The chestnut blight fungus world tour: successive introduction events from diverse origins in an invasive plant fungal pathogen

Abstract

Clonal expansion has been observed in several invasive fungal plant pathogens colonizing new areas, raising the question of the origin of clonal lineages. Using microsatellite markers, we retraced the evolutionary history of introduction of the chestnut blight fungus, Cryphonectria parasitica, in North America and western Europe. Combining discriminant analysis of principal components and approximate Bayesian computation analysis, we showed that several introduction events from genetically differentiated source populations have occurred in both invaded areas. In addition, a low signal of genetic recombination among different source populations was suggested in North America. Finally, two genetic lineages were present in both invaded areas as well as in the native areas, suggesting the existence of genetic lineages with a high capacity to establish in diverse environments and host species. This study confirmed the importance of multiple introductions, but questioned the role of genetic admixture in the success of introduction of a fungal plant pathogen.

Effects of Host Variability on the Spread of Invasive Forest Diseases

“…Later on, the fungus was also introduced from other Japanese regions, China, and Korea. Introductions into Europe occurred both from North America (into Italy) and Asia (into south-western France) [111]. Although European chestnut is slightly less susceptible to C. parasitica than the American chestnut, the spread of the pathogen on the European continent was also rapid.…”

“…Nevertheless, it is still not clear whether the low genetic diversity of C. dentata compared to that of the congeneric species is the result or also a cause of the species decline due to chestnut blight [110]. Recent population genetic analyses [111] showed that the initial introduction of C. parasitica into North America occurred from the main Japanese island Honshu. Later on, the fungus was also introduced from other Japanese regions, China, and Korea.…”

Multilocus PCR Assays Elucidate Vegetative Incompatibility Gene Profiles of Cryphonectria parasitica in the United States

“…Populations in certain localities appear to be highly clonal (3), while others are more diverse and show evidence of recombination (4). The fungus is able to reproduce sexually (5,6), and in nature, selfing and parasexual recombination are known to occur (7).…”

Endophytic Cryphonectriaceae on native Myrtales: Possible origin of Chrysoporthe canker on plantation-grown Eucalyptus

“…The trade in life plants, sometimes also referred to as "plants for planting", and timber have been identified as two of the main pathways of pathogen introductions into new regions (Brasier 2008;Liebhold et al 2012). It has for example been suggested that the chestnut blight pathogen, C. parasitica, was introduced into the United States of America with living plants (Dutech et al 2012;Milgroom et al 1992), while the most likely route of movement of Chrysoporthe species is still not well understood. A pathway of spread that has not received attention for fungi in the Cryphonectriaceae, is where they might have been carried as symptomless endophytes.…”