Association mapping and favourable QTL alleles for fibre quality traits in Upland cotton (Gossypium hirsutum L.).

Improving cotton fibre quality is a major breeding goal for Upland cotton in China.To investigate the genetic mechanisms of fibre quality, a diverse panel of 403 Upland cotton accessions was grown, and the fibre quality traits were measured in six different environments. Genotyping was performed with genomewide simple sequence repeats. A total of 201 markers were polymorphic and generated 394 allele loci, and 403 accessions were arranged into two subgroups using Structure software. Of the marker loci, 18.94% showed significant linkage disequilibrium (P < 0.05). A mixed linear model in association mapping showed that 51 associations were significant between 39 polymorphic loci and five fibre quality traits, according to best linear unbiased prediction, and in at least three of six environments. Of the 39 associated marker loci, 12 were coincident with previous studies. There were 41 typical accessions identified as containing favourable allele loci related to fibre quality traits. The identified favourable QTL alleles and typical accessions for fibre quality are excellent genetic resources for future cotton breeding in China.