Assessment of Genetic Diversity for some Candidate Edible Seed Watermelon Genotypes using SSR Markers and Morphological Traits

Edible seed watermelon is a cash crop in rain-fed condition in Khorasan provinces, with little research paid to it yet. In this study, genetic variation was evaluated among five candidate genotypes of edible seed watermelon, along with one commercial cultivar (Crimson Sweet) using 10 microsatellite primers (SSR) as well as morphological studies. 14 morphological traits were evaluated and analyzed during 45 days of early plant growth. Principal Components Analysis on morphological data could separate the genotypes into three distinct groups, including C1 and C14 genotypes in one group, C8 and SW in the next and C2 and C5 in the third one. For molecular analysis, genomic DNA was extracted and amplified further by the primers, followed by electrophoresis of the products. A total of 76 clear alleles were produced, of which 42 were polymorphic alleles. Average number of polymorphic alleles per locus was 6, ranging from 2 to 8. Polymorphic information content (PIC) varied within 0.46 to 0.85. Cluster analysis based on Jaccard's similarity coefficient and Unweighted Pair Group Method with Arithmetic Mean (UPGMA) algorithm classified the genotypes into three main clusters. C2 and C5 genotypes placed separately in different cluster that represents high genetic distance from the other genotypes. In this dendrogram, a very close genetic relationship was found between C8 and C14 genotypes. The scatter plot of genotypes based on Jaccard's correlation coefficient and Cophenetic correlation also confirmed a significant genetic difference between both C2 and C5 genotypes compared with other genotypes. The data from this experiment suggested a considerable diversity in terms of morphological and molecular aspects among the genotypes, which is very crucial for selection and breeding purposes in this crop.