Rai, A., Cherif, A., Cruz, C. & Nabti, E. (2018) Extracts from seaweeds and opuntia ficus-indica cladodes enhance diazotrophic-PGPR halotolerance, their enzymatic potential, and their impact on wheat germination under salt stress.Pedosphere, 28(2), 241-254. DOI:10.1016/S1002-0160(17)60333-3 (IF2018 3,188; Q2 Soil Science)
Soil salinity affects more than 6% of the earth’s land surface and more than 20% of its irrigated areas, being a major threat to agriculture. Diazotrophic bacteria are among the soil microbial functional groups threatened by this abiotic stress, since their activity is mostly inhibited by salt stress. Seventy soil bacterial strains were isolated from soils with distinct characteristics using the N-free Jensen’s selective medium. Based on their ability to produce metabolites of agricultural interest, four strains were selected and molecularly identified as Flavobacterium johnsoniae, Pseudomonas putida, Achromobacter xylosoxidans and Azotobacter chroococcum. The selected strains were grown under distinct NaCl concentrations (0 to 600 mM in Nitrogen-Free broth and 0 to 2 M in Luria Bertani medium) in the absence and presence of Glycine Betaine (GB), aqueous and hydro-alcoholic extracts of Ulva lactuca (UL), Enteromorpha intestinalis (EI) and Opuntia ficus-indica (OFI) cladodes. The selected bacterial strains, glycine betaine (GB) and the aforementioned extracts were tested for their ability to promote germination of wheat seeds under 0 to 300 mM NaCl. In comparison to the results obtained with the synthetic osmoprotectant GB, extracts from Opuntia ficus-indica, Ulva lactuca and Enteromorpha intestinalis significantly promoted bacterial growth and seed germination under salt stress.