Abstract
The factors affecting amylose content of the rice variety "Kirara 397" were analyzed. Temperature during grain filling, planting year, kind of seedling, heading date, and the location of grains on panicles were examined in Hokkaido a cold district. A significant negative correlation was found between temperature during grain filling and the amylose content. Temperature influenced the amylose content greatly when the accumulated temperature after heading was under 800°C. A significant negative correlation was found between the seedling age and amylose content. The standard deviation of the amylose contents of grains from panicles of the same heading date was 0.38—1.34. The amylose content differed with the location of grains; it was higer in the grains in a higher position are higher than that in a lower position. The amylose content on grains the primary rachis branch was higher than that on secondary rachis branches. This is probably because the starch content of the grains on the secondary rachis branches was lower than that on the primary rachis branch. On the other hand, the rate of milk white grains and white belly grains in a higher position was lower than that of those in a lower position. Moreover, the rate of milk white grains and white belly grains on the primary rachis branch was lower than that on the secondary rachis branches. The rate of milk white grains and white belly grains was negatively correlated with amylose content. From these results, we concluded that reducing the number of grains on the secondary rachis branches is important to improve the quality. Breeding a variety superior in primary rachis branches is useful to improve rice quality in Hokkaido.
