PGPR promotes the plant growth due to several PGP properties of rhizobacteria (Tiwari and Singh, 2017). The PGPR promotes the plant growth by two different mechanisms, direct and indirect (Vimal et al., 2017, 2018). The direct plant growth promotion is due to certain metabolites synthesized by bacteria such as, phytohormones (Vimal et al., 2016). The indirect mechanism of plant growth is due to the production of antagonistic substances produced by bacteria or by inducing resistance to pathogens (Beneduzi et al., 2012). A brief description of different indirect and direct methods of plant growth promotion by PGPR is given below.