Role of Rhizobia in Plant Growth Promotion: Agriculture Prospective

Soil is one of the most important elements of the agricultural system, and it has been suffering severe damage for several decades. Losing soil quality due to a plethora of factors has impacted the sustainability of the current environment. Therefore, the need for sustainable practices to mitigate the impact of soil quality deterioration is crucial. Nowadays, diverse sustainable practices are adopted to improve soil quality and cease soil deterioration and retard the process of losing agriculture land. Among these practices, the usage of microbial strains can help in improving plant health and soil properties. Rhizobia is one important group of soil microorganisms, which inhabit plant rhizosphere and colonize the roots of legume plants either in a symbiotic association or as plant endophytes. These bacteria enhance plant growth directly throughout their ability to fix atmospheric nitrogen into organic nitrogen available for plant utilization. In addition, they contribute to plant growth promotion in indirect ways via controlling different biotic and abiotic factors in the soil. In this chapter, we will introduce rhizobia as an important agent for plant growth promotion and will shed the light on their valuable roles for sustainable agriculture either in a direct way or in indirect way. Also, we will present the biotic and abiotic factors affecting rhizobia functions.