Saprobic and parasitic interactions of Coniochaeta velutina with mosses

Abstract

During a survey of fungi associated with boreal bryophytes in Alberta, Canada, an isolate of Coniochaeta velutina (Coniochaetaceae, Coniochaetales), an opportunistic tree-pathogen and saprobe, was obtained from Hylocomium splendens (Hedw.) Schimp. (Hylocomiaceae, Hypnales). This isolate exhibited phylogenetic affinities to C. velutina isolated from vascular plants. In vitro characterization of its interactions with the model host Funaria hygrometrica Hedw. (Funariaceae, Funariales) demonstrated that it readily forms both anamorph and teleomorph states on the moss. Infected hosts exhibited no macroscopic symptoms or, occasionally, became weakly chlorotic, suggesting that the fungus is a parasite. However, cellulase and polyphenolic oxidase enzyme production suggest it may also be a latent saprobe. Vegetative hyphae of C. velutina directly penetrated rhizoids and frequently elicited a papilla-formation host response, neither of which have been reported in vascular plants infected with C. velutina. The Lecythophora anamorph of C. velutina was produced within host rhizoids, a new phenomenon among bryophilous fungi. Ascomata were produced superficially on F. hygrometrica, although the rhizoid the ascoma is initiated on frequently becomes embedded in the mature peridium. Given the ability of C. velutina to infect, persist, and reproduce on moss hosts, understory bryophytes may represent an inoculum reservoir that contributes to the disease cycle of C. velutina on tree species.