Temperature during the growing season is a critical factor affecting grain quality.High temperatures at grain filling affect kernel development,resulting in reduced yields,increased chalkiness,reduced amylose contents,and poor milling quality.Here,we investigated the grain quality and starch structure of two japonica rice cultivars with good sensory properties grown at different temperatures during the filling stage under natural field conditions.Compared to normal conditions,rice grains grown under hot conditions showed significantly reduced eating and cooking qualities,such as higher percentage of grains with chalkiness,lower protein and amylose contents,and higher pasting properties.