A Holistic Approach to Investigating Acute Oak Decline

Sandra Denman, James Doonan, Nathan Brown, Martin Broberg, Elena Vanguelova, and James McDonald

Published May 2019 in International Oaks No. 30: 333–340

Abstract

Acute oak decline (AOD), presents a serious threat to native British oak. Decline-diseases are complex syndromes, caused by multiple factors operating over time, beginning with environmental predisposition disturbances leading to host stress, followed by invasion of biotic agents (insect pests and pathogens). Determining the role of secondary pests and pathogens presents challenges in assigning causation. The complex nature of the problem necessitates a holistic, multidisciplinary research approach to achieve preventative and remedial management. Key aims were to determine disease distribution; significant predisposition factors; spatial trends associated with predisposition factors; microbiota associated with AOD lesions, the role and mechanisms used of consistently occurring, abundant organisms in tissue degradation. Surveys and citizen-science reports enabled determination of disease distribution. Insights into predisposition factors at landscape scale were obtained using national spatial environmental datasets. Components of the pathobiome (groups of microorganisms associated with disease) were investigated using isolation, metabarcoding, metagenomics and metatranscriptomics. Spatial patterns in incidence and occurrence of AOD were identified highly correlating with environmental predisposition factors. Stem lesions have a polybacterial cause, but the bacterial species Brenneria goodwinii is dominant and interactions with Agrilus and other bacterial species amplify its effect reproducing field symptoms. We provide new insights into polymicrobial interactions and disease expression, and develop a novel conceptual and methodological template for investigating decline diseases and adapting Koch’s postulates to address the role of the multifactorial facets of this problem.

Keywords

oak decline, host predisposition, polymicrobial disease complex

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