Identification of Genes Involved in Resistance to Flavescence Dorée Disease of Grapevine: A Model Study Using Arabidopsis thaliana

Flavescence dorée (FD), caused by FD phytoplasma (FDp) and transmitted by the leafhopper Scaphoideus titanus, is a quarantine disease that seriously threatens viticulture across Europe. Research on resistance or tolerance to FDp in grapevine is limited by the perennial nature of the host, high cultivar variability and the univoltine life cycle of the insect vector. To overcome these constraints, we employed Arabidopsis thaliana as a model host to identify genes conferring resistance to FDp. RNA sequencing (RNA-seq) was first used to identify genes deregulated in A. thaliana during infection by either the woody host pathogen FDp or the herbaceous host pathogen Chrysanthemum yellows phytoplasma (CYp). A subset of these genes was then validated by monitoring their expression in the FDp–A. thaliana pathosystem at various time points during infection. Five genes were consistently deregulated upon infection, and functional analysis of the corresponding mutants revealed two lines with significantly reduced susceptibility to FDp compared with the wild type. The double mutant combining these two genes exhibited a similar phenotype, suggesting functional convergence. Electrical penetration graph (EPG) analysis indicated that this resistance is independent of vector feeding behaviour, pointing to a genetically determined defence mechanism rather than antixenosis. These findings uncover novel components of plant defence against phytoplasma infection and establish A. thaliana as a valuable system for dissecting the molecular basis of tolerance to FDp. We discussed how the genes we identified represent promising targets for developing sustainable, phytoplasma-resistant grapevine varieties.