Combining ability of seed vigor and seed yield in soybean

Studies have shown no consensus in relationships between seed yield and vigor in soybean [Glycine max (L.) Merrill]. The lack of information regarding the inheritance of seed vigor prompted this study to determine the types of gene action and combining ability estimates for seed vigor and its related traits. Five high and six low seed vigor soybean genotypes were crossed in a diallel, and selfed to produce 55 F-2 progenies, which were examined, along with the parents, for seed vigor, yield, and seed weight. Significant genotype and environment effects were found for seed vigor and yield. General combining ability (GCA) effects for seed vigor and seed yield were significant ( p less than or equal to 0.01) and larger than specific combining ability (SCA) effects. Significant GCA and SCA effects were found for seed weight, indicating that both additive and nonadditive genetic effects were involved in conditioning seed weight. The ratios of mean square, 2GCA / (2GCA+SCA), were 0.96 for seed vigor and 0.93 for seed yield. These ratios indicated that additive gene effects were more important than nonadditive gene effects for seed vigor and seed yield in these crosses. Mean seed vigor (83.8%), as determined by accelerated aging germination, and mean seed yield (2,155 kg ha(-1)) in high vigor x high vigor crosses were higher than the high vigor x low vigor and low vigor x low vigor crosses. Mean percent accelerated aging germination rates in F-2 populations from diallel crosses were significantly related to mid-parent seed vigor (r(2) = 0.52**) and midparent seed size (r(2) = 0.31**). These results indicated that levels of seed vigor can be improved through breeding, while maintaining high yields because of the predominance of GCA effects in both seed vigor and seed yield.