Preharvest sprouting (PHS), the germination of seeds on the maternal plant before harvest, is a big challenge for barley producers worldwide. It is attributed mainly to low seed dormancy. The balance between two classical plant hormones, gibberellin (GA) and abscisic acid (ABA) regulates seed dormancy and germination, and the endogenous level of these two hormones in plants is determined by their biosynthesis and catabolism. This thesis characterized the expression patterns of the major GA and ABA metabolism genes in barley cv. Betzes during seed development, and germination in both dormant and non-dormant seeds. The results indicate that specific gene family members of the two hormones play distinct temporal roles in regulating seed development, dormancy onset and release, and germination. Since only two genes encoding the GA deactivating GA 2-oxidase enzyme have been known so far in barley, this study also identified two new GA2ox genes designated as HvGA2ox1 and HvGA2ox3.

Preharvest sprouting (PHS), the germination of seeds on the maternal plant before harvest, is a big challenge for barley producers worldwide. It is attributed mainly to low seed dormancy. The balance between two classical plant hormones, gibberellin (GA) and abscisic acid (ABA) regulates seed dormancy and germination, and the endogenous level of these two hormones in plants is determined by their biosynthesis and catabolism. This thesis characterized the expression patterns of the major GA and ABA metabolism genes in barley cv. Betzes during seed development, and germination in both dormant and non-dormant seeds. The results indicate that specific gene family members of the two hormones play distinct temporal roles in regulating seed development, dormancy onset and release, and germination. Since only two genes encoding the GA deactivating GA 2-oxidase enzyme have been known so far in barley, this study also identified two new GA2ox genes designated as HvGA2ox1 and HvGA2ox3.