*3.3. Introducing Disease Resistance Genes from Related Species*

Broccoli lacks resistance to some devastating diseases, such as clubroot and black rot. To guard broccoli genotypes against these diseases, distant hybridization and MAS can be used to introduce pyramid resistance genes/loci from related species. The clubroot pathogen *P. brassicae* evolved many physiological races showing different infection responses on host plants. Only one resistant locus, *CRa* for race 4, has been introduced from *B. rapa*, which is not enough for sustainable production of broccoli under the threat of other *P. brassicae* races. More resistance genes/loci should be introduced from related species, such as turnip, radish and rapeseed, and pyramided in broccoli. For black rot disease, strong resistance sources have been reported in the A and B genomes of Brassica species, and moderate clubroot resistance has been reported in the C genome of cabbage. These resistance genes/loci can be introduced from *Brassica carinata* and cabbage to broccoli.
