Stability Parameters of Soybean Cultivars in Maturity Groups VI, VII, and VIII1

Abstract

Environmental stability parameters were estimated for adapted soybean [Glycine max (L.) Merr.] cultivars for two 3‐year periods 28 environments in central and southern Alabama. Objectives were to measure and compare relative stabilities of the cultivars and to compare the effect of the different periods and productivity levels on the stability parameter estimates. In Exp. 1 (1976–1978) nine adapted cultivars (Maturity Groups VI, VII, and VIII) and one unadapted cultivar (Maturity Group V) were analyzed.In Exp 2 (1979–1981) 12 adapted cultivars and one Maturity Group V cultivar were analyzed. Seven cultivars were common to both experiments. ‘Forrest,’ the Maturity Group V cultivar, had the lowest or nearly the lowest seed yield and highest deviations from regression in both experiments. In Exp.1, all cultivars except ‘Coker 338’ had significant deviations from regression, and ‘Coker 136’, ‘Ransom’, and ‘Hutton’ had significant regression coefficients. In Exp. 2, ‘Bragg’, Ransom and ‘Coker 488’ had nonsignificant deviations from regression, and ‘Centennial’, ‘Coker 237’, and Hutton had significant regression coefficients. Joint regression analyses of both experiments revealed that a major part of the genotype ✕ environment interaction could be accounted for by differences between the fitted regression lines. Differing levels of productivity of the two experimental periods had little effect on stability parameter estimates.