Black rot

Xanthomonas campestris pv. campestris

Members of the plant family Brassicaceae (Cruciferae), which includes cabbage, broccoli, cauliflower, kale, turnip, oilseed rape, mustard, radish, and the model organism Arabidopsis thaliana are affected by black rot

Host infection by Xcc causes V-shaped chlorotic to necrotic foliar lesions, vascular blackening, wilting, stunted growth, and stem rot symptoms. As the pathogen proceeds from the leaf margins towards the veins, water stress and chlorotic symptoms develop due to occlusion of water-conducting vessels by bacterial exopolysaccharides and components of degraded plant cell walls The darkening of vascular tissues following bacterial invasion gives the black rot disease its name Lesions produced by Xcc may serve as portals of entry for other soft-rot pathogens such as Pectobacterium carotovorum (formerly Erwinia carotovora) and Pseudomonas marginalis

These symptoms may be confused with fusarium wilt of cabbage (fusarium yellows), caused by the fungus Fusarium oxysporum f. sp. conglutinans. In contrast to black rot, in which the pathogen invades leaf margins and causes chlorotic to necrotic symptoms that progress downwards in the plant, fusarium wilt symptoms first develop in the lower portions of the plant and move upwardsFurthermore, leaf veins invaded by Xcc turn black compared to the dark brown vein discoloration found in fusarium wilt.

Symptoms of black rot may vary widely among different species of crucifers. On cauliflower, Xcc infection via stomates causes black or brown specks, scratched leaf margins, black veins, and discolored curds Additionally, the severity of symptoms and aggressiveness of the disease varies between different strains of the Xcc pathogen. The isolates can be differentiated into races based on the reaction of several Brassica lines after inoculation. A race structure including 5 races (0 to 4) was first proposed in 1992;a revised classification model with 6 races was proposed in 2001 and, more recently, the model was expanded to include nine races.

Plant Protection Products