Evaluation of genetic diversity and population structure of Citrullus colocynthis based on physiochemical and inter simple sequence repeat (ISSR) markers

Genetic characterization plays an important role in the conservation of threatened plants. In this study, the morphological, chemical, and genetic variability of 20 accessions of Citrullus colocynthis was determined by 14 phenotypic descriptors, five chemical descriptors, and 13 inter simple sequence repeat (ISSR) primers. The physiochemical variability analysis by clustering and principal component analysis classified 20 accessions into three populations. The vine length, weight, and diameter of the fruit were the main descriptors showing great morphological variations. Total flavonoids and phenolics were the main descriptors responsible for chemical variability. The phenolic contents have a positive correlation, whereas, the chlorophyll contents have a negative correlation with increasing altitude. The polymorphic information content of selected primers was found to be 0.34, indicating moderate polymorphism. The number of effective alleles, Shannon’s diversity index, and expected heterozygosity were found to be 1.22, 0.3, and 0.2, respectively. The analysis of molecular variance revealed 38% variation within populations and 62% variation among the populations. The cluster, population structure based on ΔK values, and principal coordinate analysis revealed three distinct populations. The multivariate regression analysis revealed that UBC802, UBC813, and UBC817 were significantly (P < 0.01) correlated with chemical descriptors, whereas UBC819, UBC831, and UBC834 were associated with morphological descriptors.