Phytophthora chrysanthemi sp. nov., a new species causing root rot of chrysanthemum in Japan

Abstract

A new species of Phytophthora was isolated from stem and root rot of chrysanthemum in the Gifu and Toyama prefectures of Japan. The species differs from other Phytophthora species morphologically, and is characterized by nonpapillate, noncaducous sporangia with internal proliferation, formation of both hyphal swellings and chlamydospores, homothallic nature, distinctive intercalary antheridia, and funnel-shaped oogonia. The new species can grow even at 35°C, with an optimum growth temperature of 30°C in V8 juice agar medium. In phylogenetic analyses based on five nuclear regions (LSU rDNA; genes for translation elongation factor 1α, β-tubulin, 60 S ribosomal protein L10, and heat shock protein 90), the isolates formed a monophyletic clade. Although the rDNA ITS region shows a high resolution and has proven particularly useful for the separation of Phytophthora species, it was difficult to align the sequences for phylogenetic analysis. Therefore, ITS region analysis using related species as defined by the multigene phylogeny was performed, and the topology of the resulting tree also revealed a monophyletic clade formed by the isolates of the species. The morphological characteristics and phylogenetic relationships indicate that the isolates represent a new species, Phytophthora chrysanthemi sp. nov. In pathogenicity tests, chrysanthemum plants inoculated with the isolates developed lesions on stems and roots within 3 days, and the symptoms resembled the ones originally observed. Finally, the pathogen's identity was confirmed by reisolation from lesions of infected plants.

First detection of Phytophthora chrysanthemi on Chrysanthemum indicum in Germany

“…3). Cardinal temperatures for vegetative growth on CPA and size and shape of oogonia (mean 35.4 μm; n=50) and oospores (mean 28.4 μm; n=50) grown on CA were similar to those described for Phytophthora chrysanthemi (Naher et al , 2011). Chlamydospores produced on CPA were slightly larger (mean 44.0 μm; n=50) than reported.…”

“…Phytophthora chrysanthemi was first described as a new species on Chrysanthemum in Japan (Naher et al , 2011). In 2015, it was reported from Croatia (Tomiċ & Iviċ, 2015) and in 2016 from the USA (Randall‐Schadel, 2016).…”

Fungal diversity notes 253–366: taxonomic and phylogenetic contributions to fungal taxa

“…Multi-gene phylogenies have shown that most of the 10 clades are monophyletic, except the Clades 4 and 9 (Blair et al 2008). Clade 9 is the most rapidly expanding, with most of its species recently described (Hong et al 2010(Hong et al , 2012Naher et al 2011;Rea et al 2011;Yang and Hong, 2013;Yang et al 2014a, b). Members of this clade generally produce non-papillate and non-caducous zoosporangia.…”

A high-temperature tolerant species in clade 9 of the genus Phytophthora: P. hydrogena sp. nov.

“…Analyses of ITS and cox 1 sequences grouped P. hydrogena with P. aquimorbida (Hong et al 2012), P. hydropathica (Hong et al 2010), P. irrigata , P. chrysanthemi (Naher et al 2011) (only supported by ITS sequence), P. insolita (Ann and Ko FIG. 5.…”