Are morels mycorrhizal fungi?

BUSCOT, FRANCOIS¹ & DANIEL WIPF².

¹University of Jena, Department of Environmental Sciences, Dornburger Str. 159, D-07743 Jena, GERMANY. ²University of Nancy 1, Laboratoire de Biologie Forestière, BP 239, F-54500 Vandoeuvre Cedex, FRANCE.

While higher ascomycetes in the Tuberaceae and Helvellaceae are undoubtedly ectomycorrhizal, the status of Morchellaceae remains debatable. In the XIX^th century, more or less specific relations of morels to plant roots were described and detailed analyses revealed associations ranging from parasitism to ectomycorrhizal symbiosis. Nevertheless, as the possibility for morels to complete their life cycle under strictly saprotrophic conditions was demonstrated at the beginning of the XX^th century, their associations with plants were no more investigated during about 80 years.
Till the mid of the 80th, the question was reopened, as associations in field were investigated with powerful cytological methods. Limited parasitism was detected on roots of shrubs (Rosaceae and Cornaceae) and EM with reduced Hartig net succeeding to primary EM formed by basidiomycetes were observed in associations with Picea abies. More recently, ectendomycorrhizas with Fraxinus excelsior were suspected. In synthesis attempts under strictly controlled conditions, no EM formation was obtained, but different kinds of interactions with high specificity were demonstrated.
A general interpretation on the place of these associations within the ecological strategy of morels could be proposed. Molecular biological methods open new perspectives to investigate this complex topic more thoroughly.