Molecular mapping of QTLs for fiber qualities in three diverse lines in Upland cotton using SSR markers

The improvement of cotton fiber quality is extremely important because of changes in spinning technology. The identification of the stable QTLs affecting fiber traits across different generations will be greatly helpful to be used effectively in molecular marker-assisted selection to improve fiber quality of cotton cultivars in the future. Using three elite fiber lines of Upland cotton (Gossypium hirsutum L.) as parents, three linkage maps were constructed to tag QTLs for fiber qualities using SSR markers. There were 39 QTLs, 17 significant QTLs, LOD 3.0 and 22 suggestive QTLs, 3.0 > LOD 2.0, detected by composite interval mapping for fiber traits, in which 11 QTLs were for fiber length, 10 for fiber strength, 9 for micronaire and 9 for fiber elongation. Out of 17 significant QTLs, 5 QTLs with high logarithm of odds (LOD) score value and stable effect could be found in both F₂ and F_2:3 segregating populations, showing a great potential for molecular-assisted selection in improving fiber quality. At least three common QTLs could be identified in two populations. These common QTLs detected in different populations suggested that there existed elite fiber genes and possibly of the same origin. In addition, we found three pairs of putative homoeologous QTLs, qFL-7-1c and qFL-16-1c, qFS-D03-1a, qFS-A02-1b and qFS-A02-1c, and qFE–D03-1a and qFE-A02-1c. Our results provided a better understanding of the genetic factors of fiber traits in AD tetraploid cottons.