Global threats from Phytophthora spp.; understanding drivers of emergence and opportunities for mitigation through nursery best practice

该项目将解决英国树种从疫霉引进和传播的风险; i）检查英国植物苗圃系统中Phytophthoras的当前分布和多样性，ii）提供证据基础，以完善英国范围内自愿苗圃认证计划的苗圃“最佳实践”标准，iii）根据其生物学特性和环境概况，确定目前在英国不存在但对我们的生态系统构成最大威胁的疫霉属物种，iv）确定疫霉传播的关键国际途径和生物安全重点的国家点和v）更好地了解疫霉相遇时发生遗传相互作用的风险，从而产生新的侵略类型。为了实现这些目标，从英国不同的植物苗圃管理系统收集的水和植物样品中的疫霉物种的分布和多样性，包括那些被认为在进口新疫霉属方面具有高风险的地点，将使用最先进的DNA测序技术进行研究。本署亦会在美化环境的溪涧及池塘收集水质样本，以调查苗圃相关植病菌的广泛分布情况。这项工作将确定苗圃的做法，导致疫霉病原体的密度和多样性最高，并向前传播到林地或其他自然生态系统的可能性最高。这些数据将提供证据，以指导英国范围内的自愿托儿所认证计划的发展。签署该计划的苗圃将遵守一套“最佳做法”标准，旨在减少植物病菌进口和传播的风险。可行性评估将涉及与托儿所管理人员、消费者和其他利益相关者的协商，以确定经济和社会机会和障碍，以及对实施此类计划的态度。我们亦会研究各种方案，向消费者宣传认可计划的知名度和合法性，让幼儿园参与计划，从而获得额外的利益。确定未来的全球疫霉威胁和潜在的进入途径将是必不可少的，在完善苗圃的“最佳做法”和其他国家的生物安全措施。为此，将从数据库和在广泛的国家进行的国家调查中整理关于感染木本物种的疫霉属目前已知的全球分布和可能影响定居的生物学特征的数据。模型将确定那些在类似英国气候和生态系统的地方出现的物种，以及那些在生态上与欧洲建立的Phytophthoras相似的物种，加强将病原体纳入英国植物健康风险登记册的证据基础。我们还将研究国际贸易和旅游的途径以及通过这些途径引入新疫霉的风险，根据新疫霉到达这些地点的风险增加确定国家生物安全重点。路径分析将用于告知托儿所管理人员和最高风险行业做法的认证计划标准。目前的做法是增加共存的Phytophthoras在环境中的多样性，但我们很少了解新的侵略性Phytophthoras出现通过杂交或其他机制的遗传交换时，新的物种满足的潜力。将检查疫霉属物种的全基因组序列，以确定疫霉属和相关生物之间发生遗传交换的程度，以及这可能如何使这些病原体适应树种，改变毒力或宿主范围。这项工作将增强我们对病原体进化的基本理解。

This project will address the risks to UK tree species from Phytophthora introduction and spread by; i) examining the current distribution and diversity of Phytophthoras in UK plant nursery systems, ii) providing the evidence base to refine nursery 'best practice' criteria for a UK-wide voluntary nursery accreditation scheme, iii) identifying those Phytophthora species not currently present in the UK but which pose the greatest threat to our ecosystems based on their biological traits and environmental profiles, iv) identifying key international pathways for Phytophthora spread and national points for biosecurity focus and v) understanding better the risk of genetic interaction occurring when Phytophthoras meet, resulting in new aggressive types.To achieve these objectives, 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. These data will provide evidence to guide the development of a UK-wide voluntary nursery accreditation scheme. Nurseries signing up to the scheme will adhere to a set of 'best practice' criteria designed to reduce the risks of importation and dissemination of Phytophthoras. Feasibility assessments 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. 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. 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.