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Doktorsavhandling2021Öppen tillgång

Occurrence and pathogenicity of tree-pathogenic fungi vectored by bark beetles

Davydenko, Kateryna

Sammanfattning

Fungal pathogens associated with bark beetles represent one of the most significant problems to forest health. Among these fungi, ophiostomatoid group are known to be most commonly associated with bark beetles. Some of these pathogens, such as Dutch elm disease-causing fungi, have a very long history of extensive research, while fungi causing other diseases are poorly or only partially understood and substantial knowledge gaps can exist in their ecology and spread.

The aims of the studies were to provide new knowledge on indigenous and newly massively tree-devastating bark beetles, vectored communities of fungi, and their pathogenicity to host trees. The principal methods included fungal culturing and rDNA sequencing, which allowed the investigation of composition of fungal communities associated with bark beetles. In particular, both ophiostomatoid and other phytopathogenic fungi were the most commonly detected groups. The use of pathogenicity tests revealed the ability of different ophiostomatoid fungi to infect Pinus sylvestris saplings, but with a varying degree of success for different fungal species. Long-term trials carried out in Sweden showed that Scolytus multistriatus is a vector for Dutch elm disease caused by invasive Ophiostoma ulmi complex that recently invaded the island of Gotland causing the disease to Ulmus minor.

It can be concluded that i) bark beetles are vectors for different fungi and that ophiostomatoid fungi are the most closely associated symbionts; ii) bark beetles can vector different functional groups of fungi including aggressive pathogens; iii) highly virulent fungi can help bark beetles to overcome the tree defence. The work presented in this thesis demonstrates that some fungi associated with bark beetles may significantly contribute to tree mortality. Understanding the nature of fungal-insect interactions may help more effectively to manage potential threats.

Nyckelord

phiostomatoid fungi; bark beetle; pathogenicity; Dutch elm disease

Publicerad i

Acta Universitatis Agriculturae Sueciae
2021, nummer: 2021:25ISBN: 978-91-7760-728-1, eISBN: 978-91-7760-729-8Utgivare: Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences