Phylogeny and taxonomy of the oak powdery mildew Erysiphe alphitoides sensu lato

• Published in: Mycological research Vol. 111; no. 7; pp. 809 - 826
• Main Authors: Takamatsu, Susumu, Braun, Uwe, Limkaisang, Saranya, Kom-un, Sawwanee, Sato, Yukio, Cunnington, James H.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2007
• Subjects: 28S rDNA; Ascomycota - classification; Ascomycota - genetics; DNA, Fungal - analysis; DNA, Ribosomal Spacer - analysis; Erysiphe; Erysiphe alphitoides; Erysiphe epigena; Erysiphe hypogena; Erysiphe hypophylla; Erysiphe quercicola; Erysiphe sect. Microsphaera; fungal anatomy; host plants; host-pathogen relationships; internal transcribed spacers; Microsphaera alphitoides; Molecular Sequence Data; molecular systematics; Mycological Typing Techniques; new species; Oidium alphitoides; Phylogeny; Plant Diseases - microbiology; Plant Leaves - microbiology; powdery mildew; Quercus; Quercus - classification; Quercus - microbiology; Quercus acutissima; Quercus phillyraeoides; rDNA ITS region; ribosomal DNA; RNA, Ribosomal, 28S - genetics; Sequence analyses; sequence analysis; Sequence Analysis, DNA; Species Specificity; taxonomic keys; Switzerland; Japan; Russia; Sequence analyses; 28S rDNA; Microsphaera alphitoides; Quercus; rDNA ITS region; Erysiphe sect. Microsphaera
• ISSN: 0953-7562; 1469-8102
• DOI: 10.1016/j.mycres.2007.05.013

Phylogenetic analyses of Erysiphe alphitoides s. lat. using sequences of the rDNA ITS region and the D1/D2 domains of the 28S rDNA revealed a complex consisting of several genetically and morphologically distinguished taxa, including the already described Erysiphe alphitoides s. str. and E. hypophylla. The ascomata (chasmothecia) of E. hypophylla are morphologically very similar to those of E. alphitoides, but the two species are easily distinguishable by their symptoms, as well as the shape and size of the conidia. The fungus on Quercus phillyraeoides, distributed in warmer regions in southern Japan, is genetically clearly separated from E. alphitoides s. str., and morphologically characterized by having chasmothecia with appendages consistently shorter than the chasmothecial diameter. This fungus, named Erysiphe quercicola in this paper, is also able to infect some other oak species, and it is genetically identical with anamorphs on some tropical trees of other host genera. Collections of E. alphitoides s. lat. on Quercus acutissima and Q. variabilis, both belonging to Quercus sect. Cerris, are genetically distinct from E. alphitoides s. str., E. hypophylla and E. quercicola. They form two genetically and morphologically differentiated groups. The hypophyllous taxon on Q. acutissima and Q. variabilis, named Erysiphe hypogena in this paper, is characterized by forming distinctive persistent hypophyllous mycelial patches, causing necrotic discolouration of the host tissue. The epiphyllous taxon on these hosts, for which the name E. epigena is proposed, differs in having epiphyllous mycelium, smaller chasmothecia with fewer appendages, and does not cause leaf discolouration.