Course SeminarOn

Heterosis breeding in rice (Oryza sativa L.)Supervisor

Prof. S.K. Singh

Student Monika Singh

ID. No. G-15113

DEPARTMENTOF GENETICS AND PLANT BREEDINGInstitute of Agricultural Sciences

BHU, Varanasi.

1. Introduction 2. Heterosis

History Types of heterosis Genetic basis of heterosis Moecular basis of heterosis

3. Exploitation of heterosis Hybrid rice

4. Hybrid seed production system in Rice Male sterility

a. CMS CGMS

b. EGMS TGMS PGMS

c. CHA5. status of Hybrid rice technology6. Advantages of Hybrid rice7. Constraints 8. Future Prospects9. Conclusion

Rice (Oryza sativa L. 2n = 2x = 24) is the most important food crop in Asia.

It is staple food crop of India, providing 43% of calorie

It is the requirement of more than 70% Indian population.

The area covered by rice in India is 44.0 million ha, which is largest among all the rice growing countries with an annual production of 103.5 (2016) million tonnes.

Total area: India > China > Indonesia > Bangladesh

Total production: China > India > Indonesia > Bangladesh

Productivity: USA>Japan > China > Indonesia

INTRODUCTION

In India:Area: W.B. > U.P.>Bihar > M.P.Production: W.B. > U.P. > A.P.>PunjabProductivity: Punjab > Haryana > T.N. > A.P.

Rice crop belongs to gramineae family which have six stamens.Test weight of rice is 25 g Rice is self pollinated and short day plant.cordinal temperature for rice production 30-32 0C.First rice variety T.N. 1 (Tiachung native 1) cross between Dee-geo-woo-gen x Tasai-yung-chung.Miracle rice in India is Jaya. In India, 56.68% of total rice area is grown on irrigated land, 27.21% on rainfed lowland and 5% on rainfed uplands (Rice Knowledge Management Portal,Hyderabad, 2012).

Jagannath is the first mutant variety of rice in India.

Heterosis breedingHeterosis :The term heterosis given by Shull (1914), refers to the superiority of F1 hybrid over its parents with respect to yield, growth rate, vigour etc.

Expression of heterosis is confined to the first generation only. Thus, farmers have to buy fresh seeds every season to raise a commercial crop.

Heterosis may be positive or negative. Both positive and negative heterosis used in crop improvement depend on the breeding objectives. For example, positive heterosis is desired for yield, but we look for negative heterosis for traits like days to maturity and plant height.

History• Kolreuter (1763)- hybrid vigour in tobacco.• Darwin (1876)- unrelated plant type (hybrid were more

vigorous).• Beal (1877-1882)- Intervarietal hybrids in maize.• East & Shull (1908)- given idea of over dominance is

cause of hybrid vigour.• Shull (1914)- used the term heterosis.• Schnell (1982)- heterosis is widely used phenomenon.

Types of heterosis

Midparent (%) Heterobeltiosis (%) Standard heterosis (%) F1- MP F1 – BP F1- SV —————— x 100 , ——————— x 100 , ——————— x 100 MP BP SV

Heterosis

Genetic basis of heterosis: Two major hypothesis have been proposed to explain

the genetic basis of heterosis : dominance hypothesis (Davenport, 1908) and over dominance hypothesis (East, 1908 and Shull, 1908).

Dominance hypothesis:

Model of heterosis- Aa=AA>aa

Davenport (1908) stated that heterosis is due to the accumulation of dominant genes in a hybrid derived from the two parents.

P1 X P2

AAbbCCdd aaBBccDD

AaBbCcDd(4 dominant genes)

Over dominance hypothesis: East (1908) and Shull (1908) stated that heterozygotes (Aa) are more vigorous and productive than either homozygous (AA or aa). This has been proven in traits controlled by single or few genes. Heterozygotes perform a given function, over a range of environments, more efficiently than either homozygotes. (East, 1936).

Model of heterosis-Aa>AA or aa

Epistasis (Gowen, 1952):Influence of one locus on the expression of another may be

involved in heterosis. Yet, the magnitude of epistatic variance is difficult to estimate, and may play a very important role in heterosis.

Molecular changes at epigenetic, genomic, proteomic and metabolic levels lead to heterosis traits.

A CAUSE OF HETEROSISEPIGENETICS AS

“Epigenetics” refers to heritable (through mitosis or meiosis) alterations in gene expression that are independent of DNA sequence: different epigenetically regulated forms of a gene are known as epialleles.

