Race-specific host-plant resistance against black rot (Xanthomonas campestris pv. campestris) in alien Brassicas

Black rot disease (Xanthomonas campestris pv. campestris (Pam.) Dowson, Xcc) is one of the most devastating disease in cauliflower worldwide. Potential reservoirs for black rot resistance in alien Brassicas (A and B genomes) was taken due to availability of limited resistant germplasm for black rot disease in Brassica oleracea (C genome). Total 26 accessions of Brassica species were screened against Xcc race 1, 4 and 6 during three consecutive years viz., 2015, 2016 and 2017 under artificial inoculation conditions. One accession of B. carinata, and B. napus, two accessions of B. juncea and all accessions of B. nigra were highly resistant against Xcc race 1, 4 and 6 except SRB-98 (moderate resistance). Cauliflower varieties/lines viz., Pusa Meghna, DC 41-5 and Pusa Sharad were highly susceptible against Xcc races 1, 4 and 6. On the basis of higher homoeology between A and C sub-genome, a new resistant source BN-2-1 of B. napus was identified which will be useful to develop black rot resistant genetic stock with cauliflower through pre-breeding techniques such as in vitro embryo rescue and or somatic hybridization.