Identification of Resistance of Different Varieties of Flowering Chinese Cabbage to Soft Rot Disease

Abstract

【Objective】In recent years, with the expansion of the cultivation area of flowering Chinese cabbage and the emergence of repeated cropping, soft rot diseases are increasing year by year, among which soft rot bacterial is one of the main diseases that harm the yield and quality of flowering Chinese cabbage severely. The study aims to evaluate the resistance of different varieties of flowering Chinese cabbage to soft rot disease in order to screen disease-resistant varieties.【Method】Samples of flowering Chinese cabbage with typical soft rot symptoms were collected, and the soft rot pathogens were identified by tissue isolation, morphology and molecular biology methods. Fifty-two different varieties of flowering Chinese cabbage were used as experimental materials, and the spray inoculation method was used for inoculation during seedling period: two edges of about 5 mm were lightly scratched on the stem of flowering Chinese cabbage with a blade, and 1×108 CFU/mL bacterial solution was sprayed onto the wound surface with a small hand-held sprayer. The disease index and soft rot grading were measured 3 d after the inoculation, and the resistance level of 52 flowering Chinese cabbage varieties was evaluated.【Result】The isolates were obtained by tissue isolation. The colony morphological characteristics verified by Koch's rule and 16S rDNA sequence analysis showed that the strain was a pathogenic bacterium caused by soft rot, and the colonies formed on NA medium were circular, translucent, milky white, with a central protrusion and smooth edges, which could make the tissues of flowering Chinese cabbage rotten, and the leaves showed wet rot and wilting symptoms after inoculation in flowering Chinese cabbage seedlings. Among the 52 materials, There were significant differences in the resistance of most varieties of flowering Chinese cabbage to soft rot. Among the 52 materials, 35 were highly susceptible, 16 were susceptible, 1 was intermediate resistant, and no variety showed high resistance or immunization. In general, susceptible varieties accounted for 98.1%. The results showed that there was a lack of resistant materials among the 52 flowering Chinese cabbage varieties, which may be one of the reasons for the serious incidence of soft rot in Guangdong Province.【Conclusion】Among the 52 flowering Chinese cabbage varieties, highly susceptible and susceptible varieties accounted for 98.1%, 1 was intermediate resistant, and no variety showed high resistance or immunization. The results could provide a scientific basis for the selection and promotion of flowering Chinese cabbage varieties resistant to soft rot.

Keywords

• flowering chinese cabbage
• soft rot disease
• spray inoculation
• disease index
• soft rot grading
• resistance identification