Potential of rhizobia as plant growth-promoting rhizobacteria

Abstract

Nitrogen-fixing plant growth-promoting rhizobacteria collectively known as rhizobia have been extensively investigated due to their exceptional quality to establish functional symbiosis with legumes. As a result of this incredible interaction, they supply nitrogen to plants, which is one of the major nutrient elements. Rhizobia are capable of colonizing the rhizosphere of nonhost plants (nonlegumes) thus living within plant tissues as endophytes. Due to these properties and their ability to secrete phytohormones and siderophores, and solubilize insoluble phosphate, besides eliciting plant defense reactions against phytopathogens, rhizobia have been placed along the organisms with high potential to act as efficient plant growth-promoting rhizobacteria (PGPR). Here, the mechanisms adopted by rhizobia to facilitate plant growth and yields are highlighted. In addition, the application of rhizobia as PGPR in farming practices is underlined. The information available on rhizobial application and the number of rhizobia stored in different culture collection centers around the world may provide an important microbiological resource to reduce the use of expensive synthetic fertilizers and pesticides in agricultural practices.