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Breeding for Drought Tolerance in pearl millet
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Breeding for drought tolerance in pearl millet (Pennisetum glaucum (L.) R. Br.)
Name of speaker : Patel Satishkumar Reg. no. : 04-1313-2010 Major advisor : Dr. J.A. Patel Date : 14/03/2012 Time : 1600 hrs
Content Introduction Mechanism of Drought Tolerance Screening Methods Case studies on Drought Tolerance Physiological
Variability and Correlation
Biochemical
Biotechnological Studies Breeding approaches Achievements Limitations Conclusion Future thrust 2
INTRODUCTION
Botanical Name: Synonyms: Pennisetum glaucum (L.) R. Br.
Pennisetum typhoides (Burm. F.) Stapf. and Hubbard
Pennisetum typhoideum Rich.,
Pennisetum americanum L. Leeke
Common Names:- Bajra, Bulrush millet, Spiked millet, Cat tail millet
Family: - Poeaceae Sub family: Panicoideae Tribe: Paniceae
Origin :- Sahel zone of West Africa
Chromosome No.: 2n=14
Uses:- Feed: Fodder, Fuel, Fencing,
Cross pollinated Crop Spices due to its protogynous flowering nature Annual C4 crop species.
Stable diet for the vast majority of poor farmers
3
Table:-1 Area, Production And Productivity (2010-11)
Area(million hectare)
Production(million tonns)
Productivity (kg /hectare)
India 8.75 8.89 1015
Gujarat 0.92 1.31 1365
Source: Directorate of Economics and Statistics, Department of Agriculture and Cooperation.
4
State wise Bajra production (2010-11)
Rajasthan31%
Uttar Pradesh21%
Haryana14%
Gujarat13%
MH12%
MP4%
Karnataka2%Tamil Nadu
1%Andhra Pradesh
1%
StateProduction
(Million Tonnes) Productivity
(kg/ha)
Rajasthan 2.03 394
Uttar Pradesh 1.39 1638
Haryana 0.93 1593
Gujarat 0.92 1365
Maharashtra 0.77 741
Madhya Pradesh 0.25 1495
Karnataka 0.15 502
Tamil Nadu 0.08 1513
Andhra Pradesh 0.05 1178
Source: Directorate of Economics and Statistics, Department of Agriculture and Cooperation.
5
Drought
Drought is event which implies the absence of a period of time, long enough to cause moisture-depletion in soil and water deficit with decrease of water potential in plant tissues.
Drought is highly heterogenous in time, space, degree of stress, growth stage and time of stress exposure, and it is unpredictable.
6
Types of Drought
• Meteorological Drought:- It is related to deficiencies in rainfall compared to the average mean seasonal rainfall in an area.
• Agricultural Drought:- Deficit rainfall over cropped areas during their growth cycle can destroy crop or lead to poor crop yields.
• Hydrological Drought:- It is a deficiency in surface and sub-surface water supply. It is measured as stream flows and also as lake, reservoir and groundwater levels.
7
Drought affected area in the world
The major bajra growing countries are Senegal, Mali, Niger, Nigeria, Sudan and India.1.3 Billions people are under drought-prone areas (India/Africa)
8
Source: www.milletindia.org Source : http://www.mapsofindia.com
Major Bajra Growing Regions of India
Severely Affected
Moderately Affected
States affected by Drought
Bajra is a major cereals in northwestern zone as it represents approximately 25 % of the total acreage of the crop in the country.The chronically drought-prone areas around 33 % -receive less than 750 mm of rainfall, while 35 % classified as “drought-prone ” receive rainfall of 750-1,125 mm (in India). 9
About 36% of the land area constitutes arid and semi arid zones, arid and semi arid areas are more prone to drought.
Drought leads to reduction in both yield and quality of economic product in crop plants. It has adverse effect on plant growth and development. Drought damages chloroplasts and lowers photosynthetic output.
There is an increase in proline level in the leaves of plants which are subjected to all stresses.
Drought resistance is a genetically controlled physiological property of plant species.
Breeding for drought tolerance is a major objective in arid and semiarid regions of the world due to inadequate precipitation, shortage of irrigation water and high water demand for crop evapotranspiration in such climates
Main features of drought
10
Terms of Drought
• Drought resistance : Ability of a plant to live, grow and yield
satisfactorily with limited water supply or under periodic water deficits.
