Molecular mapping of QTLs for fiber quality traits in Gossypium hirsutum multi-parent recombinant inbred lines

Cotton is a valuable fiber crop which supplies raw material to more than 50 industries and is produced in more than 70 countries worldwide. The superiority of cotton fiber over other crops is primarily dependent on its quality. However, further improvements in fiber length and strength are required for modern processing technology and for cotton to maintain its position in the global market. Association mapping enables identification of QTLs controlling fiber quality-related traits which can be useful in cotton breeding. In the present study, we performed genetic diversity, linkage disequilibrium and association mapping analyses in 157 G. hirsutum multi-parent recombinant inbred lines using a total of 102 SSR markers. The population had depressed genetic variability (14%), a result of inbreeding of modern cotton genotypes. Despite this, we identified 11 significant and stable marker-trait associations for seed cotton yield, lint percentage, fiber length and fiber strength (p < 0.005). We also detected QTL co-localizations with positive and negative marker additive effects. Our results indicate that selection against negative alleles may be as important as selection for positive alleles. Analysis of the effects of allelic combinations at different QTLs revealed significant and stable marker clusters that can be selected for or against to provide maximum quality gains in cotton fiber quality.