ANAMORPHIC AND TELEOMORPHIC CHARACTERISTICS OF A UNINUCLEATE RHIZOCTONIA SP ISOLATED FROM THE ROOTS OF NURSERY GROWN CONIFER SEEDLINGS

Vegetative, anastomosis, fruiting and basidial characteristics were an alysed in one Norwegian and five Finnish Rhizoctonia isolates from the roots of various nursery grown conifer seedlings. The isolates displa yed common hyphal and colony morphology that also confirmed their desi gnation as a Rhizoctonia sp. Hyphal cells were predominantly uninuclea te except for one isolate which contained a relatively high number (11 %) of binucleate tip and subapical cells. All isolates had similar tem perature 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 fu ngi in the presence of Scots pine (Pinus sylvestris) seedlings. Basidi al and basidiospore dimensions indicate that the isolates represent a single Ceratobasidium sp. although two selected isolates showed no hyp hal anastomosis reactions with binucleate testers of the different Cer atobasidium anastomosis groups (AG-A to AG-S). The identified teleomor ph closely resembles C. bicorne but further confirmation was not possi ble because this fungus is only available as herbarium material.