Genetic Analysis of Clubroot Resistance in Chinese Cabbage using Single-spore Isolates of Plasmodiophora brassicae and Development of RAPD Markers Linked to its Resistance Gene

To identify inheritance of clubroot disease resistance genes in Chinese cabbage, seedling tests of BC1P1, BC1P2, and F2 populations derived from F1 hybrid (var. CR Saerona) using single spore isolate (race 4 identified with William's differential host) from Plasmodiophora brassciae were conducted. Resistance (R) and susceptible (S) plants segregated to 1:0 in backcross to the resistant parent. The F2 population segregated in a 3(R):1(S) ratio. This result implied that the resistance of clubroot disease is controlled by a single dominant gene to the race 4 of P. brassicae in CR Saerona. To develop DNA markers linked to clubroot resistance genes, 185 plants of CR Saerona among F2 populations were used. A total of 300 arbitrary decamer was applied to F2 population using BSA-RAPD (Bulked segregant analysis-Randomly amplified polymorphic DNA). One RAPD marker linked to clubroot resistance gene in CR Saerona (OPJ1100) was identified. This marker was 3.1 cM in distance from resistance gene in F2 population. This marker may be useful for a marker-assisted selection (MAS) and gene pyramiding of the clubroot disease resistant gene in Chinese cabbage breeding programs