Abstract
To determine the possible cause of higher seedling vigor in F1 rice (Oryza sativa L.) hybrids, embryo weight, endosperm weight, leaf area, and seedling growth performance of 16 F1 indica crosses and their parental lines were evaluated. The embryos of 16 F1 rice hybrids showed midparent heterosis and those of 11 F1 rice hybrids showed better parent heterosis (heterobeltiosis). Lower heterosis in the F2 embryos was also observed. Midparent heterosis in endosperm weight did not always appear. Seedling growth of F1 rice hybrids grown in standard nutrient solution for 16 days showed midparent heterosis and relative growth rate in each four-day interval had little heterosis. Heterosis in embryo weight and leaf area were closely related with that in seedling weight. Higher leaf area expansion related with bigger embryo was considered the primary factor for heterosis in seedling growth of indica-indica F1 rice hybrids.
