Rhizobacteria alleviate the adverse effects of salt stress on seedling growth of Capsicum annuum L. by modulating the antioxidant enzyme activity and mineral uptake

Salinity is one of the most important factors restricting vegetative production, especially in arid and semi-arid regions. In this study,the effects of the exogenous plant growth-promoting rhizobacteria (PGPR: Bacillus pumilus UG-41, Bacillus cereus UG-50) application on seedling growth, concentration of plant nutrient elements, antioxidant activity and chlorophyll, proline, sugar, hydrogen peroxide (H2O2), malondialdehyde (MDA), hormone contents of pepper seedlings under salinity stress conditions (100 mM NaCl) were investigated. Our results showed that gibberellic acid (GA), salicylic acid (SA), indole acetic acid (IAA), leaf relative water content (LRWC) and the concentration of all plant tissue nutrients investigated except for Na were decreased by salt stress. On the other hand, PGPR treatment increased the plant growth parameters by increasing the proline, sucrose, hormone and chlorophyll contents; altering the mineral uptake and increasing the antioxidant enzyme activity in pepper seedlings under salt stress. In conclusion, PGPR treatment may be used as an effective technique to protect the plants against salinity stress since the bacteria positively impact the ability of the plant to cope with the stress by particularly increasing the antioxidant enzyme activity, hormone level and mineral uptake.