In addition, local chromatin status, mediated through epigeneticmodification, can potentially affect gene expression in cis (at the gene itself) or in trans (by regulating loci indirectly).

TYPES

DNA METHYLATION

HISTONEMODIFICATION

RNAINTERFERANCE

siRNAs, miRNAs etcCHROMATIN REMODLING

Hybrid rice is the crop grown from F1 seeds of cross between two genetically dissimilar parents.

Hybrid Rice

Hybrid Rice?Hybrid Rice?

Normal Rice Spikelet(self pollinated crop)

Sterile Rice Spikelet(Male Sterility)

Hybrid Seed Production(Male Sterile x Normal Rice)

Rice is strictly self-pollinated crop. Therefore, for developing commercial rice hybrids, use of a male sterility system is essential.

Male sterility?Male sterility?

• An inability to produce or to release functional pollen as a result of failure of formation or development of functional stamens, microspores or gametes (Kaul 1988).

Male Sterility System in Rice

The following genetic and non-genetic male sterility systems are known for developing rice hybrids:

Cytoplasmic-genetic male sterility. Environmental-sensitive genetic male sterility. Chemical-induced male sterility.

The use of male sterility system is a pre-requisite for commercial exploitation of heterosis in rice. Though several male sterility systems are known to occur in rice, cytoplasmic genetic male sterility has been widely used for developing rice hybrids. Recent discovery of a genetic male sterility mechanism influenced by environmental factors is getting serious attention from hybrid rice breeder. To a limited extent, chemical gametocides have also been used to induce male sterility in rice.

Male sterility systems:

It is caused by an interaction between present in cytoplasm and the nucleus. Absence of a sterility inducing factor either in the cytoplasm or in the nucleus makes a line male fertile.

Cytoplasmic genetic male sterility

Procedures for identifying a CMS source CMS source can be identified in- Intervarietal reciprocal crosses Interspecific crosses

Identifying CMS source in inter-varietal crosses

Differences in reciprocal cross between varieties with respect to male sterility is attributed to the cytoplasmic – genetic interaction. Example- Chinsurah Boro-11 Source

Identifying CMS sources in interspecific cross: Crossing between wild species and cultivated varieties can

also help to identifying new CMS sources.

Identification of new CMS sources in interspecific crosses

Some sources of male sterility inducing cytoplasmic type in rice

Designation Cytoplasmic source First nuclear donorCMS-WA Wild rice with abortive pollen Zhen shan 97 V20, V41

CMS-DA Dwarf wild rice with abortive pollen Xue Oin Zhao

CMS-IP Indonasian paddy 11-32CMS-DT Dessi type 297CMS-HL Hong lian Lian – Tana ChaoCMS-KR Otyza rufipogon Taichung 65CMS-BT Chinsurah boro 11 Taichung 65CMS-TN TN 1 Pankhari 203

CMS-GAM Gambiaca Chao yang 1

CMS-ARC Assam rice collection IRRI Acc-13829 IR 10179-3-2-1

CMS- O. perennis O. perihas, Acc. 104823 IR 64R

The most common used cytoplasmic sterility sources are WA, , DT, DA and IP.

Characteristics of a commercially usable line

An ideal CMS line should have:

- Stable male sterility over environments - Adaptability to target environments for which rice hybrid

is to be developed,- Easy restorability, so that many elite lines can be used

for male parents,- Good out-crossing ability to result in higher seed yield,- Good combining ability,- Good grain quality so that rice hybrids can be

developed with acceptable grain quality.

Among all the male sterility systems, the CMS system is most effective and proven method towards commercial hybrid rice production.

Advantage of the CMS

Disadvantage of the CMS system

Seed production is quite cumbersome as it is done in two steps, i.e. A x B multiplication and A x R F1 production.The choice of male parents is limited to only those genotypes which are identified as restorers. Some times the sterility inducing cytoplasm exerts adverse negative effects on the expression of agronomic traits.A CMS system may cause genetic vulnerability of the diverse hybrids if this system gets associated with susceptibility to a biotic stress.

