Towards the identification of Type III effectors associated to <em>Ralstonia solanacearum</em> virulence on tomato and eggplant

International audienceFor the development of pathogen-informed breeding strategies, identifying the microbial genes involved in interactions with the plant is a critical step. To identify Type III effector (T3E) repertoires associated to virulence of the bacterial wilt (BW) pathogen Ralstonia solanacearum on Solanaceous crops, we used an original association genetics approach combining DNA microarray data and pathogenicity data on resistant eggplant, pepper and tomato accessions. From this first screen, twenty-five Type III effectors were further full-length PCR-amplified within a 35-strain field collection, to assess their distribution and allelic diversity. Six T3E repertoire groups were identified, within which 11 representative strains were chosen to challenge the BW-resistant eggplants "Dingras multiple Purple" and "AG91-25", and the tomato Hawaii 7996. The virulence or avirulence phenotypes could not be explained by specific T3E repertoires, but rather by individual T3E genes. We identified seven highly avirulence-associated genes, among which ripP2, primarily referenced as conferring avirulence to Arabidopsis thaliana. Interestingly, no T3E was associated to avirulence to both eggplants. Highly virulence-associated genes were also identified: ripA5_2, ripU, and ripV2. This study should be regarded as a first step towards investigating both avirulence or virulence function of the highlighted genes, but also their evolutionary dynamics in natural R. solanacearum population