GENETIC LINKAGE MAP FOR WATERMELON: SEGREGATION AND DISTRIBUTION OF DNA MARKERS

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  • 1 1USDA, ARS, U.S. Vegetable Laboratory, 2700 Savannah Highway, Charleston, SC 29414
  • | 2 2China National Engineering Research, Center for Vegetables (NERCV), P.O. Box 2443, Beijing 100089, China
  • | 3 3Syngenta Seeds, Inc., 21435 Road 98, Woodland, CA 9569
  • | 4 4Biotechnology Center, Alcorn State University, MS 39096-7500
  • | 5 5South Central Agricultural Research Laboratory, USDA, ARS, P.O. Box 159, Lane, OK 74555
  • | 6 6Department of Horticultural Sciences, Texas A&M University, College Station, TX 77843-2119
  • | 7 7Department of Horticulture, North Carolina State University, Raleigh, NC 27695-7609

Genetic linkage map is being constructed for watermelon based on a testcross population and an F2 population. About 51.0% and 31.8% of the markers in the testcross and F2 populations are skewed form the expected segregation ratios. AFLP markers appeared to be clustered on linkage regions, while ISSR and RAPD markers are randomly dispersed on the genome. AFLP markers also have greater genetic distances as compared with ISSR and RAPD markers, resulting in significant increase of map distance. An initial genetic map (based on the testcross population) that contains 27 ISSR and 141 RAPD markers has a total linkage distance of 1,166.2 cM. The addition of 2 ISSR, 8 RAPD and 77 AFLP markers increased the genetic distance of the map to 2,509.9 cM. Similar results with AFLP markers were also shown in mapping experiments with an F2S7 recombinant inbred line (RIL) population that was recently constructed for watermelon. Although the skewed segregation, marker order appeared to be consistent in linkage groups of the testcross and the F2 population. Experiments with SSR, and EST markers are being conducted to saturate the linkage map of watermelon genome.

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