ESTABLISHMENT OF ECTOMYCORRHIZAS IN ASEPTIC CULTURE - EFFECTS OF GLUCOSE, NITROGEN AND PHOSPHORUS IN RELATION TO SUCCESSIONS

Birch (Betula pubescens) seedlings were grown aseptically on agar slants with variations in available glucose, nitrogen or phosphorus and inoculated with Lactarius pubescens, Tricholoma fulvum and Amanita muscaria (late-stage fungi in mycorrhizal successions) or Laccaria proxima and Hebeloma crustuliniforme (early stage fungi). Hyphal extension rates were assessed on plates of the same media. Mycorrhiza formation by late stage fungi was suppressed more than by early stage fungi at low P levels, but all were markedly suppressed by low nitrogen. With adequate mineral nutrients, early stage fungi formed mycorrhizas at low (0 or 0·01%) and moderate (0·1%) glucose levels, whereas four out of five late stage isolates required moderate (0·1%) or high (1·0%) glucose for mycorrhizal development. Sustained colony extension by early stage fungi occurred in the absence of glucose, whereas all late stage fungi required high glucose levels for continued extension. The differences in glucose- and P-dependence between early and late-stage fungi are discussed in relation to mycorrhizal successions. © 1990, British Mycological Society. All rights reserved.