Genetic dissection of lint percentage in an introgression population between Gossypium hirsutum and G. mustelinum.

Key message: Fourteen stable QTL for LP in introgression population of G. mustelinum were detected across multiple environments. GmAOC4 encoding allene-oxide cyclase was identified as the candidate gene for the major locus qLP-D12-3. Cotton (Gossypium spp.) is an important natural fiber crop for the textile industry worldwide. Lint percentage (LP) is one of the most essential yield components of cotton. However, the genetic and molecular mechanisms underlying LP in cotton remain unclear. Here, 264 introgression lines of the G. mustelinum acc. P0811704 in the background of G. hirsutum cv. Emian22 were used to dissect the LP phenotype in ten individual environments. A total of 14 stable quantitative trait loci (QTL) were identified in at least two environments, with phenotypic variation explained by them ranged from 1.12 to 13.14%. Among them, qLP-D12-3, a main-effect QTL, was validated in IL-derived F₂ segregating population (n = 2836), and was fine-mapped to a 110-kb physical region by selected F_2:3 recombinants. Among the seven annotation genes in this region, only one gene, encoding allene-oxide cyclase (AOC4), exhibited a significant expression difference between near-isogenic lines and recurrent parent when lint fibers are initiating. AOC4 contains G. mustelinum-specific variation in the promoter region, and highly expressed in fiber cells of the outer layer of ovule. This research would lay a solid foundation for further elucidating the molecular mechanism of cotton fiber initiation.