Gholamnejad J. 2017. Plants defense mechanisms against pathogens. Plant Pathology Science 6(2):24-32.
Plants have many defense mechanisms against pathogens that can be stimulated and activated by some microorganisms or chemicals. There are five types of induced resistance in plants that are included: localized acquired resistance, systemic acquired resistance, systemic gene silencing, induced systemic resistance, and systemic wounding response. Systemic acquired resistance is the most important type of induced resistance in plants that result in continuous and prolonged protection from infection against a wide range of pathogens. Formation of pathogenesis related proteins, alteration of cell wall with sedimentation and binding of polysaccharides, proteins, glycol-proteins, phenols, phytotoxins, and ligninification are the stages of occurrence of this type of resistance in plants.
The increasing resistance of plant pathogens to chemical pesticides and concerns over the environmental consequences of their use have heightened the need to develop sustainable and eco-friendly solutions. Chitosan, as a natural and biodegradable biopolymer, has significant potential for sustainable management of plant diseases due to its antimicrobial activity and ability to stimulate plant defense systems. Various sources of chitosan production include crustacean shells, fungi, insect cuticles, as well as extraction methods and quality-determining factors, especially the degree of deacetylation and molecular weight. The multiple mechanisms of chitosan action, including direct antimicrobial activity by disrupting the structure and permeability of pathogen membranes, induction of systemic resistance through activation of defense and hormonal pathways, increased activity of defense enzymes like chitinase and glucanase, and strengthening structural barriers such as lignin and callose, and the role of chitosan in reducing certain abiotic stresses and improving plant growth and performance, are described in this article. The development of smart, nanostructured formulations, the optimization of chitosan production from sustainable sources, and its strategic integration with other disease management methods could strengthen the role of this biopolymer in sustainable agriculture and enhance plants productivity.
