Inheritace of Plant Height in Cotton. II. Diallel Analyses Among Six Semidwarf Strains1

Abstract

Semidwarf cultivars of upland cotton (Gossypium hirsutum L.) have been developed to meet the requirements of narrow‐row, high‐population cotton production. Six semidwarf stocks, the diallel set of F1 hybrids among those stocks, and a “normal‐height” stock were used to compare plant height and crop maturity characters among the semidwarf stocks and the normal‐height stock and to evaluate the inheritance of those characters among the semidwarf stocks. The characters studied were plant height, mainstem and fruiting‐branch internode length, number of mainstem nodes, node of the first fruiting branch, and mean maturity date. Diallel analyses were used to estimate genetic and environmental components. Comparisons between the normal‐height and the semidwarf stocks showed that the semidwarf stocks were gen. erally shorter in plant height, had shorter mainstem and fruiting‐branch internodes, initiated their fruiting branches at a lower mainstem node, and were earlier in crop maturity than the normal‐height stock. Diallel analyses indicated that the genetic variation for the plant height and maturity traits among the semidwarf stocks was primarily additive, with a small, although significant, dominance component associated with all the traits except number of mainstem nodes. Heritability was relatively low for plant height and mainstem internode length, intermediate for number of mainstem nodes and node of the first fruiting branch, and. high for fruiting‐branch internode length and mean maturity date.