Genome-wide association study reveals novel quantitative trait loci and candidate genes of lint percentage in upland cotton based on the CottonSNP80K array

Cotton (Gossypium spp.) is an important natural textile fiber and oilseed crop widely cultivated in the world. Lint percentage (LP, %) is one of the important yield factor, thus increasing lint percentage is a core goal of cotton breeding improvement. However, the underlying genetic and molecular mechanisms that control lint percentage in upland cotton remain largely unknown. Here, we performed a Genome-wide association study (GWAS) for LP based on phenotypic tests of 254 upland cotton accessions in four environments and BLUPs using the high-density CottonSNP80K array. A total of 41,413 high-quality single-nucleotide polymorphisms (SNPs) were screened and 34 SNPs within 22 QTLs were identified as significantly associated with lint percentage trait in different environments. In total, 175 candidate genes were identified from two major genomic loci (GR1 and GR2) of upland cotton and 50 hub genes were identified through GO enrichment and WGCNA analysis. Furthermore, two candidate/causal genes, Gh_D01G0162 and Gh_D07G0463, which pleiotropically increased lint percentage were identified and further verified its function through LD blocks, haplotypes and qRT-PCR analysis. Co-expression network analysis showed that the candidate/causal and hub gene, Gh_D07G0463, was significantly related to another candidate gene, Gh_D01G0162, and the simultaneous pyramid of the two genes lays the foundation for a more efficient increase in cotton production. Our study provides crucial insights into the genetic and molecular mechanisms underlying variations of yield traits and serves as an important foundation for lint percentage improvement via marker-assisted breeding.