Environmental sensitive Genic male sterility (EGMS)Environmental sensitive Genic male sterility (EGMS)

PGMS (Photoperiod sensitive genic male sterility): it includes genic male sterile lines which respond to the photoperiod or duration of day length for expression of pollen sterility and fertility behaviour, for example, most of the PGMS lines remains male sterile under a long day (> 13.45 hrs) condition and revert back to fertility under short day (< 13.45 hrs) condition.Eg. Nongken58STGMS (Thermosensitive genic male sterile lines): These are male sterile lines whose male sterility/ fertility alteration is conditioned by different temperature regimes. For example, most of the TGMS lines remain male sterile at a high temperature (23.30 C or higher for rice TGMS line Pei-Ai645) and they revert back to partial fertility at a lower temperature (< 23.30 C). The critical sterility/ fertility points vary from genotype to genotypes;

This is a genetic male sterility system in which sterility expression is conditional by environmental factors.

Types of EGMS There are two types of EGMS which are currently being used in rice:

Maintenance of TGMS Line

Location A(<20 C)

Location B(>30 C)

Line-5460S

TGMS Line

Line-5460S MF Line

Hybrid Seed

x

MF-Selfing

TGMS and Two-line Hybrid

Based on the Based on the discovery of discovery of P(T)GMS mutantP(T)GMS mutant

Male sterility Male sterility controlled by 1 or controlled by 1 or 2 pairs of 2 pairs of recessive gene(s)recessive gene(s) Fertile

S-lineMultiplication

Critical Fertility Point

Critical Sterility Point

Reproductive Upper Limit

Reproductive Lower Limit

SterileF1 Seed

Production

Partial Sterility

Model of Sterility / Fertility Expression for TGMS Rice

Temperature

low

high

(Virmani and Sharma, 1993)

Some EGMS lines identified

EGMS lines PGMS TGMS

Nongken 58 S (China) Annong 810 S (China)EGMS (USA) Hennong S (China)

201 (USA) 5460 S (China)CIS 28 – 10 S (China) R 59 TS (China)

Zhenong S (China) Norin PL 12 (Japan)X 88 (Japan) IR 32 364 (IRRI)

PEIAI S (China) IR 68945 (IRRI)7001 S (China) IR 68949 (IRRI)

Advantage of EGMS Lines

• Maintained by selfing

• Any male fertile line can be used

• So, they require only two lines

• No negative effects which are associated with CMS and GMS lines

• Consequently, seed production is simpler and cheaper

Chemical induced male sterility

The ideal gemetocide -Selectively induce male sterility without adversely affecting the female fertility.Must not be mutagenic.Have a broad range of affectivity in order to withstand adverse environmental conditions.Should consistently produce complete (>95%) male sterility. Should not be hazardous to the environment.

This non-genetic method of inducing male sterility involves the use of chemical called hybridizing agents (CHA) or gametocides. This method is very useful for plant with bisexual flowers in which it is difficult to obtain genetic or cytoplasmic genetic male sterility.

Important gemetocides found useful in rice are given below

Chemical Concentration Growth stage for applicationEthrel 800-1000 ppm Prior to anthesis

Zink methyl arsenate (MGI)

0.02 % or 2000 ppm Uni-nucleate pollen stage

Sodium methyl arsenate (MG2)

0.02 % or 2000 ppm Five days before heading

For developing hybrids by using gametocides: The female line should have a synchronous flowering habit. The line should respond to chemical treatment. The parent should possess good out crossing trait.

Important factors that decide the efficiency of chemical gametocides are:

The correct dosage of the chemical. Appropriate stage of treatment

Hybrid rice technology

ICAR launched a mission mode project on hybrid rice in December, 1989. The research network consist of 11 active research centers and many voluntary centres spread across the country78 rice hybrids have been released in the country so far. Out or these, 38 have been developed by the public sector and 40 are from private sectors.The first superfine grained aromatic hybrid Pusa RH 10 is becoming popular in basmati belt of north-western India.Narendra Usar Sankar Dhan -3 is the first hybrid released for saline-alkaline soils of Uttar Pradesh. DRR 2 and pant Sankar Dhan-3 are the promising early hybrids. It is estimated that around 3+ Million Hectares is under Hybrid Rice cultivation in India in 2016 which is around 7% of the Total Rice cropped area in India.

