2,636 development, and 15.8% at flowering. To determine the stages most sensitive meiosis, 5.3% at pollen grain

The index of heat tolerance (% fertility at high temperature/ % sterility at normal temperature) for hybrid rices Shan You 2 and Ai You 2 were determined at 33, 35, and 37 °C in the phytotron. Heat tolerance for Shan You 2 was 1.05, 0.78, and 0.14; that for Ai You 2 was 0.84, 0.42, and 0.09, respectively. Thus Shan You 2 tolerated high temperature better than did Ai You 2.

Adopting high temperature-tolerant varieties and adjusting flowering times are strategies to avoid high temperature sterility.

Adverse soils tolerance

Modified screening method 3. At 4 wk after transplanting (WT)

for salt tolerance the plants are scored by both the percentage of dead leaves and the

Guo Wang-mo and Chen Rong-ye, Soil salt injury symptoms (visual), and Science and Plant Nutrition Department, IRRI’s standard of score 2 and China National Rice Research Institute score 1 are merged into score 1. (CNRRI), Hangzhou, Zhejiang, China We have tested 1,580 rice varieties,

We developed a practical method to susceptible checks such as Nona Bokra, screen rice varieties for salt tolerance, Pokkali, Kalarata, and Damodar, by based on IRRI’s screening techniques. this modified method. Results are Some modifications have been made: similar to those with IRRI’s technique.

including some of IRRI’s resistant and

four good uniform seedlings from each variety. • Plant them in a tray (41 × 27 × 13 cm) filled with 7 kg clay loam soil, and add 5.6 liters of 0.5% common salt solution to the soil. The ECe of the soil saturation extract should be 8-10 dS/m. Plant tolerant and susceptible checks. • Add demineralized water whenever necessary. • Score at 4 WT, using percentage of dead leaves and leaf injury symptoms (see table).

1. Rice seedlings are planted in soil The procedure is as follows: fertilized with NPK instead of • Germinate rice seeds in demineralized raised in solution culture,

Rice yield responses in a saline soil in Sri Lanka water.

simplifying the screening of more • Plant the pregerminated seeds in soil A. H. G. Mithrasena and H. D. varieties at lower cost. fertilized with NPK.

2. Screening is fixed at the 3-leaf stage • Irrigate up to 1 cm depth until to eliminate the unfavorable effects seedlings reach the 3-leaf stage. caused by 2-wk-old seedlings • Pull the seedlings without injuring the In the low country wet zone of Sri grown in different seasons. roots, wash the roots in water, and select Lanka, 10% of riceland is coastal saline.

Jayawickrama, Regional Agricultural Research Centre, Bombuwela, Sri Lanka

Results of screening rice plants for tolerance for salinity, using a modified method. CNRRI, China, 1988.

Dead leaves a Reaction to salinity

(%)

0-35 Normal growth, absence of salinity symptoms 1 Highly tolerant

Score Tolerance degree

36-50 Restricted growth and tillering, a few rolling leaves 3 Tolerant 51-70 Very restricted growth and tillering, most 5 Moderately tolerant

leaves rolling 71-90 Growth ceases, most leaves and some plants dead 7 Moderately

susceptible 91-100 Most plants dead or nearly dead 9 Susceptible

a Percentage dead leaves = no. of dead leaves/plant × 100.

no. of leaves/plant

Pokkali is one of the few adaptable varieties, particularly where soil conductivity goes up to 7-8 dS/m. However, Pokkali is not widely grown because it has low yields and is susceptible to lodging and diseases.

This study compared two promising salt-tolerant cultivars with Pokkali at 2 spacings in 1985-86 wet season in a farmer’s field with salinity up to about 7 dS/m.

Bw 297-2, and Pokkali from a dry bed Two-week-old seedlings of Bw 272-8,


nursery were planted at 3 seedlings/ hill, spaced 15 × 10 cm and 15 × 20 cm. Plot size was 6 × 3 m, with 30 cm space between plots. A 3 × 2 factorial, randomized complete block design with three replications was used.

Fertilizer and agrochemicals were applied as recommended by the Department of Agriculture. Plots were harvested after removing 2 rows around each plot, and yield estimated at 14% moisture.

weekly for measuring soil pH and soil conductivity from planting to grain filling.

when the crop was at tiller initiation.

Soil samples were randomly collected

Highest conductivity was 6.65 dS/m

Bw 272-8 and Pokkali had some scorching of leaf blade tips. Bw 297-2 had leaf rolling.

transplanting reduced soil conductivity, which gradually increased to 4 dS/m at flowering stage. No growth retardation or panicle sterility was observed.

Pokkali lodged (40-55%) at flowering, especially in 15- × l0-cm plots. Bw 297- 2 lodged slightly in the closer spacing.

Bw 272-8 yielded significantly more than Bw 297-2, and both varieties bested Pokkali (see table). For all varieties, reducing spacing from 15 × 20 cm to 15 × 10 cm significantly increased yield. Interaction between variety and spacing was not statistically significant.

Heavy rains 3 to 5 wk after

Effect of spacing on yield of 3 transplanted varieties in saline fields. Bombuwela, Sri Lanka.

Yield (t/ha) Variety Variety

15 × 15 × mean l0 cm 20 cm

BW 272-8 3.4 2.7 BW 297-2

3.1 2.8 2.0 2.4

Pokkali 1.3 0.8 1.1

Spacing mean 2.5 1.9 –

LSD for variety (0.01) – 0.7 t/ha (0.05) – 0.5 t/ha

(0.01) – 0.6 t/ha LSD for spacing

Results show that using resistant varieties at reduced spacing could increase yields in saline tracts.

Integrated germplasm improvement 2,316 m. Rice is cultivated up to elevations of 3,048 m.

Nepal’s target rice production is 5.1 Nepal releases nine rice Most Nepal ricefields (88%) lie in the million t, averaging 3.5 t/ha, by year varieties tropical to subtropical climatic region 2000. Improved varieties are needed to

that includes the Tarai region (southern help reach this goal. G. L. Shrestha, National Rice Improvement plain area), 9.5% are in the midhill In Aug 1987, Nepal released nine Program (NRIP), Parwanipur Agriculture region up to 1,372 m, and 2.5% are in varieties for different ecological regions Station, Birganj, Nepal cold high hills between 1,372 and and conditions (see table). Palung 2 is

New rice varieties recommended for ecological regions of Nepal, 1987.

Ecological region and Recommended Original conditions for cultivation variety name designation

Parents Country When Growth of origin introduced duration Y ield Grain type

in Nepal (d) (t/ha)

For high hills (1524-1981 m) Palung 2 NR10073-167-3-1-3 BG94-2/Pokhareli Temperate region

(cold temperate region) Masino Irrigated condition

Nepal bred 158-186 4.9 - 7.2 Coarse

For midhills (914-1524 m) Khumal 2 NR10068-60-3-2 Jarneli/KN-LB-36t Nepal Nepal bred 130-153 3.5 - 7.7 Coarse BLK-2-8

Warm temperate region Khumal 4 NR10078-76-14 IR28/Pokhareli Nepal Nepal bred 139-148 4.2 - 8.4 Coarse Masino

Tropical to subtropical region 1) Irrigated condition

(610-1524 m) Early season (Feb-Jun) Chaite 2 IR7151-260-3-3 BG34-8/ 1979 120-125 3.6 - 6.4 Medium

cultivation (Chaite IR2061-522-6-9 Dhan Kheti) (IRRI)

Chaite 4 IR9729-67-3 BG34-8/IR28// 1980 120-125 3.4 - 6.6 Medium IR2095-625-1-252 (IRRI)

Normal season (Jun-Oct) Barkhe 2 B4416-126-3-21 C4-63 GB/B 531b-TK-39 Indonesia 1977 130-140 3.5 - 5.3 Fine cultivation (Barkhe Khajura 2 PAU41-262 RP72/Mutant 65 India 1979 135-145 3.3 - 4.7 Medium Dhan Kheti)

For normal season Makwanpur 1 BG400-1 Ob 78/IR20/H4 Sri Lanka 1980 140-150 3.5 - 6.3 Coarse cultivation

2) Rainfed lowland condition

3) Rainfed upland condition For normal season Ghaiya 2 MW10 MTU/W. Kakaiku India 1980 110-115 2.1 - 4.7 Medium cultivation


Evaluation of African Upland Rice Advanced Trial (AURAT) at Ibadan, Nigeria

P. G. Pillai, National Cereals Research Institute, Ibadan Sub-Station, P.M. B. 5042, Ibadan, Nigeria

Nurseries of 17 entries in 1985 and 15 each in 1986 and 1987 were laid out during the wet season at Ibadan in a

randomized complete block design with 4 rep1ications. Plot size was 12 m2. Four to six dry seeds were dibbled at 25- × 25-cm spacing.

Eleven entries were tested over 3 yr. In 1985, moisture stress reduced plant height and grain yield. IRAT104, which possessed clean grains, significantly outyielded the check FARO 11. Yields in 1986 were variable but not significantly different. In 1987, plant

generally increased because of steady height, tillering, and grain yields

rainfall throughout the growing season. ITA305, ITA3 15, IRAT170, and UPLRi-5 yielded significantly higher than FARO 11.

Four entries—ITA305, IRAT161, IRAT 104, and ITA3 15—that outyielded FARO 11 by 25% were selected for national multilocation trials.

Models for panicle growth simulation

G. F. Li and D. Senadhira, Plant Breeding Department, IRRI

Panicle growth simulation helps determine rate and duration of grain

filling. Using data from 1987 wet season experiments at IRRI, we tested six growth models to find the best one for simulating panicle growth.

Richard’s function performed best, with the largest regression coefficient between simulated and actual growth. Logistic function ranked second,

followed by cubic polynomial, quadratic polynomial, negative exponential, and Gompertz function. Results indicate Gompertz function is not suitable for panicle growth simulation.

Individuals, organizations, and media are invited to quote or reprint articles or excerpts from articles in the IRRN.

recommended for cold temperate region. recommended for early season (Feb to subtropical regions. Makwanpur 1 is Khumal 2 and Khumal 4 were selected Jun) and Barkhe 2 and Khajura 2 for released for rainfed lowland and Ghaiya for warm temperate regions under normal season (Jun to Oct) cultivation 2 for rainfed lowland for the hot irrigation. Chaite 2 and Chaite 4 are under irrigation in tropical or region.

Data management and computer modeling

CROP AND RESOURCE MANAGEMENT Soils and soil characterization

Effect of soil type on draft force needed to plow soils of South Sulawesi, Indonesia

T. M. Lando and B. Abidin, Agricultural Engineering Department, Maros Research Institute for Food Crops, P. O. Box 173, Ujung Pandang, South Sulawesi, Indonesia

We measured the draft required to pull special-purpose plows on different soils in South Sulawesi. Draft was measured with a drawbar dynamometer, three times for each soil. Carabao, cow, or human power was used, depending on site condition. Cuts were 15 cm wide

Draft of soil types in South Sulawesi, Indonesia.

