Effects of high air temperature in summer of 1999 on ripening and grain quality of rice

Abstract

Although rice yield in 1999 was no less than the normal value, high air temperature during the 1999 summer season damaged the apparent quality of rice kernels in a large area of Japan. The percentage of rice kernels qualified as the first grade by inspection grade, was significantly decreased by the occurrence of milky-white kernels, white core and white-backed kernels in the Tohoku and Hokuriku area where the air temperature during the early ripening stage in 1999 was 3-5°C higher than the normal air temperature. In the Kyushu area, low solar radiation with a high air temperature continued for a long term, and it affected not only the rice yield but also the apparent quality and palatability of rice kernels. On the other hand, the release and extension of new high temperature tolerant variety, as well as proper management for rice growth under a high air temperature condition, contributed to the reduction of the damage in Chiba prefecture. In this study, we analyzed the effects of weather conditions in 1999 on the ripening and quality of rice, and the factors such as variety and cultivation method relating to the damage by high air temperature. Research subjects in crop science will be also discussed.