Host range expansion in a powdery mildew fungus (Golovinomyces sp.) infecting Arabidopsis thaliana: Torenia fournieri as a new host
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Since 2003, Torenia fournieri plants grown for experimental purposes were repeatedly infected by powdery mildew in a laboratory in Hungary. Based on morphological characteristics, the pathogen belonged to the mitosporic genus Oidium subgen. Reticuloidium, the anamorph stage of Golovinomyces. The rDNA ITS sequence was identical to that of two other powdery mildew fungi, infecting Arabidopsis and Veronica, respectively, in different parts of the world. According to a previous phylogenetic analysis of ITS and 28S rDNA sequences, those two powdery mildews belong to a recently evolved group of Golovinomyces characterized by multiple host range expansions during their evolution. Both the ITS sequence and the morphological data indicate that the powdery mildew anamorph infecting Torenia also belongs to this group. It is likely that the powdery mildew infections of the experimental T. fournieri plants, native to south-east Asia, were the result of a very recent host range expansion of a polyphagous Golovinomyces because (i) T. fournieri is absent from our region, except as an experimental plant grown in the laboratory, (ii) the powdery mildew fungus infecting this exotic plant belongs to a group of Golovinomyces where host range expansion is a frequent evolutionary scenario, (iii) cross-inoculation tests showed that this pathogen is also able to infect other plant species, notably A. thaliana and tobacco, and (iv) no Golovinomyces species are known to infect T. fournieri anywhere in the world. Although host range expansion has often been proposed as a common evolutionary process in the Erysiphales, and also in other biotrophic plant pathogens, this has not been clearly demonstrated in any case studies so far. To our knowledge, this is the first convincing case of a host range expansion event in the Erysiphales.
KeywordsErysiphales Golovinomyces orontii host-jumping phylogenetic analysis
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The support of the János Bolyai Research Fellowship, awarded to GMK and LK, is acknowledged. GMK is a postdoctoral research fellow of the Hungarian Research Fund (OTKA, D048333). We are grateful to the anonymous reviewers for their helpful comments on this work.
- Amano K (1986) Host Range and Geographical Distribution of the Powdery Mildew Fungi Japan Scientific Societies Press, TokyoGoogle Scholar
- Braun U (1987) A monograph of the erysiphales (powdery mildews). Beihefte zur Nova Hedwigia 89: 1–700Google Scholar
- Braun U (1995) The Powdery Mildews (Erysiphales) of Europe Gustav Fischer Verlag, JenaGoogle Scholar
- Braun U, Cook RTA, Inman AJ, Shin HD (2002) The taxonomy of the powdery mildew fungi In: Bélanger RR, Bushnell WR, Dik AJ, Carver TLW (eds) The Powdery Mildews: A Comprehensive Treatise American Phytopathogical Society, St. Paul, MN, USA pp 13–55Google Scholar
- Hammarlund C (1945) Beitrage zur Revision einiger imperfekter Mehltau-Arten. Erysiphe polyphaga nov. sp. Botaniska Notiser 1945: 101–108Google Scholar
- Palm ME (1999) Mycology and world trade: a view from the front line. Mycologia 91: 1–12Google Scholar
- Plotnikova J, Reuber TL, Ausubel FM, Pfister DH (1998) Powdery mildew pathogenesis of Arabidopsis thaliana. Mycologia 90: 1009–1016Google Scholar
- Szentiványi O, Kiss L, Russell JC, Kovács GM, Varga K, Jankovics T, Lesemann S, Xu XM, Jeffries P (2005) Ampelomyces mycoparasites from apple powdery mildew identified as a distinct group based on single-stranded conformation polymorphism analysis of the rDNA ITS region. Mycological Research 109: 429–438PubMedCrossRefGoogle Scholar
- Takamatsu S, Matsuda S, Niinomi S, Havrylenko M (2006) Molecular phylogeny supports a Northern Hemisphere origin of Golovinomyces (Ascomycota: Erysiphales). Mycological Research 110: 1093–1101Google Scholar