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Notes:
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Cryphonectria parasitica (Murrill.) Barr is a necrotrophic fungus that affects European chestnut populations. In Catalonia (NE Spain), this
fungus is widely spread affecting chestnut stands. In addition to vegetative compatibility (VC) types of the fungus, knowledge of the Cryphonectria
hypovirus (CHV) occurrence is important to implement a biocontrol programme. We confirmed the presence of hypoviruses in
several chestnut subpopulations of Catalonia, and we determined the VC types of CHV-infected isolates. We also studied the nucleotide
sequences of these hypoviruses from a variable region located in the hypovirus ORF-A. Our results show a low occurrence of hypoviruses
throughout C. parasitica populations in Catalonia, except for a few localized stands. From 312 sampled cankers, we obtained 179 white,
pale orange or rickety isolates. In 35 of them, we detected CHV-1. Infected isolates belonged to 5 of the 7 sampled subpopulations. We
found 12 CHV-1 haplotypes, based on the nucleotide sequence analysis. Most of the hypoviruses have the same nucleotide sequence or
show high homology at nucleotide level with isolates previously included in CHV-1 subtype-I. However, we found that 3 haplotypes share
at least 97% of their ORF-A nucleotide sequence with CHV-1 subtype-E. Phylogenetic analysis grouped these 3 isolates in a different cluster
than the other hypoviruses. These results suggest that multiple introductions of CHV-1 have occurred recently in Catalonia. Dominant VC
types of hypovirus-infected isolates are EU-1, EU-2 and EU-5, which are similar to those previously reported in this region.
We thank the financial support of Obra Social ‘La Caixa’, Diputació de Tarragona, Diputacióde Barcelona, Diputació de Girona and the Plant Health Service of the Department of Environment of Catalonia. |
