Cultivar Difference in the Yield Response to Climatic Conditions after Heading Stage in High-Yielding Rice Cultivars

Abstract

We examined the cultivar difference in the relationship between rice grain yield per solar radiation (Y/R) and air temperature (T) during 40 days after heading using high-yielding cultivars Bekoaoba, Momiroman, Takanari and Hokuriku 193, and control cultivars Akihikari and Nipponbare. The relationship was regressed to a quadratic equation in all cultivars. The maximum Y/R in the equation was higher in Bekoaoba, Takanari and Hokuriku 193 than in the control cultivars. The T value at which the maximum Y/R was obtained was 21.1 in Bekoaoba, a japonica cultivar with a large grain size, and was similar to that in the control cultivars (21.2). In contrast, the T values in the indica cultivars Takanari and Hokuriku 193, and the indica-japonica cross Momiroman was 23.9–24.7, which was higher than in the control cultivars. We concluded that there is a cultivar difference in the response of Y/R to T, and that the optimum temperature during the grain filling period could be 3 degrees higher in Momiroman, Takanari and Hokuriku 193 than in Bekoaoba.