Characterization and pathogenicity of fungal species associated with hazelnut trunk diseases in North-western Italy

Italy is the second largest hazelnut producer worldwide and Piedmont is one of the most productive regions in the country. The changing climatic condition and fungal trunk diseases (FTD) can have a severe impact on this crop. Particularly, the considerable spread of Cytospora cankers (‘Mal dello stacco’) and dieback represent a serious concern for producers. Thus, considering the limited studies on the causal agents, different surveys were conducted in seven hazelnut orchards during 2021 and 2022. Eight fungal species were identified: Anthostoma decipiens, Botryosphaeria dothidea, Diaporthe eres, Dia. rudis, Diplodia seriata, Dip. subglobosa, Dothiorella parva and Nothophoma brennandiae. Species identification was achieved through multilocus phylogeny and morphology assessment. All the fungal species were pathogenic on healthy hazelnut plants (cultivar Tonda Gentile) and A. decipiens and Dia. eres were the most aggressive. The present study is the first report of B. dothidea and Dia. eres as causal agents of FTD on hazelnut in Italy and of Dia. rudis, Dip. subglobosa and N. brennandiae worldwide. Moreover, the study provides clarification of the fungal pathogens associated with FTD on this crop in Piedmont, thus laying the base for further studies on epidemiology, ecology and management strategies.