不同苜蓿根系分离菌株及合成菌群对苜蓿种子萌发的影响

Effects of different bacterial strains isolated from alfalfa roots and synthetic microbial communities on alfalfa seed germination

摘要:

植物益生根系微生物能够增强植物的养分吸收能力与抗逆能力，进而改善植物的生长状况。目的 筛选苜蓿根系优异的微生物资源。方法 以‘草原3号’杂花苜蓿为实验材料，以从苜蓿根系分离的8个功能菌株和由不同单菌株组成的8个合成微生物菌群(synthetic microbial communities, SynComs)为研究对象，分别在0、200、250 mmol/L NaCl胁迫条件下进行菌液浸种处理，测定发芽势(率)、胚根(芽)长及胚鲜重等指标，运用隶属函数法综合评价测试菌株和合成菌群的抗逆促生效能，探究根系分离菌株对苜蓿种子萌发的影响。结果 在无盐胁迫条件下，菌液浸种对苜蓿种子萌发无显著影响，但在盐胁迫下可显著增强苜蓿种子的萌发能力。在200 mmol/L和250 mmol/L NaCl胁迫下，MS8是提升种子萌发能力最强的单菌株；与无菌水浸种对照相比，经MS8菌液浸种后种子发芽势提升76.67%。经SynCom 1处理后的种子与CK相比，发芽率提升113.04%-405.41%，胚根长显著增加47.87%-56.67%，胚芽长显著增加19.13%-24.01%，胚鲜重显著增加157.64%-1 300.00%。结论 在200 mmol/L和250 mmol/L NaCl胁迫条件下，SynCom 1是提升种子萌发能力最强的合成菌群，且提升效果优于单菌株MS8。本研究为后续开发高效提升苜蓿耐盐性的专用功能菌剂提供了重要的理论基础和技术支撑。

Abstract:

Probiotic microbiota in roots can enhance nutrient uptake and stress tolerance, thereby improving plant growth.Objective To identify elite microbial resources from alfalfa roots.Methods We used eight functional bacterial strains isolated from the roots of Medicago sativa var. ‘Caoyuan No. 3’ and eight synthetic microbial communities (synthetic microbial communities, SynComs) composed of different strains for seed soaking treatments under 0, 200, and 250 mmol/L NaCl stress conditions. The germination potential (rate), radicle (embryonic shoot) length, and seed fresh weight were measured, and the effectiveness of the bacterial strains and SynComs in improving stress tolerance and growth was comprehensively evaluated via the membership function method. The effects of strains isolated from roots on alfalfa seed germination were thus evaluated.Results Under non-saline conditions, seed soaking had no significant impact on alfalfa seed germination. However, under salt stress, seed soaking significantly enhanced seed germination. Under 200 mmol/L and 250 mmol/L NaCl stress, MS8 was the most effective strain in promoting seed germination. Compared with the control treated with sterile water, MS8 treatment improved the germination potential by 76.67%. Compared with the control, the seeds treated with SynCom 1 exhibited increases of 113.04% to 405.41% in germination rate, significant increases of 47.87% to 56.67% in radicle length, significant increases of 19.13% to 24.01% in embryonic shoot length, and significant rises of 157.64% to 1 300.00% in fresh seed weight.Conclusion Under 200 mmol/L and 250 mmol/L NaCl stress, SynCom 1 was the most effective synthetic microbial community in enhancing seed germination, outperforming strain MS8. This study provides a theoretical foundation and technical support for the subsequent development of efficient functional bacterial agents to enhance the salt tolerance of alfalfa.