asexual seed formation in plants centre for cellular & molecular biology hyderabad, india imran...
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Asexual Seed Formation in Plants
Centre for Cellular & Molecular BiologyHyderabad, India
Imran Siddiqi
WAAS 2008 – Biotechnology in the Anthropocene
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The Sexual Life Cycle
Adult
Gametes
Zygote
Seeds
2n2n
1n
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Apomixis: Asexual Seed Formation
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Asexual Reproduction in Animals: Parthenogenesis
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• Asexual Reproduction Occurs Under Conditions Where Sexual Reproduction is Unfavourable
• The Capacity for Asexual Reproduction is Embedded in Sexual Organisms and Has Adaptive Value
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Apomixis – Seed Development Without Meiosis and Fertilization
Apomeiosis – Formation of an unreduced female gamete (egg).
Parthenogenesis – Development of the egg cell into an embryo without fertilization by sperm.
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Potential For Apomixis in Plant Breeding:
• Fixation of genetic character in successive generations
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Hybrid Vigour: Hybrids Show Increased Vigour But Don’t Breed True
Parent 2
Parent 1X Hybrid
Selection,Inbreeding
F1 P2P1
Hybrid Vigour
10-15%
20-25%
Wheat
Rice
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F1P1 Parent 2
Parent 1
Apomixis Would Fix Hybrid Vigour Over Successive Generations
P2P1 Hybrid P2P1 P2P1
X
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Potential for Apomixis in Plant Breeding:
Fixation of genotype (hybrid vigour) – Nawaschin and Karpachenko (1930)
• Reduced cost of hybrid seed production
• Successive progagation of hybrids
• Accelerated breeding
• Encourage “risk” in breeding practice
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Hybrid Vigour
10-15%
20-25%
Wheat
Rice
Apomixis is rice: 3.4 b$ /yr
Value of Apomixis
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Strategies for Transfer of Apomixis To Food Crops:
Apomixis is a modified sexualpathway
Genes from sexual plants
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Normal dyad mutant
Mutation in a gene called DYAD shows female sterility
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Seeds produced by dyad have an extra setof chromosomes (triploid)and arise from
fertilization of an unreduced (Apomeiotic) female gamete
mitosis mitosismeiosis meiosis
Triploid (3n = 15) Diploid (2n = 10)
No. of plants: 17 2
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Conclusion:
Proof of principle demonstration for generating a functional component of apomixis (apomeiosis) in a sexual plant by altering a gene of known molecular identity – a first step towards synthesisof apomixis in crops
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Credits:
CCMB Funding:CSIR; Department of Biotechnology;
Maruthachalam Ravi
Mohan P. Anand
Bhavna AgasheV. SubbiahGopal Ganesh
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