Soil draft (kN)

Soil Wetland Dryland

Grassy Nongrassy Grassy Nongrassy

Grey alluvial 0.53 0.45 0.58 0.50 Old grey alluvial 0.66 0.51 0.63 Grey brownish alluvial 0.54 0.47 0.60 0.49

0.57

Yellowish grey alluvial 0.43 0.39 0.49 Hydromorphic alluvial

0.42 0.65 0.93 0.63 0.64

Brownish grey alluvial 0.54 0.46 0.65 0.59 Brownish alluvial 0.60 0.46 0.63 0.54 Complex brown Regosol, 0.44 0.40 0.48 0.37

Latosol 0.47 0.44 0.60 0.47 Reddish brown Mediterranean 0.52 0.47 0.57 Complex reddish brown

0.51 0.56 0.50 0.57 0.51

Mediterranean, and Latosol

Mediterranean and Latosol Continued on next page


and 12 cm deep at 2.0 km/h or 0.56 m/s.

Of the soils tested, grey Grumusol required the highest draft, yellowish red lateritic soil the lowest (see table). Grassy soil needed higher draft than nongrassy soil. Soil with scattered stones needed a high draft.

Wetland (previously puddled) needed a slightly lower soil draft than dryland (nonpuddled): 0.64 kN on grassy wetland, 0.57 kN on nongrassy wetland, 0.63 kN on grassy dryland, and 0.58 kN on nongrassy dryland.

power required for land preparation on different soil types:

The following formula calculates

Power (kW) = draft (kN) × speed (m/s)

For example, on vegetative grey Grumusol with a soil draft of 1.26 kN and on yellowish red lateritic with a soil draft of 0.38 kN, the required power for land preparation is 0.71 and 0.21 kW, or 0.95 and 0.28 hp, respectively.

Table continued

Soil draft (kN)

Soil Wetland Dryland

Grassy Nongrassy Grassy Nongrassy

Complex reddish brown Latosol and Latosol

Grey Grumusol Old grey Grumusol Black Grumusol Yellowish red lateritic Yellowish grey Regosol Yellowish red podzolic Yellowish brown podzolic Brown podzolic Violet podzolic Brown Mediterranean Grey Mediterranean Complex grey brown podzolic

Complex yellowish brown Mediterranean and Latosol

Complex red Mediterranean and Latosol

Yellowish red Latosol Reddish brown Latosol Brown Latosol Grey brown Regosol Brownish yellow Latosol

0.58

1.26 1.12 1.16 0.38 0.73 0.48 0.49 0.69 0.63 0.79 0.43 0.5 7 0.72

0.62

0.73 0.60 0.88 0.77 0.70

0.49

1.08 1.09 1.14 0.33 0.65 0.42 0.41 0.63 0.58 0.72 0.41 0.51 0.67

0.55

0.60 0.50 0.77 0.66 0.62

0.50

1.18 0.99 1.16 0.40 0.79 0.40 0.5 7 0.78 0.67 0.82 0.54 0.67 0.78

0.76

0.79 0.64 1.02 0.86 0.72

0.49

0.88 0.88 1.07 0.36 0.70 0.36 0.44 0.68 0.5 1 0.74 0.44 0.52 0.12

0.61

0.62 0.60 0.79 0.69 0.69

Soil microbiology and biological N fertilizer

Growth and K uptake of Azolla pinnata under different salt levels

K. Rajarathinam and M. A. Padhya, Tissue Culture Laboratory, Botany Department, The M.S. University of Baroda, Baroda 390002, India

We studied salt tolerance, growth, N content, acetylene reduction, and K accumulation of Azolla pinnata grown

under different K levels (0, 10, 20, 30, 40, 50 ppm). The plant was grown on a N-free medium containing 40 ppm Mg, 40 ppm K, 40 ppm Ca, 20 ppm P, 0.5 ppm Mn, 0.2 ppm B, 0.1 ppm Mo, 0.01 ppm Cu, 0.01 ppm Zn, and 2 ppm Fe. Salt concentration in the control medium was 770 ppm.

To test salt tolerance, NaCl was added to the medium to make 1000, 1300, 1900, 2500, 3100, and 3700 ppm. Three grams of actively growing azolla

Influence of salt concentration on growth and K accumulation in Azolla pinnata. Baroda, India.

Total salt concentration weight weight of the medium

(ppm)

Fresh Dry N C 2 H 4 formed K content (nmol/g fresh content

(g) (g) (%) weight per h) (% by dry weight)

710 1000 1300 1900 2500 3100

LSD (0.05)

25.9 25.7 25.3 17.6 10.8 7.2 1.3

1.03 1.02 1.01 0.72 0.39 0.07 0.07

3.9 3.9 3.9 3.8 3.1 2.8 0.1

685 680 668 530 411 213

76

2.98 2.93 2.90 2.61 1.98 1.14 0.28


plants were inoculated in a plastic tray (40- × 25- × 10-cm) containing 2 liters of the test medium. Cultures were incubated at 25 ± 2 °C under fluorescent light for 16/8 h light/dark cycle. Culture medium was changed once in 3 d. Plants were harvested after 21 d.

and 1300 ppm), azolla grew as well as the control. Salt levels 1900 ppm and higher significantly reduced biomass production, N content, acetylene reduction activity, and K accumulation (see table). Plants were killed at 3700 ppm salt level.

Growth and K accumulation increased with increasing level of K in the culture medium. Besides fixing N of Anabaena azollae, azolla plants efficiently accumulated K.

At lower concentrations of salts (1000

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A. T. Reddy, D. V. R. Reddy, V. S. Rao, T. V. Kumar, R. N. Pillai, and I. V. Subba Rao, Soil Science and Agricultural Chemistry Department, Agricultural College, Bapatla 522101, A.P., India

Effect of N forms on leaf nitrate reductase activity, yield, and protein content of rice

In a field experiment at TNAU in rabi 1987, we studied the weed-suppressing ability of azolla alone and with herbicides. We used a randomized complete block design with three replications.

The herbicide treatments (see table) were imposed 3 d after transplanting (DT) and azolla was inoculated 9 DT and incorporated at 30 DT (except in treatment 8). Weed dry matter (DM) was recorded at 60 DT.

The weed flora included Echinochloa crus-galli, Cyperus difformis, Marsilea quadrifolia, Ammannia baccifera, and Eclipta alba.

Hand weeding twice (HWT) + azolla (treatment 6), anilofos + 2,4-D EE + azolla (treatment 2), and thiobencarb +

a In a column any two means followed by a common letter are not significantly different from each other at the 57% level. DC = dual culture.

Herbicide-azolla integration for weed control in transplanted IR60 rice

G. Srinivasan and P. Pothiraj, Agronomy Department, Tamil Nadu Agricultural University (TNAU), Coimbatore 3, India

Effect of weed control treatments on weed dry matter (DM) and relative dry weight, and grain yield of rice. a TNAU, 1987 dry season.

Weed DM Weed Relative dry weight (%) Grain Treatment at 60 DT yield

(g/0.5 m 2 ) efficiency

Echinochloa Marsilea (t/ha) (%)

1 Anilofos 0.30 kg/ha + 2,4-D EE 6.5 cd 73.47 46.15 23.08 5.0 b

2 T1 + azolla DC at 2 t/ha 3.0 ab 87.76 60.00 16.67 5.2 b 3 Thiobencarb l.0 kg/ha + 2,4-D EE 7.5 d 69.39 40.00 26.68 4.9 bc

4 T3 + azolla DC at 2 t/ha 3.8 ab 84.49 68.40 10.53 5.1 b 5 Two hand weedings 4.8 bc 80.41 50.00 20.83 5.7 a 6 T5 + azolla DC at 2 t/ha 1.5 a 93.88 53.30 13.33 5.8 a 7 Unweeded check 24.5 f – 60.95 12.24 4.1 d 8 T7 + azolla DC at 2 t/ha 15.6 e 36.33 50.64 22.44 4.6 c

at 0.51 kg/ha

at 0.51 kg/ha

2,4-D EE + azolla (treatment 4) correlated with yield r = +0.89**. effectively reduced weed DM at 60 DT Two hand weedings alone or in (see table). Azolla effectively suppressed combination with azolla as dual culture Marsilea but not Echinochloa. recorded higher yields. Herbicide-treated

HWT + azolla recorded the highest plots either singly or in combination weed control efficiency of 93.88% at 60 with azolla recorded lower yields, but DT, followed by anilofos + 2,4-D EE + these were significantly higher than that azolla with 87.76%. Weed control of the unweeded check alone or with efficiency at 60 DT was strongly azolla.

Physiology and plant nutrition

(120 kg N/ ha) with a basal dose of superphosphate (40 kg P/ ha) and muriate of potash (40 kg K/ ha). Control was no N. N was supplied in 3 split doses-at transplanting, 25 d after transplanting (DT), and 50 DT. Experimental soil was heavy-textured clay loam with pH 7.0, 0.45% organic C, and 94-12-700 kg available NPK/ ha.

Using 4 replications, we studied the relationship of leaf nitrate reductase activity (NRA) at crop growth stages to yield and protein content of rough rice as affected by N forms during 1987 WS at Agricultural College, Bapatla.

MTU5249 (Vajram) was grown in glazed pots (6 kg soil/pot) under flooded conditions. The seedlings (3 wk) were transplanted at 2 seedlings/pot and fertilized separately with potassium nitrate, urea, and ammonium sulfate

Leaf NRA was assayed in the uppermost leaf or flag leaf at maximum tillering > panicle initiation > flowering stages. It was in the order maximum tillering gt panicle initiation gt flowering (see table). Potassium nitrate treatment recorded highest NRA, followed by urea and ammonium sulfate. Neither grain yields nor protein contents differed significantly among N forms. However, N fertilizer improved grain yield and protein content compared to the control.

Leaf NRA, grain yield, and protein content of MTU5249 rice as affected by different forms of fertilizer N. Bapatla, India, 1987 WS.

Leaf NRA (nmol NO 2 - formed/g per h) Treatment

Grain Grain Maximum Panicle Flowering yield protein

tillering initiation (g/pot) (%)

Control 150 110 90 3.10 Potassium nitrate 460 410 380

7.61

Urea 420 360 10.45 9.85

385 9.45

Ammonium sulfate 8.62

405 360 345 9.42 8.55 LSD (0.05) 38 25 31 1.15 0.92


Root and shoot growth of Oryza sativa L. as affected by redox potential

N. Sekhon, H. S. Sur, and N. T. Singh, Soils Department, Punjab Agricultural University, Ludhiana 141004, India

We compared root and shoot growth responses to levels of soil reduction.

Iron pots 1 m high and 50 cm in diameter were uniformly packed with a loamy sand (Typic Ustochrept) and different levels of redox potential created using the treatments control (soil kept near 60% field capacity), submergence (4-6 cm standing water), submergence + 0.5% starch, and submergence + 1% starch. One day after treatment, 21 seedlings of cultivar PR106 were transplanted into each pot. Recommended doses of fertilizers were used. All measures, except shoot and

grain weight, were recorded at panicle emergence.

The redox potentials created ranged from +343 mV to -396 (see table). Decrease in Eh from +343 to +70 mV significantly improved growth measures except for total chlorophyll content. Lowering Eh to -97 mV further improved all measures including the chlorophyll content. Further decrease in redox potential did not improve growth but signiticantly reduced tillers, leaf

area, and root density. The amount of roots increased in the surface 5-cm soil layer with decrease in redox potential from +343 to -3% mV.

