Fungal endophytes from grapevine have host-dependent levels of virulence and produce antibiotic compounds in dual cultures
S. LÒPEZ-FERNÀNDEZ (1), A. Campisano (2), B. Schulz (1) (1) Technische Universität Braunschweig, Germany; (2) Fondazione Edmund Mach, Italy

Endophytic fungi live asymptomatically inside plants and are engaged in multiple ecological interactions, some of which determine whether or not virulence will be expressed in planta. These interactions are mediated by multiple compounds that are often target specific and thus appealing for industrial applications. We evaluated the potential virulence of fungal endophytic strains from grapevine in tomato, Arabidopsis thaliana and grapevine, using a disease index based on weight, height and penetration length of the fungus. Virulence of endophytic fungi was greatest when the endophytes had been inoculated into A. thaliana and lowest in grapevine plantlets, showing that virulence is host dependent. Inoculation with some fungi isolated from asymptomatic grapevine (e.g. Fusarium sp.) resulted in death of all hosts, whereas the virulence of others was host specific (e.g. Giberella sp. killed tomato). Dual cultures of endophytic fungi with endophytic and non-endophytic bacteria were conducted. Minimal Inhibitory Concentrations (MIC) of their culture extracts were calculated and ranged from 78 - 2500 µg/ml against bacterial test organisms. Antibacterial activity against Bacillus subtilis DSM319 and E. coli K12 was detected primarily in extracts obtained from the dual and not from the mono cultures, e.g. with Paecilomyces variotii strain 15 and  Alternaria sp. strain 19 challenged with E. coli K12. Our results suggest that there is mutual recognition between the host, grapevine, and its fungal endophytes and that secondary metabolites are involved in the recognition and interactions between endophytic fungi and bacteria. We are presently identifying structures of the metabolites involved in these interactions.

Abstract Number: P1-7
Session Type: Poster