Testing the pathogenic potential ofCryphonectria parasiticaand related species on three common European Fagaceae

Abstract

<jats:title>Abstract</jats:title><jats:p>Invasions by non-native pathogens represent a major threat to managed and natural ecosystems worldwide. Although necessary for adopting preventive strategies, the identification of invasive species before they are introduced is particularly difficult. Indeed, most pathogenic species that have become established in the last decades were first described only after they became invasive. To prevent further biological invasions, not only the early identification of potential new invasive plant pathogens is crucial, but also the assessment of their potential host range. In this study, we determined the pathogenicity and the saprotrophic ability of three <jats:italic>Cryphonectria</jats:italic> species towards three potential hosts in the family Fagaceae. For this, seedlings and dormant stems of European chestnut (<jats:italic>Castanea sativa</jats:italic>), pedunculate oak (<jats:italic>Quercus robur</jats:italic>) and European beech (<jats:italic>Fagus sylvatica</jats:italic>) were inoculated with different genotypes of <jats:italic>C. parasitica</jats:italic> (Asian species, invasive in Europe), <jats:italic>C. naterciae</jats:italic> (European species), and <jats:italic>C. japonica</jats:italic> (Asian species, not present in Europe). Lesion growth was measured and mortality assessed for four months. The highest damage was caused by <jats:italic>C. parasitica</jats:italic> on European chestnut, while <jats:italic>C. japonica</jats:italic> and <jats:italic>C. naterciae</jats:italic> induced significantly smaller lesions on this host species. All three <jats:italic>Cryphonectria</jats:italic> species did not grow saprophytically on <jats:italic>F. sylvatica</jats:italic> and <jats:italic>Q. robur</jats:italic>, but successfully colonized dormant stems of <jats:italic>C. sativa</jats:italic>. In the context of biological invasions, our study shows that the Asian <jats:italic>C. japonica</jats:italic> most likely represents a much less severe threat than <jats:italic>C. parasitica</jats:italic> for the tested European host species. Nonetheless, the ability of <jats:italic>C. naterciae</jats:italic> and <jats:italic>C. japonica</jats:italic> to saprotrophically colonize fresh chestnut wood may suggest that they could become established in chestnut forests and eventually infect weakened chestnut trees or other hosts not tested in this study.</jats:p>

Comparative Genomics Analyses of Lifestyle Transitions at the Origin of an Invasive Fungal Pathogen in the GenusCryphonectria

“…The CAZyme profiles of the Cryphonectriaceae species analyzed in this study match those of other hemibiotrophic or necrotrophic fungi. Thus, despite substantial difference in pathogenicity ( 40 ), Cryphonectriaceae species seem to share trophic lifestyle traits, which challenges previous classifications of C. japonica , C. naterciae , and C. radicalis as predominantly saprotrophic species ( 37 ). Nonetheless, the distinct CAZyme loss in C. parasitica coincides with an increased pathogenicity toward nonnative (i.e., non-Asian) Castanea species, which seems to be absent in other Cryphonectria species.…”

“…For each treatment batch with and without wound, we selected 5 replicates per isolate and 5 negative controls (mycelium-free agar plugs), resulting in a total of 130 completely randomized inoculation spots ( n = 65 per treatment). All chestnut logs were randomly placed onto racks in plastic containers, separated by treatment, filled with 2 liters of demineralized water to avoid drying out, and sealed with plastic lids ( 40 ). Incubation was at 20°C for both treatments.…”

“…Both in the native and in the invasive range, C. parasitica has closely related sister species, which are considered weak pathogens or saprophytes ( 40 ). Among these, Cryphonectria japonica Tak.…”

“…Inoculation experiments showed that both C. japonica and C. naterciae are significantly less virulent on Ca. sativa , Quercus robur L., and Fagus sylvatica L. than C. parasitica ( 40 , 43 ). Two other Cryphonectria species occurring in Europe are C. radicalis and C. carpinicola .…”

Comparative genomics analyses of lifestyle transitions at the origin of an invasive fungal pathogen in the genusCryphonectria

“…parasitica (Dennert et al, 2020;Jiang et al, 2019;). Two other Cryphonectria species occurring in Europe are C. radicalis and C. carpinicola.…”