Genetic Improvement of Upper Half Mean Length and Short Fiber Content in Upland Cotton, Gosspium hirsutum

Desired base upper half mean length (UHML) of upland cotton (G. hirsutum) in the U.S. has been set a 27.0 mm and is shorter than the standard set by the international community. Upland cotton genotypes from China, South Africa, West Africa, and the U.S. were test crossed to an extra long staple upland (ELSU) and a short staple upland (SSU) and selected genotypes that included both ELSU and MSU phenotypes were crossed in a half-diallel mating scheme to estimate general combing ability (GCA) effects and specific combining ability (SCA) effects. A recombinant inbred line (RIL) population was established to determine the narrow sense heritability (h^2) of AFIS short fiber content by weight (SFCw) and lower half mean length (LHML) and to estimate SFCw using HVI fiber properties.

Obsolete cultivars from China are not likely sources for UHML improvement, cultivars from Africa and the U.S. could harbor alleles not being used in current elite short staple cultivars or modern ELSU cultivars. Two ELSU lines used in this study derived through interspecific hybridization with G. barbadense could contain alleles for UHML improvement in modern ELSU cultivars developed without any apparent G. barbadense introgression. A third line D&PL 45-867, might contain alleles for UHML improvement in long staple upland cotton genotypes.

Narrow sense heritability estimates indicated a much higher heritability of LHML than AFIS SFCw. Correlation between AFIS SFCw and LHML did not agree with previous studies when using an ELSU X MSU cross. Further study is needed to understand this complex relationship.