COMBINING ABILITY FOR WITHIN-BOLL YIELD COMPONENTS IN COTTON, GOSSYPIUM-HIRSUTUM L

Lint yield and fiber quality in upland cotton, Gossypium hirsutum L., are interrelated through a series of individual components that includ e bolls/unit land area, mean fiber length and weight/unit length, and a series of within-bell components. Numerous studies have investigated the relationships among various components of lint yield and yield pe r unit land area, but none have reported on the relationships among th e most basic within-bell yield components and fiber quality. The objec tive of this study was to evaluate the combining ability for within-be ll lint yield components among a group of cotton genotypes that varied by date of release, type of release, originating program, and their f iber quality parameters, especially fiber bundle strength. Four cultiv ars, one each released in 1905, 1943, 1979, and 1981, and two modern g ermplasm lines were crossed in a half diallel. Parents and F(1)s were grown at College Station, TX, in 1989 and 1992. Twenty-five and 100 no rmal bells were hand harvested from each plot of a randomized complete block design in 1989 and 1992, respectively, Fiber quality parameters were determined by high volume instrumentation. Within-bell yield com ponents were determined by direct measurement or through calculations. Genotypes having good general combining ability (GCA) estimates for f iber quality exhibited negative GCA estimates for the most basic withi n-bell yield components, Among these genotypes, three-way crosses, mod ified backcross, or recurrent selection procedures would be required t o select for improved fiber quality and simultaneously increase the nu mber of harvestable fibers per unit of seed surface area.