Evaluation of the plant growth promoting potential of some bacterial and fungal isolates under saline stress

Abstract

Plant growth-promoting microorganisms (PGPM) represent a promising strategy for enhancing plant resilience and yields under salt-stress conditions. The present study aims to test the plant growth promoting capacity of selected microbial species, isolated in a previous study, under saline stress both in vitro via the measure of halotolerance, auxin production and siderophore production and in vivo by testing the growth promoting potential of the isolates on Maize seeds. Results showed that the all the tested isolates have the ability to grow under saline concentration, at least up to 600 mM of NaCl. However, Bacillus rugosus demonstrated the higher tolerance to salt (900 mM NaCl) compared to the other isolates. In addition, all the isolates showed their ability to produce auxin under the different salt concentrations tested except for Pseudomonas granadensis that showed lower value above 600 Mm. Moreover, all the tested isolates produce siderophores at all the tested NaCl concentrations. Furthermore, in vivo plant growth parameters such as root length and shoot length showed an increase when treated with all the isolates but limited to a concentration of 50 mM NaCl. These results reflected the positive impact of the tested microbial isolates on plant growth. Our data highlight the ability of the isolated microorganism strains we used to have a high plant growth-promoting (PGP) capabilities. However, these strains need to be tested under field conditions and with more crops before being considered biofertilizer candidates.