Thines Marco, Göker Markus, Telle Sabine, Ryley Malcolm, Mathur Kusum, Narayana Yaladabagi D, Spring Otmar, Thakur Ram P
Universität Hohenheim, Institut für Botanik, Garbenstr. 30, 70599 Stuttgart, Germany.
Mycol Res. 2008 Mar;112(Pt 3):345-51. doi: 10.1016/j.mycres.2007.10.010. Epub 2007 Nov 1.
Graminicolous downy mildews (GDM) are an understudied, yet economically important, group of plant pathogens, which are one of the major constraints to poaceous crops in the tropics and subtropics. Here we present a first molecular phylogeny based on cox2 sequences comprising all genera of the GDM currently accepted, with both lasting (Graminivora, Poakatesthia, and Viennotia) and evanescent (Peronosclerospora, Sclerophthora, and Sclerospora) sporangiophores. In addition, all other downy mildew genera currently accepted, as well as a representative sample of other oomycete taxa, have been included. It was shown that all genera of the GDM have had a long, independent evolutionary history, and that the delineation between Peronosclerospora and Sclerospora is correct. Sclerophthora was found to be a particularly divergent taxon nested within a paraphyletic Phytophthora, but without support. The results confirm that the placement of Peronosclerospora and Sclerospora in the Saprolegniomycetidae is incorrect. Sclerophthora is not closely related to Pachymetra of the family Verrucalvaceae, and also does not belong to the Saprolegniomycetidae, but shows close affinities to the Peronosporaceae. In addition, all GDM are interspersed throughout the Peronosporaceae s lat., suggesting that a separate family for the Sclerosporaceae might not be justified.
禾本科霜霉病菌（Graminicolous downy mildews，GDM）是一类研究较少但经济上很重要的植物病原体，是热带和亚热带禾本科作物的主要限制因素之一。在此，我们基于细胞色素氧化酶亚基2（cox2）序列构建了首个分子系统发育树，该序列涵盖了目前公认的GDM所有属，包括具有持久孢子囊梗的属（Graminivora、Poakatesthia和Viennotia）以及具有短暂孢子囊梗的属（Peronosclerospora、Sclerophthora和Sclerospora）。此外，还纳入了目前公认的所有其他霜霉属，以及其他卵菌分类单元的代表性样本。结果表明，GDM的所有属都有漫长而独立的进化历史，并且Peronosclerospora和Sclerospora之间的划分是正确的。发现Sclerophthora是一个特别分化的分类单元，嵌套在一个并系的疫霉属中，但缺乏支持。结果证实，将Peronosclerospora和Sclerospora置于水霉纲是不正确的。Sclerophthora与疣枝藻科的Pachymetra关系不密切，也不属于水霉纲，而是与霜霉科有密切亲缘关系。此外，所有GDM都散布在广义的霜霉科中，这表明为腐霉科设立一个单独的科可能不合理。