Growth improvement with decrease in Eh to -97 mV could be explained by better tissue hydration, higher availability and uptake of nutrients, and improved soil physical conditions. Further reduction may lead to accumulation of toxic products.

Crop management

Effect of irrigation, and seedling age and number on rice yield

A. S. Sidhu, G. C. Aggarwal, and N. T. Singh, Soils Department, Punjab Agricultural University, Ludhiana 141004, India

Using variety PR106 on a calcareous sandy loam soil (Typic Ustochrept), we laid out treatments with three replications in a split-plot design. Irrigation was in the main plot and combinations of seedling age and number per hill in the subplots. Irrigation levels were daily irrigation (I 1 ), irrigation on alternate days (I 2 ), and irrigation after 2 d (I 3 ). Seedling ages were 32, 45, and 57 d and seedling rates were 2 and 3 per hill. The nursery was transplanted 5 Jul. NPK was applied at 120-18-25 kg/ ha. Irrigation treatments began, after 3 wk of continuous submergence after transplanting, with 259 cm applied in I 1 , 210 cm in I 2 , and 181 cm in I 3 . The soil had 8.0 pH, low

organic C (0.3%), and medium available P (14.5 kg P/ ha) and available K (136 kg K/ ha).

Rice yields were significantly better with daily irrigation (Table 1), but only with 2 seedlings/hill. Similarly, yields were better with younger (32 d) seedlings, but only with 2/hill. Results indicate that transplanting 3 seedlings/hill ameliorated the adverse effect of decreased irrigation as well as of advanced seedling age. Irrigation

Rice response to N rates and delayed planting

A. K. Pande and R. C. Gautam, Agronomy Department, G.B. Pant University of Agriculture and Technology, Pantnagar, Nainital 263145, U.P., India

Usually kharif rice planted late, with the onset of monsoon, yields less. We studied whether variety duration and N rate can compensate for later planting.

In 1985 wet season at the Crop Research Center (29 °N, 79.3 °E, and

frequency was significant only when younger seedlings (32 d old) were transplanted (Table 2).


Effect of soil redox potential on rice roots and shoots. a Ludhiana, India.

Soil Root Tillers Plant Leaf Total Root Straw Grain yield yield Treatment Eh porosity (no./ ht area chlorophyll density

(mV) (%) plant) (cm) (dm 2 / (mg/g (µg/cm 3 ) (g/pot) (g/pot)

Control Submergence (S) S + 0.5% starch S + 1% starch

+ 343 + 70 – 91 – 396

7.8 b 12.9 a 13.2 a 15.2 a

5.5 b 6.0 a 6.8 a 5.8 a

74.4 b 84.3 a 84.8 a 82.3 a

6.3 b 1.5 a 8.3 a 7.7 a

4.1 b 4.2 b 5.1 a 5.3 a

498 b 735 a 847 a 792 a

165 c 208 b 287 a 259 a

98 b 221 a 264 a 242 a

a In a column, values followed by a common letter are not significantly different at the 5% level.

Table 1. Effect of irrigation, and seedling age and number per hill on rice yield. Ludhiana, India, 1988.

Rice yield (t/ha)

2 3 Mean seedlings/ seedlings/

hill hill

Irrigation I 1 I 2 I 3

LSD (P = 0.05) Seedling age (d)

32 45 57

LSD (P = 0.05)

10.2 9.6 9.1 0.1

10.1 9.4 9.4 0.5

10.1 9.9 9.5 ns

10.1 9.6 9.7 ns

10.1 9.8 9.3 0.1

10.0 9.5

10.0 0.4

Table 2. Interactive effect of irrigation and seedling age on rice yield. Ludhiana, India, 1988.

Seedling Rice yield (t/ha) age

LSD (P = 0.05)

(d) I 1 I 2 I 3

32 45 57

Mean

10.6 9.8

10.0 10.1

10.1 9.6 9.5 9.8

9.4 9.2 9.3

9.3

0.9 ns ns

0.6

plant) fresh wt)

Table 1. Atmospheric temperature, rainfall, and solar radiation during planting time. Nainital, U. P., India, 1985 wet season.

Temperature (°C) Date

Rainfall Sunshine (mm) (h/d) Maximum Minimum

18-24 Jun 40.0 27.7 26.4 6.7 25- 1 Jun 35.1 24.7 48.7 8.8

2- 8 Jul 33.2 25.4 54.4 5.3 9-15 Jul 31.1 24.7 113.0 5.5

16-22 Jul 31.1 24.6 129.9 6.1

243.8 m altitude), we used Beni silty clay planting dates, two varieties and two N loam, fine-silty, mixed, hyperthermic, rates—were compared in a randomized Aquic Hapludoll with pH 7.5, 1.3% block design (Table 2). Varieties Govind organic C, 0.11% total N, 15.82 kg and Pant Dhan 4 differed in duration available (Olsen) P/ha, and 139.68 kg (105 and 130 d). available K/ha. The region enjoys Significantly higher grain yield was subhumid subtropical climate with high obtained with early planting, high N, temperature in May-Jun and heavy and with a short-duration variety under rainfall during Jul-Aug (Table 1). delayed planting. Twelve treatment combinations—three

Table 2. Grain yield as influenced by planting date, variety, and N rate. Nainital, India, 1985 wet season.

Treatment Grain yield (t/ha)

Planting date a

25 Jun 5 Jul

15 Jul

LSD (P = 0.05) Variety

Pant Dhan 4 Govind

LSD (P = 0.05) N rate (kg/ha)

60 120

LSD (P = 0.05) CV (%)

5.4 4.8 3.9 0.3

4.2 5.2 0.2

4.4 5.0

0.2 7.8

a Seed sowing date in nursery.

Soil fertility and fertilizer management

Effect of N application

source and time on rice

Center, Trivandrum (11°N, 77°E, 30 m above mean sea level). We used 3 sources of N at 90 kg N/ha and 4

N. A. Salam, E. Tajuddin, K. Varghese, application times (see table). The basal S. M. S. Hameed, and Y. Thomas, Kerala application was broadcast and Agricultural University, Karamana 695002, incorporated at transplanting time. For Trivandrum, India topdressing, all sources were broadcast,

We studied effects of N sources and increasing the water level to 2-3 cm. The application times on Jaya rice grain and soil (sandy clay loam, riverine alluvium straw yields during 1987 kharif (Jun- deposited over laterite soil) contained Sep) at the Cropping Systems Research 0.47% organic C, 120-7.7-58 ppm of

keeping soil moist and gradually

available NPK, and 390 ppm total soil N, with a pH of 5.2 and EC of 0.25 dS/m.

source and with application time. PU gave higher grain (14% moisture) and straw yields when applied in 3 splits (1/3 basal + 1/3 at tillering + 1/3 at panicle initiation). MPCU should be applied entirely as basal or in 2 splits (1/2 basal + 1/2 at tillering). LGU gave best yields when applied in 2 splits (1/2 basal 4 1/ 2 at tillering) or in 3 splits (1/ 2 basal + 1/4 at tillering + 1/4 at panicle initiation).

Results show N impact differed with

Grain and straw yields as influenced by time of application and source a of urea. Trivandrum, India, Jun-Sep, 1987.

Estimation of pH, ammonium N, Grain yield (t/ha)

Time b Straw yield (t/ha) and nitrate N of floodwater with

PU MPCU LGU Mean PU MPCU LGU Mean integrated N management of Full basal 3.0 3.4 3.0 3.1 4.2 4.1 5.0 4.5 1/2 B + 1/2 T 3.0 1/2 B + 1/4 T + 1/4 PI 2.6

3.5 3.7 3.4 6.3 5.1 5.6 5.6

1/3 B + 1/3 T + 1/3 PI 3.3 2.6 3.7 3.0 4.4 5.6 5.7 5.2 B. S. Mahapatra, K. C. Sharma, and G. L. 2.9 2.7 3.0 4.9 4.6 4.0 4.5 Sharma Agronomy Department, G. B. Pant

lowland rice

3.0 3.1 3.3 4.9 4.8 5.1 University of Agriculture and Technology, LSD (0.05) LSD (0.05) Pantnagar, Nainital 263145, U.P., India

Time (T)

T × S Source (S)

0.3 Time (T) ns Source (S)

0.5 T × S

0.5 ns

0.9 Ammonium N and nitrate N in floodwater reflect the N loss that occurs

a PU = prilled urea, MPCU = Mussoorie phosphate-coated urea, LGU = large granule urea. b B = basal, T = tillering, PI = panicle initiation. common to lowland rice. The extent of

easily in a submerged soil-water system


ammonium N in floodwater is controlled by the pH of floodwater.

and nitrate N of floodwater with integrated organic-inorganic N management. The experimental loam soil (Mollisol of Tarai of northern India) had pH (1:l) 7.6, EC (1:l) 0.115 dS/m, 2.03% organic C, 0.21% total N, 7.4 ppm available ammonium N, and 12.2 ppm available NO 3

- -N Floodwater ammonium N peaked at

3 d after transplanting (DT) in 1982-83 and at 7 DT in 1983-84. Thereafter, it decreased and was not found in either year at 30 DT (see figure).

ammonium N is attributed to floodwater pH, in turn controlled by Floodwater pH, NH 4

+ -N, and NO 3 - -N with respect to time in lowland rice. Nainital, U.P., India.

partial pressure of CO 2 . Higher concentration of ammonium N in 1983- reached zero at 30 DT both years. Results show that floodwater pH, 84 over 1982-83 is also attributed to However, its concentration was more ammonium N, and nitrate N can be floodwater pH, as pH at the initial dates than that of ammonium N, probably kept at lower levels by using organic N after transplanting was higher in 1983-84 because of nitrification in the sources (green manure and farmyard (see figure). transitional zone of the flooded soil manure) as part of integrated N

We measured the pH, ammonium N,

The low concentration of floodwater

Nitrate N peaked at 9 DT and water system. management.

Efficiency of modified urea granules in transplanted rice

T. V. R. Prasad, M. M. Hosmani, L. S. Devi, and K. R. Kulkarni, Agronomic Research Project, University of Agricultural Sciences, GKVK, Bangalore 560065, India

We tested efficiency of modified urea granules in transplanted rice in farmers’ fields, Bangalore district, Karnataka, India, in monsoon 1986.

Seven treatments (see table) were tried

in 10 randomly selected fields, using cultivar Mandya Vani (140-d duration) in clay to clay loam soils. The soils had pH 6.6, EC of 0.18 dS/m at 25 ºC, 489 kg available N/ha, 14.2 kg P/ha, and 285.4 kg K/ha. A common dose of 22 kg P and 42 kg K/ha was applied in a plot 50 m 2 .

At 56 kg N/ha, urea supergranule (USG) was superior (29.6% more yield), followed by rock phosphate-coated urea (RPCU, 24.2%), large urea granule (LGU, 18.6%), and gypsum-coated urea

(GCU, 16.7%). Modified urea granules may provide more efficient N utilization, shown by higher harvest index (ratio of yield to total biomass), more panicles per m 2 at harvest, and more filled grains per panicle (see table).

In yield per kg of added N, USG was best, followed by RPCU, LGU, and GCU, all superior to prilled urea (PU) at 56 and 84 kg N/ha. Cost-wise, PU equals LGU, with others equal to or 10- 20% higher than PU.

