Synopsis Plot error variances were large for lint yield, bolls per plant, seed per boll, and boll weight; small for lint percentage, seed and tint index, and fiber length, strength and fineness. Genotype x environment interaction variances were generally small for all traits except yield and bolls per plant. Lint yield was highly positively correlated with lint percentage and bolls per plant and negatively correlated with seed index and weight per boll.

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Synopsis Substantial amounts of genotypic variance were observed for eight yield and fiber traits. Progeny × environment and plot error variances were relatively small. Lint yield was highly positively correlated with lint percentage, and there was a strong negative relationship between these two traits and lint strength.

Three cycles of recurrent selection for increased lint yield in Upland cotton (Gossypium hirsutum L) have been completed. Yield of the third cycle selections exceeded that of the base population by 29.7%. Response to selection was linear and is predicted to continue at approximately the same rate of gain for an additional cycle.Correlated responses to selection for yield were observed for the majority of the unselected traits measured. As selection increased lint yield, simultaneous increases were observed for lint percentage, number of seed per boll, earliness, fiber elongation, and fiber coarseness. Boll size, seed size, and fiber length and strength decreased. Weight of lint per seed showed little change.There was generally close agreement between predicted and observed responses to selection. This suggests that dominance effects were lacking or of relatively minor importance. Additive genetic effects would appear to predominate in this population, although additive ✕ additive effects cannot be excluded.

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