Plant-microbe interactions in wastewater-irrigated soils

With increase in urbanization and industrialization, there has been an enormous increase in the amount of wastewater being discharged into the environment without any pretreatment, especially in developing countries. In such regions of the world, farmers are using this wastewater for irrigation purposes in agricultural fields due to unavailability and unsuitability of clean irrigation water. The wastewater discharged by the industries is loaded with huge amount of heavy metals, dyes, organic compounds, and pathogens. It has been found that soils irrigated with wastewater harbor a diverse community of microbes resistant to toxic metals, which not only contribute in the remediation of wastewater-polluted soils but also play their role in plant growth promotion. Most of them are found in close vicinity of plant roots and some of them enter in root cortical cells to act as endophytes. These microbes utilize various strategies to remediate contaminated soils such as biosorption, biotransformation, biovolatilization, bioleaching, biodegradation, etc. On the other hand, they also promote plant growth by utilizing numerous mechanisms such as phosphate solubilization, growth hormone synthesis, zinc mobilization, induction of stress tolerance, ACC deaminase activity, siderophore production, nitrogen fixation, biocontrol activity, etc. This chapter elaborates the potential of beneficial microorganisms to remediate the soils irrigated with wastewater and interaction of these microbes with plants in order to promote their growth by relieving them from toxic effects of pollutants.