Effect of modified urea granules on grain yield and yield attributes. a Bangalore, India, 1986 wet season.

Treatment b

T1 No N T2 PU d

T3 LGU (45% N) e

T4 RCPU (36.4% N, 1.85% P) e

T5 GCU (36.5% N, 4.4% Ca, 3.4% S) e

T6 USG (45% N) f

T7 PU d

Grain yield (t/ha)

3.60 g 4.51 f 5.35 bcd 5.60 abc 5.26 de 5.85 a 5.63 ab

Response c

(kg grain/ kg N)

16.2 31.2 35.7 29.6 40.1 24.2

–

Panicles (no./m 2 )

14.3 g 89.3 f

105.9 abc 109.4 a 103.8 abcd 108.0 ab 101.3 cde

Filled grains/ panicle

97 cde 101 cd 121 a 103 c 115 ab 121 a 121 a

Harvest index

0.44 e 0.46 d 0.48 c 0.52 a 0.48 c 0.52 a 0.50 b

Biomass (t/ha)

8.5 g 10.3 f 11.3 abc 11.0 abcde 11.1 abcd 11.4 ab 11.6 a

a Column means followed by common letters are not significantly different at the 5% level. b T2 - T6 at 56 kg N/ha, T7 at 84 kg N/ha. c Over 0 kg N/ha. d Applied in 3 equal splits: basal, 30 and 50 d after transplanting. e Basal broadcast incorporation. f Placement after planting.


Leucaena as green leaf manure for lowland rice

S. Jeyaraman and S. Purushothaman, Agronomy Department, Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai 625104, Tamil Nadu, India

Leucaena leucocephala is a renewable source of green manure. On dry basis, the tender loppings contain 4.3% N. We tested the contribution of 10 t leucaena/ha to growth and yield of IR20 using 4 levels of N (0, 50, 75, and 100 kg/ha) during rabi 1986-87, in 3 replications. Soil was clay loam with 0.06% total N, low Olsen’s P (8.6 kg/ha), 70 ppm exchangeable K, pH 7.4, CEC 18.6 meq/ 100 g, and 0.34% organic C.

Fresh tender loppings of 50-d-old leucaena (Hawaiian Giant Var. K8) harvested from 2-yr-old plants were

Effect of leuaena as green leaf manure on growth characters, yield components, and grain yield of rice (IR20). Madurai, India, 1986-87 rabi.

Growth character Yield component Grain

Treatment Plant Tillers Productive Panicle Filled 1000 - yield height (no./hill) tillers length grains grain (t/ha) (cm) (no./hill) (cm) (no./panicle) (g)

No N Leucaena at 10 t/ha 50 kg N/ha alone 50 kg N/ha + leucaena 75 kg N/ha alone 75 kg N/ha + leucaena 100 kg N/ha alone

LSD (0.05)

72.2 5.8 82.6 8.0 83.0 7.8 92.4 8.8 91.4 8.6 97.4 10.2 93.8 9.2

3.1 0.7

4.2 18.62 5.8 19.76 6.0 19.86 8.0 20.64 7.2 20.52 9.8 21.32 8.2 20.96 1.1 0.46

78.0 16.42 93.2 18.60 92.6 18.64

105.6 19.56 99.8 18.78

110.2 20.74 104.6 19.68

3.9 0.78

2.8 3.6 3.6 4.3 4.0 4.8 4.3

0.4

incorporated 10 d before planting rice. with fertilizer N at suboptimal levels A basal dose of 22 kg P, 41.5 kg K, and increased growth and yield over 50% of N was applied just before suboptimal N alone (see table). planting; the rest of N was topdressed in Leucaena with 75 kg N/ ha gave highest 2 equal splits 30 and 40 d after grain yield (4.8 t/ha), better than that transplanting. with 100 kg N/ ha (4.3 t/ha). Applying

Leucaena as leaf manure combined 50 kg N with leucaena gave 4.3 t/ha.

Fertilizer requirement of rice - RARS, Pattambi, 1983 to 1986. rice - green manure cropping

system raised (Feb-May) and incorporated The treatment receiving 75% of the

cropping system in Central Kerala, at available P, and 222.3 kg available K/ ha. The pH was 5.4 and cation

Green manure Sesbania speciosa was exchange capacity 12.6 meq/100 g soil.

D. Alexander, Kerala Agricultural University, Regional Agricultural Research Station (RARS), Mele Pattambi 679306; B. Mohankumar, College of Forestry, Vellanikkara, Trichur; P. H. Latif and N. R. Nair, RARS, Pattambi, Kerala, India

We assessed the fertilizer requirements of rice - rice - green manure, a major

before the kharif crop (Jan-Sep), at 4.3 t/ha (21.1% dry matter, 2.4% N, 0.31% P, and 1.42% K). The rabi crop (Sep-Jan) was given no organic manure. The kharif and rabi rices (Jaya variety) were given 50, 75, and 100% of the fertilizer dose 90-45-45 kg NPK/ ha. The sandy loam soil contained 1.38% organic C, 0.025% available N, 19.1 kg

fertilizer dose in each season yielded the same as that receiving 100% (see table).

Effect of rice plants on fertilizer N losses in flooded soil Huang Zhi-wu, South China Agricultural University, Guangzhou, China; and F. E. Broadbent, University of California, Davis, CA 95616, USA

We evaluated the influence of rice plants for the for the on fertilizer N losses from flooded soil in

Kharif Rabi system system greenhouse experiments in 1986-87 with

Effect of fertilizer treatments on grain and straw yields of rice - rice - green manure cropping system. Pattambi, Kerala, India, 1983-86.

Mean grain yield (t/ha) Mean straw yield (t/ha) Percentage of

Treatment fertilizer dose Kharif Rabi Total Kharif Rabi Total

T 1 100 100 3.3 3.8 7.1 2.9 3.2 6.1 planted (variety M201) and unplanted

T 2 100 75 3.1 3.6 6.7 3.0 3.0 6.0 treatments. Five kg of Myers clay soil T 3 100 50 2.8 3.6 6.4 3.1 3.0 6.1 (pH 6.6, 0.1% total N) in 1986, and 3 kg T 4 75 100 2.9 4.1 7.0 3.0 3.4 T 5 75 75 3.2 3.7 6.9 3.0 3.1 6.1

6.4 of Sacramento clay soil (pH 7.7, 0.1% total N) in 1987 were weighed into

T 7 50 100 3.0 3.7 6.7 2.6 3.0 5.6 plastic pots after air-drying and

T 9 50 50 2.9 3.4 6.3 2.8 2.7 5.5

T 6 75 50 3.2 3.1 6.3 2.5 2.3 4.8

T 8 50 75 3.1 3.4 6.5 2.5 2.5 5.0 screening.

0.6 urea were separately mixed with soil LSD (0.05) 0.4 Solutions of 15 N-labeled KNO 3 and


Effect of plant spacing on N release of sulfur-coated urea (SCU) in wetland rice

Department, Punjab Agricultural University, C. S. Khind and M. F. Kazibwe, Soils

Ludhiana, India

SCU’s controlled release rate helps reduce N losses in wetland soil, thereby producing higher yields than other urea materials. As the sulfur coating

decomposes, N is released. This process is affected by temperature, soil microbial activity, soil water, method of application, and coating characteristics. To examine an additional factor, we studied the effect of plant spacing on N release patterns of SCU in wetland rice.

We used 2 spacings, 15 × 20 cm and 20 × 10 cm, in a sandy loam soil (Typic Ustochrept). The soil had pH 8.5, EC 0.15 dS/m, 0.23% organic C, 0.04% total N, and 4 meq cation exchange

Table 1. Mass balance of 300 mg incorporated KNO 3 -N and urea N in flooded soil at grain maturity stage, 1986.

15 N recovery (%) Difference

15 N fraction Planted Un- treatments a between

planted (mg/pot)

Soil Plant Recovered Unaccounted

for

Soil Plant Recovered Unaccounted

for

KNO 3 3.5 3.7

4.6 3.7 1.2 –

95.4 96.3 2.8 ns

Urea 43.9 78.1

87.5 78.1 12.5 21.9 28.3*

43.6 –

a * = significant at 5%, ns = not significant by T -test.

Table 2. Mass balance of 600 mg banded urea N in flooded soil at 3 growth stages, 1987.

15 N recovery (%) Difference

15 N fraction Planted Un- treatments a between

planted (mg/pot)

Six-leaf stage Soil 81.6 91.5 Plant 13.7 – Recovered 95.3 91.5 Unaccounted 4.7 8.5 23.0 ns

for

Soil Panicle initiation stage

56.6 74.6 Plant 24.6 – Recovered 81.2 74.6 Unaccounted 18.8 25.4 39.5 ns

for

Soil Grain maturity stage

57.9 59.0 Plant 23.4 – Recovered 81.3 59.0 Unaccounted 18.7 41.0 134.0**

for a ** = significant at 1%, ns = not significant by T -test.

samples at 300 mg N/pot in 1986. In 1987, only 15 N-labeled urea solution was used at 600 mg N/pot. Band application was simulated by applying solution at a depth of 5 cm in a circle 8 cm in diameter.

Rice plants had no significant effect on losses of KNO 3 -N (Table 1). Loss was more than 95% in both planted and unplanted pots, probably through denitrification. With urea (Table 1, 2), N losses were significantly higher from unplanted pots in both years.

The difference between unplanted and planted treatments in urea N unaccounted for was greater in the banded application in 1987 (22.3%) than in incorporated urea in 1986 (9.4%). Since twice as much urea was band applied, we cannot conclude whether its losses were higher than those with

incorporation.

reduced the urea N losses from flooded soil, even though plant roots sometimes stimulated denitrification. Urea N losses were probably due to ammonia volatilization, but denitrification cannot be ruled out.

Growing rice plants effectively

Organic on rice

and inorganic N effect

S. Ramasamy, A. S. Dawood, and K. N. Chinnaswami, Tamil Nadu Rice Research Institute (TRRI), Aduthurai 612101, India

We studied the integrated effects of dhaincha Sesbania aculeata, azolla Azolla pinnata, and N, P, and K fertilizers during winter 1987 at TRRI, in medium-duration IR20. The soil was clayey loam with available status of 222 kg N, 29.9 kg P, and 12.45 kg K/ ha. pH was 7.3.

One week before transplanting rice, 60-d-old dhaincha (3.2% N, 0.31% P,

and 1.1% K on dry weight basis) was cut and incorporated at 12.5 t/ ha. One week after transplanting, azolla at 1 t/ha on fresh weight basis (3.07% N, 0.07% P, and 0.15% K on dry weight basis) was applied and allowed to multiply and disintegrate by itself.

Azolla improved grain yield when applied with inorganic N or with dhaincha (see table).

Dhaincha at 12.5 t/ ha gave significantly better grain yield than 40 kg N. Dhaincha applied with 40 kg N was even better than 80 kg N.

dhaincha and azolla was equal to 80 kg N/ha.

The combined application of

Effects of dhaincha and azolla on grain yield of IR20. Aduthurai, India, 1987 winter.

