Development of a new concept in plant protection applied to apple scab

Apple scab caused by the fungus Venturia inaequalis, is the most important disease of apples in all temperate countries. The main commercial apple cultivars are susceptible to this disease and the phytosanitary treatments applied in the orchard to get rid of it represent a considerable economic and environmental cost ( up to 30 fungicide applications year-1 against this disease). To combat apple scab, we are developing a totally new biocontrol strategy combining two inventions patented by INRAE. The first invention makes the fungus non-virulent. We target the sexual phase of V. inaequalis by forcing it to reproduce with non-pathogenic strains belonging to the forma specialis pyracanthae of V. inaequalis (PYR strains), which results in the generation of non-virulent progeny the following spring. The second invention consists of applying the PYR strains in the spring to trigger immunity in the apple tree, thus protecting it against a subsequent scab attack. This breakthrough technical itinerary should cause a drastic collapse in the size of the pathogenic population in the orchard and should thus make it possible to considerably reduce the use of fungicides. This project, co-constructed with phytopathologists, geneticists, orchards experimenters and economists of INRAE, professionals of apple sector (CTIFL, IFPC) aims to prove the concept of this innovative strategy and its sustainability in the orchard (4 experimental sites in France) and to evaluate the conditions of acceptance and appropriation of the inventions by the apple sector.