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​​Hypovirus Virulence and Vegetative Incompatibility in Populations of the Chestnut Blight Fungus

December 2012 , Volume 102 , Number  12
Pages  1,161 - 1,167

Sarah Franziska Bryner and Daniel Rigling

WSL Swiss Federal Research Institute, CH-8903 Birmensdorf, Switzerland.

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Accepted for publication 21 July 2012.

Cryphonectria hypovirus 1 hyperparasitizes the chestnut blight fungus Cryphonectria parasitica and acts as a biocontrol agent for this serious tree disease. The virus is transmitted cytoplasmatically between fungal individuals. However, highly virulent viruses strongly debilitate their host and, thus, reduce their own transmission probability. Furthermore, vegetative incompatibility between fungi is an important transmission barrier. Therefore, virulent viruses are expected to be strongly selected against in fungal populations with high levels of vegetative incompatibility, eventually leading to the erosion of biocontrol. To test this prediction, we assessed the virulence of the virus in four European C. parasitica populations with high diversity of vegetative compatibility types and in four populations with low diversity. We expected the degree of virus virulence to be lower in fungal populations with high levels of vegetative incompatibility. However, our results did not reveal such a trend. No significant differences in virus virulence between populations with low versus high diversity of vegetative compatibility types were observed. There was no evidence for an erosion of disease control due to the presence of these transmission barriers. Thus, the findings of this study are promising for the sustainability of Cryphonectria hypovirus 1 as a biocontrol agent for chestnut blight in Europe.

Additional keywords: avirulence, biological control, fungal virus, host–parasite interaction.

This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 2012.