PLANT MICROBE INTERACTIONS: MICROBIAL FRIENDS AND FOES IN PLANT HEALTH AND PRODUCTIVITY

Microbes are vital in maintaining the proper functioning of any ecosystem and are also involved in health of higher organisms. Microbes produce different molecules that have direct and indirect effects on plant growth, development and productivity. Bacteria, viruses and fungi can interact with plants in both positive and negative ways. Microbes adopt different mechanisms to stimulate growth of plants, bacteria can enhance plant growth by various mechanisms like nitrogen fixation, siderophore production and phosphate solubilization and fungi involve in phytohormones production, mobilization of nutrients and pathogen growth suppression by direct mechanisms. Viruses are infectious microbes and spread from infected cells to healthy nearby cells once they have entered the host. Plants develop a variety of defense systems in response to microbial infection. Plant response to viruses by different defensive mechanisms such as RNA silencing, virus-encoded suppressor proteins and formation of disease-free tissues. Microbes are vital in maintaining the proper functioning of any ecosystem and are also involved in health of higher organisms. Microbes produce different molecules that have direct and indirect effects on plant growth, development and productivity. Bacteria, viruses and fungi can interact with plants in both positive and negative ways. Microbes adopt different mechanisms to stimulate growth of plants, bacteria can enhance plant growth by various mechanisms like nitrogen fixation, siderophore production and phosphate solubilization and fungi involve in phytohormones production, mobilization of nutrients and pathogen growth suppression by direct mechanisms. Viruses are infectious microbes and spread from infected cells to healthy nearby cells once they have entered the host. Plants develop a variety of defense systems in response to microbial infection. Plant response to viruses by different defensive mechanisms such as RNA silencing, virus-encoded suppressor proteins and formation of disease-free tissues. Plants regulate defense against fungal pathogen by secreting plant-signaling molecules which may include intracellular calcium and other ions, reactive oxygen and nitrogen species, small RNAs and phytohormones. Plants release several allopathic compounds which inhibit several functions in lichens. Harmful bacteria are responsible for significant yearly loss in yield of crops. In different parts of the world, they are considered as the causative agent of significant economic losses in crop production and quality. Plant viruses spread from infected cells to healthy nearby cells once they have entered the host and are associated with long distance transmission through the vascular for systemic infection. Many fungal species depend upon their living host plant to complete their growth reproductive cycle and after successful infection must change host cell structure, function and as a result cause disease. The interactions of bacteria, viruses, fungi and lichen with plants which include history, beneficial and harmful aspects, their beneficial and disease-causing mechanisms and defense response of plants toward these microbes have been discussed in this chapter Plants regulate defense against fungal pathogen by secreting plant-signaling molecules which may include intracellular calcium and other ions, reactive oxygen and nitrogen species, small RNAs and phytohormones. Plants release several allopathic compounds which inhibit several functions in lichens. Harmful bacteria are responsible for significant yearly loss in yield of crops. In different parts of the world, they are considered as the causative agent of significant economic losses in crop production and quality. Plant viruses spread from infected cells to healthy nearby cells once they have entered the host and are associated with long distance transmission through the vascular for systemic infection. Many fungal species depend upon their living host plant to complete their growth reproductive cycle and after successful infection must change host cell structure, function and as a result cause disease. The interactions of bacteria, viruses, fungi and lichen with plants which include history, beneficial and harmful aspects, their beneficial and disease-causing mechanisms and defense response of plants toward these microbes have been discussed in this chapter