Response of maize (Zea mays) to auxin producing plant growth promoting rhizobacteria under saline conditions

Abstract

Soil salinity is one of the most widespread agricultural problems which reduce the field and crop productivity. Salinity disturbs the hormonal balance in plants which results in poor growth. Use of plant growth promoting rhizobacteria (PGPR) is considered an economical and environment-friendly approach to combat salinity stress. This study was carried out to investigate the effect of PGPR on the growth, antioxidant status, physiological parameters and mineral content of maize (Zea mays) in salt affected soils. Bacterial strains were isolated from the rhizosphere of maize growing under salt affected soil conditions. These strains were screened on the basis of auxin production and their ability to withstand salinity stress. Nineteen rhizobacterial strains producing auxin were further screened for their growth promoting activity under axenic conditions at 0, 4, 8, 12 and 15 dS m-1 salinity levels. Two strains were selected after this study and their ability of growth promotion in the presence and absence of L-TRP was tested alone and in combination under salt affected pot and field conditions. Results showed that soil salinity reduced the plant growth, physiological parameters, mineral nutrient uptake and yield of maize while antioxidant activity and proline concentration was increased. Inoculation with PGPR strains under saline soils alleviated the salinity effects on the antioxidant enzymes (APX and SOD), along with those on photosynthesis, mineral content and growth in the absence and presence of L-TRP application. Dual inoculation showed better results than sole inoculation. The results of the present study highlight the significance of PGPR strains to alleviate the adverse effects of salinity stress