Plant-microbe interactions in developing environmental stress resistance in plants

The chapter introduces and discusses general mechanisms of abiotic stress resistance, describes plant-specific mechanisms of sensing and response to fungi. It is not well understood how plants differentiate between pathogens and beneficial bacteria and fungi, such as rhizobia, beneficial bacteria and fungi that work as biocontrol agents and biostimulants. Plants recognize and interact with the beneficial microbiota, through attenuation of pattern triggered immunity. Plant secondary metabolites and compounds in root exudates (sugars, metabolites and proteins) are produced to recruit plant defense-assisting rhizosphere microbes, contributing to defende them from their pathogens. Soil-borne microorganisms, fungi and bacteria in the rhizosphere, play an important role in control of root and foliar pathogens, through induction of systemic resistance in plants. The transfer of specific strains to varieties sensitive to soil-born bacterium Ralstonia solanacearum was shown effective in protecting tomato from the infection. Rhizobacteria and endophytes are able to produce plant hormones, to modulate hormone synthesis and hormone crostalk in the relief from abiotic stress. Finally, the chapter focuses on Medicago, and interplay between production of JA and other oxylipins, in roots and leaves, their accumulation and potentiation under salt stress; lastly a review on the results on gene networks and gene hubs regulation transcription, through Systems Biology and transcriptome studies, on plants under combined abiotic stresses, and combined biotic and abiotic stress, are provided. It is envisaged that microorganisms can provide a useful system, alone or in combination with biochar, soil amendment, nutrient availability, to approach the increasing challenge of abiotic stresses in agriculture, for a next generation of resilient plant crops.