Phenotypic Stability of Cotton1

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Abstract
We studied the effects of level of ploidy and of heterozygosity on the phenotypic stability of certain inbred lines of cotton (Gossypium sp.) and their F1 hybrids. The experimental material consisted of four inbred lines from each of three cultivated species of cotton. These species were an Old World diploid (G. arboreum L.), and two New World allotetraploids (G. hirsutum L. and G. barbadense L.). Eight phenotypic characters or traits were measured in five environments. In each environment the material was grown in two randomized blocks, divided into split‐plots. Inbreds and their F1 hybrids were used to minimize genetic variance, and estimated environmental variances were analyzed.The level of ploidy did not significantly affect the phenotypic stability of the eight characters. The diploid G. arboreum was as well buffered against environmental variation as the two allotetraploids, G. hirsutum and G. barbadense. Thus, the intergenomic heterozygosity associated with amphidiploidy conferred no advantage to plants by enhancing their ability to adjust to fluctuations in the environment. Significant differences in phenotypic stability usually were not found in comparisons of inbred lines (F0) and hybrid progenies (F1). The expression of phenotypic stability appeared to be random with respect to five specific environments in which the plants were grown. Apparently the cultivated species of cotton we studied do not possess homeostatic systems associated with either homozygosity or heterozygosity.

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