• Drought escape : Ability of plant to mature before water stress becomes
a serious limiting factor.
• Drought avoidance: Ability of a plant to withstand water deficit as
measured by degree and duration of low plant water potential.
water savers-closing of stomata
water spenders- extract more water from soil
• Drought tolerance: Ability of a plant to recover from a dry period by
producing new leaves from buds, and those were able to survive the dry
spell.
Gupta et al., 1986 11
Symptoms of Drought
• Reduced leaf area
• Early senescence of older leaves
• Effect on flowering, largely delay in flowering (Cause
abscission of flowers.)
Injury Mechanism
• Water stress directly affects cellular processes, membrane structures
and structure of macromolecules.
• Cause severe embolism formation in the xylem vessels.
12
Morphological traits Physiological factors
Higher rate of photosynthesis
Lower rate of transpiration
Higher leaf turgidity
Higher osmotic concentration
Earliness
Stomatal characters :- Shrunken type, small size, less number per unit area, rapid closing nature
Leaf character:- Waxy leaves, small thick leaves, hairiness
Root characters:- Root length, root density, R/S ratio
Growth habit:- Indeterminate
Biochemical factors
Proline content
ABA content in Leaf
13
Drought avoiding plant must maintain
High water potential
Higher root -shoot ratio
14
Measurement of drought tolerance
1. Change in growth patterns
2. Change in seed production
3. Electrolyte leakage from leaf segments
4. Leaf wilting
5. Relative leaf water content
6. Change in the transcriptome
Traits investigated in pearl millet References
Grain and stover yield and quality
Ibrahim et al. (1985), Kumari S (1988). Bidinger et al. (1987, 2007), Singh and Singh (1995), van Oosterom et al (1996), Nepolean et al. (2006), Yadav et al. (I999a,b, 2002, 2003. 2004) Serraj et al. (2005)
ABA accumulation Henson et al. (1981). Henson (1983). Henson et al. (1983). Henson(1984)
Water potential Henson (1982)
Osmotic potential Henson (1982)
Osmolytes Patil et al. (2005), Kholova et al. (2008)
Antioxidative enzymes Patil et al. (2005), Kholova et al. (2008)
Photosynthetic pigments
Ibrahim et al. (1985), Ashraf et al. (2001)
Transpiration related traits
Ibrahim et al. (1985), Squire (1979), Black and Squire (1979), Henson et al. (1981), Henson (1984), Kholova et al. (2008, 2010 a, b.c)
Canopy temperature Singh and Kanemasu (1983)15
Drought Tolerance
Physiological processes
Expression Profiling
Reverse Genetics
Allele Mining for natural Variation
MAS/Transformation
Map Based Cloning
Forward Cloning
Forward Genetics
Comparative mapping
Fig. 1 Drought tolerance improvement tools and processes
16
Screening Criteria
17
Screening CriteriaThe selection criteria primarily based on morphological characters could be selection of parents as well as desirable segregants followed by hybridization.
During selection, characters have high heritabilities and high correlation with yield under stress across the environments.
Grain yield under stress conditions is usually the primary traits for selection.
A suitable secondary traits should have (Edmeades et al. 2001).
1) Genetically association with grain yield under drought,
2) High heritability,
3) Stable and feasible to measure,
4) Lack of association with yield loss under ideal growing conditions. 18
Screening methods for Drought tolerance in Pearl millet
19
Laboratory method In Laboratory method to identify genotypic difference in germinability, osmotic
solutions like polyethylene glycol (PEG) is used. The osmotic effect of drought are known to be comparable to true drought effects
Field method: The field is uniformly irrigated with overhead system using perforated pipes. Also used sprinkler method. The percentage of seedling that emerge is computed.
Tested Material
Tested Material
Line source irrigation method
Incr
ease
wat
er s
tres
s
Water Source/chennel
20
Case Studies
21
Table 2 :-Effect of osmotic stress on seedling traits of pearl millet genotype during drought induced by PEG in Vitro condition.
