Abstract: The high quality breeding and clubroot disease resistance material of Brassica juncea var. longepetiolata Yang et Chen was created by introducing the clubroot disease resistance gene of Brassica rapa into Brassica juncea var. longepetiolata Yang et Chen through distant and reciprocal hybridization. The resistance of 10 Chinese cabbage materials to clubroot disease was analyzed by the combination of artificial inoculation identification and molecular marker identification, and one material CCR21002 was selected as the resistant resource to be created as the breeding material for clubroot disease resistance of Brassica juncea var. longepetiolata Yang et Chen. CCR21002 was used as the male parent and female parent to provide anti-clubroot disease genes, and the hybrid F₁ was obtained with the embryo rescue technique. F₁, whose plant morphology was more favorable to Brassica juncea var. longepetiolata Yang et Chen, was backcrossed to obtain BC₁, and the BC₁ generation plants were analyzed by morphology, cytology and disease resistance identification. The results showed that the backcross generation was more difficult to obtain than the hybrid generation. Among the 13 strains of BC₁ that survived by embryo rescue, only 1 strain was screened with genotype AABB and resistance to clubroot disease. The resistance gene was identified by molecular markers as CRb, and most of the traits of Brassica juncea var. longepetiolata Yang et Chen were retained in plant morphology. It was proved that a new germplasm resistant to physiological race 4 was obtained through remote cross and backcross with anti-clubroot disease Chinese cabbage, which could be used for backcrossing breeding.

Key words: Brassica juncea var. longepetiolata Yang et Chen, resistance to clubroot, embryo rescue, reciprocal crosses, creation and identification