Defence Mechanisms in Plants Against Invading Plant Pathogenic Microbes in Nigeria

Plant cells consist of cell wall, cell membranes, and cytoplasm, which contains the nucleus and various organelles and all the substances for which the plant pathogens have as their targets. These pathogens attack plants because during their evolutionary development they have acquired the ability to live off the substances manufactured by the host plants, and some of the pathogens depend on these substances for their development and survival. Many substances are contained in the protoplast of the plant cells, and if pathogens are to gain access to them they must first overcome the physical barrier presented by the host cuticle and/or cell walls. Plants defend themselves against invading plant pathogens by a combination of weapons from two major barriers: structural characteristics that act as physical barriers and inhibit the pathogen from gaining entrance and also from spreading through the plant. Secondly through biochemical reactions that take place in the cells and tissues of the host plant and produce substances that are either toxic to the pathogen or create conditions that inhibit growth of the pathogen in the plant cells and thus defend plants. These actions against invading pathogen are controlled directly or indirectly by genetic materials (gene) of the host plants