The plant-growth-promoting bacterium Klebsiella sp. SBP-8 confers induced systemic tolerance in wheat (Triticum aestivum) under salt stress created by Rajnish Prakash Singh, Prameela Jha and Prabhat Nath Jha

Plant-growth-promoting bacteria (PGPB) with 1-aminocyclopropane-1-carboxylatedeaminase (ACCD) activity can protect plants from the deleterious effects of abioticstressors. An ACCD bacterial strain, SBP-8, identified as Klebsiella sp., also having other plant-growth-promoting activities, was isolated from Sorghum bicolor growing in the desertregion of Rajasthan, India. ACCD activity of SBP-8 was characterized at biochemical, physiological, and molecular levels. The presence of AcdS, a structural gene for ACCD, was confirmed by the polymerase chain reaction. Strain SBP-8 showed optimum growth and ACCD activity at increased salt (NaCl) concentrations of up to 6%, indicating its potential to survive and associate with plants growing in saline soil. Inoculation of wheat plants with SBP-8 when grow in the presence of salt (150-200 mM) and temperature (30-40 °C) stressors resulted inamelioration of stress conditions by increasing plant biomass and chlorophyll content, and are duction in plant growth inhibition (10-100%) occurred due to salt and temperature stressors. Moreover, strain SBP-8 also caused Na(+) exclusion (65%) and increased uptake of K(+) (84.21%) in the host plant. This property can protect plants from adverse effects of Na(+) on plant growth and physiology. Thus, SBP-8 improves growth of the host plant and protects from salt stressors through more than one mechanism including an effect of ACCD activity and on K(+)/Na(+) ratio in plants. The colonization efficiency of strain SBP-8 was confirmed by CFU (colony-forming unit) count, microscopy, and ERIC-PCR based DNA-finger-printing approach. Therefore, and the use of efficient colonizing plant-growth-promoting bacteria may provide insights into possible biotechnological approaches to decrease the impact of salinity and other stressors.