Department of Agricultural Microbiology, Faculty of Agricultural Sciences, Aligarh Muslim University, Aligarh, 202002, UP, India.
Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, 11451, Riyadh, Saudi Arabia.
Plant Physiol Biochem. 2024 Oct;215:108973. doi: 10.1016/j.plaphy.2024.108973. Epub 2024 Jul 25.
Exopolysaccharide (EPS)-producing beneficial bacteria play a multifaceted role in improving plant growth and adaptive responses against different stressors. In this study, we isolated 25 bacterial strains from pea nodules and were further studied for their sodium chloride (NaCl) and cadmium (Cd) stress tolerance. Based on our results, Rhizobium fabae SR-22 (NCBI Accession number: MG063739.1) showed better tolerance toward salinity and Cd stress and produced a wide range of plant growth-promoting compounds. However, the amount of EPS varies during NaCl and Cd stress. It was important to note that NaCl and Cd beyond the tolerant level, affected the morphology and cellular viability of R. fabae. Interestingly, plant growth-promoting (PGP) substances (indole-3-acetic acid, ammonia, siderophore, and ACC deaminase) released by R. fabae were increased with increasing NaCl concentrations. In contrast, PGP substances were greatly decreased by increasing Cd dosages. Further, the beneficial effect of EPS-producing R. fabae in Triticum aestivum grown in soil treated with different levels of NaCl and Cd was assessed. Inoculation of R. fabae in wheat seedlings grown under higher NaCl and Cd concentrations showed improved growth compared to non-inoculated plants. R. fabae exhibited maximum effect in wheat plants grown under 2% NaCl and increased seed germination (8%), root length (13%), vigor indices (19%), root biomass (20%), chlorophyll-a (31%), total chlorophyll (27%) and carotenoid content. Additionally, R. fabae increased Cd and NaCl tolerance in wheat seedlings and improved their antioxidative responses. Conclusively, this work demonstrated that EPS-producing R. fabae showed a promising role in mitigating salinity and Cd-stress in wheat possibly by reducing salt and HM stress-induced abrasions and growth promotion via inorganic phosphate solubilization, and increased nutrient absorption. In the future, R. fabae equipped with these distinguishing characteristics may be used as effective bio-inoculants/bio-formulations in agriculture to address salinity and HM stress issues.
从豌豆根瘤中分离到 25 株产胞外多糖（EPS）的有益细菌，进一步研究其对氯化钠（NaCl）和镉（Cd）胁迫的耐受性。根据我们的结果，菜豆根瘤菌 SR-22（NCBI 登录号：MG063739.1）对盐度和 Cd 胁迫表现出更好的耐受性，并产生广泛的植物生长促进化合物。然而，EPS 的产量在 NaCl 和 Cd 胁迫下有所变化。重要的是要注意，超过耐受水平的 NaCl 和 Cd 会影响菜豆根瘤菌的形态和细胞活力。有趣的是，菜豆根瘤菌释放的植物生长促进（PGP）物质（吲哚-3-乙酸、氨、铁载体和 ACC 脱氨酶）随着 NaCl 浓度的增加而增加。相比之下，随着 Cd 剂量的增加，PGP 物质大大减少。此外，还评估了在不同 NaCl 和 Cd 处理的土壤中生长的小麦中，产 EPS 的菜豆根瘤菌的有益作用。在高 NaCl 和 Cd 浓度下生长的小麦幼苗接种菜豆根瘤菌后，与未接种植物相比，生长状况得到改善。在 2%NaCl 下生长的小麦植物中，菜豆根瘤菌的效果最大，提高了种子发芽率（8%）、根长（13%）、活力指数（19%）、根生物量（20%）、叶绿素-a（31%）、总叶绿素（27%）和类胡萝卜素含量。此外，菜豆根瘤菌提高了小麦幼苗对 Cd 和 NaCl 的耐受性，并改善了它们的抗氧化反应。总之，这项工作表明，产 EPS 的菜豆根瘤菌在减轻小麦盐度和 Cd 胁迫方面可能发挥了有希望的作用，其机制可能是通过减少盐和 HM 胁迫引起的磨损和通过无机磷溶解促进生长，以及增加养分吸收。在未来，具有这些显著特征的菜豆根瘤菌可能被用作农业中的有效生物接种剂/生物制剂，以解决盐度和 HM 胁迫问题。
