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

1. MOHIT DHUKIA
M.Sc. Ag 1st
Year
dhukia.mohit@gmail.com
CCS Haryana Agricultural University, Hisar

2. Hybrid rice
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 The Father of Hybrid Rice - Yuan Longping
 Hybrid rice is the crop grown from F1 seeds of cross between two
genetically dissimilar parents.
 Rice heterosis was first reported by Jones (1926) who observed that some
F1 hybrids had more culms and greater yield than their parents.

3.  Rice is the staple food of more than 60 % of the world population.
 Rice hybrids have shown 15-20 % higher yield potential than inbred rice
varieties under farmer’s field conditions.
 Hybrids have shown their ability to perform better under adverse
condition of drought and salinity .
 Rice hybrids increases profitability at the household level and will help in
achieving food security at the national level.
Importance of Hybrid Rice
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Area under Hybrid Rice in
Asia

4. Importance of Hybrid Rice
• Genetic enhancement for yield heterosis through exploitation
of New Plant Types (NPT).
• Most of the commercial hybrids now in cultivation belong to
intra sub specific group (indica/indica or japonica/japonica)
• Grain yield in rice exhibits heterosis ranging from 2 to 369%
(Virmani et al., 1981)
• Based on the experience that the magnitude of heterosis is
found in the order……
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Indica x Japonica
Indica x Javanica
Japonica x Javanica
Indica x Indica
Japonica x Japonica

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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).
• The use of a male sterility system is a prerequisite for
commercial exploitation of heterosis in rice.

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Male sterility used in hybrid rice
Cytoplasmic
genetic male
sterility
Environment
sensitive
genetic male
sterility
Chemically
induced
male
sterility
Transgenic
male
sterility

7. Cytoplasmic genetic male sterility
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• It is caused by an interaction between genetic factor(s) 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.

8. Procedure of transferring a CMS system into an elite maintainer line.
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9. History of Three-line hybrid rice system
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1964 - Research on three-line hybrid rice initiated in China.
1970 - A pollen abortive wild rice plant (shortly called wild abortive, i.e., WA) was
discovered among the plants of common wild rice (Oryza rufipogon Griff. L.) identified
by Yuan on Hainan Island in China
1971 - China’s Ministry of Agriculture (MOA) selected three-line hybrid rice technology
as one of 22 key research projects.
1972 - Prof. Yuan developed the first CMS line: Erjiunan 1A and also other CMS lines such
as Zhenshan 97A and V20A were developed all using WA as the donor of male sterile
genes and all using successive backcrossing method
1973 - Restorer lines such as Taiyin 1, IR24 and IR661 were screened out through direct
test crossing method
1974 - Hybrids with strong heterosis such as Nanyou 2 and Nanyou 3 (20% Higher Yield
then best commercial variety of that time) were released.
1976 - Hybrid rice commercialization started in China.
1980 - Shanyou63 developed by Prof. Xie, the largest one of growth area in 1980's.1980 - Shanyou63 developed by Prof. Xie, the largest one of growth area in 1980's.

10. Environment sensitive genetic male sterility
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This is a genetic male sterility system in which sterility expression is
conditioned by environmental factors.
• Types of EGMS
There are two types of EGMS which are currently being used in rice:
PGMS - Photoperiod sensitive genic male sterility
Genic male sterile lines which respond to the photoperiod or duration of day
length for expression of pollen sterility and fertility behavior. For example, most
of the PGMS lines remain male sterile under a long-day (>14 hrs) conditions
and revert back to fertility under short-day (< 14 hrs) conditions.
Example - N9044S and N5088S
TGMS - Thermo sensitive Genic Male Sterility
Genic male sterile lines whose male sterility/fertility alteration is conditioned
by different temperature scheme. For example, most of the TGMS lines remain
male sterile at a high temperature (>30°C) and they revert back to fertility at a
lower temperature (<24°C). The critical sterility/fertility points vary from
genotype to genotype.
Example - Norin PL12, ID24, IR32364

11. PGMS
• Further Studies revealed existence of 2 types of photoperiod sensitivities:-
1. FPR (First Photoperiod Reaction):-
Short day promotes panicle differentiation and heading while Long day either
delays or inhibit it.
Most sensitive phase is – End of primary rachis branch primordia development.
2. SPR ( Second Photoperiod Reaction) :-
Short day induce normal pollen development but Long day associated with
pollen sterility.
Most sensitive phase is – Between the initiation of secondary rachis branches
and completion of pollen mother cell (PMC) formation stage.

