Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 20, 2011
Publication Date: July 12, 2011
Citation: Levi, A., Wechter, W.P., Massey, L.M., Carter, L., Hopkins, D. 2011. Genetic Linkage Map of Citrullus lanatus var. Citroides Chromosomal Segments Introgressed into the Watermelon Cultivar Crimson Sweet (Citrullus lanatus var. lanatus) Genome. American Journal of Plant Sciences. 2:93-110. Interpretive Summary: Bacterial fruit blotch is a major disease in commercial watermelon fields in the United States, and there is an urgent need to identify sources of resistance to this disease and incorporate the resistance into commercial watermelon cultivars. A wild watermelon accession that is naturally grown in southern Africa was found to contain resistance to bacterial fruit blotch. However, it is difficult to incorporate the resistance from this wild watermelon accession into commercial watermelon because of wide genetic differences that occurred during many years of cultivation. In this study, ARS researchers have collaborated with researchers at the University of Florida on developing a genetic population and on constructing a genetic linkage map useful for identifying disease resistance genes in the wild watermelon and for incorporating the resistance genes into watermelon cultivars. Breeding lines developed in this study will be tested for resistance to bacterial fruit blotch. Information in this study will be useful for plant breeders and scientists interested in enhancing disease resistance in commercial watermelon cultivars.
Technical Abstract: There is need to develop of introgression lines, useful for genetic studies and genetic enhancement of watermelon. In this study, we used an advanced recombinant population (BC2F2) to identify and map chromosomal segments of the wild watermelon Citrullus lanatus var. citroides that were incorporated in the genome of the watermelon cultivar Crimson Sweet (Citrullus lanatus var. lanatus). An advanced recombinant population (BC2F2) was constructed using a United States Plant Introduction (PI) 494817 (C. lanatus var. citroides) (known to have moderate resistance to bacterial fruit blotch) as a donor parent and the elite watermelon cultivar Crimson Sweet (C. lanatus var. lanatus) as the recurrent parent. The genetic linkage map consists of 274 markers, including 92 sequence related amplified polymorphism (SRAP), 75 targeted region amplification polymorphism (TRAP), and 107 high frequency oligonucleotide-targeting active gene (HFO-TAG) markers. The 274 markers were assembled into 51 linkage groups, covering a total genetic distance of 2,162 cM, with an average genetic distance of 7.9 cM between markers. Most of these linkage groups should represent chromosomal segments of the donor parent (PI 494817) that were introgressed into the recurrent ‘Crimson Sweet’ genome. The linkage groups and the genetic population in this study should serve as a platform for further development of introgression lines for watermelon.