Take-all or nothing

Abstract

Take-all disease ofPoaceaeis caused byGaeumannomyces graminis(Magnaporthaceae). Four varieties are recognised inG. graminisbased on ascospore size, hyphopodial morphology and host preference. The aim of the present study was to clarify boundaries among species and varieties inGaeumannomycesby combining morphology and multi-locus phylogenetic analyses based on partial gene sequences of ITS, LSU,tef1andrpb1. Two new genera,FalciphoriellaandGaeumannomycellawere subsequently introduced inMagnaporthaceae. The resulting phylogeny revealed several cryptic species previously overlooked withinGaeumannomyces. Isolates ofGaeumannomyceswere distributed in four main clades, from which 19 species could be delimited, 12 of which were new to science. Our results show that the former varietiesGaeumannomyces graminisvar.avenaeandGaeumannomyces graminisvar.triticirepresent species phylogenetically distinct fromG. graminis, for which the new combinationsG. avenaeandG. triticiare introduced. Based on molecular data, morphology and host preferences,Gaeumannomyces graminisvar.maydisis proposed as a synonym ofG. radicicola. Furthermore, an epitype forGaeumannomyces graminisvar.avenaewas designated to help stabilise the application of that name.