Genotype by Environment Interactions in Cotton — Their Nature and Related Environmental Variables1

The performance of four varieties of Upland cotton (Gossypium hirsutum L.) in 101 environments was used in (1) variance analyses to estimate the components of variance among genotypes, genotype by environment interactions, and experimental error, and (2) multiple regression analyses to relate the environment and the interaction effects to several environmental variables characterizing part of the environmental complex. The analyses were performed on lint yield per hectare, boll size, lint percent, seed index, and five fiber traits. The results of the analyses of variance showed that the interaction components were important for yield, but relatively less important for the other traits studied. In the multiple regression analyses, the independent variables were temperature, elevation, and subjective evaluations of moisture availability, disease condition, insect condition, and soil fertility level. These variables were jointly relatable to a proportion of the interaction sum of squares ranging from .245 for fiber fineness to .382 for fiber length. Of the environmental variables studied, temperature had the highest association with interaction.