The combined application of rhizobial strains and plant growth promoting rhizobacteria improves growth and productivity of mung bean (Vigna radiata L.) under salt-stressed conditions

Abstract

Salinity stress induces higher levels of ethylene in plants in arid and semi-arid regions. This increased concentration of ethylene can be inhibited by using plant growth promoting rhizobacteria (PGPR) containing ACC-deaminase. A pot trial was conducted under salt-stressed conditions to evaluate the potential of combined application of Rhizobium phaseoli (M6 and M9), and PGPR (Pseudomonas syringae, Mk1; Pseudomonas fluorescens, Mk20 and Pseudomonas fluorescens Biotype G, Mk25) to improve the productivity of mung bean. The results showed that salinity stress decreased significantly mung bean growth, yield and physiological parameters but inoculation with either rhizobia or PGPR alone enhanced these parameters significantly. However, the combined application of rhizobia and PGPR was more effective for reducing the depressing effect of salinity on mung bean. Co-inoculation increased the shoot fresh weight (145%), root fresh weight (173%), number of pods plant−1(150%), pod fresh weight (182%), total dry matter (269%), relative water content (19%), water use efficiency (51%), potassium concentration in leaves (33%), sodium concentration in leaves (56%) and nitrogen concentration in grains of mung bean (99%), compared with the uninoculated control. The results imply that combined application of Rhizobium and Pseudomonas strains can improve the productivity of mung bean. Thus, these strains could be evaluated in intensive field trials for developing biofertilizers to improve the productivity of mung bean under salt-affected conditions.