Alien genomic introgressions enhanced fiber strength in upland cotton (Gossypium hirsutum L.)

Abstract

Cotton (Gossypium) is a worldwide natural fiber crop. Fiber quality improvement lags far behind that of fiber yield. Although interspecific hybridization contributes significantly to improve fiber quality, the mechanism of alien genomic introgression to improve fiber quality has rarely been reported. In this study, a superior fiber-strength line (J02−508) derived from interspecific hybridization was used to dissect the genetic and genomic bases for fiber quality by forward-genetics technologies. Both F2 and F2:5 populations were developed from a cross between superior line J02−508 and a weak fiber-quality line (ZRI015). Based on the linkage map constructed from the F2:5 population, 27 stable quantitative trait loci (QTL) were detected for fiber yield and quality. Unexpectedly, an abnormally high segregation distortion ratio was found for all chromosomes (reaching an average of 83.13 % for each chromosome), and the highest ratio of segregation distortion markers (SDMs) was on chromosome D08, reaching 99.39 %. Taking the SDMs into account, a distinct genome region on chromosome D08 was identified, which had a sizeable physical interval (∼53 Mb length) with low recombination frequency and was significantly associated with fiber strength (named qFS_D08, LOD value = 11.49). Additionally, by integrating different approaches, we initially confirmed that this region was an alien fragment introgressed from wild diploid cotton, G. thurberi (D1), accounting for nearly 77 % of the length of chromosome D08 in the J02−508 genome. We provided molecular evidence for fiber strength improvement caused by introgression. This study is also beneficial to understand the importance of interspecific hybridization for improving fiber strength during cotton breeding.