Abstract Biological nitrogen fixation (BNF) resulting from symbiosis between legumes and rhizobia helps improve soil N fertility. Inoculated soils with specific strains of rhizobia may increase potential BNF in legumes, but the efficacy of these rhizobia in promoting BNF may be limited by competition from resident rhizobia already present in soils. We evaluated the ability of four strains to nodulate and increase BNF in Vicia villosa (hairy vetch) as individual and combined inoculants in a laboratory experiment. Plants were inoculated with a single rhizobia strain or equal ratios of 2–4 strains and grown under controlled conditions. After 46 d, entire plant shoots were harvested and analyzed for biomass, N content, nodule number, and nodule mass. Nodule occupancy was assessed using DNA fingerprinting of characteristic rhizobia genes. Negative-N and positive-N control plants averaged 6.3 and 83.2 mg total shoot N, respectively. Average total shoot N of inoculated vetch treatments was between that of uninoculated control treatments. Nodule number, total nodule mass, and BNF efficiency (total shoot N mass per total nodule mass) did not significantly differ between individual strains. Neither BNF efficiency nor nodule number were indicative of competitive ability for nodule occupancy. The rhizobia did not display any consistent synergistic or antagonistic effect on BNF when combined in inoculants and nodule occupancy did not favor any specific strain. Because vetch inoculated with local Rlv strains produced similar amounts of N as uninoculated plants fertilized with N, our work suggests that rhizobia sourced from local soils may produce sufficient BNF with vetch.

中文翻译：

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豆科植物根瘤菌菌株组合对Vicia villosa结瘤和生物固氮的影响

摘要 豆科植物和根瘤菌共生产生的生物固氮（BNF）有助于提高土壤氮肥力。接种特定根瘤菌菌株的土壤可能会增加豆类中潜在的 BNF，但这些根瘤菌在促进 BNF 方面的功效可能会受到来自土壤中已经存在的常驻根瘤菌的竞争的限制。我们在实验室实验中评估了四种菌株在 Vicia villosa（多毛野豌豆）中作为单独和组合接种剂的结瘤和增加 BNF 的能力。植物接种单一根瘤菌菌株或等比例的 2-4 菌株，并在受控条件下生长。46 天后，收获整株植物的芽并分析生物量、氮含量、根瘤数和根瘤质量。使用特征根瘤菌基因的 DNA 指纹图谱评估根瘤占有率。负氮和正氮对照植物的平均总芽氮分别为 6.3 和 83.2 毫克。接种的紫云英处理的平均总枝条 N 介于未接种的对照处理之间。根瘤数、根瘤总质量和 BNF 效率（总根瘤 N 质量/根瘤总质量）在各个菌株之间没有显着差异。BNF 效率和结核数量都不能表明结核占有率的竞争能力。当与接种剂组合时，根瘤菌对 BNF 没有表现出任何一致的协同或拮抗作用，并且根瘤占有率不利于任何特定菌株。由于用当地 Rlv 菌株接种的野豌豆产生的 N 量与未接种的用 N 施肥的植物相似，因此我们的工作表明，源自当地土壤的根瘤菌可能会用野豌豆产生足够的 BNF。