[QTL mapping for "pre-summer boll, summer boll and autumn boll" traits in cotton]

"Pre-summer boll, summer boll and autumn boll" have long been regarded as an important index for prematurity and high-yield in cotton. In this study, the prematurity and high-yield cotton cultivar, Baimian 2, was used as the central parent to cross separately with the middle-late-matury lines TM-1 and CIR12, and then two populations of F2 and F2:3 family lines were obtained, which was used to construct two genetic linkage maps. These maps were comprised of 269 and 127 marker loci with the total length 1837.8 cM and 1244.3 cM, respectively. Results of QTL location showed that a total of 29 QTLs were detected in the two combinations, including 16 suggestive QTLs and 13 significant QTLs, of which 5 significant QTLs had higher LOD values that was not only greater than 3 but also greater than the threshold calculated by permutation test. The contribution rate of 16 QTLs explained 10.9%-44.5% of the phenotypic variations. Four common QTLs, qPSB-17 for pre-summer boll, qSB-17 (qSB-17a/17b) for summer boll, and qAB-17 and qAB-12/26 for autumn boll, were detected close to common markers of the same chromosome in the two combinations, which could be applied in marker-assisted selection. Moreover, the contribution rate of qSB-17 (qSB-17a/17b) for summer boll in the two combinations was greater than 10%, and that of qAB-17, qAB-12/26 for autumn boll in one combination were greater than 10%. These common QTLs with greater contribution rates should take into consideration firstly in marker-assisted selection.