Major Gene Identification and Quantitative Trait Locus Mapping for Yield-Related Traits in Upland Cotton (Gossypium hirsutum L.)

Segregation analysis of the mixed genetic model of major gene plus polygene was used to identify the major genes for cotton yield-related traits using six generations P-1, P-2, F-1, B-1, B-2, and F-2 generated from the cross of Baimian 1 x TM-1. In addition to boll size and seed index, the major genes for the other five traits were detected: one each for seed yield, lint percentage, boll number, lint index; and two for lint yield. Quantitative trait locus/loci (QTL) mapping was performed in the F2 and F2,3 populations of above cross through molecular marker technology, and a total of 50 QTL (26 suggestive and 24 significant) for yield-related traits were detected. Four common QTL were discovered: qLP-3b(F-2)/qLP-3(F-2,F-3) and qLP-19b(F-2)/qLP-19(F-2.3) for lint percentage, qBN-17(F-2)/qBN-17(F-2:3) for boll number, and qBS-26b(F2)/qBS-26(F2:3) for boll size. Especially, qLP-3b(F-2)/qLP-3(F-2:3), not only had LOD scores >3 but also exceeded the permutation threshold (5.13 and 5.29, respectively), correspondingly explaining 23.47 and 29.55% of phenotypic variation. This QTL should be considered preferentially in marker assisted selection (MAS). Segregation analysis and QTL mapping could mutually complement and verify, which provides a theoretical basis for genetic improvement of cotton yield-related traits by using major genes (QTL).