Rice Hybrids Year of release Duration (Days)

Yield (t/ha) Developed by Recommended for

SOME Rice hybrids released in India

. APHR 1 1994 130-135 7.14 APRRI, Maruteru (ANGRAU), Hyderabad Andhra Pradesh

. APHR 2 1994 120-125 7.52 APRRI, Maruteru (ANGRAU), Hyderabad Andhra Pradesh

. MGR 1 1994 110-115 6.08 TNAU, Coimbatore Tamil Nadu

. KRH 1 1994 120-125 6.02 VC Farm , Mandya, UAS, Bangalore Karnataka

PHB 71 1997 130-135 7.86 Pioneer Overseas Corporation, Hyderabad Haryana, U.P., T. N., A.P., Karnataka

Narendra Sankar Dhan 2 1998 125-130 6.15 NDUAT & T, Faizabad Uttar Pradesh

Pusa RH 10 2001 120-125 4.35 IARI, New Delhi Haryana, Delhi, Western U.P. and Uttarakhand

HKRH-1 2006 139 9.41 RARS,Karnal (CCSHAU) Haryana

JRH-4 2007 110-115 7.50 JNKVV, Jabalpur Madhya Pradesh

Indira Sona 2007 120-125 7.0 IGKKV, Raipur Chhattisgarh

JRH- 8 2008 105-110 7.50 JNKVV, Jabalpur Madhya Pradesh

Arize Tej (HRI 169) (IET 21411) 2012 125 7. 0 Bayer Bio Science Pvt. Ltd, Hyderabad – 81. Bihar, Chhattisgarh, Gujarat, Andhra

Pradesh, Tamil Nadu and Jharkhand Arize 6444 Gold (HRI-174) (IET- 22379) 2015 130-135 NA Bayer Crop Science, Hyderabad

Assam, Chhattisgarh, Odisha, Uttar Pradesh, Bihar, Meghalaya, Karnataka and Tamil Nadu Source- DIRECTORATE OF RICE DEVELOPMENT, PATNA

Resistance/ tolerance of some released hybrids/ verities to major pests and diseases

Activity Resistant TolerantKRH-1 - Blast DRRH-1 Blast -KRH-2 Blast, Sheath rot -Sahyadri - BLBNSD-2 Blast BLB, Sheath RotPHB-71 - Blast, BLB, BPHPA-6201 Blast BPHHRI-120 (6444) Blast, WBPH BLB, Sheath Rot, BPH, GMPusa RH-10 BLB, BPHRH-204 BPH, WBPHAjay (CRHR) BLB, PBH, WBPH, GMPant Sankar Dhan-3 BLB, RTV, WBPHRajalaxmi (CRHR) BLB, BPH, WBPHNarendra Usar Hybrid BLB, BPH, WBPH

Advantages

• Hybrid varieties exploit both GCA and SCA components of heterosis

• Hybrid varieties yield 25-30% more than pure line varieties

• Employment generation• It is Greater resistant to biotic and abiotic

stresses• It is having faster growth rate• Earlier flowering and maturity

Constraints

High cost of hybrid seed Rs. 115-120/kg Farmer have to perchase new hybrid seed every year Non availability of hybrid seed in sufficient quantity. Quality of hybrid rice yet not comparable to inbred varieties.

There is a storage of skilled man power at the initial stages of seed production technology. Seed production can only be successful if it is supervised by well trained techniques and carried out by experienced growers.

Hybrid rice seed production requires a well organized seed industry, we still don’t have this.

The linkage between public sector research institute and seed production agencies working on hybrid rice is weak.

• To reduce the seed cost, two line system should be applied

• Proper technique should be adopted to enhance hybrid seed production per unit area

• Enhancing heterosis by crossing Indica X tropical Japonica rice

• Qality traits improvement• Hybrid rice should also develop specificly for drought ,

salinity and other abiotic stresses• Hybrid for longer duration should also be targeted for

replacing mega varieties like BPT 5204 and MTU 7029

Future prospects of hybrid rice technology

Rice is one of the most important staple foods.Hybrid rice exploits the phenomenon of hetrosis which can increase the yield potential over HYVs.

Heterosis Breeding is the one of the strongest tool for breeder to complete targated demand of 2030As Rice is self pollinated species male sterility is essential for hybrid rice production.In India, hybrid rice production mainly depend on CGMS system.The priority is given to maintain the purity of parental line.Heterosis is result of interacting genomes, resulting in complex changes at the genetic, epigenetic, biochemical and regulatory network levels

Genetic and molecular approaches lead to the characterization of the biological mechanisms of heterosis Improvement in hybrid rice seed production technology will further reduce the cost of hybrid rice seed. Hybrid rice seed production technology is both labour and knowledge intensive. This will also generate more and more employment.

CONCLUSIONCONCLUSION