Hybrid Rice Breeding & Seed Production

FANGMING XIE

International Rice Research InstituteDAPO BOX 7777

Metro Manila, Philippinesf.xie@cgiar.org

What is Hybrid Rice?

The first generation offspring of a rice cross between two genetically diverse parents

How Hybrid Rice?

Normal Rice Spikelet(self pollinated crop)

Sterile Rice Spikelet(Male Sterility)

Hybrid Seed Production(Male Sterile x Normal Rice)

Why Hybrid Rice?

Heterosis (Hybrid vigor) Application to Increase:• Productivity (yield/unit/time, 15-20% of

yield advantage), and• Economic returns

HeterosisA universal phenomenon that F1

generation shows superiority to both parents in agronomic traits or yield

It presents in all biological systems and has been exploited commercially in many agricultural crops.

How to Measure heterosis?

Mid-Parent (MP) heterosis(F1 performs better than mean of two parents):

F1-MP MP

X100

Better Parent (BP) heterosis(F1 performs better than better parent):

Standard heterosis*(F1 performs better than the check variety):

F1-BP BP

X100

X100F1-CK CK

* Standard heterosis is the most useful term in commercial crop production

Male Sterility Systems in Rice

Male sterility: a condition in which the pollen grain is unviable or cannot germinate and fertilize normally to set seeds.

Male Sterility Systems (genetic and non-genetic): Cytoplasmic genetic male sterility (CMS)

Male sterility is controlled by the interaction of a genetic factor (S) present in the cytoplasm and nuclear gene (s).

Environment-sensitive genic male sterility (EGMS)Male sterility system is controlled by nuclear gene expression, which is influenced by environmental factors such as temperature (TGMS), daylength (PGMS), or both (TPGMS).

Chemically induced male sterilityMale sterility is induced by some chemicals (gametocides)

Brief history of hybrid rice

1926 - Heterosis in rice reported 1964 - China started hybrid rice research 1970 - China discovered a commercially usable genetic tool for hybrid rice

(male sterility in a wild rice = Wide Abortive ) 1973 - PTGMS rice was found in China 1974 - First commercial three-line rice hybrid released in China 1976 - Large scale hybrid rice commercialization began in China 1979 - IRRI revived research on hybrid rice 1981 - PTGMS rice genetics and application was confirmed 1982 - Yield superiority of rice hybrids in the tropics confirmed (IRRI) 1990s - India and Vietnam started hybrid rice programs with IRRI 1991 - More than 50% of China’s riceland planted to hybrids 1994 - First commercial two-line rice hybrid released in China 1994 - 1998 - Commercial rice hybrids released in India, Philippines Vietnam

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Rice and Hybrid Rice Production in China

Rice Grain Yield in China

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Hybrid rice Inbred rice

Rice Grain Yield in China

Hybrid Rice Area in other Asia Countries

Country Hybrid Rice Area (1,000 ha)

1997 2001 2004 2005 2006

Bangladesh 15 50 90 150 (Exp)

India 100 200 560 NA

Indonesia 10 NA

Myanmar 2 42 NA

Philippines 13 189 367 300(DS)

Vietnam 188 480 650 NA

Total 288 710 1,445

Hybrid Rice Production in Vietnam

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Are a (1000 ha ) Hybrid Rice Yie ld (t/ha ) Na tiona l a ve ra ge rice yirld (t/ha )

Two Commercial Systems for Hybrid Rice

Requirements for 3 Lines in CMS System

A-line Stable Sterility Well developed floral traits for outcrossing Easily, wide-spectum, & strongly to be restored

B-line Well developed floral traits with large pollen load Good combining ability

R-line Strong restore ability Good combining ability Taller than A-line Large pollen load, normal flowering traits and timing

TGMS and two-line hybrid

Based on the discovery of P(T)GMS mutant

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

FertileS-line

Multiplication

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

Elite CM S line SO URCE NURSERY Elite lines from different sources

To evaluate parents and m ake testcross B & R line Breeding Program

P line Breeding Progam

CM S BACKCRO SS NURSERY TESTCRO SS NURSERY

BC2- BC4, CMS Evaluation To identify B, R & P lines R & P Line

Backcross CMS pairs (BC1)

