Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/24/2005
Publication Date: 4/29/2005
Citation: Levi, A. 2005. Traditional genetic and advanced molecular tools used for improving watermelon cultivars. Meeting Abstract. West Virgina State University. Eleventh Annual Research Symposium 2005. Page 6.
Technical Abstract: Watermelon is an important vegetable crop, with important nutritional benefits. Over 1,200 watermelon cultivars have been developed by breeders and seed savers in the USA during the last two centuries. Three-hundred of these heirloom cultivars are maintained at the USDA, ARS “National Center for Genetic Resources Preservation” in Fort Collins, Colorado, and at the “Plant Genetic Resources Conservation Unit” in Griffin, Georgia (www.ars-grin.gov). DNA fingerprinting analysis found low genetic diversity among watermelon heirloom cultivars, which is likely to be a result of many years of inbreeding and selection for watermelons with desired fruit quality. The low genetic diversity contributes to the susceptibility of cultivated watermelon to a large number of diseases and pests, and there is a need to genetically enhance the resistance of watermelon cultivars to pathogens and pests. Over 1,700 wild watermelon accessions were collected in different parts of the world and are maintained by the ‘Plant Genetic Resources Conservation Unit’. These wild watermelon accessions are being evaluated for disease and pest resistance, and a few accessions were found to contain resistance to powdery mildew, bacterial fruit blotch, gummy stem blight, and papaya ring spot virus. Also, a few accessions were resistant to whiteflies, spider-mites, and nematodes. These accessions are being crossed with watermelon cultivars in order to enhance their resistance to diseases and pests. To identify the genes conferring resistance, a genetic linkage map is constructed for watermelon based on a testcross population and an F2 population. The testcross map includes 362 markers (RAPD, ISSR, AFLP, SSR, and ASRP), and covers a genetic distance of 1,385 cM. A variety of genes are associated with watermelon fruit growth and ripening. In order to isolate and characterize these genes, a cDNA library was constructed from watermelon flesh RNA. Over 1,045 cDNA clones were sequenced, and analyzed using the Basic Local Alignment Search Tool (BLAST). The sequenced cDNA clones are being used in a microarray analysis to determine their differential expression during fruit development. Traditional breeding and biotechnology tools are being used in research and in improvement of watermelon crop.