In vitro culture of hybrid ovule between Fagopyrum esculentum Moench and F. homotropicum Ohnishi

Interspecific hybridization in buckwheat is of great importance to transfer desirable genes from wild species to cultivars as well as to broaden genetic variation in cultivars. In vitro ovule culture following the bud pollination was made to overcome postzygotic cross/self-incompatibility in interspecific hybridization between Fagopyrum esculentum Moench (common heterostylous buckwheat) and F. homotropicum Ohnishi (homostylous buckwheat). The percentage of fertilized ovaries of F. esculentum flowers (thrum-type) pollinated with F. homotropicum was 50%, while that of the reciprocal cross was as low as 10% and their ovaries were smaller. Vigorous pollen tube elongation following the bud pollination indicated the possibility for overcoming of breeding barriers in interspecific crosses between buckwheat species. Pre-embryo formation was observed 48 hours after pollination and ovules cultured up to 5 days after pollination tended to develop callus. But ovules isolated 11 days after pollination had apparently lost their viability. Hybrid plantlets were produced from only the ovules dissected 5 days after bud pollination. Regeneration rate was better in ovule culture on White medium than other mediums tested. Interspecific hybrid plants between F. esculentum and F. homotropicum were regenerated with the rate of 24.2% in average.