Abstract：
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%), H2O2 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.
摘要：
全球范围内,由于土壤盐分经常导致渗透，农业生产力面临着严重的问题，离子，和植物中的氧化还原失衡。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度胁迫的有效且有利的方法。这里,耐盐（耐受300mMNaCl），产生根瘤菌的胞外多糖（EPS）阿齐宾SR-26（登录号MG063740）通过接种菜豆（L.)在不同的NaCl制度下饲养的植物。菌株SR-26的代谢活跃细胞产生了大量的植物激素（吲哚-3-乙酸，赤霉素,和细胞分裂素），ACC脱氨酶,氨,和铁载体在盐胁迫下。NaCl浓度的增加会影响SR-26产生的EPS。NaCl对SR-26菌株的P-增溶活性有正向影响,如通过NaCl处理/未处理的NBRIP培养基中的OD偏移所证明的。通过接种耐盐菌株SR-26降低了NaCl对植物的有害作用。土壤接种后，R.azibense显着（p≤0.05）增强种子萌发（10％），根（19%）芽（23%）生物量，叶面积（18%），总叶绿素（21%），在添加40mMNaCl浓度的土壤中培养的普通P的类胡萝卜素含量（32％）。此外，菌株SR-26调节了相对叶片含水量(RLWC)，脯氨酸,总可溶性蛋白（TSP），和盐暴露植物的糖（TSS）。此外，R.azibense接种降低了氧化应激生物标志物的浓度；MDA(29%)，H2O2含量（24%），电解液泄漏(31%),当施用于40mMNaCl处理的植物时，膜稳定性（36％）和Na离子吸收（28％）。Further,R.azibense通过上调抗氧化防御反应来增加寻常型疟原虫的耐盐机制。总之,建议将合成EPS的耐盐R.azibenseSR-26作为最经济有效的选择，以提高豆科作物的产量，特别是在盐分挑战的土壤系统中。
