Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2001
Publication Date: 5/14/2001
Citation: Levi, A., Thomas, C.E., Wehner, T.C. 2001. Flow genetic diversity indicates the need to broaden the genetic base of cultivated watermelon. Journal of the American Society for Horticultural Science. 36:1096-1101.
Interpretive Summary: Watermelon accounts for 2% of the area devoted to vegetable production throughout the world. In the U.S. watermelon production has been increasing from 1.2 M tons in 1980 to 2.1 M tons in 1998, with an at the farm value of $287 million. Therefore, there is an ongoing need for improving watermelon production through development of new varieties. A large number of watermelon varieties have been developed in the U.S. during the last century. Efforts are made to preserve these varieties because they are considered a useful genetic source for the development of future watermelon varieties. However, to effectively use these varieties in breeding programs, we need to know the genetic relationships among them. Thus, we conducted experiments using molecular tools to analyze the DNA of these varieties. The results in this study indicate that a large number of watermelon varieties that were developed during the last century in the U.S. are genetically closely related. Therefore, to decrease the genetic vulnerability to diseases and pests of commercial watermelon varieties it is important to broaden the genetic base of the crop. This can be done by collecting and preserving wild watermelon plants from around the world and using them in breeding programs.
Technical Abstract: Forty-six watermelon (Citrullus lanatus) cultivars, most of them developed in the United States during the last century were examined using 30 RAPD primers. These primers produced 349 RAPD markers that could be scored with high confidence. Of these, 225 were monomorphic for all cultivars while 124 were polymorphic and could distinguish among all 46 cultivars. Twenty-eight polymorphic markers (produced by 16 primers) were used to construct a DNA fingerprint profile for each cultivar. Based on the RAPD data, genetic similarity coefficients were calculated and a dendrogram was constructed using the unweighted pair-group method with arithmetic average (UPGMA). All cultivars were contained in one major cluster and differentiated at the level of 93-99% genetic similarity. The low genetic variation among watermelon cultivars found in this study emphasizes the need to expand the genetic base of cultivated watermelon.