Growth on oat-seedling agar of isolates of Gaeumannomyces graminis and some Phialophora species from cereal roots

Abstract

Measurement of colony diameter on oat-leaf agar provides a quick and simple test for helping to distinguish between members of the Gaeumannomyces — Phialophora complex. Seventy two isolates were tested: all 19 European isolates of Phialophora radicicola var. radicicola , 18 of 20 Gaeumannomyces graminis var. tritici ( Ggt ) isolates and a Gaeumannomyces isolate from Deschampsia failed to grow out from the inoculum plug. Twelve isolates of G. graminis var. graminis spread over the agar at about the same rate as on potato dextrose agar (PDA) but three did not grow at all. Eight isolates of Phialophora graminicola , nine of G. graminis var. avenae and two oat-attacking isolates that had been identified as Ggt all showed some growth, although with most of the isolates this was retarded compared with that on PDA.