Rhizobial inoculation for improving productivity of maize and subsequent legumes under saline conditions

Abstract

Salinity is one of the serious environmental problem that caused reduction in crop productivity due to a number of direct and indirect effects in irrigated areas of arid and semiarid regions. Consortial inocula of rhizobial strains can be a competitive strategy to cope with the problem of salinity stress. In this study, a number of rhizobial strains were isolated from the root nodules of lentil and chickpea from the salt-affected fields. Fast growing rhizobial isolates were assessed for their ability to tolerate salt stress by conducting osmoadaptation assay. These strains were further screened for their ability to promote growth of maize seedlings under salt-stressed axenic conditions. Four most effective isolates (LRM- 5, LRM-10, CRM-7 and CRM-7) were selected and their compatibility for synergism was studied. Performance of these four strains and their combination was evaluated in pot and field trials for their potential to improve growth and yield of maize under salt-stressed conditions. After harvesting the maize, lentil and chickpea crops were grown in the respective pots and plots of fields to study the residual effect of rhizobial inoculation on these legumes. Results showed that salinity stress significantly reduced plant growth, physiological parameters, and yield of maize and increased the antioxidant activities of salt stressed plants many folds but rhizobial inoculation improved these, thus reducing the inhibitory effects of salinity. However, their combined application was more effective under salinity. Further residual effect of inoculated maize impart a significant improvement in nodulation and yields of legume crops grown subsequently. These rhizobial strain from different legumes in a combination could be very effective inoculant to improve productivity of maize-legume cropping system under salt affected conditions. However, the degree to which these inoculants impart benefits to plant growth can vary with soil conditions. A combination of rhizobial strains with multiple traits could be more useful under diverse conditions compared to a strains containing single trait.