Cryptococcus magnus as the causative agent of stem and branch canker of stone fruit trees in the 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 most common causal agents of bacterial canker in the world as well as in Iran are Pseudomonas syringae pv. syringae and Xanthomonas arboricola pv. pruni. To determine the predominant causative microorganism in some major fruit growing areas of the central provinces of Iran, samples were taken from the canker-affected stone fruit trees in these regions and macerates of the affected bark tissues were plated on sucrose nutrient agar (NAS). The predominant colonies appearing on NAS were whitish and yeast-like in appearance. Pathogenicity of representative isolates on peach (Prunus persica) seedlings were confirmed. Microscopic, phenotypic and genotypic characteristics of pure cultures of the isolates were determined. DNAs of representative isolates were extracted and the rDNA ITS regions were amplified and sequenced. The sequences were compared with those deposited in GenBank. Partial sequences of the 26S rRNA, RPB1 and RPB2 genes were determined and compared with those existing in GenBank. Budding globose cells were predominant in cell suspensions studied under the microscope. The isolates showed the highest identity with Cryptococcus magnus based on the sequences of the ITS regions. The identity of the isolates as C. magnus was further verified by comparison of the nucleotide sequences of their 26S, RPB1 and RPB2 genes with the homologous regions in Cryptococcus species.