ICRISAT (A. P.) Govindaraj et al. (2010) 22
Genotype Germination % Root length (cm)
Seedling height (cm)
Dry mass of seedling (g)
Vigor index
Normal Stress Normal Stress Normal Stress Normal Stress Normal Stress
X7 99.5 98.0 10.89 6.53 17.90 10.71 0.058 0.074 1781.3 1049.6
X6 97.0 96.0 10.23 6.17 17.48 10.65 0.070 0.080 1695.6 1022.4
Co7 98.3 95.5 9.28 5.58 16.17 9.03 0.073 0.094 1589.5 862.4
WC-C75 99.8 98.3 11.18 4.64 18.43 7.75 0.093 0.101 1839.3 761.8
CD (P<0.05 %)
T 0.636** 0.650** 0.755** 0.0065** 72.133**
V 0.900** 0.919 (NS) 1.068** 0.0092* 102.002 (NS)
T X V 1.272 (NS)
1.300* 1.510** 0.0131 (NS) 144.268 (NS)
Table 3 :- Germination and physiological parameters under normal (N) and induced stress (PEG) (S) treatments (T) in pearl millet cultivars (V)
Vijayalakhsmi et al. (2000)Coimbatore (T.N.)
23
Treatment Plant height (cm)
Plants/m Tillers/m Effective tillers/m
Length of ear (cm)
Weight of ear (g)
1000Grain weight (g)
Average Yield(kg/ha)
PercentReduction
T1, control154 5.0 15.9 8.1 24.2 30.4 9.45 2101 -
T2, Rain out during crop establishment
149 4.8 17.5 6.2 22.2 28.8 9.27 1852 11.80
T3, Rainout during tillering stage
144 4.8 11.8 5.8 20.4 26.3 8.89 1629 22.50
T4, Rainout during earing and flowering stage
139 5.2 11.6 6.3 21.2 27.8 8.67 1707 18.80
T5, Rainout during grain-filling and maturity stage
152 4.7 16.2 5.8 20.5 28.2 7.75 1970 6.20
CD (P < 0.05 %) NS NS 2.23 0.30 0.78 NS 0.25 - -
Table 4:-Average growth and yield attributes of pearl millet as affected by different treatments
Agra (U.P.) Prakash et al. (2008) 24
WW (36 %) MS(21 %) SS (9 %)
Ethiopia Yalew and Yemane (2011)
WW (36 %) MS(21 %) SS (9 %)
Fig. 2 Response of pearl millet cultivars (Dadda and Shella ) to post-flowering drought stress.
WW= Well WaterMS= Moderately Stress SW= Severely Stress
WW (36 %) MS(21 %) SS (9 %)25
Yalew and Yemane (2011)Ethiopia
Fig.3 Potential quantum yield of two cultivars of Pearl millet subjected to three soil moisture levels.
WW= Well Water (36 %)MS= Moderately Stress ( 21 %)SW= Severely Stress ( 9 %)
Dadda
Shella
26
Table 5:- Grain yield and physiological parameters as influenced by terminal moisture stress in B-line and inbreds
Pearl millet lines
Days to flower
Grain yield(kg/ha)
Harvest index
Threshing Relative Water content (%)
Drought susceptibilityIndex
81B 70.8 136.1 4.7 22.0 74.9 1.196 + 0.06
218B 65.7 234.4 8.7 28.4 63.4 1.259 + 0.12
89111B 59.3 263.3 11.2 26.0 77.4 1.104 + 0.12
95444B 58.7 628.9 22.4 47.7 74.2 0.812 + 0.06
J-108 57.8 648.9 18.2 40.0 72.0 0.846 + 0.10
J-998 62.8 353.3 9.3 29.7 69.0 1.057 + 0.04
J-2290 68.0 375.0 8.2 31.7 75.7 1.099 + 0.09
J-2296 59.2 376.7 15.4 37.7 75.0 0.880 + 0.08
J-2340 58.8 806.7 18.1 44.4 77.8 0.761 + 0.18
LSD (P=0.05)
4.7 304.2 5.2 13.5 6.5 -
CV % 3.9 39.7 36.4 19.0 7.1 -
Joshi et al. (2005)Jamnagar (Gujarat) 27
Table 6:- Physiological parameters in pearl millet hybrids as influenced by high temperature and receding soil moisture at seedling stage
Entries/Hybrids
Root Dry mass (mg/plant)
Shoot dry mass(mg/plant)
Total Dry Mass(mg/plant)
Root/shoot ratio(dry wt. basis)
