Determination of genetic diversity in watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] germplasm

The genetic diversity and relatedness of 90 watermelon (Citrullus lanatus var. lanatus and Citrullus. lanatus var. citroides) accessions were molecularly characterized using 30 sequence-related amplified polymorphism (SRAP) marker combinations. The accessions were collected from Turkey (59 accessions) and other regions of the world by the United States Department of Agriculture (USDA) and the molecular data were analysed using UPGMA (Unweighted Pair Group Method Analysis). The SRAP combinations were highly polymorphic (97%) with 87 polymorphic bands determined among 201 amplified fragments (43%). The UPGMA analysis characterized five major clusters (A, B, C, D and E). While minimum genetic similarity among groups A, B and C was high (83%), group E was the most distant with 63% genetic similarity. Principal component analysis (PCA) was performed and used to produce a two-dimensional plot from which two main groups could be distinguished. Based on the analyses, genetic diversity of watermelons was very low and Turkish watermelons were not distinct from other countries' accessions. These results could be used for generation of a core collection of watermelon by elimination of redundant accessions and for watermelon breeding by helping to identify useful, genetically distinct lines. In addition, the study indicated that SRAP markers are useful for analysing genetic diversity in crops like watermelon which have low variability.