RESYNTHESIS IN PURE CULTURE OF A COMMON SUB-ALPINE FUNGUS-ROOT ASSOCIATION USING PHIALOCEPHALA-FORTINII AND MENZIESIA-FERRUGINEA (ERICACEAE)

A strain of Phialocephala fortinii isolated from Luetkea pectinata was used to inoculate axenically grown 1-wk-old Menziesia ferruginea (Eri caceae) seedlings in cellulose agar petri dish cultures. After 3 mo, P . fortinii was observed in cortical cells of whole root mounts. but no t in the stele. The fungus produced dark, simple septate hyphae formin g extensive wefts on the root surface and intracortical sclerotia cons isting of compact masses of darkly pigmented and irregularly lobed, th ick-walled hyphae. Isolates of P. fortinii also formed numerous sclero tia in the cellulose agar medium. Presence of P. fortinii caused a ten -fold increase in seedling mortality over controls. Growth rates, base d on whole plant fresh weight, were not affected by the presence of P. fortinii. Cenococcum geophilum, Phialocephala dimorphospora, and Phia lophora finlandia, which were also used as inoculum for comparative pu rposes, did not form sclerotia in M. ferruginea. This is the first rep ort to show that the distinct fungus-root associations formed between P.fortinii and subalpine plants can be reproduced consistently in pure culture under laboratory conditions.