Survival (%) at 19-22DALI*
Leaf elongation Rate (cm/day) index at 15 DALI*
Chlorophyll Stability
GHB-558 26.3 30.9 57.1 0.9 44.9 0.35 0.111 + 0.016
GHB-559 29.5 26.4 55.7 1.2 68.4 0.48 0.079 + 0.007
GHB-316 26.9 25.9 52.8 1.1 61.3 0.47 0.096 + 0.019
GHB-526 38.7 37.4 76.1 1.1 76.4 0.59 0.053 + 0.016
GHB-538 32.8 34.9 67.8 1.0 72.9 0.55 0.058 + 0.014
LSD (P=0.05)
NS 5.3 NS NS 16.4 0.09 -
CV (%) 10.5 15.1 10.8 17.9 9.1 17.3 -
* DALI – Days after last Irrigation, NS- Non significant
Joshi et al. (2005)Jamnagar (Gujarat) 28
Variability and correlation studies for
drought tolerance
29
Character GCV % PCV % h2 (B.S.) % Genetic
AdvanceGA % of Mean
E % 12.83 13.52 90.1 20.783 25.09
FSL 12.21 12.85 90.3 2.806 23.89
FRL 12.57 13.65 98.7 4.987 25.73
FSW 16.32 16.60 96.6 0.02 33.05
FRW 21.36 21.91 95.0 0.015 42.87
DSW 22.48 23.14 94.4 0.002 44.99
DRW 24.99 25.32 97.4 0.002 50.79
R/S 22.87 24.03 90.6 0.203 44.83
Table 7:- Estimates on GCV, PCV, heritability in broad sense(h2 B.S.), Genetic advance as percentage of mean (GA %) of seedling traits in 63 pearl millet genotypes
Coimbatore (T.N.) Arulselvi and Selvi (2009)
E %=Emergence %, EI= Emergence index, ERI= Emergence rate, FSL=Fresh Shoot Length, FRL= Fresh Root Length, FSW=Fresh Shoot Weight, FSL= Fresh Root Weight, DSW= Dry Shoot Weight, DRW= Dry Root Weight.
30
Table 8:-Character contribution towards genetic divergence
Sr. No. Character Contribution (%)
1 Emergence % 4.86
2 Fresh Shoot Length 2.66
3 Fresh Root Length 39.63
4 Fresh Shoot Weight 26.73
5 Fresh Root Weight 2.05
6 Dry Shoot Weight 7.32
7 Dry Root Weight 16.28
8 Root/Shoot 0.36
Coimbatore (T.N.) Arulselvi and Selvi (2009) 31
Source df E % EI ERI FSL FRL FSW FRW DSW DRW R/S
Replications 1 6.2222 0.002 0.000007 0.0287 0.0229 0.00001 0.000059 0.000002 0.000001 0.0178
Genotypes 62 238.3574** 0.0069 0.000027 4.3309** 11.9518** 0.000201** 0.000107** 0.000002** 0.000001** 0.0226**
Error 62 12.4158 0.0035 0.000014 0.2211 0.0778 0.000003 0.000003 0.0000001 0.0000001 0.0011
SE 2.4717 0.0414 0.0027 0.3298 0.1956 0.0013 0.0012 0.0002 0.0001 0.0234
CD @ 5% 4.9409 0.0828 0.0053 0.6593 0.3911 0.0026 0.0023 0.0004 0.0001 0.0468
Mean 82.8254 1.0956 0.0139 11.7437 19.3833 0.0609 0.0338 0.0047 0.0021 0.4528
Table 9:- Mean Square from analysis of variance for seedling traits conferring drought tolerance in pearl millet genotypes.
** Significant at 0.01 probability level
Coimbatore (T.N.) Arulselvi and Selvi (2009)
E %=Emergence %, EI= Emergence index, ERI= Emergence rate, FSL=Fresh Shoot Length, FRL= Fresh
Root Length, FSW=Fresh Shoot Weight, FSL= Fresh Root Weight, DSW= Dry Shoot Weight, DRW= Dry
Root Weight.
32
Traits FSL FRL FSW FRW DSW DRW R/S
E %0.2782 0.4332** 0.4555** 0.5009** 0.4479** 0.3204** -0.0508
FSL 0.4688** 0.7518** 0.5672** 0.5909** 0.5542** 0.0606
FRL 0.5536** 0.4769** 0.5793** 0.5411** 0.0506
FSW 0.7682** 0.8105** 0.6978** -0.0060
FRW 0.5633** 0.8800** 0.4457**
DSW0.5176** -0.3404**
DRW 0.6158**
Table 10:- Simple Correlation coefficients Between seedling traits (conferring Drought Tolerance ) among 63 pearl millet genotypes.
