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

作者：Naher Meherun; Motohash Keiichi; Watanabe Hideki; Chikuo Yoshiaki; Senda Masako; Suga Haruhisa; Brasier Clive; Kageyama Koji^*

来源：Mycological Progress, 2011, 10(1): 21-31.

DOI：10.1007/s11557-010-0670-9

• High temperature
• Chrysanthemum
• Phylogeny
• Phytophthora
• Root rot

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 35A degrees C, with an optimum growth temperature of 30A degrees C in V8 juice agar medium. In phylogenetic analyses based on five nuclear regions (LSU rDNA; genes for translation elongation factor 1 alpha, beta-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 re-isolation from lesions of infected plants.

• 出版日期2011-3