Deciphering the key drivers of cucumber mosaic virus epidemics in Espelette

Espelette pepper farmers are currently facing devastating and recurrent viral epidemics due to a suspected recent emergence of Cucumber mosaic virus (CMV). This virus threatens the whole production of Espelette pepper, which plays a significant role in the local economy, the agricultural landscape and touristic attractiveness of the Basque Country (Southwestern France).

A collaboration between the “Syndicat du Piment d’Espelette AOP” (which federates Espelette pepper farmers) and the Virology team of the Plant Pathology unit of INRAE (Avignon) has emerged to investigate these epidemics and propose control strategies. To identify relevant and promising strategies, it is first necessary to acquire data on the virus epidemiology in the local context and understand what drives CMV epidemics in the Espelette area. In particular, it is currently unclear how CMV re-emerges every year on pepper crops despite the absence of pepper during winter (like all viruses, CMV needs a host to survive). It is also intriguing to observe such severe epidemics in Other this area, where the high level of landscape fragmentation and plant biodiversity is generally predicted to mitigate disease spread.

This project aims at exploring the possibility of year-to-year seed transmission from infected fruits, of the presence of alternative hosts (serving as viral reservoir and thus inoculum sources) around pepper fields as well as the role of aphid vectors (mediating plant-to-plant transmissions). To address these questions, we will undertake 3 different types of actions. First, field trips to collect samples (seeds, plants, aphids) and monitor CMV incidence in different elements of the agricultural landscape (pepper crops, surrounding crops, wild plants, flying aphids). Second, greenhouse experiments in controlled conditions, to assess the efficiency of seed-mediated and aphid-mediated transmissions, as well as the pathogenicity of the ‘Espelette’ isolates of CMV on the locally grown pepper cultivar (“Gorria”). Finally, genetic and spatial analyses to evaluate the respective role of the different CMV dissemination pathways, in order to decipher the key drivers of CMV epidemics in the Espelette area.

The results obtained through this project will guide future research efforts and especially help prioritize management options to be investigated next. Among others, possible options include the design of procedures to prevent the seed transmission of CMV, or the use of control methods to mitigate aphid-mediated transmissions from viral reservoirs (via auxiliary flower strips to impede aphid transmissions, or pepper cultivar mixtures and intercropping to further increase the level of biodiversity and limit disease spread). This research integrates ecological perspectives of plant viruses to assure long-lasting and efficient control strategies, while bringing the academic research into contact with the agricultural professional world and applied issues.