Abstract
High air temperatures during the summer of 2010 damaged the apparent quality of rice kernels in a large area of Japan. When the average temperature during the 20 days after heading was 28°C or higher, the percentage of first-grade rice kernels according to inspection grade in Fukuoka prefecture was higher than 90% in the heat-tolerant cultivar ‘Genkitsukushi’. Furthermore, in the fields with different soil fertility and with different crops cultivated in the previous summer, the incidence of white immature kernels was significantly lower and the rice kernel quality was superior in ‘Genkitsukushi’ than in cultivars with less heat-tolerance. In addition, the proportion of white immature kernels in ‘Genkitsukushi’ at any position within the panicle were lower than those in the heat-sensitive rice cultivar ‘Tsukushiroman’, which has a similar panicle architecture, at comparable average temperatures during the 20 days after heading. These results suggest that the tolerance of ‘Genkitsukushi’ to high air temperatures was stably excellent, and that it was not related to panicle architecture, but to some unidentified physiological factor.
