ARS | Publication request: Employing Phylogenetic and Population Structure Analyses to Identify Potential Rootstock Resources for Grafted Watermelon

Submitted to: Cucurbitaceae Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 1, 2010
Publication Date: November 14, 2010
Citation: Levi, A., Thies, J.A., Wechter, W.P., Kousik, C.S., Hassell, R., Reddy, U. 2010. Employing Phylogenetic and Population Structure Analyses to Identify Potential Rootstock Resources for Grafted Watermelon. Cucurbitaceae Proceedings. p. 55-58.

Technical Abstract: U.S. Plant Introductions (PIs) of Citrullus lanatus var. citroides collected in southern Africa are valuable rootstocks for grafted watermelon particularly in fields infested with root-knot nematodes. There is little information about genetic relationships among these PIs. In this study, genetic diversity was examined among 56 PIs of C. lanatus var. citroides collected in their center of origin in southern Africa. Also, 8 PIs and 2 cultivars (Charleston Gray and Black Diamond) of Citrullus lanatus var. lanatus and 4 PIs of C. colocynthis collected in different locations throughout the world were used as out-groups in the phylogenetic analysis of C. lanatus var. citroides. Twenty high frequency oligonucleotides - targeting active gene (HFO-TAG) primers were used in polymerase chain reaction (PCR) experiments to produce a total 240 polymorphic markers among the Citrullus PIs and cultivars. Cluster analysis produced a large distinct group which contains two subgroups of the C. lanatus var. citroides PIs and distinct groups of C. lanatus var. lanatus and C. colocynthis PIs. Population structure analysis indicated that each of C. lanatus var. citroides subgroups contains a set of alleles that are predominant in the genotypes that belong to this subgroup. Several of the C. lanatus var. citroides PIs with a wide genetic distance between them and with resistance to root-knot nematodes were identified as possible candidates for further diallele studies aiming to develop heterotic F1 hybrid rootstock lines for grafted watermelon.