Department of Agricultural Microbiology, Faculty of Agriculture Science, Aligarh Muslim University, Aligarh, U.P, 202002, India.
Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, 11451, Riyadh, Saudi Arabia.
Chemosphere. 2024 Jul;360:142431. doi: 10.1016/j.chemosphere.2024.142431. Epub 2024 May 24.
Globally, agricultural productivity is facing a serious problem due to soil salinity which often causes osmotic, ionic, and redox imbalances in plants. Applying halotolerant rhizobacterial inoculants having multifarious growth-regulating traits is thought to be an effective and advantageous approach to overcome salinity stress. Here, salt-tolerant (tolerating 300 mM NaCl), exopolysaccharide (EPS) producing Rhizobium azibense SR-26 (accession no. MG063740) was assessed for salt alleviation potential by inoculating Phaseolus vulgaris (L.) plants raised under varying NaCl regimes. The metabolically active cells of strain SR-26 produced a significant amount of phytohormones (indole-3-acetic acid, gibberellic acid, and cytokinin), ACC deaminase, ammonia, and siderophore under salt stress. Increasing NaCl concentration variably affected the EPS produced by SR-26. The P-solubilization activity of the SR-26 strain was positively impacted by NaCl, as demonstrated by OD shift in NaCl-treated/untreated NBRIP medium. The detrimental effect of NaCl on plants was lowered by inoculation of halotolerant strain SR-26. Following soil inoculation, R. azibense significantly (p ≤ 0.05) enhanced seed germination (10%), root (19%) shoot (23%) biomass, leaf area (18%), total chlorophyll (21%), and carotenoid content (32%) of P. vulgaris raised in soil added with 40 mM NaCl concentration. Furthermore, strain SR-26 modulated the relative leaf water content (RLWC), proline, total soluble protein (TSP), and sugar (TSS) of salt-exposed plants. Moreover, R. azibense inoculation lowered the concentrations of oxidative stress biomarkers; MDA (29%), HO content (24%), electrolyte leakage (31%), membrane stability (36%) and Na ion uptake (28%) when applied to 40 mM NaCl-treated plants. Further, R. azibense increases the salt tolerance mechanism of P. vulgaris by upregulating the antioxidant defensive responses. Summarily, it is reasonable to propose that EPS-synthesizing halotolerant R. azibense SR-26 should be applied as the most cost-effective option for increasing the yields of legume crops specifically P. vulgaris in salinity-challenged soil systems.
全球范围内，由于土壤盐度导致植物渗透、离子和氧化还原失衡，农业生产力正面临严重问题。应用具有多种生长调节特性的耐盐根际细菌接种剂被认为是克服盐胁迫的一种有效且有利的方法。在这里，评估了耐盐（耐受 300 mM NaCl）、产胞外多糖（EPS）的 Rhizobium azibense SR-26（登录号 MG063740）通过接种不同 NaCl 处理下生长的菜豆（Phaseolus vulgaris（L.））植物来减轻盐度的潜力。在盐胁迫下，菌株 SR-26 的代谢活性细胞产生大量植物激素（吲哚-3-乙酸、赤霉素和细胞分裂素）、ACC 脱氨酶、氨和铁载体。SR-26 产生的 EPS 量随 NaCl 浓度的变化而变化。SR-26 菌株的溶磷活性受到 NaCl 的正向影响，在 NaCl 处理/未处理的 NBRIP 培养基中 OD 位移证明了这一点。耐盐菌株 SR-26 的接种降低了 NaCl 对植物的有害影响。土壤接种后，R. azibense 显著（p≤0.05）提高了在添加 40 mM NaCl 浓度的土壤中生长的菜豆的种子发芽率（10%）、根（19%）、茎（23%）生物量、叶面积（18%）、总叶绿素（21%）和类胡萝卜素含量（32%）。此外，菌株 SR-26 调节了暴露于盐的植物的相对叶片含水量（RLWC）、脯氨酸、总可溶性蛋白（TSP）和糖（TSS）。此外，当应用于 40 mM NaCl 处理的植物时，R. azibense 接种降低了氧化应激生物标志物 MDA（29%）、HO 含量（24%）、电解质泄漏（31%）、膜稳定性（36%）和 Na 离子摄取（28%）的浓度。此外，R. azibense 通过上调抗氧化防御反应来增加菜豆的耐盐机制。总之，合理的是，建议将 EPS 合成耐盐 Rhizobium azibense SR-26 作为增加耐盐土壤系统中豆科作物特别是菜豆产量的最具成本效益的选择。
