QTL analysis for yield and fibre quality traits using three sets of introgression lines developed from three Gossypium hirsutum race stocks.

Upland cotton (Gossypium hirsutum L.) race stocks may possess desirable traits for the genetic improvement of cotton. Quantitative trait locus (QTL) analysis can assist in uncovering new alleles from unadapted race stocks. In this study, three sets of chromosome segment introgression lines (ILs) were developed from three backcrosses (BC) between three race stocks, G. hirsutum races latifolium accs. TX-34 and TX-48 and punctatum acc. TX-114, as donor parents and Texas Marker-1 (TM-1) as the recurrent parent. Based on a total of 452 polymorphic simple sequence repeat (SSR) markers in BCF genotyping, 149, 150 and 184 ILs were obtained from TM-1 × TX-34, TM-1 × TX-48 and TM-1 × TX-114, respectively. The average introgressed chromosomal segment length was 12.7 cM, and the total genetic distance was 3268 cM covering approximately 73.4% of the Upland cotton genome. The BCF, BCF and BCF progeny, which produced the ILs, were evaluated for yield and fibre quality traits. A total of 128 QTLs were detected, each of which explained 1.6-13.0% of the phenotypic variation. Thirty-five common QTLs related to eight traits were detected. Six QTL clusters were found on five chromosomes. Thirty-eight QTLs were previously unreported, and they may be footprints of cotton domestication. Domestication or artificial selection by humans successfully eliminated most unfavourable QTLs (21/38); however, some favourable QTLs (17/38) are not present in modern cultivars, demonstrating the importance of race stocks for improving cotton cultivars. The 26 elite ILs developed could be used to improve the yield and fibre quality components simultaneously. These results provide information on desirable QTLs for cotton improvement.