Peculiarities of in vitro parthenogenesis of unpollinated maize ovaries

The maize line AT-1 is characterized by a hereditary predisposition to parthenogenesis. The aim of this investigation is to study parthenogenetic embryo development in the culture of unpollinated ovaries in vitro. The unpollinated ovaries were explanted in 1, 3, 5, 7, 10, 15 days after the appearance of stigmas from ears. The nutrient medium included mineral components of MS, vitamins, sucrose (9,0%), 2,4-D (2,0 mg/l), agar-agar. The structure of megagametophytes at the time of inoculation of the ovaries and on the 3^rd, 7^th, 14^th, 21^th, 28^th day of cultivation was studied. The first divisions of unfertilized egg cells were observed on the 5^th–7^th day after appearance of stigmas from ears, independently from whether all this time the ovaries were on the mother plant or they were inoculated into the nutrient medium. The formation of the autonomous abnormal endosperm in some cultivated ovaries was detected. The abnormal endosperm disturbed normal development of the proembryo. As a rule, the ovaries with embryo and endosperm degenerated. In the absence of endosperm, the morphogenesis of parthenogenetic proembryos was carried out in one of two directions in vitro: 1) development of plants by direct embryogenesis; 2) regeneration of plants from numerous embryoids, raised on the surface of globular proembryos. The second direction was prevailed. The culture of unpollinated ovaries can be a promising method of mass haploid regenerants not only in maize, but also in other types of agricultural plants.