Identification and characterization of a new group of root-colonizing fungi within the Gaeumannomyces-Phialophora complex

A new group of darkly pigmented root-infecting fungi was isolated from cere al roots obtained from six different locations in northeastern Germany. Sim ilar random amplified polymorphic DNA (RAPD) patterns and restriction profi les of amplified rDNA were used as a basis for classifying the isolates in a separate group. The isolates demonstrating mycelial and infection charact eristics typical of Gaeumannomyces graminis could be differentiated from th e varieties of G. graminis as well as from Gaeumannomyces cylindrosporus/ P hialophora graminicola using RAPD Polymerase chain reaction (PCR) and rDNA Restriction-fragment length polymorphism (RFLP) analysis. Phylogenetic anal ysis of the Internal transcribed spacer (ITS) regions suggests that the iso lates form a distinct group (named group 'E') situated within the Gaeumanno myces-Phialophora a complex between the branch of the G. graminis varieties and Gaeumannomyces incrustans/Magnaporthe poae. Isolates of group E produc ed lobed hyphopodia and were shown in biotests to be non-pathogenic to whea t, oats, Italian Ryegrass and Chewings Fescue, suggesting it is a benign pa rasite which colonizes cereals or grasses without destroying vascular tissu e. Furthermore, curved phialospores could be found. Summarizing the results presented, this new group could be classified as a new species of Phialoph ora. Although isolates of group E were found at only six of the 32 investig ated locations, they composed up to 50% of total isolates of the Gaeumannom yces-Phialophora complex at these sites. Because of the non-pathogenic beha viour, the new group may be of value as biological control agents for patho genic fungi.