Adhesion to hyphal matrix and antifungal activity of Pseudomonas strains isolated from Tuber borchii ascocarps

Pseudomonas spp. isolates from Tuber borchii ascocarps, known to be able to produce phytoregulatory and biocontrol substances in pure culture, were us ed to perform studies on their possible physiological role in nature. Antim ycotic activity was confirmed against fungal contaminants isolated from the ascocarps, suggesting that populations associated with Tuber borchii fruit bodies may play a role in the maintenance of ascocarp health. Fifty-five p ercent of strains tested were also able to release metabolites which affect ed T. borchii mycelial growth and morphogenesis in culture. On the contrary , growth of the arbuscular mycorrhizal fungus Glomus mosseae and the ectomy corrhizal fungus Laccaria bicolor, putative competitors of Tuber for mycorr hizal infection sites on roots, was not influenced by the presence of any b acterial strain. The possibility that these bacteria, which show antifungal activity and fungal growth modulation activities, might be incorporated in the developing ascocarp by means of their preferential adhesion to Tuber m ycelium is discussed.