High risk of the formation of milky white rice kernels in cultivars with higher potential grain growth rate under elevated temperatures

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 signifi cantly 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 33°C. GIR was overall the highest at 28°C, and GIR at this temperature was considered to refl ect the potential GIR in all the grains tested. There was a close correlation between the rate of MWK and the GIR at 28°C under fi eld conditions when temperatures during the grain-fi lling period were approximately over 25°C. It was suggested that cultivars with a higher potential GIR under elevated temperature conditions have a higher risk of the formation of MWK.