Environmental Stability and Adaptation of Several Cotton Cultivars¹

Abstract

We studied the stability, adaptation, and yields of several diverse cotton ( Gossypiutn hirsutum L.) cultivars that had been grown at several locations in one or more of three, 3‐year periods of testing. We used as environmental indexes the mean lint yields of three “standard” cultivars that were common to all tests. The yields of the remaining cultivars were regressed upon these indexes. The regression coefficients (6 values) were used as measures of adaptability, and the coefficients of determination (r 2 values) were used as measures of stability. Analyses of variance of lint yields also were computed. In comparison with the three standards, most of the other cultivars were adapted to all environments (b = 1.0), and all but one were stable. However, there were several significant yield differences among the cultivars within each of the three periods of testing. Thus, yield level was the most divergent parameter measured, adaptation was next, the stability was the least divergent. Because we found significant differences among commercial cultivars in both adaptation and stability, we believe that the use of these two parameters in conjunction with yield would be of significant benefit in breeding material evaluation.