COMPETITION BETWEEN TUBER-MELANOSPORUM AND OTHER ECTOMYCORRHIZAL FUNGI, UNDER 2 IRRIGATION REGIMES .2. COMPARISON OF SOILS ARTIFICIALLY INFESTED WITH T-MELANOSPORUM AND T-BRUMALE

A glasshouse experiment was conducted to observe the behavior of the a rtificial Tuber melanosporum-hazel symbiosis after outplanting in soil infected with the same Tuber species (10(4) spores cm-3 soil) or T. b rumale (10(2) and 10(4) spores cm-3 soil). Despite a low level of Tube r-infection at planting, infection with T. melanosporum was maintained or increased, whereas infection by other mycorrhizal species remained low. In contrast, in non-inoculated control soil, infection with T. m elanosporum declined and was almost completely replaced by other speci es. This investigation emphazises the importance of the intensity of T . melanosporum infection at planting. The effects of the diversity of mycorrhizal species and density of the soil fungal-inoculum, including indigeneous Tuber species on the spread of the introduced symbiosis a fter outplanting are reported. Intra- and interspecific competition fo r infection within the genus Tuber are discussed.