Current rapeseed cultivars (Brassica napus) do not provide adequate resistance to the bacterial pathogen Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot disease in cabbage. Genetic sources of resistance are very limited, and thus far no resistance genes have been cloned. Hence, breeders are in urgent need for new sources of resistance. The goal of my thesis is to unravel the molecular mechanisms underlying black rot resistance in Brassica napus.