Mean Productive Grain Treatment plant tillers yield

height (cm) (no.) (t/ha)

1. Control 2. 0 kg N + 8.7 kg P + 16.6 kg K/ha 3. 40 kg N + 8.7 kg P + 16.6 kg K/ha 4. Azolla + treatment 2 5. Azolla + treatment 3 6. Dhaincha + treatment 2 7. Dhaincha + treatment 3 8. Dhaincha + azolla + treatment 2 9. 80 kg N + 17.4 kg P + 33.2 kg K/ha

LSD (P = 0.05)

73.3 74.4 73.7 71.2 75.6 82.7 84.5 81.9 77.1

5.3

6.8 7.0 7.6 6.2 7.5 8.5 9.9 9.0 8.4 0.9

2.7 2.9 3.2 2.9 3.7 4.0 4.6 4.4 4.1 0.4


Changes in urea N remaining at deep placement sites after application of SCU in a wetland soil. Ludhiana, India, 1988.

capacity/100 g. A nylon screen bag with 460 mg N as SCU (38.6% N) was placed between 2 layers of wet soil freshly collected from the lower layer of 3- × 5- cm or six 20- × l0 cm rice hills 5 d after transplanting of 45-d-old seedlings of cultivar PR106. The plots received a basal dose of 26 kg P and 50 kg K/ha. The experiment was laid out in a randomized complete block design.

were chosen at random and SCU granules were digested, then analyzed for urea N at 6, 10, 25, 45, and 60 d after placement. The remaining wet soil mass was extracted with 2 M KCl-PMA solution, and the extract was also analyzed for urea N.

Results showed that SCU granules released urea N at a fairly controlled rate up to 60 d after placement. Spacing significantly affected the amounts of SCU N recovered. SCU N disappeared faster in the closer plant spacing (see figure). Closer plant spacing had more impact after 30 d of SCU placement, coinciding with active proliferation of rice roots. Furthermore, dissolution rate of SCU was about 9 and 19% higher than its empirical 7-d dissolution rate of 21% with 15- × 20-cm and 20- × 10-cm spacings, respectively.

Five nylon bags from each treatment

Effect of azolla and other fertilizers on rice yields

D. Alexander, Kerala Agricultural University, Regional Agricultural Research Station (RARS), Mele Pattambi 679306; N. Sadanandan, Vellanikkara; and K. Karunakaran, RARS, Pattambi, Kerala, India

We evaluated azolla as an organic manure, varying application rate and percentage of substitution for chemical. fertilizer at RARS Pattambi during rabi seasons (Sep-Jan) of 1980 and 1981.

In the split-plot experiment, azolla at 5.0, 7.5, and 10.0 t/ha was compared with cattle manure and green leaves

( Gliricidia maculata ) at 5 t/ha. Subplot treatment was the percentage of fertilizer dose (90:45:45 kg NPK/ha) applied. The sandy loam soil contained 0.02% available N, 9.7 kg available P, and 184.4 kg K with a pH of 5.5. On dry weight basis, cattle manure has 9.4% dry matter, 1.52% N, 0.4% P, and 21.1% K; for gliricidia, the values are 21.1, 2.6, 0.5, and 1.4%.

Substituting 5 t azolla/ha for cattle manure saved 25% of the fertilizer dose (see table). Azolla at 7.5 t/ha with full dose of fertilizer recorded the highest grain and straw yields. Applying more than 7.5 t azolla/ha was not beneficial.

Effect of organic manures and fertilizer levels on grain yield of rice. Pattambi, India, 1980 and 1981 rabi (Sep-Jan).

Rate Grain yield (t/ha) with given fertilizer dose a

Organic manure (t/ha) 0 25 % 5 0% 75% 100%

Control Cattle manure Green leaves Azolla Azolla Azolla

F test b

LSD (0.05)

0 1.8 2.3 2.7 3.1 3.6 5.0 2.4 2.7 3.1 3.1 3.6 5.0 2.8 3.1 3.4 3.6 3.8 5.0 2.1 2.7 2.8 3.4 3.7 7.5 2.6 3.0 3.2 3.7 4.2

10.0 2.3 2.8 3.2 3.2 3.7 *

0.27 c 0.29 d

a Fertilizer dose: 90-45-45 kg NPK/ha. b Significant at 0.05 level. c For comparing 2 fertilizer levels at the same level of organic manure. d For comparing 2 organic manures at the same or different levels of fertilizer.

Effects of seedling age and zinc application on yield of rice

M. Datt and R. C. Gautam, Agronomy Department, G. B. Pant University of Agriculture and Technology, Pantnagar, Nainital 263145, U.P., India

We evaluated the impact of seedling age and Zn application on rice in wet season, using three seedling ages as main plots, five rates of Zn applied through soil and one foliar spray as subplots, with three replications (see table). Seedlings (30, 40, and 50 d old) of variety Pant Dhan 4 were transplanted at 2-3 seedlings / hill, 20- × 20-cm spacing. Soil was Beni silty clay loam, fine silty, mixed, hyperthermic, Aquic

Hapludoll with pH 7.6, CEC 20 meq/100 g, 1.0% organic C, 20 kg available (Olsen) P/ha, and 0.8 ppm Zn.

Grain yield declined significantly with increasing seedling age (see table). Panicles/m 2 and filled grains/ panicle were significantly higher with 30- and 40-d-old seedlings than with 50-d-old ones. Filled grain percentage and 1,000- grain weight were significantly higher with 30- and 40-d-old seedlings than with 50-d-old ones.

significantly higher yield than other Zn treatments; 4 ppm Zn was significantly superior to Zn spray, 1 ppm Zn, and the control. Panicles/ m 2 , filled grains/ panicle, and filled grains percentage were significantly higher with 8 ppm Zn than with all other

Application of 8 ppm Zn gave


treatments, but l,000-grain weight was not.

The interaction between seedling age and Zn rate was not significant.

Yield and yield attributes of rice as affected by seedling age and rate of Zn application. Nainital, India, 1988 wet season.

Grain Panicles Filled Filled 1000- Treatment yield (no./ grains grain grain

(t/ha) m 2 ) (no./panicle) percentage weight (g)

Seedling age (d) 30 40 50

LSD (P = 0.05) Zn rate (ppm)

0 1 2 4 8

Spray LSD (P = 0.05)

6.7 6.2 5.7 0.2

5.9 5.9 6.2 6.4 6 .7 6.0 0.3

197 194 182

6

180 184 190 197 208 189

6

131 127 122

2

111 118 127 132 148 122

4

90.3 91.2 86.5

1.9

87.3 87.8 89.1 90.1 92.7 88.9

1.5

29.0 29.2 28.7

0.4

28.1 28.7 28.9 29.4 29.8 28.8 1.1

The International Azolla Newsletter is published for researchers in the development and application of azolla in rice production. Its content focuses on discussions of current issues; it does not publish research reports. For more information, write Dr. I. Watanabe, Azolla Newsletter editor, IRRI, P.O. Box 933, Manila, Philippines.

Disease management

A new sheath disease of rice in India caused by Monographella albescens

N. I. Singh, Botany and Plant Pathology Department, Manipur Agricultural College (MAC), Iroisemba, Imphal 795001, India

From Oct 1986 onward, we observed a severe sheath disease of rice in MAC experimental plots and in many farmers’ fields.

The lesions develop as oblong or irregular spots 1-2 cm long and 0.5- 1.0 cm wide with dark brown margins and greyish centers. About 80-100% of uppermost leaf sheaths enclosing young panicles are rotted. Many small, black, fruiting bodies (perithecia) of M. albescens appear on infected sheaths and grains.

We isolated the pathogen from fresh diseased specimen on potato dextrose agar. It produced white mycelium during early growth. At maturity, it produced pink patches of conidial masses. We inoculated the injured sheaths with conidial suspension prepared from a 7-d-old culture. Symptoms appeared 4 d after inoculation. In 2 wk, uppermost leaf sheaths and young panicles completely


rotted. Several superficial, black perithecia were formed.

morphological characteristics exactly the same as those of leaf scald (LSc) pathogen. The anamorph and teleomorph have been identified as Gerlachia oryzae (Hashioka and

Microscopic examination showed

Improved method of purifying rice tungro spherical virus (RTSV) Y. P. Duan, Plant Virology Laboratory, Fujian Agricultural College, Fuzhou, Fujian, China; and H. Hibino, IRRI

We improved the method of purifying RTSV without using organic solvent and driselase: Infected TN plants at 45-60 d

Harvest whole plants except roots.

Homogenize in 3 volumes of 0.01 M EDTA, pH 8.4.

Filter through cheesecloth.

Stir at room temperature for

Incubate in water bath at 40 °C

15,000 g for 10 min.

Add PEG 8000 to 7%, NaCl to 0.2M and Triton X-100 to 1%.

Filtrate

2 h.

for 2 h.

Supernatant

Yokogi), W. Gams and M. albescens (Thiimen) Parkinson, Sivanesan, and Booth, respectively. The anamorph of the LSc pathogen was previously reported in India, but the teleomorph has evidently not been. This indicates that the same fungus can produce different disease symptoms.

Stir at room temperature for

30,000 g for 30 min.

Resuspend in 20 ml 0.01 M EDTA, pH 8.4.

11,000g for 10 min.

l h.

Pellet

Supernatant

Pellet 100,000 g for 60 min.

Resuspend in 2 ml 0.01 M

11,000 g for 10 min.

Layer on 10-50% linear

phosphate buffer, pH 7.2.

Supernatant

sucrose density gradient in PB.

25,000 rpm for 2 h. Collect a virus zone (ca. 3 cm

Dilute with 0.01 PB. 130,000 g for 1 h.

Resuspend in 2 ml 0.01 PB.

below the meniscus).

Pellet

11,000 g for 10 min. Supernatant (virus preparation)

recorded at RRS during 1987 kharif. They were Xanthopimpla flavolineata (Cameron), Xanthopimpla sp. (Ichneumonidae), Brachymeria sp. nr. lasus (Walker) (Chalcididae), and Tetrastichus ayyari Rohwer (Eulophidae). Parasitism rates are shown in the table. Four parasitoids of pupae of rice LF

Cnaphalocrocis medinalis (Guenée) were

The procedure takes 1.5 d. From 500 g infected plants without roots, current methods yielded 1 ml of purified preparation with an absorbance at 260 m ranging from 1.0 to 2.8. With 300 g materials, the modified method yielded 1 ml, with absorbance ranging from 13 to 20. The ratio of absorbance

Insect management

Severe outbreak of green leafhopper (GLH) in Cuddapah District, Andhra Pradesh, India

P. S. R. Reddy and V. D. Naidu, A. P. Agricultural University, Agricultural Research Station, Mellore 524004, India

Nearly 50,000 ha of transplanted- irrigated rice is grown in Cuddapah district in wet season. Predominant cropping is rice followed by groundnut during winter-summer in canal water area, and a single rice crop in tankfed areas depending on rainfall. Main cultivars are Phalguna, Mahsuri, and NLR9672, with some NLR9674, IET7575, IR50, and IR20. Low humidity, high temperature, and scant rainfall (400-500 mm) reduce insect and disease incidence.

Cuddapah received good rainfall the last 2 wk of Oct and first 2 wk of Nov 1984, when hopperburn and numerous GLH were observed in 30-40% of cropped area on most cultivars. This was the first report of GLH outbreak from Cuddapah. The crop was in tillering to active tillering phases. A 15-village survey showed nymphs and

Severity of GLH on common rice cultivars in farmers’ fields in A. P., India, 1984.

