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 include 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 per unit land area, but none have reported on the relationships among the most basic within-bell yield components and fiber quality. The objective of this study was to evaluate the combining ability for within-bell lint yield components among a group of cotton genotypes that varied by date of release, type of release, originating program, and their fiber quality parameters, especially fiber bundle strength. Four cultivars, one each released in 1905, 1943, 1979, and 1981, and two modern germplasm 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 normal 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 components were determined by direct measurement or through calculations. Genotypes having good general combining ability (GCA) estimates for fiber quality exhibited negative GCA estimates for the most basic within-bell yield components, Among these genotypes, three-way crosses, modified backcross, or recurrent selection procedures would be required to select for improved fiber quality and simultaneously increase the number of harvestable fibers per unit of seed surface area.