Genetic Dissection of Extra Long Staple Fiber Quality Traits of Gossypium barbadense Using CSILs

Gossypium hirsutum is a high yield cotton species that exhibits only moderate performance in fiber quality traits. A promising but challenging approach to improving its phenotypes is inter-specific introgression, the transfer by genetic breeding of valuable traits or genes from the germplasm of another species such as G. barbadense, an important cultivated extra long staple cotton species. One set of CSILs was developed in TM-1, the genetic standard in G. hirsutum as the recipient parent and the long staple cotton G. barbadense acc. Hai7124 as the donor parent by molecular marker-assisted selection (MAS) in BC₅S_1-4 and BC₄S_1-3 generations. After fourth round of MAS, CSIL population was comprised of 174 lines containing 298 introgressed segments, of which 86 (49.4%) lines had single introgressed segments. The total introgressed segment length covered 2,948.7 cM with an average length of 16.7 cM and represented 83.3% of tetraploid cotton genome. The CSILs were highly varied in major fiber quality traits. From the plants in four environments, a total of 43 additive QTL (LOD>3) and 6 epistatic QTLs associated with fiber qualities were detected by QTLIciMapping 3.0 and multi-QTL joint analysis. Six stable QTL were detected in various environments. The CSILs created and the analyses presented here will enhance the understanding of the genetics of long staple fiber quality traits in G. barbadense and facilitate further molecular breeding of Upland cotton cultivars.