Introduction of low temperature germinability into highly palatable cultivars of rice

In order to breed highly palatable cultivars suitable for direct sowing in rice, eve tried to incorporate the genes for low-temperature-germinability into highly palatable Japanese cultivars and selected excellent backcrossed lines with low-temperature-germinability. First, we examined ten Japanese cultivars and ten foreign cultivars for their low-temperature-germinability (the proportion of the germination rate at 15 degreesC to that at 25 degre esC after 7 days of incubation) and found that most of the foreign cultivar s which were directly sown in their own countries were extremely useful as donors of low-temperature-germinability. Secondly, we developed five backcr ossed BC2F2 populations (Koshihikari*3/M202, Hinohikari*3/M202, Koshihikari *3/Italica Livorno, Koshihikari*3/Mutashali and Kinuhikari*3/Mutashali) and selected them for low-temperature-germinability. From all populations, we obtained the lines superior to each recurrent parents. In particular, from Koshihikari*3/M202 (66 lines), Hinohikari*3/M202 (51 lines) and Koshihikari *3/Mutashali (51 lines), we obtained eight, eleven and one line, respective ly, which showed excellent (over 81%) low-temperature-germinability. Then w e picked out these excellent lines (Hinohikari*3/M202) as donors of further back-crossing. Finally, we developed backcrossed BC3F2 lines (Hinohikari*4 /M202, 35lines) and selected five excellent lines with high low-temperature -germinability. In conclusion, it would be possible to breed highly palatab le cultivars suitable for direct sowing by introducing low-temperature-germ inability derived from foreign cultivars such as M202 into good eating-qual ity cultivars.