Morphological characterization of Armillaria ostoyae and Armillaria sinapina sp.nov.

In Quebec, the root rot fungus Armillaria mellea (Vahl: Fr.) Kummer in the broad sense was found to be composed of three intersterile groups or biological species by using mating tests with standard voucher strains. Monosporous cultures of our specimens were compatible with strains of groups I, V, and VI. Groups I and V corresponding to A. ostoyae (Romagn.) Herink and A. sinapina sp.nov., respectively, are described and their occurrence and ecology documented. Morphological characteristics of fruiting bodies and of vegetative isolates can be used to differentiate A. ostoyae, A. sinapina, and A. mellea s.str. Armillaria ostoyae and A. sinapina are mild pathogens or saprotrophs on declining trees or stumps, whereas A. mellea s.str. appears to be an aggressive pathogen.