X. campestris pv. campestris, one of the most important brassica diseases worldwide, causes black rot, particularly on B. oleracea, where resistance is rare. This multidisciplinary project draws upon risk assessment, pathology, bioinformatic, molecular, imaging in a detailed analysis of Xc genomics, Xcc infection dynamics and screens for new Xcc resistance that can be ultimately be deployed in the field. There are two notable strengths to this proposal. The unique Warwick HRI collection of ~1,000 Xanthomonas isolates, curated and largely collected by Joana Vincente who spearheads the pathology component and who described the first six races of Xcc and Warwicks unique collection of brassica diversity fixed foundation sets (DFFs). To address specific biological questions outlined in the proposal we will sequence ~960 Xc isolates, including 771 Xcc isolates and multiple isolates of the apoplastic pathogen Xc. raphani. Candidate genes, variants and other genetic elements that are associated with race and infection lifestyle will be used in a variety of assays including generating diagnostic markers, with in field utility, including identification of potential threats such as X. fragariae, X. nasturtii and th X. vasicola pv. vasculorum, supporting our pathogen risk work programme. Core and variant genes will be delivered in planta, singly and in combination via Xc or P. syringae using chlorophyll imaging to quantify their contribution to virulence, resistance, or as our preliminary data suggests, masking other effector activity. We will also image Xc infections undertaken using new bioluminescence and fluorescent reporters whose emission sits between the Xanthamonadin and chlorophyll emission spectra. In parallel, we will screen Brassica oleracea, Brassica napus DFFs and also the interfertile C genome crop wild relatives DFF as well as revisiting informative historical mapping lines to identify loci showing race specific or broad spectrum resistance to Xcc.