Molecular and morphological characterization of the causal agent of potato pink rot in potato stores in Fars Province

While sampling from potato tubers infected with potato pink rot in Fars province's potato stores, several Phytophthora isolates were recovered which differed from those known to cause pink rot. Various gene analyses including three nuclear (internal transcribed spacers (ITS), ß-tubulin and heat shock protein 90) and one mitochondrial (cytochrome c oxidase subunit I) gene regions showed these isolates were hybrids between Phytophthora cryptogea and P. erythroseptica. Phylogenetic analysis using Bayesian approach showed the causal agent of potato pink rot, P. erythroseptica and P. cryptogea GII form a monophyletic group which is independent of major members of Phytophthora clade 8. Cloning of the ß-tubulin region produced both parental ß-tubulin sequences and confirmed the hybrid nature of these isolates. Isolates produced non-papillate and ellipsoid to ovoid sporangia, globose and aplerotic oogonia, and amphigynous terminal antheridia. While there were some differences, based on morphological characteristics, these isolates were most similar to their maternal parent, P. erythroseptica.