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.

From generalist to specialists: Variation in the host range and performance of anther‐smut pathogens on Dianthus *

“…2008; Tyson et al. 2018), there has been little evidence to suggest a true generalist species in Silene that is actively maintained on two or more hosts. Indeed, patterns of host‐specificity among Silene ‐infecting Microbotryum are present even in communities with sympatric host species (Van Putten et al.…”

“…These results with anther-smut fungi of Dianthus differ from patterns of host specificity of Microbotryum on host species in the genus Silene where phylogeographic studies have shown that most species of Microbotryum are specialized to a single host species (Lutz et al 2005;Le Gac et al 2007). Although host shifts can and do occur between closely related species (Antonovics et al 2002;Refrégier et al 2008;Tyson et al 2018), there has been little evidence to suggest a true generalist species in Silene that is actively maintained on two or more hosts. Indeed, patterns of host-specificity among Silene-infecting Microbotryum are present even in communities with sympatric host species (Van Putten et al 2005;Gladieux et al 2010;Hood et al 2019) and overlapping floral phenologies (Tang et al 2019).…”

“…Microbotryum species infecting hosts in the genus Silene are highly specialized; each pathogen species is generally found on just a single host species (Le Gac et al 2007). Moreover, this specificity is generally maintained even in sympatry with other closely related host species (Hood et al 2019;Tang et al 2019), although occasional host shifts have been identified (Antonovics et al 2002;Refrégier et al 2008;Tyson et al 2018;Hood et al 2019).…”

Sympatry and interference of divergent Microbotryum pathogen species

“…Research has shown that the fungi formerly grouped under the Microbotryum violaceum epithet represent a large species complex, consisting of many independent lineages, each specific (i.e., endemic) to only one or a very small number of host species (Kemler et al, ; Le Gac et al, ; Lutz et al, ; Piątek, Lutz, & Kemler, ; de Vienne, Hood, & Giraud, ). However, in marked contrast to the strong host specificity generally seen in those phylogenetic studies, several instances of cross‐species disease transmission have been observed in nature (Antonovics et al, ; Gladieux et al, ; López‐Villavicencio et al, ; Refrégier et al, ; Tyson, Antonovics, & Bruns, ). Cross‐inoculations under experimental conditions further support the potential for host‐shifts in some nonendemic host–pathogen combinations (Biere & Honders, ; Van Putten, Biere, & Damme, ; Shykoff et al, ; Sloan, Giraud, & Hood, ; de Vienne et al, ).…”