Assessment of genetic diversity of yeast isolates causing canker in stone fruit trees in some central provinces of iran

Canker is one of the most damaging diseases of stone fruit trees which incites depressed brown to black lesions, often accompanied by exudation of gum, on twigs, branches and trunk of affected trees. The disease has been reported from different areas of Iran and shown to becaused by Pseudomonas syringae pv. Syringae a fewcase by Xanthomonas arboricola pv. pruni. To assess the distribution of the causal organisms samples were taken from fruit orchards in these regions. The stem tissues with canker symptoms were surface-disinfected in sodium hypochlorite, washed with sterile distilled water minced in drops of SDW. The suspension was plated on sucrose nutrient agar. The predominant colonies appearing on SNA were grayish-white, round and pasty. Representative isolates were tested for pathogenicity on peach seedling. Genomic DNA was extracted and a fragment of the 26S rRNA of the representative isolates was amplified by PCR and sequenced. The nucleotide sequence of 26S rRNA gene of the representative isolates showed high homology with sequences of Cryptococcus species. Comparison of their sequences with those deposited in GenBank. Also 27 isolates along with reference strains of Cryptococcus adeliensis and C. magnus were genetically characterized by using ERIC, REP, and BOXAIR primers in PCR. Cluster analysis was performed using NTSYS program. The isolates were separated into 11 genotypic groups by the concatenated data of rep-PCR at 33 % similarity level. The results demonstrated the existence of a considerable genetic diversity among isolates causing canker of stone fruit trees in the central provinces of Iran.