Benign infections or damaging epidemics: the influence of biology, the environment and agricultural practice on vector-borne phytobacteria

导致某些病虫害在一个地方而不是另一个地方成为严重问题的因素在很大程度上是未知的。确定这些因素对于更好地了解通过植物和植物产品的全球化贸易将病虫害引入新环境的相关风险至关重要。青枯杆菌（Lso）是一种对包括马铃薯、番茄、胡萝卜和芹菜在内的一系列作物的新威胁，在欧盟受到法定控制。在马铃薯中，Lso诱导斑马片，这是一种破坏性疾病，表现为块茎中的棕色条纹，在新鲜和加工市场中造成巨大损失。这种疾病在美洲迅速蔓延，最近进入新西兰。在斯堪的纳维亚、法国北方和地中海盆地，一种遗传上不同的细菌亚群（单倍型）导致胡萝卜的破坏性疾病。尽管这种单倍型可以感染马铃薯，但这种作物的疾病在欧洲并不明显。这种疾病是由木虱传播的，木虱是一种以树液为食的昆虫。木虱Bactericera cockerelli在美洲和新西兰传播Lso，而两个本地物种（Trioza apicalis和Bactericera trigonica）和可能的第三个物种（B. nigricornis）在欧洲传播细菌。在英国，在胡萝卜、杂草和捕虫器中捕获的木虱中发现了这种病原体。尽管存在病原体和有能力的载体物种，但这种细菌目前并没有在马铃薯或胡萝卜中造成广泛的作物损害。该项目的重点是更好地了解可能导致LSO成为英国更重要病原体的因素。因素可能包括Lso单倍型之间的差异，Lso单倍型和木虱载体的地理分布和遗传变异，景观设计（如杂草围绕农田）和农业实践/政策。这项工作的总体目标是调查英国景观中Lso单倍型，宿主和载体的复杂网络，重点是胡萝卜，相关作物和豌豆科杂草。在这一系统内工作，我们的目标是：（一）生成Lso单倍型和木虱的基因组序列信息，以了解联合王国存在的病原体和媒介的遗传变异，并利用这一信息开发快速诊断测试;（二）研究Lso和木虱媒介在作物和周围环境中的空间和时间分布; ㈢增进我们对病媒寄主植物的偏好和传播细菌的能力的了解; ㈣利用生态网络分析全面了解病理系统;以及（v）使用生态和贸易模型来研究未来的政策选择（英国与贸易伙伴的关税结构的变化以及英国栖息地的管理方式）如何改变这种传播风险。最终，建模将考虑系统抵御风险变化的准备情况，并提供有关影响病原体成为破坏性致病因子的潜在驱动因素（生物、生态和人为）的信息。研究结果将引起植物健康领域政府利益相关者的兴趣，研究将为Lso和其他复杂病虫害的优先应对提供见解。整体方法应提高我们预测风险的能力，并将监视活动优先考虑最具破坏性的威胁。就农业-粮食-环境而言，关于土地和作物管理变化的影响以及评估方法的信息将有助于我们更好地了解现有的复杂网络以及未来环境和贸易政策的影响。对于工业界来说，更好地了解新出现的病原体将有助于他们主动管理这一问题和未来的问题。最后，跨学科联盟将提供创新的科学感兴趣的学者在一些领域。

Factors that contribute to some pests and diseases being serious problems in one location and not another are largely unknown. Identifying these factors is fundamental to better understand risks associated with introductions of pests and diseases into new environments via globalised trade of plants and plant products. The bacterium Candidatus Liberibacter solanacearum (Lso) is an emerging threat to a range of crops including potato, tomato, carrot and celery and is under statutory control in the EU. In potato Lso induces zebra chip, a damaging disease manifest by brown stripes in the tubers, which cause large losses in fresh and processing markets. The disease has spread quickly through the Americas and more recently into New Zealand. A genetically different sub-group (haplotype) of the bacteria causes a damaging disease of carrots in Scandinavia, Northern France and the Mediterranean basin. Whereas this haplotype can infect potato, disease in this crop is not evident in Europe. The disease is transmitted by psyllids, which are sap-feeding insects. The psyllid Bactericera cockerelli spreads Lso in the Americas and New Zealand, whilst two native species (Trioza apicalis and Bactericera trigonica) and possibly a third species (B. nigricornis) spreads the bacteria in Europe. In the UK the pathogen has been detected in carrots, weeds and in psyllids caught in insect traps. Despite the presence of the pathogen and competent vector species, the bacteria is not currently causing widespread crop damage in either potato or carrots. The focus of this project is to better understand the factors that may contribute to Lso becoming a more important pathogen in the UK. Factors may include differences between Lso haplotypes, the geographical distributions and genetics variations of Lso haplotypes and psyllid vectors, landscape designs (such as weeds that surround crop fields), and agricultural practice/policy. The overall aim of the work is to investigate the complex network of Lso haplotypes, hosts and vectors in the UK landscape, focussing on carrots, related crops and apiaceous weeds. Working within this system our objectives are to: (i) Generate genome sequence information for Lso haplotypes and psyllids to understand genetic variations of the pathogens and vectors present in the UK, and use this information to develop rapid diagnostics tests; (ii) Study the spatial and temporal distributions of Lso and psyllid vectors in crops and the surrounding environments; (iii) Improve our understanding of vector host plant preferences and ability to transmit the bacteria; (iv) Use ecological network analysis to build a comprehensive picture of the pathosytem; and (v) Use ecological and trade models to examine how future policy options (changes in the UKs tariff structure with trading partners and how UK habitats are managed) might alter this transmission risk. Ultimately the modelling will consider the systems readiness to withstand changes in risk and provide information on the drivers (biological, ecological and man made) that influence the potential of a pathogen to become a damaging disease-causing agent.The outcomes will be of interest to government stakeholders working in Plant Health, where the research will provide insights into prioritising responses to Lso and other complex pests and diseases. The overall approach should improve our ability to predict risk and prioritise surveillance activity on the most damaging threats. For agri-food-environment, information on the impact of changes in land and crop management and approaches to assess this will help us to better understand the complex networks that exist and the impact of future environmental and trade policies. For industry, better understanding of emerging pathogens will help them to proactively manage this and future problems. Finally the interdisciplinary consortium will deliver innovative science of interest to academics in a number of fields.