Abstract
Fungicide resistance is a serious problem for agriculture. This is particularly apparent in the case of powdery mildew fungi. Therefore, there is an urgent need to develop new agrochemicals. Chitin is a well-known elicitor of plant immunity, and fungal pathogens have evolved strategies to overcome its detection. Among these strategies, chitin deacetylase (CDA) is responsible for modifying immunogenic chitooligomers and hydrolysing the acetamido group in the N-acetylglucosamine units to avoid recognition. In this work, we tested the hypothesis that CDA can be an appropriate target for antifungals using the cucurbit powdery mildew pathogen Podosphaera xanthii. According to our hypothesis, RNAi silencing of PxCDA resulted in a dramatic reduction in fungal growth that was linked to a rapid elicitation of chitin-triggered immunity. Similar results were obtained with treatments with carboxylic acids such as EDTA, a well-known CDA inhibitor. The disease-suppression activity of EDTA was not associated with its chelating activity since other chelating agents did not suppress disease. The binding of EDTA to CDA was confirmed by molecular docking studies. Furthermore, EDTA also suppressed green and grey mould-causing pathogens applied to oranges and strawberries, respectively. Our results conclusively show that CDA is a promising target for control of phytopathogenic fungi and that EDTA could be a starting point for fungicide design.
Highlights
Chemical control practices have been critical in preventing losses due to plant diseases, especially fungal diseases
Given the important role of chitin-triggered immunity in plant basal defence, in this work, we aimed to determine the role of chitin deacetylase in powdery mildew virulence using the pathosystem P. xanthii-melon
Two mechanisms have recently been described: suppressors of chitin signalling in P. xanthii, the secretion of EWCA effectors at pathogen penetration sites, and the activity of a haustorial-expressed LPMO
Summary
Chemical control practices have been critical in preventing losses due to plant diseases, especially fungal diseases. Fungicides marketed for the control of diseases on food crops are under pressure. One of the best examples of fungal diseases in which chemicals play a key role in disease management is powdery mildews. Immense expenditures are made annually for fungicides to control powdery mildews; they are considered “strategic diseases” by the agrochemical industry. The problem of fungicide resistance is of paramount importance in powdery mildew fungi. In southern Spain, resistance to the most popular antipowdery mildew fungicides has been reported [3,4,5], with multiresistant isolates found in the areas of more intense cropping [5]. To be able to maintain chemical diversity for disease management, there is a pressing demand to identify and develop new agrochemicals
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