Molecular detection of Phytophthoras in the soil environment in Scotland

Phytophthora molecular detectionInvasive soil and water-dwelling Phytophthora species are posing serious threats to forest ecosystems in Britain, yet the distribution and diversity of Phytophthora spp. present in this country is largely unknown. This project uses Illumina high throughput metabarcode DNA sequencing to examine the diversity of Phytophthoras in soil at a range of forest and woodland sites in order to better predict risk.

Research objectives

  • Examine Phytophthora diversity in soil at a range of public garden/amenity/woodland sites in Scotland.
  • Provide evidence to inform biosecurity and remediation policy aimed at limiting the introduction, spread and impact of Phytophthora diseases.
  • Assess the feasibility of using llumina metabarocde technology for longer-term monitoring of Phytophthora diseases in Britain.

Results

Soil samples were collected from around ten trees/shrubs at each of fourteen public garden/amenity/woodland sites in Scotland. Sites chosen either had previous Phytophthora outbreaks or were regarded as high risk for Phytophthoras due to importation of plants/soil in recent years. Soil samples were processed for Illumina sequencing. Bioinformatics analyses of DNA sequence data identified twenty-four known Phytophthora species across the fourteen sites, including quarantine-regulated species as well as species not previously recorded in the UK. The seven most abundant Phytophthoras (in descending order) were P. pseudosyringae, P. austrocedri, P. gonapodyides, P. cambivora, P. syringae, P. ramorum and P. cactorum. Each of these species was found to be present at at least eleven of the sites.

Practical conclusions for site managers

  • There is high diversity of Phytophthoras, including species pathogenic on woody hosts, at the sites sampled in this study. Similar diversity can be expected at other highly disturbed woodland, public garden and amenity sites in Scotland.
  • Establish good hygiene practice to avoid transfer of soil-borne Phytophthoras within site, and from one site to another. For example keep public access to hard-core pathways and ensure staff clean boots, tools and vehicles before moving from one location to another on the site.
  • Avoid introducing new Phytophthora species to a site by purchasing healthy planting stock from reputable nurseries with a documented disease management plan. These criteria should be stipulated in the procurement process.
  • Keep vigilant for signs of disease and report any new symptoms as soon as they appear to enable a rapid diagnosis and initiation of control strategies, if necessary.
  • Metabarcoding is a powerful tool and should form part of a wider surveillance strategy for invasive pathogens in Britain.

Status

This project started in September 2014 and was completed in 2017.

Related Products/Services

To report a possible finding of Phytophthora on a tree host to Forest Research scientists please use TreeAlert

Contact

Sarah Green