Abstract
Unfertilized ovule culture for the production of somatic embryos and its histological observations were carried out in Cucurbita moschata. About 17% ovules produced somatic embryos when ovules, excised from the ovaries at anthesis which were pretreated at 5°C for 2 days, were cultured on a liquid half-strength Murashige and Skoog (MS) medium supplemented with MS organics and 30g/l sucrose. At the initiation of culture, the embryo sac began to degenerate. From about 10 days of culture, some of the nucellar cells became conspicuous by large nuclei, dense cytoplasm and thick walls, and divided to give rise to proembryos. Further cell division and differentiation of proembryos led to globular, heart and cotyledonary stages similar to zygotic embryogenesis. Among the obtained embryos, only a fewshowed normal morphology and many developmental variants were observed, such as embryos with secondary embryos or abnormal cotyledons. Upon transfer of the somatic embryos to the same nutrient medium supplemented with 5g/l sucroseand 8g/l agar, most of them underwent callusing, and only a few developed normal shoots and roots. The regenerated plants were diploid (2n=40) or tetraploid. Our histological and cytological investigations indicate that the embryos from cultured unfertilized ovules of C. moschata develop directly from single cells of the nucellus.
