Exploiting the immune system to tackle emerging filamentous diseases in tomato

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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.