Alleviation of Abiotic and Biotic Stresses in Plants by Azospirillum

Abstract

In the face of global changes, plants must adapt to a wide range and often combined biotic and abiotic stresses that seriously impaired plant growth and development. Plants develop complex strategies to deal with water stress conditions, soil fertility losses, soil pollutions, pests, and disease. Emerging evidence suggest the involvement of common hormonal players in plant defense signaling pathways triggered in response to biotic and abiotic stresses. Besides plant strategies, plant growth-promoting rhizobacteria (PGPR), which colonize the root system and establish cooperative interactions with plants can improve their growth and help them to adapt to and cope with multiple stresses including drought, salinity, heavy metal pollutions, and parasites. Accordingly, PGPR supply added values to the plant defense strategies by expressing many relevant functions for modulating the plant hormonal balance, increasing nutrients supply to the plant, improving the functional and physical properties of protective barriers against plant parasites. Among PGPR, Azospirillum strains were long viewed as biofertilizers and less as biocontrol agents. It is becoming evident that Azospirillum is able to protect plants against a myriad of detrimental conditions. This review provides an update of works regarding the ability of Azospirillum strains to alleviate plant stress and brings out the relevant involved plant-beneficial functions. Developing PGPR-based bio-inoculants is a promising strategy to improve the growth and health of crops and develop sustainable agriculture.