Rice (Oryza sativa L. 2n = 2x = 24) is a staple food for over half of the world's populationproviding 43% of calorie. Rice yield has experienced many fold jumps since the 1950s. This happened primarily as the result of genetic improvement and increasing harvest index by reducing plant height using the semi-dwarf genes and utilization of heterosis by producing hybrids. Heterosis is the improved or increased function of any biological quality in a hybrid offspring. An offspring exhibits heterosis if its traits are enhanced as a result of mixing the genetic contributions of its parents. Genetic basis of heterosis included overdominance, dominance, and additive effects.

1. Course Seminar
On
Heterosis breeding in rice (Oryza sativa L.)
Supervisor
Prof. S.K. Singh
Student
Monika Singh
ID. No. G-15113
DEPARTMENTOF GENETICS AND PLANT BREEDING
Institute of Agricultural Sciences
BHU, Varanasi.

2. 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. CHA
5. status of Hybrid rice technology
6. Advantages of Hybrid rice
7. Constraints
8. Future Prospects
9. Conclusion

3. 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

4. In India:
Area: W.B. > U.P.>Bihar > M.P.
Production: W.B. > U.P. > A.P.>Punjab
Productivity: 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 0
C.
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.

5. HeTeROsIs bReeDINg
Heterosis :
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.

6. 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.

7. 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).

8. 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)

10. 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.

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

12. A CAUSE OF HETEROSIS
EPIGENETICS 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 epigenetic
modification, can potentially affect gene
expression in cis (at the gene itself) or in
trans (by regulating loci indirectly).
TYPES
DNA
METHYLATION
HISTONE
MODIFICATION
RNA
INTERFERANCE
siRNAs, miRNAs etc
CHROMATIN REMODLING

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

14. 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.

15. 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).

16. 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:

17. 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

18. 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

19. 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

20. Some sources of male sterility inducing cytoplasmic type in rice
Designation Cytoplasmic source First nuclear donor
CMS-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 11-32
CMS-DT Dessi type 297
CMS-HL Hong lian Lian – Tana Chao
CMS-KR Otyza rufipogon Taichung 65
CMS-BT Chinsurah boro 11 Taichung 65
CMS-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.

22. 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.

23. 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.

24. 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. Nongken58S
TGMS (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:

25. 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

26. TGMS and Two-line Hybrid
 Based on theBased on the
discovery ofdiscovery of
P(T)GMS mutantP(T)GMS mutant
 Male sterilityMale sterility
controlled by 1controlled by 1
or 2 pairs ofor 2 pairs of
recessiverecessive
gene(s)gene(s)
Fertile
S-line
Multiplication
Critical Fertility Point
Critical Sterility Point
Reproductive Upper Limit
Reproductive Lower Limit
Sterile
F1 Seed
Production
Partial Sterility
Model of Sterility / Fertility Expression for TGMS Rice
Temperature
low
high
(Virmani and Sharma, 1993)

27. 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)

28. 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

29. 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.

30. Important gemetocides found useful
in rice are given below
Chemical Concentration Growth stage for application
Ethrel 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

31. 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 country
78 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.

32. 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 NaduSource- DIRECTORATE OF RICE DEVELOPMENT, PATNA

33. Resistance/ tolerance of some released hybrids/ verities to major pests
and diseases
Activity Resistant Tolerant
KRH-1 - Blast
DRRH-1 Blast -
KRH-2 Blast, Sheath rot -
Sahyadri - BLB
NSD-2 Blast BLB, Sheath Rot
PHB-71 - Blast, BLB, BPH
PA-6201 Blast BPH
HRI-120 (6444) Blast, WBPH BLB, Sheath Rot, BPH, GM
Pusa RH-10 BLB, BPH
RH-204 BPH, WBPH
Ajay (CRHR) BLB, PBH, WBPH, GM
Pant Sankar Dhan-3 BLB, RTV, WBPH
Rajalaxmi (CRHR) BLB, BPH, WBPH
Narendra Usar Hybrid BLB, BPH, WBPH

34. 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

35. 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.

36. • 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

37. 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 2030
As 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