Global threats from Phytophthora spp. (PHYTO-THREATS)

Research Objectives

• Examine the distribution, diversity and community interactions of Phytophthora in UK plant nursery systems
  

The distribution and diversity of Phytophthora species in water and plant samples collected from different UK plant nursery management systems, including those locations considered to be high risk in terms of importing new Phytophthoras, will be studied using state-of-the-art DNA sequencing technology. Water samples from streams and ponds in amenity environments will also be collected to investigate the wider distribution of nursery-associated Phytophthoras. This work will identify nursery practices resulting in the highest density and diversity of Phytophthora pathogens and the highest probability of onward spread into woodland or other natural ecosystems.

• Provide the evidence base to support nursery accreditation based on ‘best practice’ to mitigate further spread of Phytophthora
  

For this element of the project we are working with the HTA, Defra and industry to provide the scientific basis to support nursery accreditation. Data from the plant nursery survey (above objective) will provide evidence to guide the development of nursery best practice. Feasibility assessments carried out as part of this objective will involve consultation with nursery managers, consumers and other stakeholders in order to identify economic and social opportunities and barriers, and attitudes towards implementation of such a scheme. We will also explore options to promote the visibility and legitimacy of the accreditation scheme to consumers such that there is an added advantage for nurseries to take part.

• Identify and rank global Phytophthora risks to the UK
  

Identifying future global Phytophthora threats and potential routes of entry will be essential in refining nursery ‘best practice’ and other national biosecurity measures. To do this, data on current known global distribution of Phytophthoras infecting woody species and biological characteristics that may affect establishment will be collated from databases and national surveys conducted in a broad range of countries. Models will identify those species occurring in locations resembling the UK’s climate and ecosystems and those species that are ecologically similar to Phytophthoras that have established in Europe, strengthening the evidence base for inclusion of pathogens in the UK Plant Health Risk Register. We will also look at the pathways of international trade and tourism and the risks of new Phytophthora introductions via these routes, identifying national focus points for biosecurity based on a raised risk that new Phytophthoras will arrive at these locations. Pathway analyses will be used to inform nursery managers and accreditation scheme criteria of the highest risk trade practices.

• Gain a greater understanding of the evolutionary pathways of Phytophthoras

Current practices are increasing the diversity of co-existing Phytophthoras in the environment, yet we have little understanding of the potential for new aggressive Phytophthoras to arise through hybridisation or other mechanisms of genetic exchange when new species meet. Whole genome sequences of Phytophthora species will be examined to determine the extent to which genetic exchange has occurred among Phytophthoras and related organisms, and how this might have enabled these pathogens to adapt on to tree species, change virulence or host range. This work will enhance our fundamental understanding of pathogen evolution.