Biotrophic associations between lodgepole pine seedlings and postfire ascomycetes (Pezizales) in monoxenic culture

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Twenty-two species of postfire ascomycetes belonging to the order Pezizales were screened for biotrophic interactions with roots of lodgepole pine (Pinus contorta Dougl.). Biotrophic associations ranged from pathogenicity to mycorrhizal symbiosis, but most species tested did not show any affinity for roots. Pyropyxis rubra (Peck) Egger and Rhizina undulata Fr. were aggressive pathogens that infected the vascular cylinder and killed the seedlings. Tricharina praecox (Karst.) Dennis var. intermedia Egger, Yang & Korf also had some ability to infect the vascular cylinder, but usually did not kill the seedlings. Geopyxis carbonaria (A. & S.) Sacc. and Trichophaea hemisphaerioides (Mont.) Graddon invaded the cortex, forming complex intracellular structures, but did not penetrate the vascular cylinder. They may form mutualistic associations under certain conditions. The only confirmed mutualistic species was Sphaerosporella brunnea (A. & S.) Svrcek & Kubicka, which formed ectendomycorrhizae. Anthracobia maurilabra (Cooke) Boud. and A. tristis (Bomm., Rouss. & Sacc.) Boud. appear to be primarily root-surface inhabitants with limited capacity to infect cortical tissues through breaks in the epidermis. Gyromitra infula (Schaef.) Quél. penetrated the epidermis but was unable to overcome host defences against pathogenic infection.