Analysis of Factors Contributing to Superior Appearance Grain Quality in the High Yield Rice Variety ‘Niji-no-kirameki’

Abstract

Superior grain quality and high yield variety ‘Niji-no-kirameki’ and popular variety ‘Koshihikari’ were cultivated for 2 years under the conditions of 2 transplant times and 3 fertilization methods. Their grain qualities were compared from the viewpoints of the growth and cross-sectional traits of grain according to different positions within the panicle.‘Niji-no-kirameki’ was superior in grain quality to ‘Koshihikari’ under all cultivation conditions: clearly fewer white-back grains in the inferior position under a high temperature, fewer ventral white and white core grains in the superior position, fewer core white grains by rachis-branch removal and fewer milky white grains by leaf removal. These results indicate that the quality of‘Niji-no-kirameki’ decreases less under high temperature conditions and under the conditions of excess or shortage of assimilates. This might be due to the slow growth of grain at every position within the panicle in ‘Niji-no-kirameki’. On the other hand, the causal relationship between the cross-sectional traits of grain and grain qualities was unclear, although the dorsal-ventral ratio of grain became lower under a high temperature. From these results and our previous reports, the long ripening period is considered to be a factor contributing to the high yield and superior grain quality in ‘Niji-no-kirameki’.