Prem arily heterosis evaluation, 2 rows w/ parent Hybrid Seed Production for O YT

Iso lation Bags or hand-crossing

AxB Paircross RETESTCROSS NURSERY (O YT)

Breeder Seeds Re-evaluate F1 hybrids

Stage 1, 1 rep, 3 rows Hybrid Seed Production for PYT

Isloated Net or bags

AxB Increase Prelim inary Yield Trial (PYT)

Core Seeds Stage 2, 1 rep, plot

Hybrid Seed Production for AYT & NYT

AxB Seed Production Advanced Yield Trial (AYT) Isolation B lock

Foundation Seeds Stage 3, 3 reps, p lot

AxB Seed Production National Yield Trial Hybrid Pilot Seed Production

Certified Seeds Stage 4, 3-4 reps, m uti-location, 2-years Isolation B lock

A & B Line Release O n-Farm Trial (Strip Trial) Hybrid and R line Release

Flow chart of 3-Line Hybrid Rice Evaluation and Seed Production

SO UR CE N U R SE RY Elite lines from d ifferent sources

TG M S L in e B reed ing T o evalua te paren ts and m ake tes tcross B & R line B reed ing Program

P ollinator lin e B reeding Progam

B reeder Seeds TES TCR O SS N U R SER Y

To identify TG M S & P lines H ybrid Seed P rodu ctio n for O YT

C ore Seeds P rem arily heterosis eva luation , 2 rows w/ parent Iso la tion Bags o r hand-crossing

F ound ation Seed R ETES TCR O S S NU RS ER Y (O YT)

R e-evaluate F1 hybrids Hybrid Seed Prod uction for PYT

C ertified S eeds Stage 1, 1 rep, 3 row s Is loated Net or bags

TG M S Line R elease Prelim inary Y ield Tria l (PYT)

Stage 2 , 1 rep, p lo t H ybrid Seed Pro duction for AYT & N YT

Iso la tion B lock

Advanced Y ield Tria l (AYT)

Stage 3, 3 reps, p lo t

Hybrid P ilot S eed Production

N ational Y ield Tria l Iso la tion B lock

S tage 4, 3-4 reps, m uti-location, 2-years

H ybrid an d R line R elease

O n-Farm Tria l (S trip Tria l)

Flow chart o f 2 -L ine H ybrid R ice E va luation and S eed P roduction

Advantage & Disadvantage of 3-line hybrid rice system

AdvantagesStable male sterility

DisadvantagesLimit germplasm source (CMS, Restorer)

Dominant CMS cytoplasm in large area (WA) One more step for parental seed productionTime consuming of CMS breeding

Advantage & Disadvantage of 2-line hybrid rice system

Advantages Simplified procedure of hybrid seed production Multiple and diverse germplasm available as parents

Any line could be bred as female97% (2-line) vs 5% (3-line) of germplasm as male

Increased chance of developing desirable & heterotic hybrids

Multiple cytoplasm courses as female parents

Disadvantages Environmental effect on sterility could cause seed purity

problem

Two-line hybrid production in China

Tw o Line Hybrid Rice In China

6200

6400

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2-line Hybrid Y ield A ll Hybrid Y ield Area

H y b r id R ic e S e e d S ta n d a r d (G B 4 4 0 4 .1 - 1 9 9 6 , C h in a )

P u r i t y C le a n l in e s sG e r m in a t io n( > % ) ( > % ) ( > % )

S t e r i le L in e

1 3 .0 ( in d ic a )

1 4 .5 ( ja p o n ic a )

R e s t o r e

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2 n d 9 6 .0H y b r id

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9 9 .9

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C la s sS e e d

M a ia n t a ie r

C o r e

F o u n d a t io n

Hybrid Rice Seed Standard

Mission of IRRI Hybrid Rice Program

Developing germplasm, parents and hybrids as internationally public goods

Research new technology for breeding and seed production

Collaboration with NARS and private sectors in hybrid rice research and production

