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Abstract
Mendelizing quantitative trait loci (QTL) and identifying 'stable' QTL are prerequisites for marker-assisted selection in crop improvement. Here, we used molecular markers to study genetic basis of quantitative variation introgressed into bermudagrass and Upland cotton. Bermudagrass lags in genomic and molecular breeding resources. We screened 2,017 sugarcane primer pairs (PPs) for transferability and polymorphisms in bermudagrass germplasm. A subset of useful markers was used to build genetic linkage maps of two bermudagrass species, Cynodon dactylon (T89) and Cynodon transvaalensis (T574) and genetic architecture of one foliage (canopy height, HT), two stolon (stolon internode length, ILEN and length of the longest stolon LLS), and two leaf traits (leaf length, LLEN and leaf width, LW) in 110 F1 individuals was reported. This early QTL study in bermudagrass adds to molecular breeding resources and information in the genus. In Upland cotton, we developed QTL-stacked populations in genetic backgrounds of six elite G. hirsutum backgrounds targeting nine fiber QTL alleles introgressed into advanced-backcross G. hirsutum lines affecting fiber elongation (three each from G. tomentosum and G. mustelinum), fiber fineness (one from G. tomentosum), fiber strength (one from G. mustelinum), and fiber length (one from G. barbadense). A total of thirty-eight QTL-stacked F1 were selfed to generate F2 populations segregating at two to four QTL regions, which were field tested for fiber quality traits, genotyped at target QTL regions, selectively advanced to F2:3 generation and assessed at two different locations (Athens and Tifton, GA). Favorable shifts in average phenotypes of selected traits were partially explained by genotypes at introgressed QTL regions, while a subset of QTL and some digenic combinations was also consistent across backgrounds and/or between generations. Our results attest to the promise of MAS as a molecular breeding tool for simultaneously validating QTL effects and developing QTL-stacked germplasm in different genetic backgrounds. Resources developed in this study are valuable for molecular breeding applications in bermudagrass and Upland cotton.