Roles of the fungal and oomycetes species in the decline of birch in South-central Kootenay area in British Columbia, Canada

Abstract

Increasing reports of large-scale birch dieback in British Columbia could have huge implications towards the health of future forest stands. Many studies suggest that birch decline is caused by stress from changing climatic conditions. However, recent studies in Europe have determined that fungal and water mold species can play a key role in the birch decline. In this study, a survey of logs, fruiting bodies, soils and roots associated with birch species was conducted around the South-central part of the Kootenay Area of British Columbia, Canada, to determine the role of fungal and water mold species in the current decline of birch. Pure fungal cultures were isolated from roots and small sections of wood from the sampled logs. Soils were tested for Phytophthora species using a baiting technique. DNA barcoding was used for species identification. Thirteen species with max identity < 95% and E-value of 0 were identified from the logs and fruiting bodies. No Phytophthora species were detected in soils. This is sifnificant since this group of pathogens is known worldwide to cause sever epidemics in forests (eg. Sudden Oak Death, Jarrah Dieback). This is the first timea thorough survey for Phytophthora species in association with birch decline was conducted in North America. From the species identified, Fomes fomentarius, Cryptosporella tomentella, Armillaria ostoyae and Cerrena unicolor are possible pathogens that could be contributing to birch decline thus, suggesting that pathogens could play a role in the current decline in British Columbia. However, they can also be secondary pathogens saprobes, and not be primary agents. There was not a singe pathogenic species associated with all declining birches, suggesting that other factors are involved in the decline. This work was important to eliminate potential pathogen species following a thorough survey.