QTL Mapping of Fiber Quality in Low-Generation Upland Cotton Populations and Functional Annotation of Candidate Genes

Objective] This article aims to provide a theoretical basis for molecular marker-assisted breeding by quantitative trait loci (QTLs) mapping and gene function annotation of fiber quality. Method] F₂ populations were constructed using the two cotton cultivars (lines), CCRI 49 and 396289, as parents. Based on high-density genetic maps, the F_2:3 families with three environments were included in the F2 population. The QTL mapping of seven fiber quality traits including fineness and maturity, etc., was performed using the Clusters of orthologous groups (COG), Gene ontology (GO), and Kyoto encyclopedia of genes and genomes (KEGG) databases to annotate QTLs for gene function. Result] A total of 157 QTLs related to fiber quality were obtained and distributed on 20 chromosomes. QTLs with more traits on A03, A04, D02, A11 and D07 chromosomes clustered and may be the key chromosomes controlling fiber quality traits. A total of 13 stable QTLs were obtained, of which qFL-A03-1 and qFin-A11-4 were repeated in three environments, and nine other QTLs were repeated in two environments. And 4 763 candidate genes were annotated, with 2 416, 4 188, and 2 512 genes being annotated in COG, GO, and KEGG, respectively. Among them, 429 genes were annotated in stable QTLs. Some of these genes may be closely related to fiber quality. Conclusion] The high-density genetic map obtained by high-throughput sequencing can help to obtain more QTLs, which is beneficial to the screening of candidate genes related to fiber quality and the improvement of fiber traits, and improves the breeding efficiency.