Evaluation Methods For Hybrid Japonica Rice Varieties And Further Improvement Strategy Of Characters In The Rice Breeding

The gray relation-degree way was used to evaluate comprehensively the main agronomic characters of 13 hybrid japonica rice varieties, which were qualified by the Committee for Approval of Crop Varieties Jiangsu Province from 1987 to 2002. The results showed that 8-you-682,69-you-8 and 9-you-418 had not only very high value for relation-degree, also the elite comprehensive performance in the field. These varieties should be extensively grown in the various area in Jiangsu Province.Further the path analysis way was used to explore the relationship among yielding character and their contribution to the final yielding based the data from 15 hybrid japonica-rice varieties for extension and examine-experiment in the experiment of 2002. The grain numbers per spike and the percentage of fertile grains had higher direct path coefficients, and that is P4y=0.8549 and P5y =0.4527 respectively. The path and relationship coefficients between these two characters and final yielding were also high, it suggested that as the model for high or super high yielding hybrid japonica rice it should be paid more attention to the total grain number per spike and the rate of fertile grain. For 10 tons per hm2 it was necessary that was 0.9-1 million of basal seedlings, the most seedling lower than 3.7-3.9 million, spike number higher than 2.9-3.1 million, total grain number per spike between 170-200, fertile grain percentage up to 80% and 27-29g per 1000 grains.It was finally discussed that the key problems and strategy in the breeding for hybrid japonica rice.