Armillaria species in Newfoundland

Crosses with standard testers were used to identify 96 haploid Armillaria isolates from 34 collections made in Newfoundland. Isoenzyme patterns were also used to identify 36 diploid and 3 haploid Armillaria isolates from 39 other collections. Diagnostic electromorphs at Rf 0.70 for esterases, Rf 0.32 for succinate dehydrogenase, and Rf 0.31 for 6-phosphogluconate dehydrogenase permitted positive identification of Armillaria ostoyae (Romagn.) Herink for all isolates tested by electrophoresis, and the method worked with haploid and diploid isolates. Crosses of the 96 haploid isolates collected on hardwoods and conifers were all positive for A. ostoyae, except for eight isolates. These eight isolates from three collections made on or near an American mountain-ash (Sorbus americana Marsh.) in a St. Johnʹs city park, where numerous exotic tree species are present, were found to be Armillaria sinapina Bérubé & Dessureault. These isolated collections in an area of limited natural hardwood presence may be the result of an introduction from the mainland; thus, A. ostoyae appears to be the only Armillaria species found in natural habitats in Newfoundland.