Genetic Analysis and Stable QTL Detection on Fiber Quality Traits Using Two Recombinant Inbred Line Populations and Their Backcross Progeny in Upland Cotton

Cotton fiber as the raw natural fiber material is widely used for the textile industry. Understanding the genetic mechanism of fiber traits is helpful for fiber quality improvement. In present study, the genetic basis of fiber quality traits was explored using two recombinant inbred lines (RILs) and corresponding backcross (BC) populations under multiple environments in Upland cotton based on marker analysis. In backcross population, no significant correlation was observed between marker heterozygosity and fiber quality performance and it suggested that heterozygosity was not always necessarily advantageous for the high fiber quality. In two hybrids, 111 quantitative trait loci (QTLs) for fiber quality were detected using composite interval mapping, in which 62 new stable QTLs were simultaneously identified in more than one environments or populations. QTL detected at the single-locus level mainly showed additive effect. In addition, a total of 286 digenic interactions (E-QTLs) and their environmental interactions (QTL × environment interactions, QEs) were detected for fiber quality traits by inclusive composite interval mapping. QE effects should be considered in molecular marker-assisted selection breeding. On average, the E-QTL explained a larger portion of the phenotypic variation than the main effect QTL did. It is concluded that additive effect of single-locus and epistasis with few detectable main effects play an important role in controlling fiber quality traits in Upland cotton.