Resistance Characteristics of Chinese Cabbage Cultivars to Black Rot

Abstract

Black rot of Chinese cabbage caused by <i>Xanthomonas campestris</i> pv. <i>campestris</i> (<i>Xcc</i>) is one of the most severe diseases in crop cultivation. To define the resistance characteristics of Chinese cabbage to <i>Xcc</i>, we tested the virulence of eight <i>Xcc</i> isolates in four susceptible cultivars of Chinese cabbage. The isolates of <i>Xcc</i> showed different the virulence on the cultivars. On the other hand, we selected 22 resistant or moderately resistant cultivars of Chinese cabbage to <i>Xcc</i> and tested the occurrence of black rot on the cultivars caused by the isolates of <i>Xcc</i>. Mean disease severity of black rot on the Chinese cabbage caused by each isolate was also positively correlated with the virulence of <i>Xcc</i> isolates. Furthermore, the development of black rot in each cultivar increased according to virulence of <i>Xcc</i> isolates. The number of resistant cultivars of Chinese cabbage to eight isolates of <i>Xcc</i> decreased according to the virulence increase of bacteria. Taken together, these results suggest that resistance of Chinese cabbage cultivars to <i>Xcc</i> is likely affected by the virulence of <i>Xcc</i> isolates, but not result from race differentiation.