1. WAAS 2008 – Biotechnology in the Anthropocene
Asexual Seed Formation in Plants
Centre for Cellular & Molecular Biology
Hyderabad, India
Imran Siddiqi

2. The Sexual Life Cycle 1n
Gametes 2n 2n
Zygote
Adult
Seeds

3. Apomixis: Asexual Seed Formation

4. Asexual Reproduction in Animals: Parthenogenesis

5. Asexual Reproduction Occurs Under Conditions
Where Sexual Reproduction is Unfavourable
The Capacity for Asexual Reproduction is Embedded
in Sexual Organisms and Has Adaptive Value

6. 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.
Apomixis is found in several plant species and can occur by different developmental mechanisms. There are two major components of apomixis: Apomeiosis and Parthenogenesis.

7. Potential For Apomixis in Plant Breeding:
Fixation of genetic character in successive generations
Navashin and Karpachenko in the 1930s pointed out that the transfer of apomixis to crop plants held many benefits to agriculture

8. Hybrid Vigour: Hybrids Show Increased Vigour
But Don’t Breed True
Parent 2
Parent 1 X
Hybrid
Selection,
Inbreeding F1 P2 P1
Hybrid Vigour
10-15%
20-25%
Wheat
Rice

9. Apomixis Would Fix Hybrid Vigour Over Successive
Generations
Parent 1 P2 P1
Hybrid P2 P1 P2 P1 F1 P1
Parent 2 X

10. 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
Navashin and Karpachenko in the 1930s pointed out that the transfer of apomixis to crop plants held many benefits to agriculture

11. Value of Apomixis Hybrid Vigour 10-15% 20-25% Wheat Rice
Apomixis is rice: b$ /yr

12. Strategies for Transfer of Apomixis
To Food Crops:
Apomixis is a modified sexual
pathway
Genes from sexual plants

13. Mutation in a gene called DYAD shows female sterility
Normal
dyad mutant
We isolated several mutants and one of them which we named dyad is shown here.
Dyad shows female specific sterility. Pollen development is normal
The ovule is the precursor of the seed and the wild type ovule contains the female gametophyte which is haploid and formed by postmeiotic divisions of one of the spores formed after meiosis. It contains the egg cell and associated cells that are required for fertilization, embryogenesis, and seed development.
The reason for sterility in the mutant is immediately apparent because it lacks the entire female gametophyte and instead contains two enlarged cells where the gametophyte would normally be found.

14. Seeds produced by dyad have an extra set
of chromosomes (triploid)and arise from
fertilization of an unreduced (Apomeiotic)
female gamete
mitosis
meiosis
Triploid (3n = 15)
Diploid (2n = 10)
No. of plants: 17 2

15. 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 synthesis
of apomixis in crops

16. Credits: CCMB Funding: CSIR; Department of Biotechnology;
Maruthachalam Ravi
Bhavna Agashe
V. Subbiah
Gopal Ganesh
Mohan P. Anand
CCMB
Funding:
CSIR; Department of Biotechnology;