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

Abstract

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.