NOVEL PERSPECTIVES IN THE CONTROL OF PLANT PATHOGENIC OOMYCETES

Plant pathogenic oomycetes pose significant threats to the productivity, quality and sustainability of agricultural production. Traditionally, the control of oomycete-borne diseases is achieved by means of chemical control based on fungicides. However, the negative impact of these molecules on the environment and the increase of resistant strains in the pathogen populations put stakeholders and government agencies in demand for new solutions characterized by high specificity towards the target species and low impact on human health and the environment. However, the effective development of such solutions requires overcoming interdisciplinary challenges by integrating various skills and research expertise. Moreover, it has to face some limitations caused by the biotrophic adaptation of several oomycetes species, which greatly hampers pathogen handling thus limiting the study of their biology and the efficacy screenings for new antifungals. In the present study, methods for characterizing the biology and epidemiology, and quantifying infections caused by oomycetes have been developed and/or implemented to assess the efficacy of innovative, target-specific fungicides (peptide aptamers) in limiting the growth and infection by important oomycetes such as Phytophthora infestans, Phytophthora capsici, Pythium ultimum, and Plasmopara viticola. An innovative protocol combining flow cytometry and cell sorting was successfully designed and employed to analyze the composition and efficiency of the secondary inoculum of the oomycete pathogen Plasmopara viticola, offering new insights into the epidemiology of this important pathogen and offering a new paradigm for the study of its biology. Moreover, an accessible and open-source solution for disease severity estimation at the laboratory level using digital imagery and supervised machine learning was developed and tested across three different oomycete pathosystems. The pipeline effectively detected and quantified disease symptoms with high reproducibility, offering a cost-effective and accessible solution to the plant pathology community. Lastly, the potential use of peptide aptamers targeting proteins involved in oomycete cell wall biosynthesis was investigated as a novel tool for controlling oomycete-borne diseases such as potato late blight, blight and fruit rot of cucurbits, Phytium root rot and grapevine downy mildew. Out of the 77 compounds tested, two promising molecules showed a consistently high efficacy and were characterized for their antimicrobial activity and mode of action. Overall, this research provides novel perspectives in the study of plant pathogenic oomycetes, introducing novel techniques, tools, and approaches to better understand, assess, and control plant diseases caused by oomycetes.