Screening of endophytic Bacteria from stress-tolerating plants for abiotic stress tolerance and plant growth-promoting properties: Identification of potential strains for bioremediation and crop enhancement

Abstract

Enhancing plant productivity and fortifying defense mechanisms against biotic and abiotic stresses is crucial for sustainable agriculture. To achieve this, researchers have investigated the use of endophytic bacteria as a viable alternative to chemical fertilizers and pesticides. In this study, 50 endophytic microbes were isolated from stress-tolerant parts of different plants, including Lantana camara, Phoenix dactylifera, Hemerocallis fulva, Salvia rosmarinus, Commiphora wightii, and Abutilon indicum. These microbes were evaluated for their tolerance to abiotic stresses and ability to promote plant growth. Among the isolates, R1L2 and A2L2L2 exhibited the highest tolerance to salt stress, withstanding up to 16% NaCl. DL2R2, R1L2, and A1S1S were the most tolerant to lead stress, tolerating up to 6% w/v lead. For cadmium stress, R1L2, DL3R2, and DP1L1L1 showed the highest tolerance, enduring up to 6% w/v cadmium. The isolates were also assessed for their plant growth-promoting (PGP) activities, including the production of IAA, Gibberellin, Cytokinin, HCN, siderophore, phosphate solubilization, and nitrogen fixation. All isolates were positive for nitrogen fixation attribute. However, under specific stress conditions, all isolates showed negative results for HCN production, siderophore production, or inorganic phosphate solubilization. Isolates A1S1S and DL3R2 demonstrated positive results for producing phytohormones such as IAA, Gibberellin, and Cytokinin. Through phenotypic and biochemical characteristics, as well as 16S rDNA gene sequencing, isolate A1S1S was identified as Pelomonas aquatic (accession no. OP984335), and isolate DL3R2 was identified as Solibacillus silvestris (accession no. OP854919). These findings suggest that the endophytic strains Pelomonas aquatic and Solibacillus silvestris have potential applications as multi-stress reducers, bioremediation agents, and crop growth promoters in essential crops.