ABSTRACT
ABSTRACT Epiphytic and endophytic bacteria can cause severe losses in plants at each stage of growth. Plant pathogenic bacteria induce characteristic leaf spots, chlorosis, blights, scabs, wilting, cankers, and tumors that may be produced in the infected leaves, fruits, roots, or stems. The traditional detection protocol, which is based on cultural, morphological, physiological, and biochemical properties, requires skilled taxonomical expertise to conrm the identity of the causal bacterium. New detection tools will be used not only for rapid, sensitive, and specic diagnosis but also to help to understand plant-pathogen relationships and the structure and function of pathogens and their communities. Molecular techniques are widely recognized as powerful plant pathogen-detection techniques. The DNA sequences from which the primers are designed for bacteria come from three main origins: pathogenicity/virulence genes, ribosomal genes, and plasmid genes. The selection of appropriate diagnostic methods is mainly focused on eradication, certication of mother plants, sanitation, quarantine programs or large surveys to evaluate incidence, and screening tests for surveillance of the spreading of a disease, especially for quarantine pathogens or in critical cases of export-import. Propagating material such as seeds, cuttings, root-stocks, buds, tubers, rhizomes, and bulbs can carry pathogens to new areas, either in or on plant tissues. Certication schemes ensure that seed and vegetative propagation material are free from particular diseases. Close association with seeds facilitates the long-term survival, introduction into new
4.1 Introduction ............................................................................................................................ 82 4.2 Diagnosis ................................................................................................................................ 82
4.2.1 Morphology ................................................................................................................ 82 4.2.2 Symptomatology ......................................................................................................... 83 4.2.3 Biological Assays ........................................................................................................85 4.2.4 Molecular Detection ...................................................................................................86
