What bacteria is responsible for Black rot disease of crops?

Xanthomonas campestris pv. campestris, is the Gram-negative bacterium responsible for Black rot, one of the most devastating diseases of cruciferous crops worldwide especially Brassica oleracea var. capitate and B. rapa in warm and humid climate. The bacterium is a seed-borne pathogen, as well as transmitted through infection or natural openings. The systemic vascular disease debilitates the plant, thus favoring the attack of other pathogens but even in mild attack, can cause several V-shaped necrotic lesions on leaves, which decrease the quality of the product for fresh market. Symptoms include yellow lesions, wilted tissue, necrosis, defoliation and plant death.

The roles of GSLs and their respective hydrolysis products, against X., campestris infection on brassica plants have been highlighted by the report of Aires. They concluded that GSLs play complex roles disease resistance, particularly in the early growth stages when the young plants are in metabolic flux. Nonetheless, they successfully showed the susceptibility of brassica to X. campestris is generally higher in brassica species with lower contents of aromatic GSLs and 4-methyl sulfinyl butyl (glucoraphanin). These compounds are effective inhibitors of X. campestris in vitro. Mores so, experiment results of Velasco showed that but-3-enylglucosinolate and isothiocyanate have direct antimicrobial activities on X. campestris. Their results demonstrated that gluconapin and its ITC possess antibacterial effect on the development of X. campestris and this effect strongly correlate with the concentration of the above compounds.