New SSR Markers for Use in Cotton (Gossypium spp.) Improvement.

SSR markers, also known as microsatellite DNA markers, are very useful for saturation of the large and complex upland cotton (Gossypium hirsutum L.) genetic linkage map. Monsanto has invested heavily in development of cotton SSRs and has implemented molecular breeding technologies for the genetic improvement of cotton globally and the acceleration of the integration of biotechnology traits into the most elite upland cotton germplasm in the commercial pipeline. Genomic clones from microsatellite-enriched cotton DNA libraries were sequenced to identify SSR-containing target regions and SSR-containing EST collections were searched. PCR primer pairs were generated for 5,475 target sequences and utilized to amplify SSR marker loci which provide useable levels of polymorphism in interspecific and intraspecific genetic populations. Bioinformatics analysis of these sequences and primer pairs relative to SSR sequences already present in current public databases reveal that approximately 2,937 of these SSR primer pairs and target genomic sequences are unique and amplify about 4,000 unique marker loci in a tetraploid cotton genome depending on the germplasm analyzed. A subset of the Monsanto SSR markers were placed on a consensus genetic map along with a selected set of public anchor SSR markers (BNL and JESPR markers). Chromosome-marker bins, each 20 cM in size, were constructed on the genetic linkage map containing the two public marker sources. This generated 207 marker bins for a total of about 4,140cM which is approximately the size of the tetraploid cotton genetic map. These bins contain 945 unique Monsanto SSR marker loci and 615 public anchor SSR markers. In order to contribute to the expanding genomic resources for cotton research and improvement, Monsanto is facilitating the uploading of the unique SSR primer sequences, their respective target clone sequence, and chromosome bin designation (if known) to Cotton DB (http://cottondb.org/) and CMD (http://cottonmarker.org) databases. These will be available for general use in the cotton research community without restriction.