Significance of Plant Growth Promoting Rhizobacteria in Grain Legumes: Growth Promotion and Crop Production

Grain legumes are an important component of sustainable agri-food systems. They establish
symbiotic association with rhizobia and arbuscular mycorrhizal fungi, thus reducing the use of
chemical fertilizers. Several other free-living microbial communities (PGPR—plant growth promoting
rhizobacteria) residing in the soil-root interface are also known to influence biogeochemical cycles
and improve legume productivity. The growth and function of these microorganisms are aected
by root exudate molecules secreted in the rhizosphere region. PGPRs produce the chemicals which
stimulate growth and functions of leguminous crops at dierent growth stages. They promote plant
growth by nitrogen fixation, solubilization as well as mineralization of phosphorus, and production of
phytohormone(s). The co-inoculation of PGPRs along with rhizobia has shown to enhance nodulation
and symbiotic interaction. The recent molecular tools are helpful to understand and predict the
establishment and function of PGPRs and plant response. In this review, we provide an overview of
various growth promoting mechanisms of PGPR inoculations in the production of leguminous crops.