Genetic variation in Tunisian melon (Cucumis melo L.) germplasm as assessed by morphological traits

The morphological variation and the systematical status of 28 traditional melon including two ancient varieties collected from different geographical and bioclimatic areas of Tunisia were assessed based on 34 qualitative and quantitative traits. Yellow Canary was used as a reference variety. Significant differences among accessions within and among sites of collection were revealed for the majority of traits. The accessions from the Sahel were more polymorphic than those from Tozeur's oasis. However, the classification of the local accessions according to Munger and Robinson's varietal groups did not allow clear segregation of several of them because of their high heterogeneity. The principal component analysis (PCA) performed on all measured traits, allowed a distinction among the introduced varieties clustered according to their varietal group, and the local accessions grouped separately according to their geographical origin and bioclimatic zone. Mahalanobis distances among PCA's groups were significant. The correlation found between Mahalanobis distance matrix and geographical distance matrix among origins corroborated isolation per distance. Conservation strategies should be made appropriately according to origins. Accessions from the Sahel showing the highest polymorphism within and among sites of collection should be firstly preserved.