Molecular and pathogenic characterization of Iranian isolates associated with leaf spot disease of potato

Alternaria alternata (Fr.) Keissler is one of the main causal agents of leaf spot on potato in Iran and worldwide. In this study, random amplified polymorphic DNA (RAPD) and pathogenicity assay were employed to analyze 28 A. alternata isolates obtained from potato plants. The isolates were collected from main potato growing regions of Iran, including Ardebil, Hamedan, Isfahan and Fars provinces. Cluster analysis of genotypes produced by RAPD marker, using UPGMA method indicated that the isolates have been clustered into different groups with no correlation to geographical origins of the isolates. Pathogenicity assay indicated that all A. alternata isolates were pathogenic on potato;however, virulence variability was observed among the isolates. The findings revealed that because of extant diversity in pathogenicity and genetics of A. alternata isolates, a single isolate should not be used for evaluating resistance of potato.