Articles by Eeva Terhonen

With ongoing climate change, the risk caused by both native, well-known pathogens and new, invasive ones is increasing. Diplodia sapinea (Fr.) Fuckel is responsible for Diplodia tip blight, a new fungal disease in Finland, that kills the current-year shoots of Scots pine (Pinus sylvestris L.). This can lead to the death of young trees and increase the susceptibility of trees of all ages to other stressors. Since D. sapinea spreads by airborne spores, it cannot be eradicated. In this study, we present the first screening to evaluate the potential for harnessing the genetic variation of Scots pine to improve its resilience against D. sapinea. Further, we wanted to test if predisposing this warm-preferring pathogen to higher temperature will increase its virulence. On the contrary, higher temperature initially reduced the virulence of D. sapinea, but the effect diminished over time. Based on necrosis length, we observed between-family variation in seedling resistance. These findings support the need for larger future trials to explore the potential for harnessing genetic variation to enhance resistance against D. sapinea.

• Terhonen, Natural Resources Institute Finland (Luke), Forest health and biodiversity, Latokartanonkaari 9, 00790 Helsinki, Finland https://orcid.org/0000-0002-9288-440X E-mail: eeva.terhonen@luke.fi
• Kujala, Natural Resources Institute Finland (Luke), Forest tree breeding, Paavo Havaksen tie 3, 90570 Oulu, Finland https://orcid.org/0000-0003-0949-6156 E-mail: sonja.kujala@luke.fi
• Pyhäjärvi, University of Helsinki, Faculty of Agriculture and Forestry, Department of Forest Sciences, Viikki Plant Science Centre, Latokartanonkaari 7, 00014 University of Helsinki, Finland https://orcid.org/0000-0001-6958-5172 E-mail: tanja.pyhajarvi@helsinki.fi
• Sutela, Natural Resources Institute Finland (Luke), Forest health and biodiversity, Latokartanonkaari 9, 00790 Helsinki, Finland E-mail: suvi.sutela@luke.fi

• Terhonen, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: et@nn.fi
• Marco, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: tm@nn.fi
• Sun, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: hs@nn.fi
• Jalkanen, Finnish Forest Research Institute, Rovaniemi Research Unit, Rovaniemi, Finland E-mail: rj@nn.fi
• Kasanen, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: rk@nn.fi
• Vuorinen, Finnish Forest Research Institute, Suonenjoki Research Unit, Suonenjoki, Finland E-mail: mv@nn.fi
• Asiegbu, University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: fa@nn.fi

Diplodia sapinea (Fr.) Fuckel causes shoot blight on Scots pine (Pinus sylvestris L.). This fungus has been discovered in Finland as a saprophyte in 2015 on Scots pine cones. The endophytic mode of this fungus was later discovered in healthy Scots pine twigs. In 2021 the disease, Diplodia tip blight was observed on Scots pine in Finland. Currently, the disease symptoms are poorly identified so the role of D. sapinea in disease outbreaks in Finland are easily overlooked. The identification of the fungi is challenging in field conditions and requires targeted identification in laboratory. In this research note I report the first Diplodia tip blight outbreaks observed in Finland, the typical disease symptoms, and methodology for the species identification. Samples were collected from symptomatic trees based on observations made by the citizens. Diplodia sapinea was isolated from defoliated and surface sterilized twigs. The species identification by morphological characters was further confirmed with sequencing of ITS region of rDNA and with species-specific primers. A pathogenicity test confirmed that D. sapinea was the disease agent causing shoot blight. This is the first report of Diplodia tip blight on Scots pine in Finland.

• Terhonen, Natural Resources Institute Finland (Luke), Forest health and biodiversity, Latokartanonkaari 9, FI‐00790 Helsinki, Finland 0000-0002-9288-440X E-mail: eeva.terhonen@luke.fi