Quantitative Genetic Analysis For Flowering Time In Primitive Upland Cotton, Gossypium Hirsutum L., And Chromosome Assignment Of Bac-Derived Ssr Markers

Cotton is a very important economical crop in the U.S. and throughout the world. The developments in molecular biology offer new and innovative approaches toward evaluating and understanding genetic mechanisms of important agronomical traits. Bacterial artificial chromosome (BAC) libraries have rapidly become the preferred choice for physical mapping. BAC-derived microsatellite or simple sequence repeats (SSRs) markers facilitate the integration of physical and genetic recombination maps. The first objective in this research was to identify chromosome locations of a set of BAC-derived SSR markers in tetraploid cotton. A total of 192 SSR primer pairs were derived from BAC clones of an Upland cotton (Gossypium hirsutum L.) genetic standard line TM-1. Using deletion analysis method, we assigned 39 markers out of the 192 primer pairs to 18 different chromosomes or chromosome arms. Chromosomal assignment of these markers will help to improve the current cotton genetic linkage maps and facilitate positional candidate gene cloning, comparative genome analysis, and the coordination of chromosome-based genome sequencing projects. Wild race stocks (Gossypium spp.) represent valuable resources for genetic improvement. Most primitive accessions are photoperiod sensitive; they do not flower under the long days of the U.S. cotton belt. Molecular markers were used to locate quantitative trait loci (QTLs) for node of first fruiting branch (NFB), node of first open boll (NOB), and fruiting score (FS). An F2 population consisted of 251 plants from the cross of a day neutral cultivar Deltapine 61, and a photoperiod sensitive accession Texas 701, were used in this study. For each trait, three major QTLs were mapped to chromosome 16, 21, and 25. QTL analysis was also conducted in two F2 populations generated from the cross between Deltapine 61 and two photoperiod sensitive accessions (T1107, PI 607174; T1354, PI 530082) of Upland cotton (G. hirsutum L.). QTL analysis indicated that NFB differed between the two F2 populations. Two major QTLs (q-NFB-c21-1 and q-NFB-c25-1) were found in population 1107; whereas, only one (q-NFB-c25-1) was important in population 1354. Discovering QTLs associated with flowering time may have the potential to facilitate day neutral conversion of wild photoperiod sensitive accessions