Screening for resistance to black rot in Brassica oleracea crops

Xanthomonas campestris pv. campestris (Xcc), causal agent of black rot, is widely distributed around the world in cabbage and kale crops causing severe yield losses. Nine races of the pathogen were described, being races 1 and 4 the most aggressive and widespread. The objective of this work was to identify new sources of resistance to races 1 and 4 of Xcc in different Brassica oleracea crops. Two hundred and twenty-one landraces and 35 commercial and improved cultivars were evaluated. Most accessions were susceptible to both races, except cabbage cultivars ‘Balón’ and ‘Quintal de Alsacia’ and kale landrace MBG-BRS0070, which showed some plants with different level of resistance to races 1 and 4, thus indicating that race-non-specific resistance can be involved. Kale landrace MBG-BRS0286 showed an intermediate mean disease score for race 1. These accessions can be crossed with cabbage cultivars and may provide new combinations of resistance genes with protection against black rot.Research was supported by the project AGL2009-09922. Authors thank J. Vicente for supplying the bacterial isolates and susceptible and resistant checks and Susana Calvo and Rosaura Abilleira for their collaboration in laboratory and greenhouse works. Marta Francisco acknowledges an I3P fellowship from the CSIC.MICINNCSICPeer reviewe