Evaluation of various screening systems for high grain quality in rice cultivars under high-temperature grain-filling conditions, and the selection of their standard cultivars

Abstract

Opaque grain caused by high temperatures at the ripening stage is a major constraint for the commercial production of rice. I evaluated the selection methods for the breeding of high temperature-tolerant rice cultivars and selected standard cultivars. Twenty-six nonglutinous paddy rice cultivars were grown under four high-temperature stress conditions; a test field with warm water irrigation at 35°C, a bottom-ventilated PVC greenhouse, a pot cultivation in a pool with 35°C water circulation and a phytotron. Any of the high-temperature treatments given at the rice-ripening stage decreased the percentage of high-quality grains and increased the quality differences among cultivars compared with the non-stressed condition. The order of the cultivars in high-temperature tolerance was consistent in all four treatments with a correlation coefficient of r = 0.58∼0.73. We, therefore, judged that it is possible to apply those methods to breeding process. We also proposed to use the following cultivars as the standard: Fusaotome for tolerant, Tentakaku, Hanahikari and Koshijiwase for moderately tolerant, Hitomebore, Haenuki and Hounenwase for intermidiate, Ajikodama, Kagahikari and Ougiwase for moderately sensitive, and Todorokiwase and Koshinohana for sensitive cultivers.