Beneficial Microbes for Disease Suppression and Plant Growth Promotion

Abstract

Plant growth-promoting microorganisms (PGPMs) constitute the microbes that are intricately associated with the plant system and may consist of rhizospheric bacteria, fungi, mycorrhiza, endophytic fungi, actinomycetes, or those having the mutualistic relationship or nonsymbiotic relationship with plants. One of the most remarkable features of these microbes is the adoption of certain ecological niches or may be occupied with multiple niches at a time in the soil ecosystem that makes way for other species to establish the mutual interactions (physical or biochemical) with other microbes (bipartite) or with plants (tripartite). The plant growth promotion by these microbes involves common mechanisms such as nitrogen fixation, siderophore production, phytohormone production, solubilization of mineral phosphates and secretion of novel secondary metabolites having positive effect on plant health. Some beneficial fungi have been found to promote plant growth through increased photosynthetic rate with improved mineral use efficiency and nutrient uptake, as inoculating these microbes with plants lead into increased chlorophyll content and biomass. These indigenous microbes have been also reported to counteract the different abiotic and biotic stress conditions. The mutual interaction observed between beneficial fungi and pathogenic microbes has been investigated at microscopic level which involves certain physical changes such as coiling of beneficial hyphae around the pathogenic hyphae and some cellular changes such as dissolution of host cytoplasm or secretion of antimicrobial compounds or lytic enzymes in the nearby localities that check the growth and reproduction of pathogenic species. The comprehensive knowledge of the functional mechanism of plant growth promotion by these microbes will help to develop strategies against damages covered by various abiotic and biotic stress conditions, and therefore will help in increasing the agricultural production at a global scale.