Haplotypes distribution and virulence of Gnomoniopsis castaneae in Italy

In the last decades, productivity of Italian chestnut groves has been seriously impacted by the infection of the emerging fungal pathogen Gnomoniopsis castaneae, causing nut rots. Despite the widespread distribution of this pathogen in Italy, its genetic diversity and phylogeographic structure is still largely unexplored. In this study, we analysed the genetic diversity and spatial distribution of G. castaneae haplotypes by investigating 107 isolates from the northwest, the northeast and central Italy, as well as Sardinia. In Sardinia, where little was known about the occurrence of G. castaneae as a nut rot agent, a thorough investigation was conducted in three sites on a total of 1500 nuts. Phylogenetic analyses of sequences of & beta;-tubulin revealed the occurrence at a worldwide scale of two distinct evolutionary lineages (here reported as haplotype A and B), with different frequencies in Italy depending on the geographic area. Based on the outcomes of inoculation experiments on nuts, both haplotypes proved to be pathogenic, although with marked differences in aggressiveness.

Automated summary

In recent decades, the productivity of Italian chestnut groves has been severely affected by the emergence of the fungal pathogen Gnomoniopsis castaneae, resulting in nut rots. Despite its widespread distribution in Italy, the genetic diversity and phylogeographic structure of this pathogen have not been fully explored. This study analyzed the genetic diversity and spatial distribution of G. castaneae haplotypes in different regions of Italy and Sardinia. The results showed the existence of two distinct evolutionary lineages (haplotype A and B) at a global scale, with varying frequencies in different geographic areas of Italy. Inoculation experiments confirmed the pathogenicity of both haplotypes, although their aggressiveness differed.