| Heterosis is a widespread biological phenomenon. It is an important method to improve the unit yield of japonica rice in cold region by utilization of heterosis. However, Heilongjiang province is located in the northern cold region of japonica rice, short growth period, low temperature, less effective accumulated temperature. Therefore, it is still controversial about the prospective of utilization and japonica rice heterosis in cold region. Based on the ecological environment and rice production conditions in Heilongjiang province, the improvement of rice yield become major work for agricultural technologists with declined cultivated land and increased population. Hybrid japonica rice is of very great on yield potential. Recent study showed that super hybrid japonica was estimated to increase the yield by 15 to 30% than common japonica. The uses of heterosis on hybrid japonica greatly improve the yield and will play an important role on the stability and development of Northern Japonica rice production.Heilongjiang province is an important commercial production grain and export bases in China,which has a good condition for grain and a stable supply ability in grain. Therefore, the uses of heterosis on hybrid japonica play a positive role on food security in the programs of japonica high-yield breeding.As the northern cold rice region, Heilongjiang province has short growth period, a low temperature and less effective temperature. Therefore, the uses of japonica heterosis are still on controversial.7 japonica varieties different on the yield traits and 15 hybrid combinations were investigated in our study. Our studies thus reveal the heterosis variance on dry matter weight, the activity of enzyme involved in carton and nitrogen mechanism, yield traits, and cooking and eating quality. The results indicated that the biochemical and physiological mechanism of heterosis and thus reveal a hitherto undiscovered novel pathway that controls the use of japonica rice heterosis. The heterosis of dry matter weight positively correlated with grain weight per plant at tillering period and reached a significant level at middle tillering period. However, the correlation between the heterosis of dry matter weight and grain number per panicle, 1000-grain weight and grain setting were not significant.The accumulation of dry matter in combination with strong heterosis was higher significantly than with weak heterosis. The result showed that dry matter affect the heterosis of grain number per panicle.During tillering stage, the activities of enzymes involved in nitrogen metabolism in combinations with strong heterosis were higher significantly than in combinations with weak heterosis. The results showed that there was a strong nitrogen metabolism in combinations with strong heterosis. The heterosis of grain number per plant was related with nitrogen metabolism and the heterosis of grain number per plant was higher in combinations with high enzyme activity in nitrogen metabolism.During tillering stage, the activities of glutamine synthase, soluble starch synthase, ADPG phosphorylation and protease in combinations with positive heterosis were higher significantly than in combinations with negative heterosis. During filling stage, the activity of key enzymes involved in carbon and nitrogen metabolism were positive correlated with 1000-grain weight and yield per plant.During filling stage, the activities of glutamine synthase, soluble starch synthase, ADPG phosphorylation and protease was increased, and then reduced gradually, showed the single-peak curves. The activity of key enzyme in combinations with positive heterosis was higher significantly than combinations with negative heterosis. During filling stage, the activities of glutamine synthase, soluble starch synthase, ADPG phosphorylation and protease in combinations with positive heterosis were higher significantly than in combinations with negative heterosis. During filling stage, the activity of key enzymes involved in carbon and nitrogen metabolism were positive correlated with 1000-grain weight and yield per plant.During tillering stage, key enzyme activity showed positive heterosis in combinations with strong heterosis and showed negative heterosis in combinations with weak heterosis. During filling stage, the activities of glutamine synthase, soluble starch synthase, ADPG phosphorylation and protease in combinations with positive heterosis were higher significantly than in combinations with negative heterosis.The heterosis of dry matter weight and grain number per plant was related with the enzyme involved in nitrogen metabolism. The enzyme involved in nitrogen metabolism play a positive role in strong heterosis during filling stage.We investigated the quality of combinations with different heterosis and the results showed that the amylase content and protein content in combinations with positive heterosis were higher significant than in combinations with negative heterosis. There was no significant difference among combinations with different heterosis.In view of cold ground grain weight per controlled japonica varieties advantage is very weak, narrow, effective genetic basis between JiWen lower reason, cold heterosis japonica tries to improve yield very difficult. Moreover, the current and future for the people most under the situation of quality rice in Heilongjiang promotion hybrid japonica rice will lose market competitiveness and geographical advantages, that would limit to the promotion of japonica hybrid rice cold use. Currently cold japonica breeding programs to cross breeding between varieties still in for the main way advisable.There was narrow genetic basis and weak heterosis of grain weight per plant and in cold japonica comparisons. It is difficult to improve the yield through increasing the heterosis. The market competitiveness and geographical advantages of high-quality rice were low and the promotion of cold japonica hybrid will be inhibited. Our results showed that cross breeding between varieties will be benefit to cold japonica breeding programs. |
PDF Full Text Request