Saprophytic survival of Gaeumannomyces graminis and Phialophora spp. at various temperature-moisture regimes

The saprophytic survival of the pathogen, Gaeumannomyces graminis var. tritici and two isolates each of three avirulent fungi, G. graminis var. graminis, Phialophora graminicola and a lobed-hyphopodiate Phialophora sp. was studied in two soil types under controlled temperature and moisture conditions in the laboratory. In general, the fungi survived longest in the cool, dry soil (15°C, < -10 MPa) followed by the warm dry soil (30°C, < -10 MPa). All the fungi were virtually eliminated from the warm, moist soil (30°C, -0.3 MPa) after 3 months. Survival was intermediate under cool, moist conditions (15°C, -0.3 MPa). Under cool, moist conditions, G. graminis var. graminis survived better than the other three fungi in the first 3 months in both soil types and continued to do so for a further 3 months in one soil. Both isolates of the lobed-hyphopodiate Phialophora sp. survived poorly in the two soil types being almost eliminated after 3 months. There were considerable differences between the survival of the two isolates each of G. graminis var. graminis and P. graminicola, especially under cool, moist conditions. Of the six avirulent isolates studied, one isolate of G. graminis var. graminis (DAR24167) survived best under the three temperature-moisture regimes which showed differences. It also survived better than the take-all fungus under moist, cool conditions and at a comparable rate under dry conditions. Therefore, this variation in survival should be considered when selecting antagonists for the biological control of take-all.