Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 21, 2011
Publication Date: April 2, 2011
Citation: Chen, N., Lu, Y., Yuan, Y., Percy, R.G., Ulloa, M., Zhang, J. 2011. Mapping resistance gene analogs (RGAs) in cultivated tetraploid cotton using RGA-AFLP analysis. Euphytica. DOI: 10.1007/s10681-011-0421-2. Interpretive Summary: Identifying, locating, and incorporating important genes for cotton improvement can be greatly expedited by the use of molecular markers and molecular mapping techniques. However, there have been insufficient markers to adequately map cotton. In this work, new markers have been created using DNA sequences associated with disease resistance genes. These new markers have been mapped to 18 chromosomes of cotton. However, these disease resistance associated markers did not map randomly among the cotton chromosomes, but clustered in three chromosomes. Several of the markers mapped to the same region as a known root knot nematode resistance gene. Mapping of these markers will provide tools for marker assisted selection and improved, more efficient disease resistance breeding.
Technical Abstract: Diseases cause significant losses in cotton production throughout the US Cotton Belt. Growing resistant cultivars can significantly improve cotton yields and effectively reduce production inputs. Disease resistance (R) genes have been isolated in numerous plant species and the R genes with domains of nucleotide binding sites (NB) and leucine rich repeats (LRR) represent the largest R gene family. Degenerate primers designed based on conserved motifs of plant disease resistance genes were used alone or in combination with AFLP primers to analyze disease resistance gene analogs (RGAs) in a recombinant inbred line (RIL) population of Pima (Gossypium barbadense) 3–79 and Upland cotton (G. hirsutum) line NM 24016. Eighty-eight polymorphic RGA markers were amplified by 8 pairs of RGA degenerate primers, while 131 polymorphic RGA-AFLP markers were produced from six pairs of RGA-AFLP primer combinations. Of the 219 polymorphic RGA and RGA-AFLP markers that were identified, 212 were assigned to 18 chromosomes and linkage groups based on existing SSR markers that are on known chromosomes. However, the RGA and RGA-AFLP markers are not evenly distributed among chromosomes in that 189 RGA and RGA-AFLP markers (88%) are assigned onto three ‘‘giant’’ chromosomes, i.e., C6, C12, and C15, suggesting RGA clusters in the cotton genome. Several RGA and RGA-AFLP markers were mapped to the same linkage group carrying a root-knot nematode resistance gene. The identification and mapping of RGA and RGA-AFLP markers provide a framework to facilitate marker-assisted selection of disease resistance in cotton breeding and to understand the physical relationship of cotton resistance genes.