Abstract
Acute Oak Decline (AOD) is complex syndrome affecting Britain’s keystone native oak species, (Quercus robur L. and Q. petraea L. (Matt.) Liebl.), in some cases causing mortality within five years of symptom development. The most distinguishable symptom is weeping stem lesions, from which four species of bacteria have been isolated: Brenneria goodwinii, Gibbsiella quercinecans, Lonsdalea britannica and Rahnella victoriana. We do not yet know where else these bacteria exist, and little is known about the relationship of the wider oak leaf microbiome (phyllosphere) to acute oak decline. Here we investigate whether incidental evidence from a large oak genome re-sequencing dataset could be used to detect these bacteria in oak foliage, and whether bacterial incidence co-varied with AOD status or location. Oak leaves and buds were sampled from 421 trees at five sites in England. Whole genomic DNA from these samples was shot-gun sequenced with short reads. Non-oak reads were extracted from these data and queried to microbial databases. Reads uniquely matching AOD-associated bacterial genomes were found to be present on trees from all five sites and included trees with active lesions, trees with historic lesions and trees without AOD symptoms. The abundance of the AOD-associated bacteria did not differ between tree health categories but did differ among sites. We conclude that the AOD-associated bacteria may be members of the normal oak microbiome, whose presence on a tree is not sufficient to cause AOD symptoms.
Highlights
Introduction published maps and institutional affilThe native oak trees, Quercus robur L. and Q. petraea (Matt.) Liebl. are the most common native broadleaf species in Britain [1]
We aim to discover whether the four Acute Oak Decline (AOD)-associated bacteria, previously identified in stem bleeds, could be identified in these foliar data using metagenomic classification of reads that do not map to the oak genome
In the BLAST searches of the reads identified by Kraken2 as being from AOD-related bacteria, 57% of B. goodwinii classified reads, 60% of G. quercinecans, 57% of L. britannica, and 61% of R. victoriana matched their respective genomes with 95% or more of the full read aligning to the genome
Summary
Introduction published maps and institutional affilThe native oak trees, Quercus robur L. and Q. petraea (Matt.) Liebl. are the most common native broadleaf species in Britain [1]. Are the most common native broadleaf species in Britain [1]. The native oak trees, Quercus robur L. and Q. petraea (Matt.) Liebl. A recent study found 2300 macro-species of arthropods, fungi and lichens, mosses and liverworts, birds and mammals associated with British native oaks, of which 326 were obligate (found only on Q. robur/petraea) [4]. Decline disorders are complex interactions of multiple factors such as long- and short-term adverse environmental conditions and the actions of secondary pests and diseases [8]. With no clear universal key factors, Manion defined tree decline disorders as “an interaction of interchangeable, ordered abiotic and biotic factors to produce a iations
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