Analysis of the Genetic Diversity in Citrus (Citrus spp.) Species Using SSR Markers

Determination of genetic diversity level is important in clarifying genetic relationships, characterizing germplasm and the registration of new cultivars. In this study, genetic variation among 56 accessions (G1~G56) of Citrus including several undefined local or native genotypes and some known varieties in Jiroft, Kerman province, Iran was investigated using SSR markers. In total, 12 SSR primers produced 54 alleles. The lowest number of alleles was observed on cAGG9 locus with 2 alleles and the highest number of alleles was observed in TAA41 locus with 8 alleles. Polymorphic Information Content (PIC) varied from 0.19 to 0.37 with mean of 0.28. The percentage of heterozygosity per marker detected in our samples ranged from 25% to 96% with an average of 67%. Grouping of the accessions using Jaccard similarity coefficient and based on the Neighbor-Joining method assigned the 56 accessions into four major clusters. The SSR data indicated a high relationship between G2 and G41 (unknown natural types) with grapefruits (Citrus paradisi) (G50 and G51), G17 (unknown natural type) with orange (C. sinensis) (G56) and G40 (unknown natural type) with pummelo (C. grandis) (G49). Unidentified genotype G43 in a single-accession cluster didn’t show any close molecular similarity to control samples [mandarin (C. reticulata), pummelo, sweet orange, sour orange (C. aurantium), etc.]. Mandarin, pummelo and citron (C. medica) were clustered into three particular groups as major species of Citrus. Also, our results demonstrated that SSR markers can be useful in evaluating citrus genetic diversity and in classifying accessions to phylogenetic groups based on their genetic similarity values.