NITROGEN FIXATION ACTIVITY DURING WHITE TRUFFLE MATURATION

Tuber magnatum, the Italian white truffle, is the ectomycorrhizal fungal species most appreciated among edible fungi. The flourishing T. magnatum market has encouraged large-scale programs for cultivating through the planting of nursery-produced mycorrhizal trees in suitable sites. However despite the success obtained for other species of truffles, such as Tuber melanosporum, Tuber aestivum, Tuber uncinatum and Tuber borchii, T. magnatum cultivation was mostly unsuccessful showing that important factors which may control T. magnatum life cycle are still unknown. It has been demonstrated that certain bacteria influence the sporocarp formation; in this study we analyzed the potential activity of nitrogen fixing bacteria in T. magnatum ascocarps. These bacteria could play an important role in the ascoma formation supplying the nitrogen required during the ascoma development in the soil. We performed a combined molecular and biochemical approach to determine whether the Tuber-associated bacteria posses the nitrogen fixation genes and whether these genes are expressed. To verify the presence of the nitrogenase operon universal primers for the conserved domain of nifH gene (371nt) were applied for a nested PCR on the total DNA extracted from ascomata at different degree of maturation and the nitrogen-fixation activity has been evaluated in the same samples by the ARA-test under axenic condition. The results obtained in this study presented the first evidence of nitrogen-fixation activity in truffles and offered the first sequences for the nifH gene described in Tuber-associated bacteria