Plant Genetic Resources

Research Article

Genetic reticulation and interrelationships among citrullus species as revealed by joint analysis of shared AFLPs and species-specific SSR alleles

Padmavathi Nimmakayalaa1 c1, Yan R. Tomasona1a2, Jooha Jeonga1, Sathish K. Ponniaha1, Anoji Karunathilakea1, Amnon Levia3, Ramasamy Perumala4 and Umesh K. Reddya1

a1 Department of Biology and Gus R. Douglass Institute, West Virginia State University, Institute, WV 25112, USA

a2 Department of Selection and Seed Production, Dnepropetrovsk State Agrarian University, Voroshilov 25, Dnepropetrovsk 49600, Ukraine

a3 USDA, ARS, US Vegetable Laboratory, 2875 Savannah Highway, Charleston, SC 29414, USA

a4 Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843-2132, USA


Thirty-one accessions of Citrullus spp. belonging to Citrullus lanatus var. lanatus, C. lanatus var. citroides and Citrullus colocynthis were subjected to phylogenetic analysis using combined datasets of amplified fragment length polymorphisms (AFLPs) and simple sequence repeats (SSRs). Tree topologies inferred by neighbour-joining analysis have resolved the phylogenic relationships among the species with special reference to established taxonomic classification. In this study, we have clearly resolved species boundaries of various taxa of citroides, lanatus and colocynthis into three well-supported clusters. Clustering pattern of principal component analysis with the shared polymorphisms using the subsets of data between any two taxon combinations helped to elucidate the introgression and interrelationships among the species. We report two major groups of C. lanatus taxa, one of which has undergone wide introgressions with the taxa of C. lanatus var. citroides and C. colocynthis. In this paper, we identified 583 AFLP bands that are polymorphic within the var. lanatus of C. lanatus, which is the largest set ever reported. The species-specific diagnostic SSRs and polymorphic AFLPs that are informative within and between the taxa reported in this paper would be immensely useful for future studies of these economically important genera.

(Received April 16 2009)

(Accepted June 26 2009)

(Online publication July 22 2009)


c1 Corresponding author. E-mail:


Authors contributed equally.