Resistance to Xanthomonas campestris pv. campestris in Brassica spp

Six races of Xanthomonas campestris pv. campestris have been identified on the basis of their reactions on a series of differential Brassica genotypes. Races 1 and 4 are the most important races worldwide. Searches for resistance in a collection of Brassica oleracea (C genome) were mainly unsuccessful, but partial or total resistance to races 2, 3, 5 and 6, which are rare races, was present in a number of accessions. Strong resistance to race 4 was widespread in B. rapa (A genome) and B. napus (AC genome) indicating an A genome origin. Resistance to races 1, 3 and 4 was found in B. nigra (B genome), B. carinata (BC genome) and B. juncea (AB genome) suggesting a B genome origin. Potential race non-specific resistance was also found in these three species and in B. rapa. Resistance to races 1 and 3 is quantitative and recessive in the cabbage line Badger Inbred-16, while resistance to race 3 is controlled by a single dominant locus in several B. oleracea lines. Resistance to race 4 is controlled by a single dominant locus in B. napus and probably in B. rapa. Resistance to races 1, 3 and 4 appears to be dominant in B. nigra and B. carinata.