Arulselvi and Selvi (2009) Coimbatore (T.N.) ** Significant at 0.01 probability level
E %=Emergence %, EI= Emergence index, ERI= Emergence rate, FSL=Fresh Shoot Length, FRL= Fresh Root Length, FSW=Fresh Shoot Weight, FSL= Fresh Root Weight, DSW= Dry ShootWeight, DRW= Dry Root Weight.
33
Table 11:-Means and F ratios of genotypes for growth and yield components measured in the irrigated control (c) and drought stress (s) treatments.
Characters 1988 (34 Genotypes) 1989 (34 Genotypes) 1990 (32 Genotype)
Treatment Means F ratio Means F ratio Means F ratio
Time to flowering (days) Control 64 5.80** 66 5.92** 67 11.90**
Stress 62 5.40** 65 5.99** 68 15.60**
Biomass (g m-2) Control 621 3.02** 858 1.79** 662 2.49**
Stress 437 2.49** 585 3.28** 598 2.76**
Stover (g m-2) Control 398 3.29** 482 1.91** 431 6.50**
Stress 300 4.38** 359 4.57** 423 3.91**
Panicle (g m-2) Control 223 2.54** 378 1.77** 230 0.97
Stress 137 2.05** 228 2.19** 175 1.41
Grain yield (g m-2) Control 156 2.30** 271 1.66** 158 1.07
Stress 83 2.48** 140 2.64** 121 0.78
Panicle No. m m-2 Control 9.8 1.58* 11.5 3.61** 10.3 1.50*
Stress 8.2 1.47 10.0 2.33** 8.4 1.51*
Panicle yield (g) Control 16.2 4.02** 23.7 3.81** 15.0 2.46**
Stress 9.8 3.00** 13.7 3.23** 14.2 0.72
No. Grains panicle-1 Control 2440 4.47** 3090 3.75** 2260 1.96**
Stress 1840 1.90** 2300 3.16** 2330 0.72
Grain mass (g 100-1) Control 0.67 10.39** 0.77 3.96** 0.66 5.90**
Stress 0.53 7.30** 0.53 2.86** 0.61 2.55**
No. Grains m-2 (*103) Control 2.306 3.34** 35.3 1.93** 23.5 1.16
Stress 15.4 1.88** 23.3 2.43** 19.6 0.81
Harvest index Control 25.4 4.04** 32.0 3.20** 23.0 2.01**
Stress 18.6 4.38** 24.0 3.81** 20.0 0.65
Threshing Percentage Control 70 3.61** 71 1.90** 67 2.30**
Stress 58 3.44** 60 3.76** 69 0.61
Sadore Peter (1992) 34
CharactersCorrelation Coefficients
Flowering DRI1988 1989 1990 1988 1989 1990
Time to flowering (days) --- ----- --- -0.07 0.07 -0.02Biomass (G m-2) 0.53** 0.47** 0.56** 0.56** 0.59** 0.20Stover (G m-2) 0.76** 0.63** 0.77** 0.26. 0.37** 0.06Panicle (G m-2) -0.31 -0.21 -0.35* 0.73** 0.74** 0.31Grain yield (G m-2) -0.46** -0.35* -0.28 0.69** 0.71** 083**Panicle No. M-2 -0.55** -0.47** -066** 050** 0.11 0.10Panicle yield (g) -0.29 -0.16 0.06 0.62** 0.78** 0.88**No. Grains per panicle 0.13 0.22 0.04 0.55** 0.63** 0.92**Grain mass (G) -0.47** -0.57** 0.04 0.28 0.36* -0.01No. Grains m-2 (x103) -0.22 -0.08 -0.28 0.65** 0.62** 0.85**Harvest index -0.74** -069** -044* 0.44* 0.25 0.82**Threshing % -0.60** -057** -0.09 0.48**
0.44*0.44* 0.91**
Table 12 :- Correlations of yield parameters in the drought stress treatment to time to flowering under drought stress and Drought Response Index.