Cultivar Crop phase GLH (no./hill)

Mahsuri Active tillering 100-150 Phalguna Active tillering 30-55 IET1515 Active tillering 20-40 NLR9612 Initial tillering 45-75 NLR9674 Initial tillering 45-75 IR50 IR20

Panicle emergence 10-15 Grain hardening 5-10

at 260 nm and 280 nm of the purified virus ranged from 1.70 to 1.75.

Purified preparations were injected into rabbits, and antiserum with a titer of 1/1280 in the ring interface precipitin test was obtained.

We also attempted to improve the purification method for rice tungro

bacilliform virus (RTBV). Without using driselase and organic solvent, the virus yield was not significantly improved. The rabbit antiserum to RTBV had a titer of 1/640. The antisera did not cross-react and did not react with healthy rice extracts in ELISA and the latex test.

adults (30-150/ hill), with adults more district after harvest of the 1984 summer numerous. rice crop (May-Aug) where about 20,000

IR20 and IR50 had fewer GLH and ha were devastated by tungro (RTV). no hopperburn (see table). Phalguna, The early crop, planted in late Aug, Mahsuri, NLR9672, and NLR9674 escaped infestation but the late crop showed hopperburn in patches. Mahsuri showed severe infestation. Despite heavy showed 100-150 GLH/hill. IET7575, a GLH population, there was no RTV, brown planthopper-resistant variety, had even though adjacent Mellore and 20-40/ hill. Prakasam districts had severe RTV the

migration from adjoining Mellore This outbreak appeared due to same season.

Parasitoids of leaffolder (LF) pupae from Haryana, India

L. R. Bharati and K. S. Kushwaha, Haryana Agricultural University, Rice Research Station (RRS), Kaul 132021, Haryana, India

Parasitism rates of 4 parasitoids of LF pupae. Haryana, India, 1987.

Parasitism (%) Days after

transplanting Xanthopimpla Xanthopimpla sp. Brachymeria lasus Tetrastichus ayyari flavolineata

55 23.3 65 7.5 1.0 75 10.7 2.0 85 20.0 –

– 1.5 –

– –

2.5 –

– –

An expert system for insecticide control of brown planthopper (BPH)

J. Holt and T J. Perfect, Overseas Development Natural Resources Institute, College House, Wrights Lane, London W8 5SJ, UK

Using insecticides to control BPH can promote rather than limit BPH

population development. Insecticides can kill natural enemies that keep BPH populations below serious levels. Insecticides must be used only when this natural balance has been lost, and then must be timed carefully.

An expert system (see figure) can show when insecticide use is appropriate. Expert systems are computer programs that offer information or advice as a human


expert would. They can improve decisionmaking in agriculture, either directly or as a training device.

The system, built using an expert system shell (Crystal), searches for the appropriate recommendation. The computer asks the user questions, via a series of interactive screens (starting at the top of the figure). The answers lead to a recommendation.

The expert system is programmed to recommend that insecticides be applied against BPH only in certain circumstances, at particular stages of crop growth. For example, if only large nymphs are present between 31 and 79 d after transplanting and insecticide was previously applied, the computer program assumes that natural enemy action has been disrupted and that the absence of small nymphs reflects absence of eggs—therefore it is the best time to spray. The computer suggests an alternative insecticide because nymphs now present may be resistant to the previous insecticide.

Any expert system requires considerable refinement and development before it manages effectively. This one needs detailed advice about insecticides and application methods, integrated with advice for controlling other pests, in tune with local conditions. It shows the potential value of the technique in pest management. A version in PROLOG will be available shortly, for comments, on receipt of an IBM MSDOS formatted 5.25” diskette.

Effect of neem on yeast-like symbionts (YLS) harbored by brown planthopper (BPH)

S. Raguraman and S. Jayaraj, Entomology Department, Tamil Nadu Agricultural University, Coimbatore, India, and R. C. Saxena, Entomology Department, IRRI

In the biology of many homopterous insects, endosymbionts seem to fulfill the lipid and sterol requirements of sap- sucking insects, such as planthoppers, which feed on sugar and amino acid-


A search graph representing an expert system designed to identify insecticide application tactics for BPH control. A recommendation (rectangular) may be reached by a variety of routes, depending upon the answers, often a simple yes (Y) or no (N), to a series of questions (oval).

rich, but lipid-deficient, phloem (1:1 wt/wt) had been incorporated, and photosynthates. Endosymbionts also untreated plants as control. Each of evidently produce antibiotic defense treated and control plants was then substances. If endosymbionts are killed infested with 25 first-instar BPH by heat treatment, the insect body nymphs. Insect survival was recorded at becomes covered with mold. We tested 4-d intervals. whether exposure of BPH nymphs to When nymphs reached the fifth-instar rice plants treated with neem seed stage, they were collected, weighed derivatives would affect the YLS individually, and homogenized with populations that BPH harbor. 0.8% saline solution to a known volume.

Treatments were 20-d-old IR20 plants Aliquots of homogenates were taken sprayed with various neem preparations using Thoma pipettes. An improved (see table), IR20 seedlings grown in soil Neubauer hemocytometer (Weber, where a neem cake-coated urea mixture England) was used under a phase

contrast microscope for counting symbionts.

5 squares (each 1 mm 2 ) of the hemocytometer. Symbionts per insect was calculated and expressed per mg body weight as follows: Symbionts = a(x+m)/n.v, where a = symbionts in a known volume of homogenate, m = weight of insects homogenized, n = number of insects homogenized, v = volume of homogenate sampled in the hemocytometer, and x = volume of saline solution used to homogenize nymphs. The experiment was replicated four times.

A second experiment (see table) used 30-d-old IR20 plants sprayed with various neem preparations with untreated plants as controls. Treated and control plants were infested with 30 4-d-old nymphs/replication. Nymphal mortality was recorded 4 and 8 d after treatment. Surviving individuals were removed and homogenized to count endosymbionts.

The YLS population was significantly smaller in BPH that fed on neem-treated IR20 plants than on untreated ones (see

The symbionts were counted from the

A new tarsonemid mite, Ogmotarsonemus sp. (Tarsonemidae: Acari), on rice in Tamil Nadu, India

M. Mohanasundaram and S. Parameswaran, Agricultural Entomology Department, Tamil Nadu Agricultural University, Coimbatore 641003, India

In a survey of phytophagous mites, brown discoloration and necrosis were noted in rice leaf sheaths near ground level. Investigation revealed a tarsonemid mite Ogmotarsonemus sp. infestation at all development stages.

Eggs are almost round, transparent, and in clusters. Nymphs are translucent to light white, found between sheaths and culms and inside sheaths. They are oblong with two pairs of legs in the anterior propodosoma and one pair in the metapodosoma. They move sluggishly, staying in the necrotic area even when disturbed.

Effect of neem seed derivatives on survival and body weight of fifth-instar BPH nymphs and YLS they harbor. a

Treatment b Mortality c Body wt YLS

(%) (mg/nymph) (x10 4 /nymph)

NO 3% NO:CAO (2:l) NSKE 5 % NCE 10% NCU (basal) Control (untreated)

NO 3% NO:CAO (2: 1) NSKE 5% NCE 10% NSB (2500 ppm) Control (untreated)

14 b 18 ab 80 a 63 c 67 c

–

86 a 83 a 84 a 15 b 66 c

–

Experiment I 1.05 a 1.12 a 1.02 a 1.12 a 1.16 a 1.42 b

Experiment II 1.10 ab 1.07 ab 0.93 a 1.09 ab 1.38 b 1.88 c

24.72 a 27.45 a 24.91 a 27.42 a 31.08 a 40.35 b

20.95 ab 19.63 ab 17.21 a 21.04 ab 26.80 b 42.32 c

a Within an experiment, means in a column followed by the same letter are not significantly different at the 5% level by DMRT. Each treatment was replicated four times. b NO = neem oil, NO:CAO = neem oil:custard-apple oil (vol/vol), NSKE = neem seed kernel extract, NCE = neem cake extract, NCU = neem cake-coated urea, NSB = neem seed bitters. c Corrected mortality recorded when nymphs were 12 d old.

table). This decrease could be due to component in neem. direct antibiotic effect of neem’s active Nymphs developing on treated plants principals on the endosymbionts or weighed less than those on control indirectly through BPH fat bodies which plants. Nymph mortality was store YLS. Insect brains and fat bodies significantly higher on treated plants are highly sensitive to triterpenoid than on controls, mainly because of azadirachtin, the principal bitter molting impairments.

Adults are light brown with four pairs of legs, more sclerotized, and quite active. Females are oblong; males are broader, with characteristic flange-like enlargement in the femorogenu of the fourth leg.

The first species described under this genus is Ogmotarsonemus erepsis Lindquist (1986), attacking Spartina sp., a saltmarsh grass in Georgia, United States. This species on rice is new, and is being described for publication elsewhere.

Rice thrips Stenchaetothrips biformis (Bagnall) can damage leaves in nursery plants and in the young transplanted crop. The randomized block design had three replications using variety TM8089. When incidence was severe, neem products and chemical insecticides (standard checks) were applied at 20 d

Effect of neem products on rice thrips at Chengalpattu, India, 1987.

Thrips a

Treatment (no./ Rate sweeps) 2 DAT

Neem for control of rice Neem seed extract 5% 24.5 bc

thrips Neem seed extract 10% 19.5 ab Neem cake extract 5% 34.6 c

M. A. K. Pillai and S. Ponniah, Rice Neem cake extract 10% 32.1 bc Neem oil 2% 7.5 a

Research Station, Tamil Nadu Agricultural Phosphamidon 100 EC 250 ml/ha 11.2 a University, Tirur 602025, Tamil Nadu, India Fenthion 100 EC 500 ml/ha 6.6 a

Untreated control – 96.3 d

We evaluated neem products for thrip a Mean of 3 replications. Means followed by a control in late sornavari in rice planted common letter are not significantly different

at the 5% level based on LSD value. DAT = in Jun-Jul 1987 in Chengalpattu district. days after treatment.


Abbreviations of fungal species and strains.

Fungus species Strain

Beauveria bassiana BbE Metarhizium anisopliae Ma12

M. flavoviride var. minus Mfmll

Hirsutella citriformis Hc490

Ma16

Mfm16

after transplanting with a hand-operated sprayer.

Thrips populations were counted with 5 sweeps/plot using a plastic bat 20 cm in diameter, 48 h after spraying. All treatments significantly reduced thrips intensity (see table). Neem oil at 2% was as effective as insecticides in controlling rice thrips.

Infection of brown planthopper (BPH) with insect fungi in the laboratory

R. M. Aguda, Entomology Department, IRRI; M. C. Rombach, Insect Pathology Resource Center, Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853-0331, USA; and B. M. Shepard, Entomology Department, IRRI

The BPH Nilaparvata lugens (Stål) is commonly infected with insect fungi (Deuteromycotina; Hyphomycetes) in the field and in insect rearing cages. The fungi can be isolated on artificial media and mass-produced in liquid fermentation media. To select the most virulent fungus species or strain for BPH control on rice, we bioassayed selected isolates.

We tested infection of BPH by Beauveria bassiana (Bals.) Vuill., Metarhizium anisopliae (Metsch.) Sorokin, M. flavoviride var. minus Rombach, Humber and Roberts, and Hirsutella citriformis Speare (see table).

