Seed dormancy and seedling vigour as influenced by planting time environment and date of harvest in rice (Oryza sativa L.)

Seed dormancy is a genetically inherited trait whose intensity is modified by the environment during seed development and maturation. In order to study the effect of harvest time on the seed quality and optimum time of sowing to obtain good quality seeds, freshly threshed seeds of ten diverse rice genotypes harvested from six environments were evaluated for seed dormancy and seedling vigour index as a measure of seed quality. There were significant differences in germination in different genotypes in all the six environments as well as days after harvest. The germination percentage was initially low and gradually increased with increasing in days after harvest (0. 15, 30 and 45th day after harvest). Out of these six genotypes viz., IET 8116, KMP 101, IR 30864, KRH-1, IR-64 and MTU 1001 were found dormant, immediately after harvest. The studies indicated that sowing in the first (June 2nd fortnight) and second environment (July 1st fortnight) were resulted in production of non-dormant seeds. Whereas all the six environments were favorable to take up seed production of new promising rice genotype KMP 101.