Alleviation of salt stress in lettuce (Lactuca sativa L.) by plant growth-promoting rhizobacteria

Abstract

Purpose: The effect of Pseudomonas sp. rhizobacteria as plant growth-promoting rhizobacteria (PGPR) in alleviating salt stress in the lettuce plant was studied under greenhouse condition. Research Method: The experiment was conducted following a completely randomized design with three replicates. The treatments include four Pseudomonas sp. strains (B0 (non-inoculated), B1, B2 and B3) as PGPR and three levels of irrigation water salinity (0, 4 and 8 dS m-1 as NaCl). Findings: The results showed that with rising salinity levels the lettuce fresh and dry weight, chlorophyll and carotenoids content and K concentration decreased but, the content of membrane stability index (MSI), Na and Na/K ratio ncreased. However, inoculation of the lettuce plants by PGPR significantly increased the lettuce fresh and dry weight, chlorophyll and carotenoids content, K concentration and K/Na ratio under various salinity levels. Among the PGPR strain, the B2 strain was more effective in the improvement of the lettuce resistance to salinity stress. Research limitations: If antioxidant compounds and enzymes were measured in this study, it would be helpful to interpret the results. Originality/Value: with regards to the useful impact of the PGPR on the lettuce plant under soil salinity, these microorganisms can be used as biofertilizer to provide nutrients and increase plant resistance to salt stress.