QTL analysis of cotton fiber quality using multiple Gossypium hirsutum x Gossypium barbadense backcross generations

Cotton fiber properties are essential predictors of yarn performance. The suite of fiber quality traits that collectively affect the utility of the fiber for the textile industry include the length, the strength, the fineness and the color. These properties have been shown to be moderately to highly heritable. In an attempt to overcome the limitations of conventional breeding we undertook a marker-assisted selection program aimed at introgressing fiber quality QTLs from Gossypium barbadense L. into G. hirsutum L. We describe the QTL analysis of 11 fiber properties measured on three phenotypic data sets. The three populations studied were the 1st (BC1) and 2nd (BC2 and BC2S1) backcross generations derived from the cross between 'Guazuncho 2', G. hirsutum, and 'VH8', G. barbadense. Collectively we detected 80 QTLs, of which 50 surpassed the permutation-based LOD thresholds (3.2-5.7). The most economically important traits, length (two correlated properties), strength, fineness (four properties), and color (two properties) were influenced by 15, 12, 21, and 16 QTLs, respectively, that could be detected in one or more populations. As expected, for the majority of QTLs, the favorable alleles came from the G. barbadense parent. Altogether one third (26) of the QTLs confirmed the map position and phenotypic effect of QTLs reported in the literature also detected in interspecific G. hirsutum X G. barbadense populations. Cases of colocalization of QTLs for different traits were more frequent than isolated positioning. Taking these QTL-rich chromosomal regions into consideration, 19 regions on 15 different chromosomes, were identified as target regions for the marker-assisted introgression strategy.