The importance of inoculum size for the competitive ability of wood decomposing fungi

Competition among wood decay fungi was studied with a technique using sectors of various sizes of 8 cm diameter wood discs. The sectors representing 8–92% of the discs were precolonized by Heterobasidion annosum (Fr.) Bref., Resinicium bicolor (Alb. & Schw. ex Fr.) Parm, Phanerochaete sanguinea (Fr.) Hjortstam and Coniophora sp. DC. ex Me'rat before they were combined pairwise in close contact on top of water agar in 9 cm Petri dishes. Discs were regularly inspected for mycelial overgrowth and after 10 weeks mycelia were reisolated. Competitive success, measured as the replacement of the opposing fungus, was generally greatest for mycelia with sectors representing 92% of a disc and smallest for 8% sectors. R bicolor was the most, and H. annosum the least, competitive of the species investigated. The results indicate that mycelial size could be one major factor influencing the competitive success in nature. However, when paired on nutrient agar, the results of the interactions between the four species did not correspond to those in wood discs.