Chapter 7 Role of Beneficial Microbes for Plant growth Improvement
Amir Ali Khan, Mohd Shahid Anwar Ansari, Touseef Hussain, Abrar Ahmad Khan
Abstract
Plant growth-promoting microbes comprise of microorganisms in the plant system including rhizospheric bacteria, fungi, mycorrhiza, actinomycetes, endophytic fungi, or those having either symbiotic or nonsymbiotic relationship with plants. Promotion of plant growth by microorganisms is associated with mechanisms such as phytohormone production, siderophore production, nitrogen fixation, solubilization of mineral phosphates, and release of potent secondary metabolites (SMs) that affect the plant health easily. Some fungi such as arbuscular mycorrhizal (AM) fungi have been found in almost all land plant species as obligate root symbiont and increase the uptake of mineral elements in their host plant in exchange of carbon and enhance the plant growth by increasing biomass and chlorophyll content. Such microorganisms are also involved in the management of both biotic and abiotic stresses on plants. Management of biotic stress involves the interaction between pathogenic and nonpathogenic microbes that includes various changes like twisting of hyphae of beneficial microbes around the hyphae of pathogenic microbes as well as certain changes at the cellular level like secretion of lytic enzymes or secretion of antimicrobial compounds and dissolution of host cytoplasm, and such changes inhibit the reproduction and growth of harmful microbes in the nearby places. The exact understanding of the mechanism by which these microbes promote growth of plants will help evolve approaches against damages by several biotic and abiotic stress conditions and help in sustainable agriculture at global scale.