気温上昇が水稲品種の玄米外観品質，食味におよぼす影響

The effects of high temperatures on grain quality and palatability of cooked rice of four rice cultivars were examined in a temperature gradient chamber (TGC). Experimental plots going from TG1 (near the air intake side) to TG3 (near the air exhaust side) along the temperature gradient in TGC, corresponding to low and high temperature, and an open field plot (outside of TGC) were arranged. The mean and maximum air-temperatures in TG3 were 3.6℃ and 7.2℃ higher, respectively, than those in TG1. Brown rice yield per m2 in the outside was the highest, and those in the TGC plots were lower than outside in all cultivars. This yield decline was due to the decrease in the percentage of ripened spikelets. The increase in the percentage of sterile spikelets due to high temperatures in Nikomaru and Akimasari was larger than that in Hinohikari and Akebono. The yield difference among TGC plots was not significant. High temperature increased the white berry grains and white back grains in Hinohikari and Akebono, respectively. The overall eating quality (＋3 to －3) in the outside was in the order of Nikomaru (0.56) ＞Akimasari (0.50)＞Hinohikari (0.00)＞Akebono (－0.06). The overall eating quality in TG3 was lower than outside, especially in the quality of appearance. However, the decreasing degrees of appearance quality in Nikomaru and Akimasari were smaller than those in Hinohikari and Akebono. The protein content of milled rice in TG3 (6.0−7.8%) was higher than that in the outside (8.6−10.4%) in all cultivars. The increase in protein content by higher temperature was in the order of Akebono (4.4%)＞Hinohikari (1.9%)＝Akimasari (1.9%)＝Nikomaru (0.8%). In terms of grain quality, the cultivation of new cultivars, Nikomaru and Akimasari are recommended when air temperature exceeds normal years. However, yield reductions in Nikomaru and Akimasari caused by high temperatures were larger than those in the conventional cultivars, Hinohikari and Akebono.