Metabolomic analysis reveals differential metabolites and pathways involved in grain chalkiness improvement under rice ratooning

Metabolomic approaches provide new insights into studying changes in yield traits and grain chalkiness under a ratoon cropping system. In this study, when rice plants were grown as ratooning season rice, seed setting percentage, chalky grain percentage and chalkiness degree were highly improved, as compared to their counterparts in main-cropping season rice and late-cropping season rice. Furthermore, such improvements were proven to be associated with a shift in the metabolomic composition of the grain, especially regarding variations in sugar components in carbohydrate metabolism. Moreover, rice ratooning specifically increased the total ascorbate content combined with an enhancement of oxidative stress tolerance in grains. Finally, a potential mechanism was revealed: rice ratooning caused compositional changes in sugar metabolism in addition to promoting starch synthesis during the early stage of grain filling, ultimately improving the level of grain chalkiness.