Strategies to increase durability of host resistance for effective control of phoma stem canker on oilseed rape

在英国，由真菌病原体黄斑细螺旋体（leptosphaia maculans）引起的茎溃疡病是一种对油菜具有破坏性的疾病，尽管使用杀菌剂花费了2000万英镑，但每年造成的产量损失高达100亿英镑。由于最近欧盟立法和预测的全球变暖导致最有效的杀菌剂（如Punch C）的损失，潜在的产量损失将增加。利用宿主的抵抗力来控制这种疾病正变得越来越重要。然而，由于病原体种群的变化，新的耐药来源往往变得无效。本项目的目的是监测新的毒力小种的出现，并制定新的控制策略，以提高宿主的抗性持久性。为了保持品种对黄斑乳杆菌抗性的有效性，本项目将利用分子技术研究不同地区黄斑乳杆菌毒力小种在孢子样本和作物植物样本中分布的差异。研究结果将用于指导在相应的无毒致病小种占优势的地区部署具有适当抗性的品种。对黄斑乳杆菌的抗性依赖于主抗性(R)基因介导的定性抗性和次抗性基因介导的定量抗性。真菌L. maculans具有很高的进化潜力来克服宿主的抗性。在2-3年的时间里，由于黄斑乳杆菌种群从无毒到有毒的变化，耐药性可能失效。本项目将利用新的基因组信息，研究导致黄斑乳杆菌毒力突变的分子事件。建模工作表明，在预测的全球变暖下，瘤茎溃疡病的范围和严重程度将会增加。为了研究环境因素（如温度）对不同R基因对黄斑杆菌抗性作用的影响，将在不同地区（即不同环境）和不同温度的受控环境试验中，对不同R基因品种的茎溃疡病严重程度进行评估。最近的研究表明，R基因介导的对maculans（一种脂质体病原体）的抗性是通过受体样蛋白（receptor-样protein， rlp）识别病原体效应物来实现的。利用在高温下稳定的R基因序列和宿主甘蓝型油菜及其近缘种B. rapa和B.甘蓝的基因组序列，鉴定编码rlp的候选R基因。本项目获得的新知识将用于制定有效的栽培抗性策略，以改善对植物茎溃疡病的控制。改善对这种疾病的控制将通过减少产量损失使种植者受益。它还将解决粮食安全的挑战。环境也将受益于减少使用杀菌剂。

Phoma stem canker, caused by the fungal pathogen Leptosphaeria maculans, is a damaging disease on oilseed rape in the UK, causing annual yield losses > £100M despite use of fungicides costing £20M. With recent loss of the most effective fungicides (e.g. Punch C) through EU legislation and predicted global warming, potential yield losses will increase. Use of host resistance to control this disease is becoming ever more important. However, new sources of resistance are often rendered ineffective due to pathogen population changes. The aims of this project are to monitor the emergence of new virulent races of L. maculans and to develop new control strategies to increase durability of host resistance. To maintain effectiveness of cultivar resistance against L. maculans, this project will use molecular technology to investigate the differences between different regions in distribution of virulent races of L. maculans in populations assessed from spore samples and from crop plant samples. Results will be used to guide deployment of cultivars with suitable resistance for the region where the corresponding avirulent pathogen races are predominant. Resistance against L. maculans relies on major resistance (R) gene-mediated qualitative resistance and minor gene-mediated quantitative resistance. The fungus L. maculans has high evolutionary potential to overcome host resistance. Resistance can be rendered ineffective in 2-3 years due to L. maculans population changes from avirulent to virulent. This project will investigate the molecular events leading to virulent mutations in L. maculans by exploiting new genomic information about L. maculans. Modelling work shows that the range and severity of phoma stem canker will increase under predicted global warming. To investigate the effects of environmental factors (e.g. temperature) on operation of different R genes for resistance against L. maculans, severity of phoma stem canker on cultivars with different R genes will be assessed in field experiments in different regions (i.e. different environments) and in controlled environment experiments at different temperatures. Recent work showed that R gene-mediated resistance against L. maculans (an apoplastic pathogen) operates by recognition of pathogen effectors through receptor-like proteins (RLPs). The sequences of R genes stable at increased temperatures and the genome sequences of host Brassica napus and its related species B. rapa and B. oleracea will be used to identify candidate R genes coding for RLPs. New knowledge obtained from this project will be used to develop strategies to improve control of phoma stem canker by using effective cultivar resistance. Improved control of this disease will benefit growers by reducing yield losses. It will also address the challenge of food security. The environment will also benefit from reduced use of fungicides.