Xanthomonas plant diseases: mitigating existing, emerging and future threats to UK agriculture

芸苔属植物的栽培是一个价值数十亿美元的产业，黄单胞菌属是一种细菌性植物病原体，可以感染包括许多芸苔属植物在内的350多种植物。这个多学科项目汇集了微生物学，基因组学，病理学，成像，分子生物学和风险评估方面的专家，采用涉及大规模基因组测序，植物成像和使用一套独特的芸苔多样性系筛选病原体抗性的方法，对植物病原体野油菜黄单胞菌（Xc）进行首次大规模综合研究。其目标是提高知识和支持有效的育种和部署适当的控制策略，为黄单胞菌在英国和其他国家面临类似的挑战。campestris或简称Xcc），其可攻击所有栽培芸苔属植物。Xcc是一种种子传播的维管（允许水和营养物质流动的组织）疾病，并且可能是世界上蔬菜（甘蓝;例如卷心菜、花椰菜、花椰菜、布鲁塞尔芽和羽衣甘蓝）的最重要的疾病。Xcc也感染B。napus（油籽油菜，瑞典）、B. juncea（muscle）和B.芜菁（萝卜、大白菜）。因此，这是非常重要的。XCC会导致作物完全损失，尽管在英国，它通常会导致质量和销路下降。Xcc有两个主要问题。首先，与大多数细菌性植物病原体一样，没有简单的化学干预，不像真菌病原体。传统的杀菌剂如氯氧化铜正退出销售。其次，也是这一提议的一个关键驱动力，商业化的甘蓝品种几乎没有抗性--这可能已经被培育出来了。因此，我们回到野生亲戚和幸运的是，沃里克的英国蔬菜种质收集保持超过6000芸苔属加入。显然，这是太多的处理，但我们最近（与Defra的资金）产生了我们所谓的芸苔多样性固定基础集（DFFs）。这些设计用于捕获纯合品系群体中的大部分遗传变异，然后可以筛选对Xcc的抗性。该项目将使用DFFS为甘蓝，甘蓝型油菜和可干涉C基因组作物野生亲缘植物。我们也很幸运地拥有欧洲最大的黄单胞菌分离株（约1，000）以及英国最有知识的黄单胞菌病理学家Joana Vincente博士。我们将对来自该集合的900多个黄单胞菌分离株进行测序，以便我们能够解决该领域的一些关键挑战，例如病原体的构成，黄单胞菌病原体需要部署哪些关键基因才能在特定植物上引起疾病，以及病原体如何随时间变化。这项工作的一个主要成果将是一个大的诊断标记，可用于确定特定的致病型黄单胞菌，即使在外地！我们将结合这些研究来了解病原体如何感染和繁殖的植物使用两种互补的成像方法，荧光/生物发光报告和植物内源性叶绿素荧光-随着疾病的进展而变化。我们还想问一些问题，我们是否可以使用一种有益的土壤真菌来防止Xcc疾病，以及蚜虫等害虫在取食受感染的植物后是否可以在田间传播疾病？全球社会真实的关注之一是病原体的入侵。因此，除了拟议的诊断工作外，我们还将对一种破坏性的玉米黄单胞菌病进行详细的风险评估，这种病正在美国迅速蔓延，在某些地区造成超过50%的损失。这项评估还将考虑对其他被认为可能“有风险”的作物的风险。

Brassica cultivation is a multi-billion dollar industry worldwide and Xanthomonas is a bacterial plant pathogen pathogens that can infect more than 350 plant species including many brassicas. This multidisciplinary project brings together experts in microbiology, genomics, pathology, imaging, molecular biology and risk assessment to take one of the first large scale integrated studies of the plant pathogen Xanthomonas campestris (Xc), using approaches involving large scale genomic sequencing, in planta imaging and screening for pathogen resistance using a unique set of brassica diversity lines. The objectives are to enhance knowledge and support effective breeding and deployment of appropriate control strategies for Xanthomonas in the UK and other countries that face similar challenges.Our central focus is on black rot of crucifers (Xc pv. campestris or Xcc for short) which can attack all cultivated brassicas. Xcc, is a seed-borne vascular (the tissue that allows water and nutrients to flow) disease and probably the most important disease of vegetable Brassicas (Brassica oleracea; e.g. cabbage, cauliflower, broccoli, Brussels sprouts and kale) in the world. Xcc also infects B. napus (oilseed rape, swede), B. juncea (mustards) and B. rapa (turnip, Chinese cabbage). It is therefore really important. Xcc can cause complete crop loss, though in the UK it usually leads to reduced quality and marketability. There are two main problems with Xcc. First, as with most bacterial phytopathogens, there is no simple chemical interventions, unlike for fungal pathogens. Traditional bactericides such as copper oxychloride are being withdrawn from sale. Secondly, and one key driver of this proposal, there is virtually no resistance in commercial Brassica oleracea varieties - this has probably been bred out. So we are going back to wild relatives and are fortunate that Warwick's UK Vegetable Germplasm collection maintains more than 6000 brassica accessions. Obviously this is far too much to deal with, but we recently (with Defra funding) generated what we call Brassica diversity fixed foundation sets (DFFs). These are designed to capture the majority of the genetic variation in a population of homozygous lines which can then be screened for resistance to Xcc. This project will use DFFSs for Brassica oleracea, Brassica napus and also interfertile C genome crop wild relatives.We are also fortunate to have the largest collection of Xanthomonas isolates in Europe (~ 1,000) as well as the UKs most knowledgable Xanthomonas pathologists Dr Joana Vincente on board. We will sequence more than 900 Xanthomonas isolates from this collection so we can address some of the key challenges in the field, such as what makes a pathogen, what are the key genes a Xanthomonas pathogen needs to deploy to cause disease on specific plants and how the pathogen changes over time. A major output of this work will be a large set of diagnostic markers that can be used to identify specific pathovars of Xanthomonas, even in the field!We will couple these studies to understanding how the pathogen infects and multiplies in the plant using two complementary imaging approaches, fluorescent/bioluminescent reporters and the plant endogenous chlorophyll fluorescence - which changes as disease progresses. We also aim to ask the questions, can we use a beneficial soil fungus to protect from Xcc disease and can insect pests such as aphids transmit the disease in the field following feeding on infected plants?One of the real concerns in a global community is incursions of pathogens. So aside from the diagnostic work proposed, we will also undertake a detailed risk assessment on a devastating Xanthomonas disease of maize, which is rapidly spreading in the US and causing over 50% of losses in some regions. This assessment will also consider risks to other crops considered potentially "at risk".