Microbial inoculation has been unequivocally established as an effective strategy for promoting plant growth and enhancing salinity tolerance. The objective of this work was to examine the influence of AMF (Funneliformis mosseae) inoculation, whether applied singly or together with PGPR (Bacillus mycoides and Sinorhizobium meliloti), on osmotic balance, ionic homeostasis, soil nutrient status, and enzyme activities in salt-stressed alfalfa (Medicago sativa L.). The results showed that salt stress significantly inhibited soil enzyme activities, reduced soil nutrient contents, and significantly increased the contents of osmolytes and Na+ in both leaves and roots of alfalfa. Additionally, the accumulation of Na+ in roots and leaves exhibited a significant negative correlation with soil nutrient contents (NH4+-N, NO3−-N, available phosphorus and available potassium) as well as with soil enzyme activities (sucrase and alkaline phosphatase). However, microbial inoculation significantly alleviated these adverse effects, mainly by increasing osmotic adjustment substances (e.g., proline), enhancing soil enzyme activities (e.g., urease), improving soil nutrient contents (e.g., soil organic matter), and promoting the uptake of K+ and Ca2+, thereby raising the K+/Na+ and Ca2+/Na+ ratios. Comprehensive analysis revealed that the co-inoculation treatments were superior to the single inoculations, with T7 (AMF + Rhizobium) exhibiting the best performance. This study provides a theoretical reference for the application of microbial inoculants to improve alfalfa performance under saline–alkali conditions.
Wenbo Xu, Hong-You Li, Tuo Yao· Agronomy· 0 citations
Salt stress is a prevalent abiotic stress worldwide, which markedly inhibits crop growth and triggers yield losses. In this study, salt-tolerant plant-growth-promoting rhizobacteria of Cerasus humilis—Bacillus pumilus and B. velezensis, which possess nitrogen-fixing, phosphate-solubilizing, and indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase-producing traits—were co-inoculated with Sinorhizobium meliloti. The effects of these bacterial combinations on alfalfa (Medicago sativa L.) were systematically evaluated during seed germination and plant growth under salt stress simulated using NaCl, Na2SO4, NaHCO3, and Na2CO3 at varying intensities. The results showed that under salt stress, inoculation significantly increased the seed germination rate by 11.33–41.33%. Pot experiments further revealed that inoculation significantly enhanced symbiotic nitrogen fixation efficiency in alfalfa and effectively maintained K+/Na+ homeostasis (K+ concentration increased by 4.23–125.34%, while Na+ concentration decreased by 7.15–102.09%). Concurrently, inoculation upregulated antioxidant enzyme activities and promoted the accumulation of non-enzymatic antioxidants, thereby significantly reducing reactive oxygen species levels. Moreover, inoculation substantially increased the content of osmoregulatory substances such as proline and soluble protein; proline accumulation surged more than fivefold (39.97–551.05%) compared with the non-inoculated control, effectively alleviating cellular dehydration. Through these multi-pathway regulations mediated by Bacillus sp. and S. meliloti, the inhibitory effect of salt stress on alfalfa growth was significantly mitigated, with dry weight increasing by 45.9–92.4%. Principal component analysis indicated that inoculation with the B. velezensis–S. meliloti microbial combination was the most promising strategy for promoting alfalfa growth and alleviating salt stress. The results provide a theoretical basis for developing microbial fertilizers and establishing alfalfa pastures in saline lands, thereby promoting their sustainable utilization.
Jie Bai, Tuo Yao, Wenbo Xu et al.· Agronomy· 0 citations
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