Chapter 18 - Diversity of methylobacterium species in the plant phytosphere and their different strategies to mitigate biotic and abiotic stress responses

Abstract

Abiotic and biotic stresses are important factors that plays a vital role in plant growth promotion (PGP) and development. For sustainable agriculture practices and to meet the increasing crop production demand, plants develop certain strategies to overcome the abovementioned stress conditions. Being sessile, plants cannot escape from various types of biotic and abiotic stresses during their life cycle and adapted certain genetic and epigenetic strategies to cope with the abovementioned stress conditions. In addition to this, the methylotrophic bacterial community is an important group of microbes that utilize reduced carbon compounds as their energy source and plays a significant role in enhancing plant growth, crop productivity, and soil fertility. Methylotroph is a diverse group of bacteria that belongs to the class proteobacteria and colonizes various parts of plants such as the rhizosphere and phyllosphere. Several earlier studies reported the abiotic stress tolerance ability of various methylotrophic bacteria under extreme conditions such as high temperature, low temperature, drought, acidic/alkaline habitats, and high salt environments. The methylotrophic bacterial community helps plants with growth and development through direct and indirect methods. They enhance plant health directly by mineral solubilization, production of phytohormones, nitrogen fixation, production of Fe-chelating compounds, ACC deaminase activity, and indirectly through ammonia production, secondary metabolite production, and siderophores. These bacteria colonize various plant parts and may promote plant growth in terms of an increase in biomass, leaf chlorophyll content, seed germination rate, root and shoot length, higher yield, and tolerance to various abiotic stresses. Methylotroph secretes certain exude osmo-protectants on plant surfaces such as sugars and alcohols, which plays a significant role in protecting plants from desiccation and harmful radiations. The use of these potent methylotrophic strains in agriculture practices might be beneficial for proper crop production and mitigation of various types of biotic and abiotic stresses.