Principles of Plant Breeding

Development of apomictic embryo

1. Parthenogenesis :
The development of embryo from egg-cell without fertilization, e.g.in some cases in corn, wheat, tobacco. This is also of two kinds :
(i) Haploid parthenogenesis: The embryo develops from egg-cell without fertilization ina haploid embryo-sac produced by generative apospory. It is non-recurrent in nature.
(ii) Diploid parthenogenesis: The embryo develops from egg-cell without fertilization ina diploid embryo-sac arising from somatic apospory. It is recurrent type.

2. Apogamy :
The development of embryo not from the egg-cell but from any one of the synergid or antipodal cells within the embryo sac, without fertilization. This is haploid or diploid. In the haploid apogamy, the embryo arises from any cell other thanthe egg-cell without fertilization in haploid embryo -sac formed by generative apospory. By virtue of its haploid nature, it is also non-recurrent apomixis. Whereas in case of diploid apogamy, embryo develops from any cell other than the egg-cell without fertilization in a diploid embryo-sac developed by somatic apospory. It is recurrent type.

3. Androgamy :
The development of embryo neither from egg cell nor from synergidsorantipodals, but from one of the male gametes itself, inside or outside the embryo-sac. Since it is haploid, it is non-recurrent apomixis. In another phenomenon, i.e. parthenocarpy, seedless fruits are formed fromovary without fertilization. Normally, fertilization stimulates the ovary to become enlarged and form fruit. But in case of parthenocarpy, such stimulation may be received even from incompatible pollination.