Assessment of plant growth-promoting stress-tolerant endophytes screened from Bougainvillea glabra for the growth of Triticum aestivum L. and Zea mays

Globally, more than 5.2 billion hectares of farming fields are damaged through erosion, salinity, and soil deterioration. Salt stress-tolerant bacteria have plant growth-promoting (PGP) characteristics that can be used to overcome environmental stresses. Isolation and screening of salt-tolerant endophytes from Bougainvillea glabra were achieved through surface sterilization of leaves, followed by their cultivation on 0.5% NaCl-supplemented media. The performance of isolates for indole acetic acid (IAA) production, phosphate solubilization, ACC deaminase activity, ammonia production, siderophore production, and stress tolerance was determined. In the present study, 5 morphologically distinct salt-tolerant endophytic bacteria were cultured. Out of 5 isolates, 60% salt-tolerant endophytes showed phosphate solubilization, 100% IAA production, 40% ACC-deaminase activity, 100% siderophore production, 40% ammonia production and 60% HCN production. Dendrogram generated based on stress tolerance showed three clusters: clusters 1 and 2 containing two isolates and cluster 3 containing 1 isolate. Based on the highest PGP activities, BoGl17 and BoGl21 isolates were chosen and further tested for wheat and corn growth promotion. The isolates increased wheat shoot and root dry weight by 40% and 80%, and by 69% and 126% for BoGl17 and BoGl21, respectively. The bacterial isolates identified as Pseudomonas reidholzensis BoGl17 had 95.59% identity with Pseudomonas reidholzensis strain ID3, while the isolate Bacillus aerius BoGl21 had 90.96% identity with Bacillus aerius strain 24K based on phenotypic features and 16S rRNA gene sequencing results. Both isolates significantly improved plant growth as compared to uninoculated plants.