Response to selective pressure in early generation progenies of upland cotton (Gossypium hirsutum L.)

Summary Combining high fiber strength with high yield in upland cotton (Gossipium hirsutum L.) was been difficult. The cross combination, 69–120 × 6M-10, was chosen for this study because of the divergence of parents for fiber strength, seeds per boll and crop maturity. Forty F₂ plants were selected in 1974 solely on the basis of visual yield and 20 plants were randomly chosen to serve as a bulk check. The F₃ progenies, the bulk check, the parents and a commercial check were tested in 1975. From these results, five groups were established, consisting of four (10%) progenies each to represent high seed/boll, low seeds/boll, high fiber strength, low fiber strength and high yield in the 1976 test of F₄ progenies. This experiment was conducted to (a) compare the contributions of yield components to lint yield among groups of early generation progenies (F₃ and F₄) and (b) determine the phenotypic correlations between yield and quality attributes. The yield components, bolls/m², seeds/boll, fibers/seed, mean fiber length and micronaire, were included as well as fiber strength.No significant lint yield differences were found among the five groups. Progenies within groups did, however, differ in lint yield. The low and high seeds boll groups gave similar yield and fiber quality results. The low and high fiber strength groups gave similar yield but longer fiber was obtained with the high strength group.Stepwise regression analyses estimates show that the number of bolls produced per unit area, although the major contributor to lint yield for all groups, contributed only 66.9% of the total variation in the progeny group selected for high yield, with fibers/seed, mean fiber length, micronaire and seeds/boll accounting for 13.2%, 8.1%, 6.0%, and 5.8%, respectively. Correlations between the various yield components and fiber strength were low and mainly insignificant, indicating that minor alterations might be made in later generations without serious consequences.Potential gains from second-stage selective pressure upon yield-per-boll components following initial selection for lint yield are discussed.