Fungi isolated from insects were grown on Emerson’s YpSs agar (Ma, Mfm), and Sabouraud dextrose agar (Bb, Hc). Conidia were washed off plates in a 0.02% Tween 80 solution after 2 wk of incubation at 25-28 °C. Conidia were counted by standard hemocytometer techniques, and

suspensions of l0 2 to l0 8 conidia/ml prepared by serial dilution in the Tween 80 solution.

Each treatment had 50 BPH alates. Insects were dipped in conidia suspension in Tween 80 (0.02%), submerged for 60 s, and transferred to filter paper to drain off liquid. Insects of the control treatment were dipped in pure Tween 80 (0.02%) solution before transfer. The insects were kept on potted rice plants in mylar cages in a greenhouse at 25-30 °C (day) and 15- 20 °C (night), with humidity near

Effect of Dimilin (R) and Dipel (R)

on leaffolder (LF) larvae

R. M. Aguda, Entomology Department, IRRI; M. C. Rombach, Insect Pathology Resource Center, Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853-0331, USA; and B. M. Shepard, Entomology Department, IRRI

Rice LF (Pyralidae: Lepidoptera) infests irrigated rice in Southeast Asia. Broad-

saturation. After 5 d of incubation, live and

infected (dead and covered with fungus) insects were counted and mortality calculated: Mortality (%) = 100 × ((no. infected insects)/(no. infected insects + no. living insects))

Mortality in the fungus treatments was corrected for control mortality (8%) by Abbott’s formula.

Results showed mortality increased with increasing dosage, but did not differ among fungi.

spectrum insecticides sprayed to control LF larvae can also kill such natural enemies as predators (mainly spiders) and parasites. That can lead to outbreaks of secondary pests, such as brown planthopper Nilaparvata lugens

Selective insecticides kill only target pests. We tested Dimilin (R) , containing diflubenzuron, a chitin inhibitor, and the Bacillus thuringiensis product Dipel (R)

(Stål).

Mortality of LF Cnaphalocrocis medinalis populations caused by Dimilin (Dim) and Dipel (Dip) treatments, IRRI, 1988. Vertical lines on bars represent standard deviations.


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For instructions on preparation of brief reports of rice research to submit for publication in IRRN, see the inside front cover of this issue.

From these collections, we isolated P. oryzae on potato dextrose agar. To test pathogenicity, we sprayed mycelial fragments of the isolated fungus, prepared from 7-d-old culture, onto weed hosts. Weeds sprayed with sterile water served as control.

Among the weed hosts, L. hexandra, C. compressus, Cyperus rotundus, and

C. iria consistently harbored P. oryzae. The ocurrence on C. rotundus and C. iria constitutes a first report from India.

To study pathogenicity, we raised highly susceptible HR-12 and popular, high-yielding KD, 2-6-3 in pots and inoculated seedlings at 3-4 leaf stage with different isolates of P. oryzae. All isolates produced Bl symptoms on HR- 12. Only the isolate from C. compressus failed to infect KD,2-6-3 (see table).

for selective LF control in the greenhouse.

Because sprays do not reach larvae in folded leaves as well as they do larvae on fresh, unfolded leaves, we compared spray effectiveness before and after leaf folding.

Pots of 24 rice plants (3

pots/ treatment) were randomly infested with 25 2d- to 3d-instar larvae of LF Cnaphalocrocis medinalis Guenée. Insecticides were applied either just before infestation or 1 d after infestation, when more than 90% of larvae had folded leaves. After 3 d, living and dead larvae were counted.

Treatment before leaf folding was more effective than treatment after folding (see figure). All treatments except Dip b1 and Dip a1 differed significantly from control. Dimilin was more effective than Dipel, but not always significantly so.

Weed management

Weed control in direct seeded rice under puddled condition

C. R. Vijayaraghavan, B. Uthayakumar, and T. B. Ranganathan, Rice Research Station, Tirur, Tamil Nadu 602025, India

In samba 1985 in Chingleput district, weed control treatments were compared in irrigated direct seeded CO 43 rice under puddled condition. There were 7 weedicide treatments, 1 farmer's method of weeding on 20 and 40 d after seeding (DAS), and an unweeded control in a randomized block design with 4 replications (see table).

The farmer’s method of hand weeding 20 and 40 DAS gave highest grain yield of 3.9 t/ha, on par with butachlor at 1.0 kg ai/ha plus 1 hand weeding in 40

Unrecorded weed hosts for rice blast (BI) pathogen Pyricularia oryzae Cav. in India

N. I. Singh and K. U. Singh, Botany and Plant Pathology Department, Manipur Agricultural College, Iroisemba, Imphal 795001, India

In India, weeds such as Leersia hexandra, Panicum repens, Arundo donax, Brachiaria mutica, and Cyperus compressus have been reported to harbor P. oryzae.

During 1986-87, we searched for weed hosts of P. oryzae in Manipur ricefields, field bunds, and irrigation channels. We collected diseased weeds in districts of Imphal, Thoubal, Bishenpur, Churachandpur, and Senapati.

Economics of weed control treatments on irrigated direct seeded CO 43 rice variety. a Tamil Nadu, India, 1985 samba.

Treatment Yield increase Weed

Yield dry wt control (t/ha) t/ha % at 40 DAS

Weed Cost Savings

(g/m 2 ) (%)

($/ha) ($/ha)

Unweeded control 3.2 – – 160 Hand weeding 20 and 40 DAS 3.9 0.7 20 41 75 36 Butachlor 1.0 kg ai/ha 3.7 0.5 15 40 75

Fluchloralin 1.0 kg ai/ha 3.5 0.3 9 42 74 Piperophos 1.0 kg ai/ha 3.7 0.5 14 38 76 – Butachlor 1.0 kg ai/ha + 1 3.9 0.7 20 35 78 25 10

Oxyfluorfen 0.1 kg ai/ha 3.7 0.5 14 39 76 17 19 Oxadiazon 0.5 kg ai/ha 3.7 0.5 14 59 63 17 19

– – – –

2,4-D EE 0.8 kg ai/ha –

3.5 0.3 9 47 71 17 19 –

– – –

hand weeding

LSD 0.1

a A dash = data not available.

DAS. These yields were 0.7 t/ha (20%) control. more than that of the control. Thus, in direct sown rice under

The weed dry matter 40 DAS was puddled condition, butachlor plus 1 least with butachlor application plus 1 hand weeding can control weeds and hand weeding (35 g/m 2 ), or 78% better produce yields as well as can 2 weedings than that of the control. The farmer’s with manual labor, saving $10/ha in hand weeding gave 75% more weed weeding cost.

Rice reaction to P. oryzae isolates from 4 weed hosts. Manipur, India, 1986-87.

Disease reaction a on Weed host

HR-12 KD, 2-6-3

Leersia hexandra + +Cyperus rotundus + + C. compressus + –C. iria + +

a + = infected, – = noninfected.


Weed flora in rice in Bhubaneswar (Orissa, India)

G. K. Patro and K. C. Nanda, Agronomy Department, Orissa University of Agriculture and Technology, Bhubaneswar 3, Orissa, India

Weeds seriously limit rice production at Bhubaneswar, Orissa. In 1985 wet season, we surveyed weeds in ricefields in uplands, medium lands, lowlands, and swampy and waterlogged fields, using random sampling of 10 farmers from each site type. From each field, we randomly selected five 1- × 1-m areas.

Only weeds common in all samples are reported here. 1. Uplands

Grasses: Digitaria sanguinalis, Echinochloa colona, Eleusine indica, Eragrostis nutans, Panicum antidotale, Cynodon dactylon.

Sedges: Cyperus rotundus, C. iria, Eimbristylis dichotoma.

Broadleaved weeds: Senna obtusifolia, Crotalaria juncea, Celosia argentea, Sida rhombifolia. 2. Medium lands

Eragrostis nutans, Paspalum conjugatum.

Grasses: Echinochloa crus-galli,

Sedges: Cyperus elatus, C. esculentus,

Broadleaved weeds: Murdannia C. brevifolius.

nudflora, Ludwigia perennis, Corchorus aestuans, Aeschynomene americana, A. aspera.

The fern Marsilea quadrifolia was also found. 3. Lowlands

rice), Cyperus exaltatus, Scirpus supinus. 4. Swampy lands and waterlogged fields Pistia stratiofes, Glyceria sp., Glycine sp., Ulothrix sp., Spirogyra sp., and Chara sp.

Eragrostis cilianensis, Oryza sp. (wild

Integrated weed and water management in transplanted rice

S. Purushothaman, S. Jeyaraman, and M. Chandrasekaran, Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai 625104, India

We studied weed control and water use efficiency (WUE) with three irrigation

regimes and six weed control treatments (see table) in transplanted rice during 1985-86 dry (DS) and wet (WS) seasons. The treatments were in a split-plot design, replicated three times.

Weeds at the experimental site (sandy clay loam) were Echinochloa colona, E. crus-galli, Cyperus rotundus, C. iria, C. difformis, Fimbristylis miliacea, Eclipta alba, Ammannia baccifera, Marsilea quadrifolia, Monochoria vaginalis, and

Ludwigia paryzflora.

continuous submergence than with irrigation with 5-cm water 1 d after water disappeared, saving 40% water in WS and 33% in DS. Grain yields were comparable.

Among weed control treatments, preemergence butachlor (1.25 kg ai/ ha) plus postemergence 2,4-D (sodium salt) (0.75 kg ai/ ha) effectively controlled

WUE was better with 5-cm

Effect of weed control treatments under different irrigation regimes on grain yield, weed dry matter, water use efficiency, and total water requirement of transplanted rice, Madurai, India, 1985-86.

Grain yield Weed dry matter Water use efficiency Total water (t/ha) at harvest (g/m 2 ) (kg/ha per cm) requirement (cm)

WS DS WS DS WS DS WS DS Treatment

IR50 IR20 IR50 IR20 IR50 IR20 IR50 IR20

Irrigation regimes 5 cm continuous submergence 7.0 5.9 10 26 43 62 166 94 5 cm submergence 1 d after 6.9 5.8 14 32 61 92 100 63

Maintenance of 5 cm submergence at 6.6 5.4 15 33 50 65 131 83 water disappeared

reproductive stage and 5 cm submergence 1 d after disappearance at vegetative and ripening stages LSD (0.05) 0.3 0.4 0.9 ns – – 1.4 1.2

Weed control methods Unweeded check 5.8 4.9 34 75 44 60 136 HW 15 and 30 DT 7.2 6.0 9 20 57 78 Butachlor 1.25 kg ai/ha + HW 30 DT 7.1 5.8 9 24 56 74 Thiobencarb 1.50 kg ai/ha + HW 30 DT 6.9 5.6 10 23 55 73 Butachlor 1.25 kg ai/ha + 2,4-D 7.5 6.2 8 18 60 81

Thiobencarb 1.50 kg ai/ha + 2,4-D 6.8 3.6 9 22 54 73

84 132 80 132 80 132 80 131 79

131 81 (sodium salt) 0.75 kg ai/ha 30 DT

(sodium salt) 0.75 kg ai/ha 30 DT

LSD (0.05) 0.8 0.4 1.7 1.5

LSD (0.05) ns ns ns

– – 0.6 2.0

Interaction (weed control × irrigation) ns – – ns ns


Rice yield equivalent and net profit of rice-based cropping systems in Gomti River floodplain. Faiza- bad, India.

