The effect of applied lime and phosphorus on the competitiveness of Tuber melanosporum and other ectomycorrhizal fungi found in Tasmania

Hazel (Corylus avellana L.) seedlings inoculated with the Perigord black truffle fungus (Tuber melanosporum Vitt.) are being planted in Tasmania in an attempt to culture truffles. Competition from other ectomycorrhizal fungi has a significant impact on truffle production in Europe and can be expected to have some effect on the Tasmanian industry. This thesis examines ectomycorrhizal fungi occurring in Tasmania with respect to their ability to form mycorrhizas with hazel and compete with T melanosporum under various soil treatments. Stands of hazel previously established for nut production or as ornaments were surveyed for the sporocarps of ectomycorrhizal fungi. Several species were found ; including species that are new either to Australia or Tasmania. The endemic species Descomyces albus (Klotzsch) Bougher & Castellano and Podohydnangium sp., previously thought to. be Eucalyptus specific were. fruiting under hazel. T melanosporum occurs naturally on calcareous soils in Europe. Truffieres in Tasmania are heavily limed to create a calcareous soil environment. The response of selected introduced and endemic ectomycorrhizal fungi to applied lime was studied in a glasshouse experiment. Some of the endemic species, which would normally inhabit acidic soils, were unable to survive high rates of lime application and therefore should not pose a threat to the truffle industry. The introduced species were generally more tolerant to lime application. A subsequent glasshouse experiment sought to separate the effects of pH and calcium on colonisation by T melanosporum. Seedling hazels were inoculated with T melanosporum. After twelve months, they were transplanted using soil amended with fourteen rates of either CaCO3 , CaSO4, or MgCO3 . The seedlings were then exposed to spores of two endemic fungal species. Applied CaCO 3 and MgCO3 increased level of colonisation by T melanosporum, whereas CaSO4 had little or no effect. Soil pH appears to have a stronger influence on colonisation by T melanosporum than the level of applied or exchangeable calcium. Colonisation by endemic species was low and sporadic across all treatments. Another glasshouse experiment of similar design to that above was established to observe the effect of lime and phosphorus interaction. Applied lime significantly increased the level of colonisation of T melanosporum, but phosphorus had no effect, even at very high rates of application (150 mg P / Kg soil). A commercial truffiere was surveyed for the level of colonisation by T melanosporum and other ectomycorrhizal fungi. Descriptions were compiled of the mycorrhizas of fungal species found in the glasshouse and field experiments to assist in their future identification. The morphological identification of Tuber mycorrhizas was confirmed using PCR and RFLP of DNA extracted from single mycorrhizal tips.