Promotion of exchange of information, technology, scientist and germplasm

Strategy of IRRI Hybrid Rice Program

Focusing on conventional tools and integrate them with proven non-conventional methods to develop the technology

Developing parental lines, especially female parents with high outcrossing and high quality, to promote hybrid rice spreading

Facilitating development of close partnership between public and private sectors in national programs

Intensifying agronomic research to get maximized manifestation of heterosis in hybrids

Release of IRRI Hybrids in Different Countries (1994-2005)

IRRI Hybrid Released as Country Year released

IR64610H MGR-1 India 1994

IR64611H KRH-1 India 1994

IR64616H Magat Philippines 1994

IR65489H DRRH-1 India 1996

IR68284H Mestizo 1 Philippines 1997

IR69690H Sahyadri India 1998

IR69690H HYT-57 Vietnam 1999

IR69690H BRRI Dhan Hybrid 1 Bangladesh 2001

IR69690H Rokan Indonesia 2002

IR75207H Mestizo 2 Philippines 2002

IR75217H Mestizo 3 Philippines 2002

IR78386H Mestizo 7 Philippines 2005

Release of Hybrids by using IRRI Germplasm in Different Countries (1994-2004)

Hybrid name CountryYear

released

APHR-1 India 1994

APHR-2 India 1994

CNRH-3 India 1995

KRH-2 India 1996

Pant Sankar Dhan-1 India 1997

ADTRH-1 India 1998

CORH-2 India 1998

Narendra Sankar Dhan-2 India 1998

Rokan Indonesia 2002

Maro Indonesia 2002

Hipa 3 Indonesia 2004

Hipa 4 Indonesia 2004

Hybrid name CountryYear

released

Biganti Philippines 2004

Intani 1 Indonesia 2001

Intani 2 Indonesia 2001

PHB-71 India 1997

Proagro 6201 India 2000

HR 120 (6444) India 2001

Hybrids released by NARS using IRRI-bred CMS lines

Hybrids derived from IRRI-bred parental lines and commercialized by private sector

Germplasm Shared

“Super high-yielding” hybrid rice breeding in China

P ro g re s s o f " S u p e r H ig h -Y ie ld in g " H y b r id R ic e P r o g ra m in C h in a

S ta g e Y ie ld ( t /h a ) Y e a r s B r e e d in g C o m m e r c ia liz a t io n

S ta r t 8 .2 5 1 9 9 7

P h a s e I 1 0 .5 1 9 9 6 - 2 0 0 0 F in is h e d L a r g e a r e a e x te n s io n

P h a s e I I 1 2 .0 2 0 0 0 - 2 0 0 5 F in is h e d S ta r te d

P h a s e I I I 1 3 .5 2 0 0 5 - 2 0 1 0 S ta r te d

G o a l (s in g le -s e a s o n ) P r o g r e s s (2 0 0 6 )

Morphological Model of Super High-yielding Hybrid Rice

Plant height = 100 cm, with culm length = 70 cm Uppermost three leaves:

Flag leaf, long, 50 cm, higher than the panicle top 20 cm. The 2nd leaf from the top: 10% longer than the flag leaf, and over the top of the panicle. The 3rd leaf = the middle position of the panicle

Erect: the leaf angles of the flag, 2nd and 3rd leaves are around 5, 10, 20 degrees, till mature

Narrow, V-shape and thick: narrow with 2 cm when flattened. Plant type: moderate compact with moderate tillering capacity; drooping

panicles after filled, above ground ~ 60 cm, erect-leaved canopy without appearance of the panicles

Panicle weight and number: grain weight per panicle = 5 g, 2.7 million panicles per hectare.

Leaf area index (LAI) and ratio of leaf area to grains: the LAI is ~ 6.5 based on the uppermost three leaves, the ratio of leaf area to grain weight is 100 : 2.2-2.3, meaning that to produce 2.2-2.3 grams of rice, 100 cm2 of the upper three functional leaves are needed.

