Combining varieties to compel the adaptation of plant pathogen populations: how to solve the efficiency - sustainability - adoption trade-off – COMBINE

The deployment of plant genetic resistances to pathogens is essential to limit the use of pesticides in agriculture. The deployment of such varieties one by one on large surfaces leads to the adaptation of pathogen populations, making them ineffective. Mobilizing intraspecific diversity by combining different varieties would make it possible to constrain this adaptation through the existence of antagonistic host-pathogen interactions. Based on this concept, the COMBINE project aims to define new strategies for the deployment of resistance combinations in order to find the best compromise between efficiency, durability and technical- and cost-effectiveness. We propose a global multidisciplinary approach combining biology (epidemiology and evolutionary biology), modeling and socio-economics. Several pathosystems with different biological features, causing diseases on different crops (wheat, grapevine, pepper, banana, rice) will be studied via three complementary tasks. In the first task, we will study the impact on the dynamics and evolution of pathogen populations of the combination of resistances in varietal mixtures, using experimental or existing on-farm situations, in order to understand whether antagonistic interactions are at play and their impact on the evolution of pathogen populations. In the second task, we will analyze the socio-economic constraints and levers that impacts the farmers' strategies for diversification. In the third task, a generic model based on the existence of antagonistic interactions will be improved and parameterized for a diversity of pathogens, in order to simulate a wide range of strategies on several pathosystems, and to derive optimal deployment strategies of plant resistances at different spatial scales that solve the durability / efficiency / technical- and cost-effectiveness trade-off. The consortium, which has been active for a year, brings together teams at the forefront of the disciplines concerned. COMBINE will provide new insights and generic tools for the sustainable use of genetic resistances in a pesticide-free agriculture.