Grain yield (t/ha) Total Total yield Net Cropping system yield equivalent profit

Wet season Dry season (t/ha) (t/ha) ($/ha)

Rice - wheat (C-306) Rice - barley (Azad) Rice - chickpea (Radhey) Rice - lentil (T36) 1.24 0.41 1.65 2.06 124.00 Rice - safflower (T45) 1.22 0.34 1.59 1.77 88.64 Rice - taramira (T-136) Rice - mustard (Varuna)

1.31 1.96 1.24 2.11 1.21 0.11

1.33 0.29 1.62 2.02 36.00 1.31 0.59 1.90 3.46 223.28

3.27 3.50 3.35 3.33 1.32 1.40

216.72 212.88

32.16 S. B. Singh and R. D. S. Yadav, N. D. University of Agriculture and Technology, Crop Research Station, Masodha, Faizabad 224001, India

weeds and recorded least weed dry matter and maximum WUE, followed by 2 hand weedings (HW) (15 and 30 d after transplanting [DT]) both seasons.

The combined approach of irrigation to 5-cm submergence 1 d after water disappeared and weed control through preemergence butachlor plus

postemergence 2,4-D sodium salt could save irrigation water in transplanted rice that otherwise would be used by competing weeds.

Managing other pests

A crab trap for a deepwater rice (DWR) pest

D. N. Das, B. Roy, and P. K. Mukhopadhyay, Deepwater Rice Pest Management Project (IRRI/ICAR/Government of West Bengal Cooperative Project), Rice Research Station (RRS), Chinsurah, West Bengal 712102, India

In West Bengal, common freshwater crabs Paratelphusa hydrodromus Herbertson and P. spinigeru Wood- Manson (Family Potamidae) damage DWR by cutting elongating stems. Damage is most severe in fish - rice culture. Chemical methods, including bleaching powder (calcium chloro hypochlorite), fail to control them.

We designed a crab trap of fine bamboo sticks bound with nylon thread

(see figure). Smooth entry points let crabs in, bamboo sticks projecting inside the box keep them from leaving. DWR farmers use similar devices to trap wild fish and prawns in their fields. We tested

the crab traps in 1987 wet season. Traps were baited with snail-meat and left in the water ovenight. Each trap collected 30-40 crabs/d during Aug-Sep. The crabs can be eaten.

Device used to trap field crabs in Chinsurah, West Bengal, India, 1987 kharif.

Farming systems

Performance of rice- based cropping systems in river floodplains

We evaluated seven rice-based cropping systems for Gomti river floodplain in 1983-84. Soil had 0.20% organic C, 6.2 kg P, and 119 kg K with pH value of 7.7. Rice ( Oryza sativa ) variety Saket 4 was directly seeded in rows 20 cm apart in 6- × 5-m plots. After harvesting the wet season rice crop, wheat ( Triticum aestivum ), barley ( Hordeum vulgare ),

chickpea ( Cicer arietinum ), lentil ( Lens esculenta ), safflower ( Carthamus tinctorius ), taramira ( Eureca sativa ), and mustard ( Brassica juncea ) were sown during dry season (DS). The experiment was in a randomized block design with four replications. Grain yields of DS crops were converted to rice yield

equivalents and net profits computed (see table).

Rice yield equivalents of rice - wheat and rice - mustard crops were highest, with rice - barley next. Rice - chickpea produced least. Rice - mustard gave net profit of $223.281/ha, followed by rice - wheat with $216.72/ ha.


The river floodplain area of Uttar Pradesh State occupies nearly 1.5 million ha; main rivers are the Ganga, Yamuna, Sarda, Gomti, Saryu, and Gandak. The Gomti accounts for 0.20 million ha. Adopting cropping sequences of rice - mustard or rice - wheat could significantly improve its agriculture.

Rice cultivation practices in a Negrito foraging society in northeastern Luzon, Philippines

T. N. Headland and J. D. Headland, Summer Institute of Linguistics, 7500 West Camp Wisdom Road, Dallas, Texas 75236, and Department of Linguistics, University of Texas at Arlington

The Casiguran Agta, a Negrito population in northeastern Luzon, Philippines, are nomadic hunters and gatherers. Many households, however, also make swiddens (slash-and-burn fields), and a few cultivate wet rice paddies. In 1984,609 Agta were living in a 700-m2 rainforest area in northern Aurora Province. Rainfall averages 3,448 mm/yr.

For 19 mo in 1983-84, we studied Agta cultivation practices by measuring and recording crop data and interviewing field owners. It was a good year, with no significant crop damage from insects or weather. Twenty-two percent of households planted crops, sharing harvests with others. They cultivated 43 swiddens and 5 irrigated rice paddies.

agriculture. Overall, men and women gave 6% of their days to this task (range 0-36%). Total cropped area was 8.6 ha, 91% in rice, only 141 m2 per capita. Rice cropping was 128 m2 per capita. Mean swidden size was 0.14 ha (s.d.: 0.11 ha), mean paddy size was 0.53 ha.

Total annual rough rice production was 9.1 t, 4.7 t from swiddens and 4.4 t from paddies, enough to feed the population for only 15 d. Mean rough rice yield from swiddens was 0.9 t/ ha (n=17). One paddy yielded 1.7 t/ha.

The Agta spend little time in


The Agta planted 10 different rice varieties in the swiddens. They grew 47 cultivars of all crops in swiddens, averaging 7.5 cultivars/ swidden, including rice (s.d.: 6.3, range: 1-27).

To our knowledge, the Agta have the smallest swiddens of any cultural group in SE Asia (1/7 ha), the fewest rice varieties/ swidden (1.5), and the fewest cultivars/swidden (7.5). Though they eat rice at 92% of their meals, only 5% of

the rice they eat comes from their own fields. They secure most of it by trading minor forest products and through casual wage labor for outsiders. The Agta cultivate rice mainly as a hobby and for prestige, rather than to produce food. They are not farmers, and since Spanish records show they were making swiddens in the 1700s, they are not evolving from foraging to farming.

Cassava varieties for 5-mo summer rice fallow in Kerala

K. K. Santha, K. Karunakaran, and N. R. Nair, Regional Agricultural Research Station, Pattambi 679306, India

Extensive rice areas in Kerala have a pattern of two rice crops—one medium- duration rice for rainy (May-Aug) season and one long-duration for dry season (Aug-Dec)—followed by a 5-mo summer fallow. We tested five cassava

varieties for summer fallow in a replicated yield trial during summer 1987. We used 75- × 75-cm spacing, 50- 50-50 kg NPK/ ha, a basal application of cattle manure at 12.5 t/ ha, and irrigation every 2 wk.

Tamil Nadu) and M4 (already popular in Kerala for a 9-10 mo season) are suited to the 5-mo summer rice fallow season under Kerala conditions (see table).

Varieties Co 2 (recently released from

Performance of 5 cassava varieties in the 5-mo summer rice fallow season. Pattambi, Kerala, 1987.

Plant Tuber Variety height yield

(cm) (t/ha)

Tuber characteristics

Length Girth Softening (cm) (cm) on cooking

Co 2 102 12.6 22 12 Very good M4 123 11.6 22 11 Very good Malavella 117 10.0 26 12 Very good 12/77 141 9.1 25 11 Good 11/76 124 10.3 24 12 Good

LSD (P = 0.05) – 2.0 – – –

Data management and computer modeling

Modeling feeding rates of rice consumed can be measured by exposing leaffolder (LF) Cnaphalocrocis larvae of known age to susceptible rice. medinalis on different plant The cumulative consumption by a larva stages at age t represents the total leaf

consumption from hatching to that age. K. L. Heong and L. T. Fabellar, The first three instars fed little. More Entomology Department, IRRI than 90% of feeding was done by the 4th

The rice LF damages plants by feeding hatching. The data fit an exponential on the leaves, removing patches of model extremely well. The model is photosynthetic tissue. Daily leaf area

and 5th instars age 11-19 d after

cpsadmin

Text Box

Ct = ebt - 1.0

Parameters of data fitted to the model C t = e ß t - 1.0 relating the total leaf area consumed (cm 2 )/ larva with larval age in days at different plant stages. a IRRI, 1988.

Plant stage Goodness of fit c

(DAS) b ß ± SE MSR VR

40 0.1815 ± 0.0007 6205** 3820** 60 0.1692 ± 0.0007 7673** 7438** 80 0.1536 ± 0.0009 3487** 10929**

100 0.1360 ± 0.0011 2024** 8547**

a ß = feeding rate coefficient and SE at 95% confidence. b DAS = days after sowing. c MSR = mean square ratio of mean squares for regression and residual from nonlinear curve fitting, VR = variance ratio from regression analysis of linearized data. ** = significance at P = 0.001.

Relationship between leaf consumption, age of LF larvae, and plant stages. IRRI, 1988.

where C t is the age-specific total leaf area consumed from age 0 to age t and ß is the feeding rate.

plants of different ages (see table). The rate constants related well to the plant stages expressed in days after sowing (DAS) by a linear model = 0.213 - 0.0008*DAS ( r 2 = 0.99). Combining the two models, the relationships between leaf area consumption, age of LF larva, and plant stage can be shown (see figure). On plants 40 DAS, the LF larva could consume as much as 30 cm 2 leaf area, while on plants 100 DAS, it could consume only 11.5 cm 2 .

Since the leaf area consumed by LF larvae can be quantified using these two models, the effects of the pest’s damage may now be computer simulated using an existing rice growth model. This coupling will allow us to predict yield reductions by a known population.

Feeding rates differed significantly for

The International Rice Research Newsletter is mailed free to individuals and institutions engaged in rice research and training. For further information, write IRRI, Communication and Publications Dept., Division R, P. O. Box 933, Manila, Philippines.

ANNOUNCEMENTS Irrigation symposium planned economics, and the social sciences will

An Asian Regional Symposium on Papers selected for the symposium are Modernisation and rehabilitation of based largely on the Asian experience. irrigation and drainage schemes is Invited papers from other parts of the scheduled 13-15 Feb 1989 at the world will show different approaches to Development Academy of the solving common problems in different Philippines. environments.

The symposium is planned to Organizers and sponsors are encourage a dialogue among the various Hydraulics Research Limited, disciplines involved at all stages of Wallingford, England; National irrigation and drainage rehabilitation. Irrigation Administration, Manila, Papers presented on scheme selection, Philippines; Overseas Development design, implementation, monitoring, and Administration, London; and Asian evaluation will include case studies. Development Bank, Manila. Specialists in engineering, agriculture, Copies of papers, special lectures, and

participate.

discussion reports will be available from the Overseas Development Unit, Hydraulics Research, Wallingford, Oxfordshire OX10 8BA England. Copies are free to organizations in developing countries; individuals pay £25.

Origin of Cultivated Rice

This book by Hiko-Ichi Oka, National Institute of Genetics, Mishima City, Japan, updates current understanding of the origin of cultivated rice, from biological and archaeological-historical perspectives. Recent discoveries are reviewed and new questions posed.

The content emphasizes ecological and genetical aspects, comparing the


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International Rice Research Newsletter Vol.13 No.5