Resolving host and species boundaries for perithecia-producing nectriaceous fungi across the central Appalachian Mountains

Abstract

The Nectriaceae contains numerous canker pathogens. Due to scarcity of ascomata on many hosts, comprehensive surveys are lacking. Here we characterize the diversity of perithecia-producing nectriaceous fungi across the central Appalachians. Ten species from twelve hosts were recovered including a novel Corinectria sp. from Picea rubens.Neonectria ditissima and N. faginata were most abundant and associated with Fagus grandifolia with beech bark disease (BBD). N. ditissima was also recovered from additional cankered hardwoods, including previously unreported Acer spicatum, Ilex mucronata, and Sorbus americana. Cross-pathogenicity inoculations of N. ditissima confirmed susceptibility of Acer and Betula spp. Neonectria magnoliae was recovered from cankered Liriodendron tulipifera and Magnolia fraseri and pathogenicity on L. tulipifera was confirmed. Fusarium babinda was consistently recovered from beech with BBD, although its role remains unclear. This survey provides a contemporary snapshot of Nectriaceae diversity across the Appalachian Mountains. The following nomenclatural changes are proposed: Neonectria magnoliae comb. nov.

Pathogen and endophyte assemblages co-vary with beech bark disease progression, tree decline, and regional climate

“…Applying the findings of this study to other Neonectria and Corinectria canker disease systems has potential to uncover a native reservoir for N. faginata, which not unlike N. ditissima on beech, might be less competitive on other host substrates. Such differences in fruiting abundance are already known for N. ditissima: perithecium production is high on Acer pensylvanicum compared to limited production on Ilex mucronata and Sorbus americana and no confirmed production on Liquidambar styraciflua (Stauder et al, 2020a;Kasson and Stauder, unpublished observations). Since N. ditissima is present on over one quarter of infected beech trees, the potential for amplification of spillover of this pathogen in ways that influence nonbeech hosts could also be an important mechanism by which this disease impacts forest structure, function, and diversity.…”

“…In addition, one of the C. rosea ASVs was an indicator of high Neonectria perithecia density, consistent with its hypothesized mycoparasitic status in this system (Stauder et al, 2020a). This species has long been used as a biocontrol agent against plant pathogenic fungi (Schroers et al, 1999).…”

“…However, the two warmest sites in our dataset were also of intermediate infection duration (19 and years) and so infection duration is unlikely to fully explain the climatedriven distribution patterns we observed. Indeed, nongrowing season heat accumulation was the strongest predictor of N. faginata occurrence while infection duration was the second strongest predictor, suggesting climate as an important influence on prevalence of these species within the Interestingly, the only site from which Clonostachys rosea was recovered in West Virginia in a previous study also had the highest incidence of N. ditissima (Stauder et al, 2020a). A second fungus, Fusarium babinda, may also interact differentially with N. faginata and N. ditissima.…”

“…This fungus has previously been recovered from Neonectria perithecia (Kasson and Livingston, 2009;Stauder et al, 2020a), possibly suggesting it opportunistically colonizes these tissues (though we note that perithecia were removed from our samples prior to DNA extraction in the current study). Nevertheless, both time course studies on perithecium production and co-plating assays are needed to further resolve these relationships.…”

“…While apparently ecologically similar within the BBD system, the life histories of these fungi differ in important ways. For example, Neonectria ditissima is a generalist that infects many diverse tree hosts including species of birch, maple, walnut, mountain ash, and holly, among others (Castlebury et al, 2006; Stauder et al, 2020a). The species is also an important pathogen of apple (Gomez-Cortecero et al, 2016).…”