Resynthesis in Pure Culture of a Common Subalpine Fungus-Root Association Using Phialocephala fortinii and Menziesia ferruginea (Ericaceae)

Abstract

A strain of Phialocephala fortinii isolated from Luetkea pectinata was used to inoculate axenically grown 1-wk-old Menziesia ferruginea (Ericaceae) seedlings in cellulose agar petri dish cultures. After 3 mo, P. fortinii was observed in cortical cells of whole root mounts, but not in the stele. The fungus produced dark, simple septate hyphae forming extensive wefts on the root surface and intracortical sclerotia consisting of compact masses of darkly pigmented and irregularly lobed, thick-walled hyphae. Isolates of P. fortinii also formed numerous sclerotia in the cellulose agar medium. Presence of P. fortinii caused a ten-fold increase in seedling mortality over controls. Growth rates, based on whole plant fresh weight, were not affected by the presence of P. fortinii. Cenococcum geophilum, Phialocephala dimorphospora, and Phialophora finlandia, which were also used as inoculum for comparative purposes, did not form sclerotia in M. ferruginea. This is the first report 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.