A GENETIC LINKAGE MAP OF TETRAPLOID COTTON WAS CONSTRUCTED USING SSRs, RAPDs and SRAPs

¹ National Key Laboratory for Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China

A genetic linkage map of tetraploid cotton was constructed using SSRs, RAPDs and SRAPs. A total of 368 SSR primer pairs, 600 RAPD primer and 238 SRAP primer combinations were used to screen polymorphisms between parents and revealed 749 loci in total (205 SSRs, 107 RAPDs and 437 SRAPs). Sixty-nine F2 individuals from the interspecific cross of Gossypium hirsutum 'Handan208' and G. barbadense 'Pima90' were genotyped for the 749 polymorphic markers. 566 loci were amalgamated into 41 linkage groups with at least 3 markers in each group at a LOD¡Ý3.0. The map covered 5141.8 cM with a mean interlocus space of 9.08 cM. The significance of deviations of observed allelic frequency from the expected ratio (1:1 or 3:1) was tested by ¦Ö2. 135 loci (18.0%) showed skewed segregation and most of which had an excess of female parent alleles. Distorted loci distributed in 34 linkage groups with the tendency of clustering at the ends of some linkage groups. This map was used to screen QTLs for fiber and yield traits and 21 QTLs for fiber traits were detected. There were 3 QTLs for fiber strength, 7 QTLs for fiber length, 4 QTLs for fiber elongation and 7 QTLs for micronaire value. Fiber uniformity ration was not mapped because of abnormal distribution. These QTLs located on 14 linkage groups and explained from 9.26% to 28.92% of the trait variation. The QTL near m7e11-360 located on LG1 affected fiber length and micronaire value simultaneously. The 'Pima90' parent with long, strong and fine fiber properties did not contribute all QTLs for good fiber quality, which meant that 'Handan 208' also contain good fiber properties, although that is a poor variety in fiber quality. A total of 39 quantitative trait loci (QTLs) were detected; which distributed on 21 linkage groups. The number of QTLs per trait ranged from one to seven. Of these QTLs detected, one controlling lint index can explain 24.3% of PV (phenotype cariation), six controlling seed index can explain 16.15%~39.21% of PV, seven controlling lint yield can explain 13.01%~28.35% of PV, two controlling seed cotton yield can explain 22.76%, 39.97% of PV, respectively. Five QTLs control lint percent, which explain 17.24%~34.23% of PV. The directions of most additive effects of QTLs are accord with the pheotype of the parents.