Evaluation of Genetic Diversity in Blackberry Germplasm in Iran by Using Inter Simple Sequence Repeats (ISSR) Markers

History and background of blackberry cultivars and wild species is unclear in the south coast of the Caspian Sea as an origin of diversity center in Iran. In the present study, genetic diversity of 45 genotypes of blackberries (thorny and thornless) from the collection of Sari Agricultural Sciences and Natural Resources University (SANRU) located in south of the Caspian Sea were studied by using Inter Simple Sequence Repeats (ISSR) markers. Jaccardchr('39')s similarity coefficient was used to plot the cluster diagram according to the Unweighted Pair-Group Method with Arithmetic averages (UPGMA) algorithm. Results showed that 10 ISSR primers amplified 345 fragments, of which 344 were polymorphic. The average numbers of bands were 34.5 per primers. Based on the Principal Coordinate Analysis (PCA) results, blackberry genotypes were classified in three groups. Some wild genotypes were located closed to commercial thorny cultivars. Cluster analysis divided the genotypes to six groups. Introduced genotypes that were in the same group were separated in sub-groups according to maturity time (early, mid, and late ripening cultivars). These genetic traits separated them and confirmed the morphological results, identifying them as thorny cultivars Silvan, Marion, and Tupi. The results indicated that gene pool of thornless blackberry is not limited to chimera type (as first generation of thornlessness) and it probably includes the two further steps in evolution, and even include some new and evolved types of native thornlessness.