Survival and persistence of bioluminescent Xanthomonas campestris pv. campestris on host and non-host plants in the field environment

Dispersal and persistence of a pathogenic strain of Xanthomonas campestris pv. campestris , genetically engineered to bioluminesce, was followed in and on host and non-host plants in the field environment. Black rot susceptible cabbage plants were mist inoculated with the bioluminescent strain only, or were mist inoculated with X. campestris pv. vesicatoria or a weakly pathogenic strain of X. c. campestris 1 week before challenge inoculation with the bioluminescent strain. Growth of the bioluminescent strain was detected with a low-light, charge-coupled device camera or through bioluminescence measurements of broth-enrichment cultures of leaf disk samples. Bioluminescent X. c. campestris could often be observed as populations on symptomless leaves or in lesions, and persisted as a vascular endophyte for more than 6 months throughout the winter growing season. Dispersal to cruciferous and non-cruciferous weeds was frequently detected. Pre-inoculation with X. c. vesicatoria or the weakly pathogenic X. c. campestris did not significantly affect the movement and persistence of the bioluminescent strain nor reduce the incidence of black rot disease.