LEPTODONTIDIUM-ORCHIDICOLA (MYCELIUM-RADICIS-ATROVIRENS COMPLEX) - ASPECTS OF ITS CONIDIOGENESIS AND ECOLOGY

The Mycelium radicis atrovirens complex is a group of usually sterile hyphomycetes associated with the roots of plants growing in cool, humu s-rich soils. Leptodontidium orchidicola is a relatively common, but p oorly known, species in this complex. The cultural and vegetative morp hology of L. orchidicola make it superficially similar to Phialocephal a fortinii but differences are discernible at the microscopic level. W e have obtained in pure culture several sporulating strains from alpin e habitats in Alberta and have observed conidiogenesis using light and scanning electron microscopy. Observations indicate that the single-c elled conidia develop blastically at non-specific loci along the later al or terminal walls of conidiogenous hyphae. Mature conidia are varia ble in shape and may be sessile or short-stalked. Secondary conidia of ten develop blastically from the distal end of undehisced primary coni dia. When grown in axenic culture with native host plants in the gener a Picea, Betula and Potentilla, the fungus penetrated and colonized ep idermal and cortical cells but did not cause any discernible pathogeni c effects.