The GEDUNEM project: Varietal and technical innovations for the sustainable and integrated management of root-knot nematodes in protected vegetable cropping systems

The recent banning of the most active chemical nematicides raised root-knot nematodes (RKN) as themajor problem of vegetable growing in the south-east of France, with over 40% of horticultural farmsaffected. Resistant (R) cultivars successfully limit nematode attacks of the crop itself and reducenematode abundance in soil in the short term. But their use in commercial fields faces two majorconstraints: (1) the limited number of cultivated species with RKN R-genes available (tomate. pepper),which would lead to major changes in crop rotations with socio-economic constraints; (2) theemergence of virulent root-knot nematode populations, able to overcome the resistance conferred bysome of the R-genes. Recent research showed that the durability of the resistance per se was possiblyincreased with an optimal choice of the R-gene or allele combination, and of the genetic background inwhich the major R-genes where introgressed. However, the requirement for agronomic performance,does not always allow the breeder to fully use the genetic diversity available in R-genes and geneticbackgrounds. ln such cases, spatio-temporal deployment strategies of resistant cultivars in the rotationwere proposed and provided some success. But combination of genetic resistance with cultivationpractices including multicrop rotations, intercultural management and/or prophylactic treatments waspoorly tested for its ability to provide complementary selection pressures on the pathogen populationsand to increase the durability of the protection.The project aims at identifying innovative strategies across the agrosystem, cornbining varietalresistance in crop rotations with agronomic practices, for a sustainable control of RKN that infectvegetable crops in protected crop systems. This pilot and demonstrative project involves analytical andsystemic aspects: il the validation of previous results on the durability of RKN genetic resistance intomato and pepper by long-term experiments in research stations and in farms, ii/ the impact ofagronomic practices on the parasitic pressure in the soil and its contribution in the increase of resistancedurability, and iii/ the impact of such innovations on the yield and the economie viability for protected crop systems in a Mediterranean climate. The added value here is to combine together currentlydispersed approaches based on synergistic and long-term effects, towards a satisfying level of nematodecontrol over pluri-annual crop sequences. The diversity of partners (research, experimental stations,technical institutes) and associated forces (growers' development structures, 'chambres d'agriculture')brings ail the complementary expertise needed for answering specifie short-term questions as weil asgeneric mid-long term expectations.'GEDUNEM' has been launched in the framework of the INRA metaprogramme SMaCH (SustainableManagement of Crop Health).