** P<0.01 * P<0.05Peter (1992)Sadore 35
CharacterDays to 50
per cent Flowering
Days to Maturity
Ear head
length(cm)
Ear headgirth(cm)
No. of produc-
tive tillers
per plant
Ear head
weight per
plant (g)
Total biomass
accumulation per
plant (g)
Grain yield per plant (g)
Harvest index
Panicle harvest index
Test weight
(g)
Root length
per plant (cm0
Proline content
(µ g g-1 f. w.)
Drought response index (DRI)
Days to 50 % Flowering 1.00
Days toMaturity 0.14** 1.00
Ear head length -0.22** -0.07 1.00
Ear headGirth -0.06 0.07 0.07 1.00
No of Productive tillers per plant
-0.06 0.04 0.03 -0.18** 1.00
Ear head weight per plant
-0.08 -0.08 -0.01 -0.16** 0.13* 1.00
Total biomass accumulation per plant
-0.05 -0.08 -0.10 -0.06 0.20** 0.24** 1.00
Grain Yield per plant -0.06 -0.12 0.13* -0.20** 0.44** 0.48** 0.19** 1.00
Harvestindex -0.18** -0.15** 0.27** -0.08 0.22** 0.11 -0.26** 0.65** 1.00
Panicle harvest index -0.14** -0.08 0.16** -0.08 0.39** -0.21** 0.03 0.74** 0.66** 1.00
Test weight -0.14** -0.15** 0.14** -0.12 0.23** 0.13* 0.09 0.59** 0.42** 0.55** 1.00
Root length per plant -0.00 0.03 0.17** 0.11 0.21** 0.04 0.09 0.35** 0.26** 0.36** 0.33** 1.00
Proline Content 0.04 -0.00 0.04 -0.09 0.36** 0.10 0.13* 0.49** 0.31** 0.45** 0.50** 0.37** 1.00
Drought response index -0.01 0.00 -0.11 -0.30** 0.35** 0.53** 0.01 0.74** 0.28** 0.41** 0.30** 0.17** 0.35** 1.00
Table 13:-Phenotypic correlation coefficient for different characters under terminal drought condition in pearl millet.
*, ** Significant at 5 and 1 percent level of probability, respectively
AAU (Anand) Patil and Jadeja (2005) 36
Transpiration Rate
37
Fig 4:-Water Conserving mechanisms with the terminal drought tolerance of pearl millet
Kholova et al. ( 2010)ICRISAT (A.P.)
Drought Tolerant PRTL 2/89-33 863B-P2Drought Sensitive H 77/833-2 ICMB-841-P3
38
ABA content in Leaf
39
Fig. 5:- ABA content in pearl millet test cross hybrids (Drought Tolerant Drought Sensitive) in well-water (WW) and water stress (WS) condition
Vegetative Stage Reproductive Stage
NIL-QTLs Drought Tolerant PRTL 2/89-33 863B-P2Drought Sensitive H 77/833-2 ICMB-841-P3
Kholova et al. ( 2010)ICRISAT (A.P.) 40
Drought Tolerance QTL under salt stress
41
02468
10121416
843A X H 77/833-2 (Drought
sensitive parent)
843A X 01029 (QTL-NIL)
843A X PRTL 2/89-33 (Drought tolerant parent)
pH 8.5
pH 9.0
pH 9.4
L
eaf
Na
(mg/
g d
ry w
t.)
FIG. 6:- Na+ accumulation in the leaves of drought- sensitive and drought-tolerant parents, at three Alkalinity levels.
Sharma et al. (2010)CSSRI (Karnal) 42
Lea
f N
a (m
g/g
dry
wt.
)
0
5
10
15
20
25
843A X H77/833-2 (Drought Sensitive parent)
843A X 01029 (QTL-NIL)
834A X PRTL 2/89-33
(Drought tolerant parent)
EC 2 ds/m
EC 9 ds/m
EC 12 ds/m
FIG. 7:- Na+ accumulation in the leaves of drought- sensitive and drought-tolerant parents, at three salinity levels.
CSSRI (Karnal) Sharma et al. (2010)43
Table 14:- Correlation analysis between enzymatic activities and pigments contents and ratios under well water and water stress condition.
