Optimization of germination inhibitors for controlling pre-harvest sprouting in hybrid rice

The present study was conducted to screen different growth inhibitors i.e. ethephon (125 mM), methyl jasmonate (1 mM MeJA) and their combinations (125mM ethephon + 1mM MeJA) for minimizing the harmful effects of pre-harvest sprouting during hybrid rice seed production. The combination of both growth inhibitors significantly reduced germination and growth attributes with a more prominent decrease in cultivar Zhu Liang You 06 (ZY) as compared to cultivar Qian You No.1 (QY). Moreover, the activities of α-amylase, peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and malonaldahyde (MDA) contents were significantly increased with the combination of both growth inhibitors as compared to the control. CAT activity was significantly increased with 1mM of MeJA as compared to the control. The combination of both growth inhibitors resulted in the increase of abscisic acid (ABA) contents and the decrease of gibberellins (GA) contents as compared with the control. Gene expression analysis showed that the transcription levels of ABA genes (OsNCED1, OsNCED3 and OsABA80x1) were up-regulated with the combination of both growth inhibitors. While, GA genes (OsGA3ox1, OsGA20ox1 and OsGA2oox2) were down-regulated by seed soaking with both growth inhibitors and their combination.