Formation characteristics of endosperm structures in different rice genotypes

To explore the formation characteristics of endosperm structures in different rice genotypes, different rice genotypes of (indica, japonica, and glutinous) were used and grown in the paddy field. The endosperm structures in the grain during the filling period were investigated. The results showed that the compactness of amyloplast arrangement was positively correlated with grain filling percentage. The endosperm structure varied with the position within a grain. At maturity, the structure was the best in the back, the intermediate in the center, and the worst in the belly of a kernel. However, the filling was better in the center than in the back and in the belly from 5 to 10 days after flowering (DAF). The endosperm structure was different among genotypes. From 5 to 25 DAF, starch accumulation was the earliest in glutinous rice genotypes, followed by indica and japonica genotypes. Gaps and pores in endosperm were closely associated with rice transparency. The starch crystallinity in endosperm was negatively correlated with amylose content. Among the three genotypes, glutinous showed the highest crystallinity, followed by japonica and indica rice. The starch crystallinity in a grain was lower on a primary branch than that on a secondary branch. Among all grain s, the second grain on a primary branch showed the lowest starch crystallinity. The results indicated that the starch structure of endosperm not only differ between rice genotypes, but also varies with the location of a grain on the panicle, and that it affects the grain-filling, transparency and amylose content of rice. (author)