HERITABILITIES, GAINS FROM SELECTION, AND GENETIC CORRELATIONS FOR CHARACTERISTICS OF SOYBEANS GROWN AT WIDE AND NARROW ROW SPACING

Heritabilities, gains from selection, and genetic correlations among maturity, lodging, height, and seed yield were calculated and compared for 30- and 76-cm row spacings in soybeans {Glycine max (L.) Merrill} over two years at Lafayette, Indiana. Experimental material consisted of three adapted cultivars and 37 randomly selected F(,5) and F(,6) lines each in maturity groups II and III, representing typical early generation breeding material. A randomized complete block design with a split plot was used, with row spacings as whole plots and genotypes as sub plots. A different experiment was conducted for each maturity group. Heritability estimates and expected response to selection were similar for both row spacings and all characteristics with the exception of seed yield. The absence of a year x genotype interaction for seed yield in narrow rows for both maturity groups resulted in a higher heritability estimate for yield in narrow than in wide rows. This suggests more efficient selection for seed yield in narrow-row test plots, especially when selection is based on only one year\u27s evaluation. Genotype x row spacing interactions for all characteristics were not significant, and genetic correlations between wide and narrow rows were approximately 1.0, suggesting that genotypes ranked similarly for all characteristics in both environments. In maturity group II, yield response to narrow rows (increased yield in narrow rows compared to wide rows averaged over all observations) was negatively correlated with canopy width, indicating that genotypes with narrow canopies tended to show a greater yield response to planting in narrow rows. In group III, yield response to narrow rows was negatively correlated with height x yield. It was concluded that there was no penalty for early generation selection and evaluation in wide-row plots with later evaluation and production in narrow rows