Breeding Methods for Improving Yield and Fiber Quality of Upland Cotton (<i>Gossypium hirsutum</i> L.)¹

In the introgression of Gossypium arboreum L. ✕ G. thurberi Tod. fiber strength to medium staple Upland cotton ( G. hirsutum L.), we have been most successful with the pedigree method of hybridization and selection. Hybridization is required for the recombination of genes for high lint yield and fiber strength or length, and selection is necessary to locate the desirable recombinants in segregating populations. In 25 years of selection within breeding lines after the F 5 generation, only two highly desirable recombinants, Earlistaple‐7 and Pee Dee 4381‐54, have been found. Yield improvement in Earlistaple‐7 is attributed to fusarium wilt resistance rather than to recombination of genes for lint yield and fiber quality. We cannot rule out the possibility of intercrossing or outcrossing in the isolated seed increase of Pee Dee 4381 from which Selection‐54 was obtained. Random intermating, backcrossing, and composite‐crossing also were tried as methods to improve yield and fiber quality of Upland cotton. A valuable breeding line (Q) was developed by three cycles of backcrossing to three G. hirsutum parents (with selection only for high lint percentage) and a composite‐cross of progenies from each of these backcross populations. No desirable recombinants were found with random intermating. Failure of this method was attributed to: 1) broad germplasm pools, 2) nonelimination of undesirable plants from the populations, and 3) study of small populations of 10,000 plants. We believe that any breeding method that gives maximum combinations of genes for yield and fiber quality is desirable, and selection of promising recombinants in early generations is necessary to maintain populations of practical size.

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