Plant Growth-Promoting Rhizobacteria Isolated from the Jujube (Ziziphus lotus) Plant Enhance Wheat Growth, Zn Uptake, and Heavy Metal Tolerance

In recent years, the low Zn content of wheat has become critical. Consequently, solutions that can improve the Zn nutrition of wheat are highly researched. In the present investigation, we aimed to evaluate the potential benefits of phosphate-solubilizing bacteria isolated from Ziziphus lotus on wheat seedling growth. Based on the phosphate-solubilizing criteria, four isolated strains, J16, J143, J146, and J158, were identified by 16SrRNA gene sequencing as Pseudomonas moraviensis, Bacillus halotolerans, Enterobacter hormaechei, and Pseudomonas frederiksbergensis, respectively. Studies of the conventional properties of plant growth-promoting rhizobacteria (PGPR) showed that E. hormaechei J146 produced up to 550 mg·L−1 of indole-3-acetic acid (IAA). Siderophores and ammonia were produced by all strains but cellulase was restricted to B. halotolerans J143, whereas proteases were missing in E. hormaechei J146 and P. frederiksbergensis J158. E. hormaechei J146 tolerate up to 1.5 mg·L−1 of copper and cadmium, while B. halotolerans J143 withstood 1.5 mg·L−1 of nickel. Strains B. halotolerant J143, E. hormaechei J146, and P. frederiksbergensis J158 remarkably improved wheat seed germination, plant growth, and Zn absorption. Lastly, nutrient measurement revealed that a wheat plant inoculated with E. hormaechei J146 and P. frederiksbergensis J158 increased its nitrogen and potassium uptake by up to 17%.