Abstract
Interspecific hybrids between cultivated rice (Oryza sativa, 2n = 24, AA) and two wild species (O. minuta, 2n = 48, BBCC and O. officinalis, 2n = 24, CC) have been produced by cross pollination. The embryo development in these interspecific hybrids was observed to study the deterioration features in detail. All hybrids showed either abnormal embryo development with degenerating endosperm or embryo retardation itself. Abnormally developed embryos were observed by the end of 7 days after pollination and the percentage of abnormally developed embryos increased from 7 to 14 DAP. The embryos were excised at 7 to 14 DAP and cultured on MS medium supplemented with 1, 3 and 5 mg/l benzylaminopurine, 1 g/l casein hydrolysate, 0.8% agar and 3% sucrose. The optimal time for rescue turned out to be 11-14 DAP. There was a significant difference (P = 0.05) in the regeneration efficiency rate with rescue time but no significant difference with of culture medium in these cross combinations. The F1 hybrids were morphologically intermediate between their parents. All F1 hybrid plants thus obtained were completely sterile. Chromosome doubling was attempted by treating F1 hybrid tillers with colchicine to overcome their sterility. The morphology of the colchicine-treated F1 plants closely resembled the female parent and fertility.
