Exploiting the immune system to tackle emerging filamentous diseases in tomato

未来40年，世界人口预计将增加16亿，人类面临的挑战是将粮食产量提高70%。尽管目前采取了控制措施，但经过有效控制后，杂草、害虫和病原体仍占我国主要作物产量的40%。丝状病原体（如霉菌、霉菌和晚疫病）的控制特别困难，因为它们的进化能力使它们在克服基因或化学杀虫剂提供的抗性方面非常精通。在过去的一个世纪里，有越来越多的毒力强的新出现的致病真菌。由于粮食流动性和气候变化，农业系统极易受到丝状疾病的出现和流行的影响。此外，在受控环境下种植作物，即使在提高产量方面具有优势，但在控制丝状疾病的传播方面显然是不利的。目前的控制方法主要依赖于使用杀菌剂，由于其对人类健康和环境的毒性，欧洲对杀菌剂实行严格的管制。因此，迫切需要制定控制疾病的替代战略。植物通过组成和诱导的防御策略来保护自己免受有害微生物的侵害。另外，植物已经进化出了一种能力，可以让它们的免疫系统对攻击者做出更快更强的反应。这种所谓的启动防御可以由各种警告即将到来的攻击的信号触发，包括使用b-氨基丁酸（BABA）等启动剂的治疗。BABA已被证明对多种丝状疾病提供保护。这种出色表现的原因是由于它在不同的防御信号通路上的启动活动，这些信号通路被植物用于对抗不同生活方式的疾病。BABA已被证明能有效地诱导对番茄等作物的广谱病害产生抗性。丝状病原体在这种作物中尤其成问题，因为它们是收获前和收获后产量损失的原因。因此，新出现的丝状病害对番茄市场构成了严重威胁。番茄是茄科研究的模式植物，因为它的基因组已经测序，并且与它们的野生近缘种杂交可以研究不同过程背后的遗传学。然而，只有一项研究调查了拟南芥诱导抗性反应的遗传变异。该项目将研究BABA在番茄中引发的诱导抗性遗传变异，其总体目标是确定可能最大限度地提高商业品种诱导抗性能力的有利性状。为了实现这一目标，我将在一个商业番茄品种与野生近缘品种杂交的重组自交系（RIL）群体中测试baba诱导的对破坏性病原体疫霉（晚疫病）的抗性。诱导抗性的量化将通过使用复杂的表型扫描仪来完成，该扫描仪可以高通量地成像和分析不同的疾病参数。通过对显著数量性状位点（qtl）的测序鉴定诱导抗性性状（ir -性状），并对诱导抗性反应的分子机制进行研究。该项目的最后一部分将测试这样一种假设，即由于ir特性而产生的多向抗性提供了有效的保护，以抵御新发现的具有高出现风险的丝状病原体菌株，例如晚疫病或枯萎病（由多宿主病原体镰刀菌引起）。这项工作的结果将确定番茄免疫系统的遗传特征，以增强对广泛疾病的防御，包括可能具有巨大破坏潜力的新出现的病原体。

The world's population is expected to increase by 1.6 billion in the next 40 years, which challenges humanity to increase food production by 70%. Despite current control measures, weeds, pests and pathogens claim up to 40% of our major crop yields after use of effective control. Filamentous pathogens (e.g. mildews, molds and late blight) are exceptionally problematic to control as their evolutionary capacity makes them highly proficient on overcoming the resistance offered by genes or chemical pesticides. In the past century, there has been an increasing number of virulent emerging pathogenic fungi. Agricultural systems are extremely vulnerable to emergence and epidemics of filamentous disease due to food mobility and climate change. Moreover, crop cultivation under controlled environment, even when it provides advantages in terms of increased production, it represents a clear disadvantage in controlling the spread of filamentous diseases. Current methods of control depend largely on the use of fungicides, which are under strict European regulation due to its toxicity to human health and the environment. Therefore, it is urgent to develop alternative strategies to control diseases. Plants are equipped to defend themselves against harmful microbes through constitutive and inducible defence strategies. Alternatively, plants have evolved the capacity to prepare their immune system to respond faster and stronger against attackers. This so-called priming of defence can be triggered by a variety of signals that warn of an upcoming attack, including treatments with priming agents such as b-amino butyric acid (BABA). BABA has been shown to provide protection against a wide spectrum of filamentous diseases. The reason for this outstanding performance is due to its priming activity at different defence signalling pathways that are used by plants to fight diseases with different lifestyles. BABA has been shown to be effective in inducing resistance against a broad-spectrum of diseases in crops such as tomato. Filamentous pathogens are particularly problematic in this crop as they are responsible for yield loses pre- and post-harvest. Therefore, emerging filamentous diseases are a serious threat to the tomato market.Tomato is a model plant for research in Solanaceae as its genome has been sequenced and crosses with their wild relatives allow the study of the genetics behind different processes. However, only one study in Arabidopsis has investigated genetic variation in the induced resistance response. This project will investigate genetic variation in induced resistance trigger by BABA in tomato with the overarching aim to identify advantageous traits which could potentially maximise the inducible resistance capacity of commercial varieties. To achieve this aim, I will test BABA-induced resistance against the devastating pathogen Phytophthora infestans (late blight) in a Recombinant Inbred Line (RIL) population from the cross between a commercial tomato cultivar, and an accession of the wild relative. Induced resistance quantification will be done by using a sophisticated phenotyping scanner that can image and analyse different disease parameters in a high-throughput manner. The induced resistance traits (IR-traits) will be identified by sequencing of the significant quantitative trait loci (QTLs) and the molecular mechanisms behind the response will be investigated. The last part of the project will test the hypothesis that multi-directional resistance as a result of the IR-traits offers effective protection against newly identified strains of filamentous pathogens with a high risk of emergence, such as strains of late blight or Fusarium wilt (caused by the multi-host pathogen Fusarium oxysporum). The results coming from this work will identify the genetic traits to exploit the tomato immune system for enhanced defence against a broad-spectrum of diseases, including emerging pathogens that can have a huge devastation potential.