Harvest index > 0.55

Hybrid Heterosis in Rice

Indica x japonica

Indica x javanica

japonica x javanica

indica x indica

japonica x japonica

Inter-subspecific hybrid rice breeding

Difficult in breeding inter-subspecific hybrid rice Low seed set Tall plant height Poor grain-filling Late maturity Grain quality market

Solution for breeding of inter-subspecific hybrid rice wide compatibility (WC) genes allelic dwarf gene indica/javanica hybrids in indica rice growing region japonica/javanica hybrids in japonica rice growing

Future Opportunity: Enhance yield heterosis

Exploiting subspecies heterosis Applying biotechnology for parent selection (heterotic groups

and/or heterotic gene blocks

Enhanced yield heterosis in indica / NPT hybrids compared to indica / indica hybrids (retestcross, IRRI, 2004WS)

Hybrid # of heterotic hybrids

Total # of hybrids

% of heterotic hybrids

Yield advantage (%) over best inbred check

Range Mean

indica / indica 34 85 40 1-80 29

Indica / NPT 20 40 50 6-131 42

Performance of hybrid seed production in tropical countries (2003-2004)

Yield (kg/ha)Country Mean RangeIndia 1,600 1,000 – 4,500

Vietnam 2,000 1,500 – 3,500

Philippines 810 (04DS) 600 – 2,000

Bangladesh 800 600 – 2,000

Indonesia 500 300 – 1,600

China 2,750 1,500 – 6,000

Future Opportunity:Increase yield of hybrid seed production

Developing high outcrossing parents Improving seed production technology Training seed growers Selecting adequate location / season

Hybrid Rice Seed Production in China

Hybrid Rice Seed Production in China

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Hybrid Rice Seed ProductionIn Asia In United Sates

Measurements of Rice Grain Quality: Milling yield

Total milling yieldWhole milling yield

Chalk Amylose content Gel Temperature (ASV) Length, width, L/W Protein Aroma

Future Opportunity:Improve hybrid rice grain quality

Rice grain quality of inbreds and hybrids*

Trait Inbred Hybrid

Total Milling (%) 69.1 68.2

Whole Milling (%) 48.7 45.4

Chalk (%) 13.5 20.6

Amylose (% 19.8 20.6

GT 4.3 5.5

Length 6.9 7.1

L/W 3.2 3.3Data from National Cooperative Testing (NCT), Philippines, 2004-2005

Future Opportunity:Improve hybrid rice grain quality

Difference of Whole Milling Yield and Chalk between Inbreds and Hybrids

Whole Milling Yield and Chalk in Hybrids and Inbreds(NCT, 2004-2005, Philippines)

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Whole Milling Yield (%)

Ch

alk

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Hybrid Inbred

AverageWhole Milling (%)

Hybrid = 45.4Inbred = 48.7

Average Chalk (%)

Hybrid = 20.6Inbred = 13.5

Difference of Whole Milling Yield and Chalk between Inbreds and Hybrids

Data source: 2004 and 2005 NCT, Philippines

< 3 0 3 0 - 3 5 3 5 - 4 04 0 - 4 5 4 5 - 5 0

5 0 - 5 5> 5 5

In b r e d ( n = 1 6 )

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M i l l i n g Y i e l d R a n g e

D i s t r i b u t i o n o f W h o l e M i l l i n g Y i e l d

< 55 - 1 0

1 0 - 1 51 5 - 2 0

2 0 - 2 5> 2 5

In b r e d ( n = 1 4 )

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C h a l k R a n g e

D i s t r i b u t i o n o f C h a l k

IRRI DS 2004-5

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Full A lternate Wetting &drying

Drought

Ir r igation M ethod

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Hybrid (n=2) Inbred (n=6)

IRRI DS 2005

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Non-stress Stress

Environm ent

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Hybrid (n=3) Inbred (n=7)

Hybrids Have Substantially Improved Yield under Severe Lowland

Stress (ca. 1 t/ha). (IRRI, G. Atlin, 2005)

100% 43%83%

100% 89% 29%

18.1%

10.5%

78.6%

Yield advantage

100% 67%

100% 46%

1.9%

49.8%

Future Opportunity:Develop hybrids for unfavorable environments

Future Opportunity:Improve agronomic management and deployment strategy

ShanYou 63 grown under different nitrogen management (S. Peng, IRRI)

Unhealthy Healthy canopy