Responses of Upland Cotton to Selection for Fiber Length and Fineness in a Nonirrigated Semiarid Environment¹

Fiber length and fineness were used as the selection criteria in the development of four groups of lines from a composite‐cross of upland cotton ( Gossypium hirsutum L). These groups consisted of lines with long‐coarse, longfine, short‐coarse, and short‐fine fibers. These fiber groups were used to evaluate selection for fiber length and fineness on fiber strength and elongation, lint yield, earliness of crop maturity, stormproofness, lint percent, lint index, and seed index. All selections and evaluations were made in a semiarid environment without irrigation. Orthogonal comparisons, based on the fiber groups, were used to determine the response of these characters to selection for fiber length and fineness. Comparisons of linear regression coefficients from the parental and selected lines were used to estimate the changes in character relationships that occurred during selection. Significant residual variation for most characters, existed among the selected lines within each group. This residual variation suggested that selection had not eliminated all genetic variance. The orthogonal comparisons showed that fiber length was associated with fiber fineness and elongation, lint yield, stormproofness, lint percent, and seed index and that fiber fineness was associated with fiber strength and elongation, earliness of crop maturity, stormproofness, lint percent, lint index, and seed index. Correlation coefficients from the parental and the selected lines suggested that the relationships between fiber length and both lint yield and lint percent did not change during the selection process, but that the associations between fiber length and earliness of crop maturity, stormproofness, lint index, and seed index did change. The relationships between fiber fineness and both fiber strength and lint index were the same in both the parental and selected lines, whereas fiber elongation, earliness of crop maturity, stormproofness, and seed index did not show the same degree of relationship with fineness in the parental and selected lines.