Effects of harvest time on seed vigor, enzyme activity and gene expression of conventional japonica rice

Abstract

ABSTRACT Seed vigor is greatly influenced by harvest time. In this study, three conventional japonica rice varieties were used to investigate the optimal harvest time. Germination potential (GP), germination rate (GR), germination index (GI), vigor index (VI), mean germination time (MGT), field emergence rate (FER) and controlled deterioration germination rate (CDGR) were determined in 2018 and 2019. The results showed that seed vigor was firstly increased and then decreased with the increase in harvest time. Seed vigor reached maximum at approximately 50 days after flowering (DAF) while their yields had no significant changes compared to those at the normal harvest time (69 DAF). Compared to 69 DAF, GP, GR, GI, VI, FER, CDGR at 50 DAF were enhanced by 17.9%-113.3%, 1.4%-13.5%, 9.1%-35.8%, 19.8%-64.4%, 18.8%-130.3%, 7.5%-44.1%, respectively, and MGT was decreased by 10.0%-100.2%. On the basis, the changes in law of enzyme activity and gene expression related to seed vigor were analyzed. Interestingly, there were similar changing trends with seed vigor in peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), ascorbic acid peroxidase (APX), and gene expression of CAT3, OsAPX2, OsCSD3 with the increase of harvest time. Our study suggests that timely early harvest is effective for seed production of conventional japonica rice.