Detecting and monitoring populations of Xanthomonas campestris pv. dieffenbachiae in plants, tissue culture and in the environment

The epidemiology of anthurium blight, caused by Xanthomonas campestris pv. dieffenbachiae, was studied using a panel of 11 monoclonal antibodies (MAbs) and monitoring the movements of bacterial strains of differing serotypes in anthurium plants over a three year period. The introduction of inoculum, establishment in propagative stock, and spread of X. c. pv. dieffenbachiae in anthurium fields was examined. The primary inoculum source of the pathogen in anthurium fields was determined to be asymptomatic latently infected plants. A miniplate enrichment/ELISA system was developed to handle large sample numbers. Sensitivity was determined to be as low as one bacterial cell per well, and specificity was achieved using a MAb (Xcd 108) specific for pathogenic strains of X. c. pv. dieffenbachiae from anthurium. The miniplate enrichment/ELISA system demonstrated the presence of epiphytic populations of pathogenic and nonpathogenic xanthomonads on asymptomatic anthurium plants. The establishment and spread of X. c. pv. dieffenbachiae within in vitro anthurium tissue culture also was demonstrated. The pathogen remained latent as long as four months in callus tissue and one year in asymptomatic in vitro plantlets. An indexing protocol was developed using the miniplate enrichment/ELISA system for production of blight-free anthurium plants. Plants in an indexed propagation block were used as a source of disease-free explants for tissue culture. The indexing protocol was used over a period of 15 months to detect latent infections. These plants were removed resulting in a pathogen-free mother block. The miniplate enrichment/ELISA system proved to be a tool for gaining a better understanding of the epidemiology of the latent infection aspect of the disease.