The Arrangement of Endosperm Cells and Development of Starch Granules Are Associated With the Occurrence of Grain Chalkiness in Japonica Varieties

The endosperm chalkiness in grains is one of the most important traits in rice grain qualities, and grain chalkiness directly determines grain quality and market price. Therefore, the endosperm chalkiness reduction is an important goal of breeding scientist in rice. However, little is known about the relationship of the formation of rice endosperm chalkiness and the morphological structure and development in fragrant japonica and conventional japonica varieties. In this study, we have mainly investigated the chalkiness characters such as degree of endosperm chalkiness (DEC), chalkiness rate (CR) and chalkiness area (CA) in 12 fragrant japonica varieties and 9 conventional japonica varieties. Furthermore, the endosperm structure and starch granules of rice grains were also observed with scanning electron microscope (SEM). The results indicated that the 21 varieties including the different fragrant japonica and conventional japonica varieties has a linear relationship between the DEC and the CR (P < 0.05). Among the fragrant japonica and conventional japonica varieties, the biggest difference is the CR, follow by CA and DEC. In addition, there is a certain correlation between the arrangement of endosperm cells, the distribution of starch granules and the occurrence of chalkiness characters in the different fragrant japonica and conventional japonica varieties. For the same fragrant japonica or conventional japonica variety, there is no significant difference between the starch granules from the transparent parts of chalkiness and non-chalky, while the starch granules of grains between chalky and non-chalky has obvious difference. Our results would provide important references for high quality rice breeding.