Anther smut disease caused by Microbotryum on berry campion Silene baccifera: endemic pathogen or host shift?

Abstract

This research investigated whether anther smut disease caused by Microbotryum violaceum agg. on Silene baccifera in Europe is caused by a host-specific lineage, or if it represents a host shift of the pathogen from a related species. Characterization of ITS sequences of anther smut from S. baccifera confirmed their strong similarity to the pathogen endemic on Silene latifolia. Cross-inoculation studies showed that S. baccifera was susceptible to anther smut isolates from S. latifolia, S. dioica and S. vulgaris; conversely isolates from S. baccifera could cause disease on S. latifolia. In an experimental field study, spore transmission from diseased S. latifolia to healthy S. baccifera was rare relative to intraspecific transmission within S. latifolia. The distribution of anther smut in natural populations based on herbarium specimens indicated that disease occurrence on S. baccifera was very sporadic. These findings strongly suggest that anther smut disease on S. baccifera in Europe is usually a temporary host shift from the self-sustaining populations of Microbotryum on other species.