Population genetic diversity and genetic affinity analyses of sweet orange cultivars (Citrus sinensis (L.) Osbeck) by using IRAP molecular markers

Citrus plants are one of the most important fruit plants which are consumed all over the world. The breeding of these valuable fruit plants is based on selection of elite genotypes and grafting. Large number of fruit trees with different local names and labels are available in the country, but very limited knowledge is in hand on their genetic content and their relationship. The present study was conducted on 15 sweet orange populations of Iran, with the aim to produce data on their genetic structure, diversity and affinity by using IRAP molecular markers. The studied cultivars produce 24 IRAP loci or bands. In total each cultivar studied contained 5–16 IRAP bands with no private/specific bands formation. Genetic diversity parameters determined revealed that genetic polymorphism vary from 0 in to 45% in the studied sweet orange trees. Discriminating power of IRAP loci was determined by multivariate canonical correspondence analysis. Analysis of molecular variance (AMOVA) revealed significant genetic difference among these cultivars, and pair-wise AMOVA identified those sweet oranges which differed genetically from each other. Unweighted pair group method with arithmetic mean dendrogram of the studied samples grouped these cultivars and their replicates in four distinct clusters, which was also supported by discriminate analysis of principal components plot. Therefore, cultivars which are genetically similar and labeled differently were identified and genetic affinity of the cultivars are discussed. These findings will be used in future sweet orange conservation and breeding.