QTL alleles for improved Wber quality from a wild Hawaiian cotton, Gossypium tomentosum

Seventeen backcross-self families from crosses between two Gossypium hirsutum recurrent parent lines (CA3084, CA3093) and G. tomentosum were used to identify quantitative trait loci (QTLs) controlling fiber quality traits. A total of 28 QTLs for fiber quality traits were identified (P < 0.001), including four for fiber elongation, eight for fiber fineness, four for fiber length, four for fiber strength, six for fiber uniformity, one for boll weight, and one for boll number. Three statistically significant marker-trait associations for lint yield were found in a single environment, but need further validation. Two-way analysis of variance revealed one locus with significant genotype × family interaction (P < 0.001) for fiber strength and a second locus with significant genotype × environment interaction (P < 0.001) in the CA3084 background, and two loci with significant genotype × background interaction (P < 0.001) for the 28 common markers segregating in both of the two recurrent backgrounds. Co-location of many QTLs for fiber quality traits partially explained correlations among these traits. Some G. tomentosum alleles were associated with multiple favorable effects, offering the possibility of rapid genetic gain by introgression. Many G. tomentosum alleles were recalcitrant to homozygosity, suggesting that they might be most effectively deployed in hybrid cottons. DNA markers linked to G. tomentosum QTLs identified in the present study promise to assist breeders in transferring and maintaining valuable traits from this exotic source during Upland cotton cultivar development. This study also adds further evidence to prior studies indicating that the majority of genetic variation associated with fiber quality in tetraploid cotton traces to the D-subgenome from a diploid ancestor that does not produce spinnable fiber.