Water stressChlorophyll a Chlorophyll b Carotenoids Chl a/Chl b Chl/Car
APX (Ascorbic peroxidase)APX 2 ns ns ns ns 0.9344*APX 4 ns ns ns ns 0.9037*/0.9881*
APX 8 ns ns -0.9104* ns nsAPX 9 ns ns ns ns 0.8929*SOD (Superoxide dismutase)Mn-SOD2 ns ns ns ns 0.969**Mn-SOD3 ns ns ns ns 0.9516*
CAT (Catalse)CAT1 ns ns ns ns 0.9439*CAT2 ns ns ns ns 0.8911*
Well-wateredChlorophyll a Chlorophyll b Carotenoids Chl a/Chl b Chl/Car
APX (Ascorbic peroxidase)APX5 ns ns ns ns -0.8821*APX 6 ns ns ns ns -0.8972*APX Sum ns ns ns ns -0.9417*
Kholova et al. ( 2011)ICRISAT (A.P) 44
Fig. 8:- Gene networks involved in drought stress response and tolerance
Function in stress tolerance Signal transduction and gene expression
Shinozaki and Shinozaki (2007)Japan 45
Breeding Strategies46
Lines of pearl millet used in crosses to developed genetic maps
Lines Characteristics
1 H 77/833-2 Elite male parent of grain hybrids in north-western India, Susceptible to downy mildew but with seedling thermotolerance, high tillering capacity and earliness
2 PRLT 2/89-33 Inbred 33 in ICRISAT potential R- line Trail conducted in 1989; derived by selfing in the ICRISAT bold seeded Early Composite, low tillering, large seeds, drought tolerant which is largely based on lniadi landrace germplasm from West Africa.
47
Fig. 9:- Strategy for development of Genetic linkage map to identify QTLs linked to traits
Yadav et al. 2010ICRISAT48
Fig:-10 Genetic map
Genetic map of a pearl millet population that segregates for drought tolerance showing the distribution of molecular marker on the different linkage group. The highlighted regions indicate parts of the genome controlling grain yield, and its components, during drought stress.
49
Linkage Group
(QTL on)
Drought Response for Grain yield
Genetic Background References
LG2 Up to 32 % H 77/833-2 x PRTL 2/89-33 Yadav et al., 1999,2002
LG 3 & 4 11.6-17.3 % ICMB 841 x 863 B Bidinger et al., 2007
LG 5 14.8 % ICMB 841 x 863 B Yadav et al., 2004
LG 6 & 1 QTL has Pleiotropic to decreased panicle
number
H 77/833-2 x PRTL 2/833 Yadav et al., 2010
Table:- 15 QTLs associated with drought tolerance of grain yield
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Fig:-11 Marker Assisted Backcross Breeding for Drought Tolerance
51
Fig. 12:- Fine mapping population or High Resolution Cross
Yadav et al. 2010
Objective of HRC1. To fine map the DT-QTL interval
on LG 2 2. To Pyramid this DT-QTL with
the Downy-mildew resistance QTLs on LG 1 & 4
52ICRISAT
Table 16:-Comparison of the DT-QTL based and Field performance- based Hybrids.
Moisture Environment Crop Trait
QTL topcross Hybrids Field topcross hybrids LSD (P=0.05)
Non- Stress
Flowering (d) 39.1 41.3 0.19
Biomass (g /m2) 777 845 15.6
Harvest Index (%) 49.6 45.9 0.55
Grain Yield (g/m2) 381 393 7.7
Terminal Stress
Flowering (d) 41.1 43.5 0.15
Biomass (g /m2) 581 619 11.4
Harvest Index (%) 41.7 38.3 0.60
Grain Yield (g/m2) 245 239 5.6
Line Source
Flowering (d) 35.1 38.1 0.12
Biomass (g /m2) 537 562 7.9
Harvest Index (%) 49.5 43.8 0.5
Grain Yield (g/m2) 268 255 5.1
Serraj et al.(2005)ICRISAT 53
Fig. 13:-Marker Assisted Selection
1. Marker-assisted selection. Genetic composition at the drought tolerance QTL ( to constitute a MAS TCP)2. Phenotypic selection. Field performance (best 16) in the drought trials used to identify QTLs (to constitute a phenotype TCP)3. A Random control. A random sample from within the mapping population (to constitute a random TCP).
Bidinger et al. (2005)ICRISAT54
55
The mapped progeny were phenotyped as testcross hybrids
rather than as the skeleton-mapped F2 plants.
