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Epigenetic diversity in natural populations of the invasive fungus Cryphonectria parasitica from south-eastern Europe

Epigenetic modifications, such as DNA methylation, may play an important role in the process of adaptation of natural populations to different environmental conditions, without involvement of genetic variation. Although the interest on natural epigenetic variation of non-model organisms recently increased, there are no studies on a population level concerning plant pathogenic fungi. The fungus Cryphonectria parasitica is an invasive pathogen of sweet chestnut that has spread throughout the chestnut-growing areas of Europe. A study based on microsatellite markers showed that in south-eastern Europe a single haplotype dominates the C. parasitica population. The aim of this study was to analyse the epigenetic diversity and structure within and among C. parasitica populations from south-eastern Europe, which are grouped together within the same microsatellite haplotypes. We compared general methylation patterns of different haplotypes - S12 (dominant haplotype), S1, and S2, from south-eastern Europe using the methylation sensitive amplified polymorphism (MSAP) approach. The highest level of epigenetic diversity was found in S1 haplotype (H' = 0.4095), followed by the S2 haplotype (H' = 0.3787), while the lowest level of diversity was found in S12 haplotype (H' = 0.345). MSAP analysis also showed the highest number of hemimethylated epiloci in all three haplotypes. In five populations in which S12 is the dominant haplotype, the highest level of epigenetic diversity among S12 isolates was observed in the Italian populations (the oldest populations in the researched area). Diversity is lower in the populations that have been invaded recently. Our data suggest that epigenetic plasticity, observed especially in the older populations, might improve C. parasitica success in expanding into new regions. This study presents a first insight into the epigenetic diversity within and among natural populations of an invasive fungal species.

chestnut blight; DNA methylation; population structure

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