Phylogeny, morphological and physiological characterization of Phytophthora erythroseptca isolates, the causal agents of potato pink rot in different geographic regions

Pink rot, caused by Phytophthora erythroseptica, is an important soil-borne disease of potato causes significant losses in the field and storage. A selection of P. erythroseptica isolates from potato-growing regions in four continents including America, Asia, Europe and Australia was assessed using phylogenetic, morphological and physiological analyses. In all nuclear (internal transcribed spacers, ß-tubulin and heat shock protein 90) and mitochondrial (cytochrome c oxidase subunit I) trees as well as combined nuclear and mitochondrial tree, P. erythroseptica isolates formed a separate phylogenetic lineage containing the type isolate. Additionally, no morphological and physiological diversities were observed among the isolates. All isolates were homothallic and produced amphigynous terminal antheridia and globose aplerotic oogonia as well as non-papillate and ellipsoid to ovoid sporangia. The results showed that P. erythroseptica isolates belonged to different geographic regions are phylogenetically and morphologically similar. This uniformity could be due to the homothallic nature of P. erythroseptica or distribution of a single clone of pathogen by infected potato.