Differential defence responses of susceptible and resistant kimchi cabbage cultivars to anthracnose, black spot and black rot diseases

Abstract

The resistance of 27 commercial kimchi cabbage cultivars against Colletotrichum higginsianum causing anthracnose was evaluated. Among the cultivars with different disease severity, three cultivars, CR-Hagwang, CR-Hwangrock and Houseking-125, showed moderate resistance. Two cultivars, Buram-3-ho (susceptible) and CR-Hagwang (moderate resistance), were chosen for further investigation. Severe necrotic lesions were observed on the C.higginsianum-inoculated leaves in cv. Buram-3-ho, whereas only a few scattered spot lesions were formed on the inoculated leaves of cv. CR-Hagwang. Interestingly, similar susceptibility and resistance were shown in both cultivars when inoculated by fungal (Alternaria brassicicola) or bacterial (Xanthomonas campestris pv. campestris) pathogens causing black spot or black rot disease, respectively. Pathogenesis-related (PR) gene expression was analysed during resistant and susceptible responses to anthracnose, black spot and black rot diseases. Semiquantitative RT-PCR analysis revealed that the transcriptional activation of PR1, BGL2, Chi1, PR4, VSP2, LOX2 and GST1 were differentially regulated in the kimchi leaves during resistant, as compared to susceptible, responses. In addition, the PR gene expression was regulated by defence-related hormones salicylic acid, jasmonic acid and ethylene. Taken together, these results suggest that differential defence signalling crosstalk and PR gene expression are involved in cultivar-specific resistance of kimchi cabbage plants to anthracnose, black spot and black rot diseases, and that resistance is strongly associated with the hormone-dependent transcriptional induction of defence genes.