The interrelationship between temperature, genetic diversity and virulence in the chestnut - Cryphonectria - hypovirus pathosystem

Swiss chestnut coppice forest Photo: Sarah Bryner, WSL

Chestnut blight canker on chestnut bark caused by C. parsitica Photo: Sarah Bryner, WSL

Morphological effect of the interaction between different C. parasitica strains and CHV1 subrtypes Photo: Sarah Bryner, WSL

The aim of this PhD thesis is to detect and describe factors that govern the evolution of virulence in the host–parasite interaction between Cryphonectria parasitica and Cryphonectria hypovirus 1 (CHV1).

C.parasitica is and introduced fungus and causes one of the most serious tree diseases, i.e. chestnut blight. This pathogen devastated the native chestnut forests in North America. In Europe, chestnut blight incidence is high but has been maintained at low severity due to infection of C. parasitica with CHV1. CHV1 reduces the pathogenicity of C. parasitica to the chestnut tree and is also used for biological control.

This PhD thesis will provide insight into both fundamental and applied questions. We will analyze whether a genotype-by-genotype-by-environment interaction exists in this host–parasite system and test the hypothesis of a trade-off between the virus transmissibility – resulting from the host population structure – and  the degree of virulence. These results will have practical implications for the management of chestnut blight: the sustainability of biological control by hypovirulence depending on the diversity of host population, the design of biological control strategies in different geographic regions and their effectiveness under the scenario of climate change.

The project is part of GEDIHAP (GEnetic DIversity Host And Parasite), a joint project within the Competence Center Environment and Sustainability (CCES) of the ETH domain. More information: http://www.cces.ethz.ch/projects/feh/gedihap

• Sarah Bryner
  

• Daniel Rigling