Assessment of genetic diversity and population structure in melon (Cucumis melo L.) germplasm using microsatellite markers: Implications towards its varietal improvement

A total of 96 melon germplasm from four horticultural groups were undertaken for genetic characterization using 107 microsatellite markers. The average diversity indices of microsatellite markers, viz., allele number, major allelic frequency, gene diversity, expected heterozygosity and polymorphic information content, were 2.69, 0.84, 0.25, 0.06 and 0.22, respectively. The neighbor-joining dendrogram grouped the melon germplasm into four major clusters with distinct separation of Indian reticulatus germplasm from that of the exotic germplasm adapted in India and wild agrestis germplasm. Population structure analysis deciphered two main subpopulations broadly corresponding sweet melon preferred by consumers from sub-species melo and non-sweet wild agrestis melon separately along with admixtures. This finding was validated by principal coordinate analysis. AMOVA analysis further partitioned the whole genetic variation among individuals (74%), within individuals (22%) and among populations (4%) with low genetic differentiation and high levels of gene flow among subpopulations. A total of 12 microsatellite markers produced 19 unique alleles among 24 germplasm, which would act as a distinct DNA fingerprint for germplasm identification and legal protection. The present study provided a deeper understanding of the genetic structure of melon germplasm and will assist in formulating future breeding programmes.