Plant Growth-Promoting Rhizobacteria Significantly Improves Growth Attributes and Photosynthetic Machinery in Wheat

Despite of extensive research in isolating and identifying plant growth-promoting rhizobacteria, the rhizosphere of weeds is still ignored. The current study demonstrates a great opportunity to isolate and identify novel beneficial microbes from weed rhizosphere having the potential to improve plant growth. Nine bacterial strains were isolated from the rhizosphere of Cyperus rotundus L. found in three different crops, i.e., cotton, maize, and rice, and screened for plant growth-promoting (PGP) traits. Out of nine isolates, two isolates (WBN01 and WBN02) possessed all PGP traits and showed the potential for ammonia production, protease activity, and catalase activity. Both strains were N₂ fixers, secreted indole acetic acid (IAA), and showed phosphate (P)-solubilizing potential, among which WBN01 had higher IAA production (8.69 µg/mL) and P-solubilization (53.83 µg/mL) capacity. These strains were identified as Enterobacter spp. based on their morpho-physiological characters, 16S rRNA gene analysis, and phylogenetic analysis. Greenhouse experiment showed that the inoculation of isolates to wheat plants significantly improved their growth and photosynthetic machinery. On the other hand, these isolates down-regulated photosynthetic electron transport, absorption, and trapping fluxes, consequently increasing PSII photochemistry. The enhanced antioxidant catalase enzyme activity, protein content, and greater accumulation of proline contents due to bacterial inoculation have more significant effect on improving PSII machinery. This study reveals that weeds rhizosphere possesses novel Enterobacter spp. microbes, which can serve as potent biofertilizers, while reducing the application of chemical fertilizers without affecting normal plant growth.