12. TGMS and Two-Line Hybrid

13. Two-line system hybrid rice
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14. History of Two-line hybrid rice system
1981- Spent eight years studying how photoperiod and temperature conditions affected
the male sterility of this material and announced his discovery as a
“ Dual-purpose rice line Nongken 58S ”
(1982 – 1986 ) - Many rice researchers studied the plant physiology, biochemistry, and
genetics of Nong-Ken 58s and it later known as HPGMR (Hubei Photoperiod-
sensitive Genic Male-sterile Rice)
1987 - Yuan proposed a strategy for the two-line system hybrid rice breeding using the
EGMS materials, including Nong-Ken 58S and China initiated a Collaborative Research
Project for exploitation of P(T)GMS lines
1973 - Shi Mingsong discovered the source material Nong-ken 58s for the two-line system
male sterile line in rice in Hubei, China
1994 – The first two-line hybrid Pei-Ai 64s showed remarkably strong heterosis (12.96
ton/ha) was released in China and this technology was successfully commercialized in
China. 14

15. Chemical Induced Male Sterility
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This non-genetic method of inducing male sterility involves the use
of chemical called hybridizing agents (CHA) or gametocides.
The ideal gametocides should :
 Selectively induce male sterility without adversely affecting the female
fertility.
 Have systemic effects so as to sterilize both early and late panicles.
 Have a broad range of effectivity in order to withstand adverse
environmental conditions.
 Have minimum side effects on plant growth and panicle development.
For developing hybrids by using gametocides :
- The female line should have a synchronous flowering habit
- The line should respond to chemical treatment
- The parents should possess good outcrossing traits

16. Important gametocides found useful in rice
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Chemical Concentration Growth stage for
application
Ethrel 8000-10,000 ppm Pre-boot and boot stage
Monosodium Methyl
Arsenate (MGI)
0.02 % or 2000
ppm
Uni-nucleated pollen
stage
Sodium Methyl
Arsenate
0.02 % or 2000
ppm
5 days before heading

17. Transgenic male sterility
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Also known as “ Third-generation” hybrid rice system.
 A new recessive nuclear male sterile rice mutant, Oryza sativa No
Pollen 1 (osnp1) is identified .
 OsNP1 encodes a glucose-methanol-choline-oxidoreductase
required for tapetum degeneration and pollen exine formation.
 The osnp1 mutant plant displays normal vegetative growth but
complete male sterility insensitive to environmental conditions.
 OsNP1 was coupled with an α-amylase gene to devitalize transgenic
pollen and the red fluorescence protein (DsRed) gene to mark
transgenic seed.

18. Transgenic male sterility
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Self-pollination of the transgenic plant carrying a single hemizygous
transgene produced non transgenic male sterile and transgenic fertile
seeds in 1:1 ratio
They can be sorted out based on the red fluorescence coded by
DsRed Cross-pollination of the fertile transgenic plant.
Fig. Panicle under bright field (BF) and a red fluorescence filter (RFP), respectively.

19. Super Hybrid Rice
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 Yuan proposed an ideal rice plant type with the following traits: long, erect,
narrow, V-shaped uppermost three leaves; and large, uniform, and droopy
panicles below a taller erect-leaved canopy.
 Developing Super hybrid rice varieties through morphological improvement
and the use of inter-subspecific (indica/japonica) heterosis.
Phase
Hybrid Rice
Yield
increase(%)
Early season Late season Single season
1996 level 7.50 7.50 8.25 0
Phase Ⅰ
1996-2000
9.75 9.75 10.50 More than 25%
Phase Ⅱ
2001-2005
11.25 11.25 12.00 More than 45%
Phase Ⅲ
2006-2015
NA NA 13.50 More than 60%
* Tons/ha at 2 sites with 6.67 hectares in each site in 2 consecutive years.
(Source: Yuan 2008)
Phase Ⅳ
2015-2020
NA NA 15.00 More than 100%

20. 1989- International Rice Research Institute (IRRI) proposed the plan of breeding ‘New
plant type rice’ (also called ‘super rice’) with the aim of getting yield up to 13 – 15
ton/ha.
1996 - China's MOA endorsed the Chinese “Super rice” program and the goal was to
upturn yield by at least 15% over control varieties.
More than 20 super rice varieties or hybrid rice combinations such as Liangyoupeijiu and
Xieyou 9308 were bred in this project.
1997- The MOA proposed a three-phase “super hybrid rice breeding” strategy as part of
the program (1996–2000, 2001–2005, and 2006–2015).
2000 - Phase I objective (10.5 t/ha) was achieved with release of hybrid such as
Liang-You-Pei-Jiu.
2004 - Phase II objective (12 t/ha) was achieved with release of hybrid such as Ming-You 8
and P88s/0293
2012- Phase III objective (13.5 t/ha) was achieved with yield increases of 60 %
History of Super Hybrid Rice
1982- Japanese government initiated the Super high- yielding rice breeding program and
varieties such as Akenohoshi and Akichikara, which attained nearly 10 ton/ha in the high
yielding areas, were established.

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 Major breakthroughs were made in molecular mechanism research
of rice heterosis in 2009.
 Used gene chip technology to carry out the super hybrid rice
LYP9 and its parents transcriptome studies and identifed potential
associated with super hybrid rice heterosis functional genes.
Super Hybrid Rice

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23. SYMBOL OF TRUST