The role of endophytes in affecting symptom development of European apple canker caused by Neonectria ditissima

欧洲溃疡病是近年来在世界各主要苹果产区发生的危害最大的病害。现代栽培品种缺乏对这种病原体的抗性，在欧洲，最有效的化学防治方法不再可用。品种间感病性不同，但没有绝对抗性。我们获得的初步数据表明，拮抗真菌内生菌与品种耐N。ditissima。这种疾病最具破坏性的方面是来自苗圃中的潜伏感染，这些感染在果园种植后不久就变得活跃并在主干上发展成溃疡-导致树木死亡。大量的经验证据表明，种植后的压力可以促进这些苗圃来源的潜伏感染的症状表达。本研究的目的是探讨品种间耐氮性的差异。ditissima与特定的内生菌相关，如果是这样，则鉴定生物体用于进一步的生物防治测定。在接种候选内生菌后，将测定SA和JA途径中特定基因的表达，以确定内生菌是否诱导可能有助于溃疡抑制的宿主防御反应。接下来，我们将使用一个映射人口之间的交叉溃疡病的抗性和敏感的品种来映射QTL负责招募特定的内生菌，并确定这些QTL的重叠程度与映射溃疡病抗性。然后，我们将研究在何种程度上内生菌配置文件的一个特定的基因型受到个别或组合的土壤水分亏缺，AMF和PGPR治疗。最后，我们将进行一个共同的花园实验，以评估（1）在何种程度上招募内生菌配置文件的影响，土壤特性，土壤微生物群，和主机基因型，（2）溃疡病的发展是否受到特定的内生菌和植物防御信号的影响，以响应生物和非生物因素（由不同的网站）。植物激素反应是根据特定的激素- JA，SA和阿坝来测量的;内生菌的组成将通过下一代测序技术来表征。这项工作的成果不仅将加深对溃疡病的生物学和流行病学的理解，还将为实际的疾病管理开发工具和知识，由于业界积极参与该项目，这些工具和知识可以有效地被业界采用。业界通过LINK计划支持这一建议，因为他们认识到需要一个全面的战略来管理溃疡病。六个行业合作伙伴将为该提案提供现金和实物捐助。

European Canker, caused by Neonectria ditissima, has become the most damaging disease of apple in recent years across all major apple growing regions worldwide. Modern cultivars lack resistance to this pathogen and in Europe most effective methods of chemical control are no longer available. Cultivars differ in their susceptibility but there is no absolute resistance. We obtained preliminary data that indicate a possible link of antagonist fungal endophytes with cultivar tolerance to N. ditissima. The most damaging aspect of the disease is from latent infections in nurseries that become active and develop into canker on the main trunk soon after planting in orchards - leading to tree death. Ample empirical evidence suggests that stresses following planting can promote symptom expression of those nursery-origin latent infections. In this proposal, we aim to investigate whether cultivar differences in tolerance to N. ditissima are associated with specific endophytes and, if so, identify the organism(s) for further biocontrol assay. Expression of specific genes in the SA and JA pathways will be assayed following inoculation of candidate endophytes to ascertain whether endophytes induce host defence responses that may contribute to canker suppression. Next, we will use a mapping population from a cross between canker resistant and susceptible cultivars to map QTLs that are responsible for recruiting specific endophytes and to determine the extent of overlapping of these QTLs with those mapped for canker resistance. Then, we shall study the extent to which endophyte profiles of a specific genotype are affected by individual or combined soil water deficit, AMF and PGPR treatments. Finally, we shall conduct a common garden experiment to assess (1) to what extent recruitment of endophyte profiles is influenced by soil characteristics, soil microbiota, and host genotypes, and (2) whether canker development is influenced by specific endophytes and plant defence signalling in response to biotic and abiotic factors (represented by different sites). Plant hormone response is measured in terms of specific hormones - JA, SA and ABA; endophyte composition will be characterised by next generation sequencing technology. The output of this work will not only lead to a deeper understanding of the biology and epidemiology of the disease, but also develop tools and knowledge for practical disease management, which can be efficiently adopted by the industry due to their active involvement in the project.The industry is supporting this proposal through the LINK scheme, as they recognise the need for a comprehensive strategy to manage the canker disease. Six industry partners will provide both cash and in-kind contribution to this proposal.