Plant growth promoting rhizobacteria and their biopriming for growth promotion in mung bean (Vigna radiata (L.) R. Wilczek)

Abstract

Abstract Plant growth-promoting rhizobacteria (PGPR) are beneficial rhizosphere derived bacteria that have the capability to colonize plant roots and are used to enhance plant growth or suppress disease caused by various phytopathogens. The fourteen isolates were screened on the basis of in vitro antagonistic activity against the root rot pathogen Rhizoctonia solani but in the present study, we have selected, two strains of rhizobacteria (Pseudomonas aeruginosa BHU B13-398 and Bacillus subtilis BHU M) through initial screening as well as their in vitro antagonistic potential activity against the root rot pathogen Rhizoctonia solani. These isolates were then tested in vitro for their specific PGPR traits, such as phosphate solubilization, ammonia, siderophore and HCN production. Both the isolates were found to be promising agents for all the tested PGPR traits. Among the two isolates, BHU B13-398 showed highest plant growth promoting attributes. Pot experiments were conducted on mung bean to evaluate their plant growth promotion potential under the controlled green house conditions (14 h light, 10 h dark, and temperature at 27 ± 2 °C). The results revealed that both the isolates (BHU B13-398 and BHU M) enhanced the growth parameters of mung bean such as root length, shoot length, root as well as shoot fresh and dry weight, leaf area and chlorophyll content compared to uninoculated control plants. Our results clearly demonstrated that both the isolates BHU B13-398 and BHU M displayed 32.26%, 84.60% and 13.38%, 61.94%, increase in shoot length, and root length respectively, as compared to uninoculated control. Mung bean root sections inoculated with respective strains were observed through scanning electron microscopy (SEM) to validate mung bean root colonizing abilities of the strains. The SEM observation confirmed that both strains BHU B13-398 and BHU M seem to be a good root colonizer and have high population densities on the root surface.