LACK OF ANTAGONISM BETWEEN THE BIOCONTROL AGENT GLIOCLADIUM-VIRENS AND VESICULAR ARBUSCULAR MYCORRHIZAL FUNGI

The effect of the fungal biocontrol agent Gliocladium virens Miller, Giddens & Foster on the colonization of cucumber by the VA mycorrhizal fungi Glomus etunicatum Becker & Gerdemann and Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe was investigated. Inoculum of G. virens, grown on wheat bran or peatmoss-Czapek substrate, was added to soil artificially infested with Pythium ultimum Trow. Both damping-off of cucumber and pathogen population density were reduced in treatments with G. virens. Inoculum of G. virens was also added to soils containing increasing propagule densities of Glomus etunicatum or Glomus mosseae. After one week of incubation, the soils were planted with cucumber seeds, and the percent mycorrhizal colonization of roots was determined after 12 d. When grown on wheat bran, G. virens was phytotoxic and increased mycorrhizal colonization by Glomus etunicatum. However, G. virens had no effect on Glomus etunicatum when added as peatmoss-Czapek inoculum. Amendment of soil with peatmoss-Czapek inoculum of G. virens reduced colonization by Glomus mosseae when compared to a non-amended control. Inoculum colonized by other fungal biocontrol agents and sterilized with propylene oxide gave a similar reduction, suggesting that the substrate, not G. virens, was responsible for the reduction in VA mycorrhizal colonization. This evidence suggests that the fungal biocontrol agent G. virens does not have a detrimental impact on these VA mycorrhizal fungi, and would be compatible if applied as a dual-inoculum.