Genome-wide association study reveals genetic variation and candidate genes of lint yield components under salt field conditions in cotton (Gossypium hirsutum L.)

Abstract

Background Salinity is one of the most decisive environmental factors limiting the productivity of cotton. However, the key genetic components leading to the reduction of cotton yield in saline-alkali soils are still unclear. Results Here, we evaluated three main components of lint yield across 316 G. hirsutum accessions, including single boll weight (SBW), lint percentage (LP) and boll number per plant (BNPP), under four salt conditions for two years. Phenotypic analysis indicated that LP showed no change under different salt conditions, however BNPP decreased significantly while SBW increased slightly under high salt condition. Based on 57,413 high-quality single nucleotide polymorphisms (SNPs) and genome-wide association studies (GWAS) analysis, a total of 42, 91 and 25 stable quantitative trait loci (QTLs) were identified for SBW, LP and BNPP, respectively. Few overlapped QTLs and no significant phenotypic correlation among the three traits was observed. Gene Ontology (GO) analysis indicated that their regulatory mechanisms were also quite different. There were 8 overlapped QTLs for LP while fewer for SBW and BNPP identified by comparing different salt conditions. We detected that 10 genes from the 8 stable LP QTLs were predominantly expressed during fiber development. Further, haplotype analyses found that a MYB gene ( GhMYB103 ) with the two SNP variations in cis-regulatory and coding regions, was significantly correlated with lint percentage, implying the crucial role in lint yield. With transcriptome analysis, we identified that 40 candidate genes from BNPP QTLs were salt-inducible. However, these genes exhibited different regulation pattern. Genes related to carbohydrate metabolism and cell structure maintenance were rich in high salt condition, while genes related to ion transport were active in low salt condition. Conclusions This study provides a foundation for elucidating cotton salt tolerance mechanism and contributes gene resources for developing varieties with high yield and salt stress tolerance in upland cotton.