Release of a Cord-Forming Basidiomycete Antagonistic to Heterobasidion Annosum and Its Subsequent Reisolation and Identification

Abstract

After initial competition experiments done in the laboratory, the most successful species, Resinicium bicolor (Alb. & Schw. ex Fr.) Parm., was chosen as a potential control agent of Heterobasidion annosum (Fr.)Bref (Holmer & Stenlid, 1993). Three different field experiments in first rotation field plantations of Norway spruce (Picea abies) were conducted in three places in Sweden. Wood blocks, preinoculated with one strain of R. bicolor, were buried in the soil beside stumps at different time interval after thinning and with different number of wood blocks. In two of the experiments, half of the stumps were treated with a suspension of H. annosum conidia from one strain sprayed on the surface. After 2–3 years, stump roots were investigated and the length of growth of both species were noted. Reisolations of mycelia were made from the roots as well as from wood debris in the experiment area. The isolates were paired on agar plates against the original strains (somatic incompatibility test). The used strain of R. bicolor was found again all over the experimental areas, no other strains of the species were found. The used strain of H. annosum was only reisolated from roots of artificially H. annosum treated stumps. Other strains of the fungus were frequently found from the untreated stumproots. R. bicolor was found to have limited effect on die growth and occurence of H. annosum.