FEMALE STERILE MUTANT IN PEARL-MILLET - EVIDENCE FOR INITIATION OF APOSPORY

Apomixis is an asexual mode of reproduction through the seed that results in maternal offspring. A female sterile mutant in pearl millet was identified previously as having apomictic characteristics. The objectives of this study were to observe the cytology of female sterile ovules after pollination to determine possible reasons for sterility and a possible link to the aposporous apomictic developmental process. Cytological examination of 273 ovules revealed that they are small and deformed; 50% failed to form embryo sacs, and 35% formed multiple embryo sacs, which indicates the potential for apospory. Only 12% contained antipodal cells typical of sexual embryo sacs. In general, the embryo sacs occupied most of the ovule area limiting the amount of nucellar tissue available for endosperm and embryo development. Only six of the 273 ovaries observed had endosperm and/or proembryo development. This recessive mutation represents a possible step in the genetic regulation of apomictic development.