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Title: Molecular Phylogeny of Citrullus Species as Inferred from AFLPs and SSRs

item JEONG, J
item Levi, Amnon
item REDDY, U

Submitted to: Plant Genetic Resources
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2009
Publication Date: 4/1/2010
Citation: Nimmakayala, P., Jeong, J., Tomason, Y., Levi, A., Perumal, R., Reddy, U.K. 2010. Molecular Phylogeny of Citrullus Species as Inferred from AFLPs and SSRs. Plant Genetic Resources. 8:16-25.

Interpretive Summary: There is little genetic diversity among watermelon cultivars because many years of cultivation and selection for desirable fruit qualities. Watermelon belongs to the cucurbit species ‘Citrullus’, which includes wild watermelon types grown in Africa and Asia. Many of these wild watermelons are resistant to diseases and pests and can be useful for enhancing the resistance in watermelon cultivars. In this study, we used amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) DNA markers to examine the genetic relationships among the wild watermelon groups collected in Africa and Asia and the watermelon cultivars developed in the US. The DNA data in this study were used to define the genetic relationships among the wild watermelon groups; two groups of watermelon accessions were identified that linked the wild watermelons with the watermelon cultivars. These findings will be useful to plant breeders interested in enhancing disease and pest resistance in watermelon cultivars using wild watermelon accessions as parental lines.

Technical Abstract: Thirty-one accessions of Citrullus spp. belonging to C. lanatus var. lanatus, C. lanatus var. citroids and Citrullus colocynthis were subjected to phylogenetic analysis using combined data sets of AFLPs and SSRs. Tree topologies inferred by Neighbor Joining analysis have resolved the phylogenic relationships among the Citrullus species with special reference to established taxonomic classification. In this study, we have resolved species boundaries of C. lanatus var. citroids, C. lanatus var. lanatus and C. colocynthis into three well-supported clusters. The clustering pattern based on principal coordinate analysis (PCA) with the shared polymorphisms using the subsets of data between any two taxon combinations helped to elucidate the introgression and interrelationships among the Citrullus species. Two groups of C. lanatus var. lanatus were identified. One group is positioned in-between C. lanatus var. lantaus and C. lanatus var. citroides, and a second group is integrated with C. lanatus var. citroids and C. colocynthis.