Biochemical Defense Agents Against Bacterial Pathogens

Plant diseases caused by bacterial pathogens place major constraints on crop production and cause significant annual losses on a global scale. The attainment of consistent effective management of these diseases can be extremely difficult, and management potential is often affected by grower reliance on highly disease-susceptible cultivars because of consumer preferences, and by environmental conditions favoring pathogen development. During their evolution, all plants have developed a real "immune system" capable of detecting a danger, whether the latter is of a biotic nature (pathogenic microorganism, insect pest) or abiotic (rain, hail, frost, wind). A plant’s exterior protection can be compromised by mechanical damage, which may provide an entry point for pathogens. If the first line of defense is breached, the plant must resort to a different set of defense mechanisms which include structural and biochemical defense. The Biochemical defense mechanism includes the biochemical substances produced in the plant cells before or after the infection. These substances are considered as the agents of biochemical defense such as phytoanticipins which are described as "low molecular weight, antimicrobial compounds that are present in plants before challenge by micro-organisms”, phytoalexins are lipophilic compounds in response to mechanical or chemical injury or infection, phenolic compounds are a large class of plant secondary metabolites that show a large diversity of structures (simples and polyphenols) and phytohormones (auxins, jasmonic acid, ethylene, etc). These defensive strategies, activated by aggression, leads to considerable changes in the metabolic activity of plant cells, resulting in a cascade of events designed to restrict the progression of infectious agents and reduce damage from injury. Keywords: Bacterial diseases, Chemical defense, phenolic compounds, phytoalexins, phytohormones