A Peniophora lycii Isolate Simultaneously Parasitizes Vitis vinefera Host and Associated Fungi, and Possibly Contributes to Grapevine Trunk Disease Development.

An isolate of Peniophora lycii was obtained from grapevine, and its interactions with several grapevine-associated fungi and the plant host were examined. The fungus was not able to infect intact leaves, but necrotized the margins of foliar disks and caused necrosis and white rot in woody tissues. In dual cultures, P. lycii and Aureobasidium pullulans showed mutual antagonism. Mycoparsitism of P. lycii was observed on epiphytic Botrytis cinerea, Alternaria sp., and endophytic Botryosphaeria dothidea interaction partners. In contrast, P. lycii showed trophic growth towards endophytic Phaeomoniella chlamydospora without any signs of harmful interactions. Dual inoculations of foliar disks with epiphytic fungi revealed no effects of fungal interactions on necrosis development by pathogens and verified mycoparasitic interactions in planta. Co-infection assays of cuttings with endophytic pathogen fungi showed cumulative effects of fungal interactions on wood symptom expression, with the exclusive contribution of P. lycii to white rot development. In addition to providing the first isolation of P. lycii from grapevine and the description of its mycoparasitic behavior, the present study suggests that the fungus may act as an opportunistic grapevine pathogen, probably as a secondary colonizer in trunk diseases. The observed dual host preference may allow trunk disease pathogens to initially feed on fungi, followed by damage to the grapevine. This may be in connection with the exceptionally long latency of these syndromes.