Anamorphic and teleomorphic characteristics of a uninucleate Rhizoctonia sp. isolated from the roots of nursery grown conifer seedlings

Abstract

Vegetative, anastomosis, fruiting and basidial characteristics were analysed in one Norwegian and five Finnish Rhizoctonia isolates from the roots of various nursery grown conifer seedlings. The isolates displayed common hyphal and colony morphology that also confirmed their designation as a Rhizoctonia sp. Hyphal cells were predominantly uninucleate except for one isolate which contained a relatively high number (11%) of binucleate tip and subapical cells. All isolates had similar temperature dependent growth rates and formed a single anastomosis group within which killing reactions were detected in opposing fusion cells of all non self pairings. Fruiting was induced in all but one Finnish isolate using a novel method involving axenic liquid culture of the fungi in the presence of Scots pine ( Pinus sylvestris ) seedlings. Basidial and basidiospore dimensions indicate that the isolates represent a single Ceratobasidium sp. although two selected isolates showed no hyphal anastomosis reactions with binucleate testers of the different Ceratobasidium anastomosis groups (AG-A to AG-S). The identified teleomorph closely resembles C. bicorne but further confirmation was not possible because this fungus is only available as herbarium material.