• To restore heterotic vigour to partially inbred mapping progeny that might
otherwise be too weak for effective screening under stress conditions (Inbreeding depression)
• To reduced variation in flowering time among the test units, in order to focus the mapping on specific drought tolerance traits rather than traits or responses associated with variation on capacity for drought escape
• To have test units that approximate the genetic structure of the F1 hybrids grown by farmers rather than partially inbred F3 or F4 lines.
56
Framework of an integrated strategy for genetic enhancement of crop grain yield (GY) and its components under water-limited conditions at ICRISAT. TR=total plant water transpired; TE=transpiration efficiency; HI= harvest index.
57
Breeding Approaches
Breeding under optimum (water-stress free) condition
Breeding under actual drought condition Breeding under artificially created
environment
Incorporation of drought tolerance
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1. Introduction (PRLT 2/89-33, lniadi landrace germplasm from West Africa.)
2. Interspecific and intergeneric hybridization Single backcross Three way cross (Gene pyramiding)
3. Pedigree selection4. Back cross breeding5. Mutation breeding6. Ideotype breeding : Breeding activity aimed at producing new genotypes with novel morpho-physiological features that fit a
pre-defined architecture thought to be advantageous based on experimental physiology and/or modelling.
Breeding Methods
C
onve
ntio
nal m
etho
ds
59
7. Marker assisted breeding
8. Marker-assisted backcrossing (MABC): Repeated backcrossing of the F1’s to reconstitute the recipient genome without losing the desirable gene.
9. Tissue culture (in vitro Screening by using PEG 6000)
10.Development of Transgenic
N
on-C
onve
ntio
nal m
etho
ds
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Achievements
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Table:-17 Recommended drought-tolerant/drought-avoiding hybrids/varieties of pearl millet in India
State Hybrids Varieties
Maharashtra Nandi 35,Saburi, PAC 903PPC 6, HC 20, JBV 2, ICTP 8203, ICMV 221, AIMP 92901
Tamil Nadu GHB 558, CoH (Cu)8, X7 Co7, ICMV 221, ICMV 155
Andhra Pradesh PB 106, GHB 558 AIMP 92901, ASP-1, ICTP 8203
Karnataka PB 106, GHB 558 ICMV 221, ICTP 8203
RajasthanHHB 67, RBH 121, GHB 538, PB 180 CZP 9802, Raj 171
GujaratGHB 577, GHB 526, PB 172, PB 112, ICMB 356 JBV 2, HC 20
HaryanaHHB 67, GHB 538, HHB 117, ICMB 356 CZP 9802
ICRISAT REPORT (2007) 62
63
Limitations• There is no single major gene, which has a remarkable effect on
the drought tolerance• Drought tolerance is an environmental and developmental stage
specific character• Drought reduces nutrients uptake, and is associated with
temperature stress and at higher elevation with cold. This associations make the breeding programme more complicated.
• Most of the physiological and metabolic processes are affected by water deficits: cell growth, stomatal regulation, photosynthesis,
translocation, etc.• Large number of genes regulated up- or down- by drought• Large genetic populations and replicates are required• Even drought component traits are often complex and difficult to
screen
64
Conclusion• Tillering stage (30-45 DAS) is most susceptible to drought; wherein 23-
25 % of yield reductions occurres, followed by drought at grain filling and
maturity stage.
• The osmotic (PEG 6000) stress at the seedling stage is the most suitable
method for drought tolerance screening owing to their significant
relationship with declining the germination percentage, root and shoot
length.
• Selection for seedling traits conferring drought tolerance such as root
length, root weight and root shoot ratio will be useful for identifying
genotypes with drought tolerance capacity.
• Post-flowering drought stress is one of the most important
environmental factors reducing the grain yield and yield stability of pearl
millet and increasing the incidence of crop failure in dryland production
environments
• Marker Assisted Selection is the most appropriate method to improve
drought tolerance genotype.
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Future thrust
• Consolidation of yield grains through multiple resistance to various abiotic and biotic stresses.
• To develop a plant ideotype by restructuring the morphological attributes these can withstand drought conditions.
• Need to saturate QTL areas to increase the efficiency• Pyramiding with other QTLs• In pearl millet, it need to be tested whether high leaf ABA
content and the lower Tr are linked or not.• Need to develop Transgenic for Drought Tolerance,
though difficult because of polygenic inheritance.
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