Changes inCryphonectria parasiticaPopulations Affect Natural Biological Control of Chestnut Blight

Abstract

Invasive species, especially plant pathogens, have a potential to completely eradicate native plant species and remodel landscapes. Tripartite interactions among sweet chestnut (Castanea sativa), chestnut blight-causing invasive fungus Cryphonectria parasitica, and hyperparasitic virus Cryphonectria hypovirus 1 (CHV1) were studied in two populations. The number of different vegetative compatibility (vc) types of C. parasitica more than doubled over the 10 years, while the hypovirulence incidence dropped in one population and slightly increased in the other one. Over the course of our 3-year monitoring experiment, the prevalence of hypovirulent isolates obtained from monitored cankers increased slowly (i.e., more hypovirulent isolates were being obtained from the same cankers over time). Within studied cankers, considerable changes in vc type and CHV1 presence were observed, indicating a highly dynamic system in which virulent and hypovirulent mycelia, sometimes of discordant vc types, often appeared together. The increase in hypovirulence prevalence did not have any observable curative effect on the cankers and, occasionally, reactivation of healed cankers by new, virulent C. parasitica isolates was observed. Both short- and long-term observations and revalidation of the infected plant populations are necessary to accurately estimate disease progress and formulate an adequate disease management strategy.

Long-read sequencing reveals the evolutionary drivers of intra-host diversity across natural RNA mycovirus infections

“…This has likely fueled a single genetic founder in Kast, which in turn drove population differentiation through founder effect–derived genetic drift and no subsequent migrant exchange. Reduced landscape connectivity between the sites in Croatia is supported by previous studies, which showed a reduced diversity of the fungal host in Kast relative to other Croatian sites ( Ježić et al. 2018 , 2021 ).…”

Diversity of Cryphonectria parasitica in callused chestnut blight cankers on European and American chestnut

“…In North Macedonia, all isolates were initially paired with EU‐12, the dominant vc type (Milgroom et al, ; Sotirovski, Papazova‐Anakieva, Grünwald, & Milgroom, ), and in case of registered incompatibility, isolates were paired with EU‐2. In Croatia and Switzerland, isolates were initially paired with vc testers for the most common Croatian vc types (EU‐1, EU‐2, EU‐12 and EU‐13) (Ježić et al, ; Krstin, Novak‐Agbaba, Rigling, Krajačić, & Ćurković‐Perica ), and the most common Swiss vc types (EU‐1, EU‐2, EU‐5 and EU‐6) (Robin & Heiniger, ). If an incompatible reaction was observed, additional pairings with other vc types present in those countries were performed.…”

“…Across chestnut populations in Europe and North America, isolations from chestnut blight cankers yielded a mixture of virulent and hypovirulent C. parasitica isolates, as well as non‐ C. parasitica fungi (Akilli, Katircioglu, & Maden, ; Bryner, Prospero, & Rigling, ; Double et al, ; Ježić et al, ; Robin, Anziani, & Cortesi, ). It has been shown that isolation of C. parasitica from completely callused cankers was more difficult than from virulent cankers (i.e.…”

“…This diversity on the microscale was considered as a potential limitation of viral transfer between C. parasitica isolates present within the same canker. Ježić et al () analysed C. parasitica strains in individual cankers for three consecutive years and showed that callused cankers could be re‐invaded by virulent strains of C. parasitica .…”

Link between epigenetic diversity and invasive status of south‐eastern European populations of phytopathogenic fungus Cryphonectria parasitica

“…All isolates used in this study, were sampled previously in North Macedonia and Greece (Sotirovski et al, ), Turkey (Gurer et al, ), Italy (Milgroom and Cortesi, ; Milgroom et al, ), Bulgaria (Milgroom et al, ), and Croatia and Slovenia (Ježić et al, ). For control experiment, additional samples were recently collected in Croatia ( n = 24; Ježić et al, ). Croatian population served as a control population due to its high variation in genetic diversity of C. parasitica .…”