Phenotypic variability, diversity and genetic-population structure in melon (Cucumis melo L.) Associated with total soluble solids

Abstract

Abstract This study evaluated the phenotypic variation in Total Soluble Solid (TSS) quantified in different environments, together with allelic diversity and genetic-population structure based on 18 microsatellites loci (SSR) in QTLs (Quantitative Trait Loci). The phenotypic characterization in 41 Brazilian accessions of melon and three commercial cultivars revealed a wide variation in TSS, with values higher than 9.0 % for commercial cultivars and lower than 4.0 % in traditional melon accessions. The genetic parameters inferred by the phenotypic analysis revealed low variances but high heritability, indicating that the expression in TSS is highly related to the genotypic potential. In contrast, the significant effect of genotype and environment interaction (G x E) on the studied trait suggests that the selection or recommendation of promising plants for breeding should be based on the behavior of these accessions in more than one environment. High allelic diversity was verified with amplification of SSR loci, ranging from two to ten alleles per locus. High polymorphic content indicates the use of markers such as CMATN22 for mapping and binding analysis. The graphical representation of genetic diversity revealed the formation of two large groups of variation, both in the main components analysis graph and in the weighted neighbor-joining dendrogram. The certification of the distribution was validated by the inclusion of two genotypes of the Spanish access “Piel de Sapo” (PS) in a group different from the exotic Korean access “Songwhan Charmi” (PI161375) and the hybrid PI161375 X A16. The genetic-population structure was inferred using the ad hoc and ΔK method, indicating two well-defined populations and corroborating the graphical information of genetic diversity distribution. However, eight subpopulations were defined, structuring genetic diversity in the analyzed germplasm. The distribution of PS and PI161375 varieties in different subpopulations, despite the structural similarity between the two PS genotypes, indicates an expected pattern in the population structure. The results show the studied germplasm is structured but diversified both from the phenotypic point of view and from the variation in alleles in QTLs for TSS.