Abstract
A high temperature during the grain-filling period in rice plants causes abnormal rice grains such as white-back, basal-white and milky-white grains. The abnormal grain quality may be caused by the imbalance between assimilate supply and its uptake by grains under high temperatures conditions. The objective of the present study was to determine the effect of partial excision of the root system during the grain-filling period on the quality of rice grains. Six Japanese cultivars, Koshijiwase, Kokoromachi, Akitakomachi, Hitomebore, Chiyonishiki and Hatsuboshi used for the analysis showed a wide range of variation in the frequency of white-back grains caused by a high temperature during the grain-filling period. Partial excision of the root system caused a marked increase in the frequency of white-back grains. Abnormal grain quality due to partial excision of the root system varied with the cultivar. No significant difference was found in grain-filling percentage, weight of 1000 grains and grain size between plants with and those without a partially excised root system. On the other hand, the grain-filling period and the number of fresh leaves during the ripening stage were significantly decreased by root excision. These results suggest that a severe decline of root function during the grain-filling period causes abnormal grain quality, in particular white-back grains in rice.
