High Risk of the Formation of Milky White Rice Kernels in Cultivars with Higher Potential Grain Growth Rate under Elevated Temperatures

Abstract

Our objective was to clarify whether rice cultivars with a higher grain dry-matter increase rate (GIR) under elevated temperature condition show a higher percentage of milky white rice kernels (MWK). The rate of MWK judged using a rice-quality selector significantly varied with the cultivar and experimental year. The spikes of the cultivars detached 5–7 days after heading were solution-cultured with an adequate nutrient supply for one week at 25, 28 and 33ºC. GIR was overall the highest at 28ºC, and GIR at this temperature was considered to reflect the potential GIR in all the grains tested. There was a close correlation between the rate of MWK and the GIR at 28ºC under field conditions when temperatures during the grain-filling period were approximately over 25ºC. It was suggested that cultivars with a higher potential GIR under elevated temperature conditions have a higher risk of the formation of MWK.