Submitted to: Journal of Heredity
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/21/2004
Publication Date: 3/1/2005
Citation: Ulloa, M., Saha, S., Jenkins, J.N., Meredith, Jr., W.R., McCarty, Jr., J.C., Stelly, D.M. 2005. Chromosomal assignment of RFLP linkage groups harboring important QTLs on an intraspecific cotton (Gossypium hirsutum L.) joinmap. Journal of Heredity. 96(2):132-144. Interpretive Summary: Cotton is the world's most important fiber producing crop, and research efforts are ongoing at many locations to breed varieties with increased fiber quality, yield, and other traits. Traditional breeding techniques rely on the crossing of two different plants, collecting seed from the cross, planting the seed, and evaluating the resultant plant. To help speed the process, it would be useful to know the location of the gene or genes that control a particular trait, such as fiber length. The objective of this study was to assign molecular markers, which represent possible genes, to specific chromosomes. A total of 92 quantitative trait loci (QTL, combinations of closely linked genes that control traits) were identified on their respective chromosomes. In addition, approximately 40% of the putative QTLs for agronomic and fiber quality traits were placed on two major linkage groups (linkage groups 1 and 2) on two different chromosomes indicating that cotton chromosomes may have regions of high and low genetic recombination like some other plants and animals. This information will be useful to other geneticists working with cotton and will facilitate future efforts to map the cotton genome.
Technical Abstract: Chromosome identities were assigned to fifteen linkage groups of the RFLP joinmap developed from four intraspecific cotton (Gossypium hirsutum L.) populations with different genetic backgrounds (Acala, Delta, and Texas Plain). The linkage groups were assigned to chromosomes using probes common to the previously published joinmap report by deletion analysis using the genomic DNA of the aneuploid chromosome substitution lines. Our results revealed 63 QTLs on five chromosomes of the A sub-genome: chromosome 3 (linkage groups 1, 3, 12, 20, and 36), chromosome 7 (linkage group 11), chromosome 9 (linkage group 26), chromosome 10 (linkage group 43), and chromosome 12 (group 42), and 29 QTLs on the three different D sub-genome chromosomes: chromosome 14 Lo (group 45), chromosome 20 (group6), the long arm of chromosome 26 (groups 2, 13 and 14). Linkage group 1 (chromosome 3) harbored 21 QTLs, covering 117 cM with 54 RFLP loci. Linkage group 2, (long arm of chromosome 26) harbored 16 QTLs, covering 77.6 cM with 27 RFLP loci. In addition, the two chromosomes harbored approximately 73% of the total putative QTLs, 38 and 29 for chromosome 3 and long arm of chromosome 26, respectively. Approximately 40% of the putative QTLs for agronomic and fiber quality traits were placed on these two major linkage groups (linkage groups 1 and 2) in two different chromosomes indicating cotton chromosome may have regions of high (hot spot) and low (cold spot) meiotic recombination like some other eukaryotic organisms. QTLs for agronomic and fiber quality traits on the joinmap also reveal highly recombined and putative gene abundant regions in the cotton genome. Identification of chromosomal location of RFLP markers common to different intra and interspecific populations would facilitate in future to develop portable frame work markers and genetic and physical mapping of the cotton genome.