Background Soybean [ Glycine max (L) Merr.] is an annual leguminous crop serving as a source of food and feed, green manure, biodiesel and fiber. It is nodulated by diverse slow growing and fast growing rhizobia belonging to the genus Bradyrhizobium and Sinorhizobium , respectively. In Ethiopia, it has been cultivated since 1950s with lower grain yield history. Yield improvement efforts have been more concentrated on agronomic studies, inoculation of exotic Bradyrhizobium japonicum including TAL379 and/or fertilizer application. The results have usually been unsatisfactory and inconsistent. This study was initiated to identify promising indigenous soybean rhizobial inoculant that can enhance yield of the crop in the country. Methods Native soybean rhizobia, designated GMR for Glycine max rhizobia, were trapped using soybean (cv. Ethio-Yugoslavia) from soils collected across agro-ecologies of Ethiopia. They were screened for in vitro tolerance against physico-chemical stresses, plant growth promoting (PGP) traits and symbiotic performances at greenhouse and field levels. A reference B. japonicum (TAL379) was included in all experiments. A soybean plant growth promoting Achromobacter sp. was also included in field trials for co-inoculation. Quantitative data were assessed by analysis of variance (ANOVA) employing SAS computer software package version 9.3. Mean separations were undertaken using Duncan’s Multiple Range Test at p ≤ 0.05. Phenotypic variability of the test bacteria was undertaken using PAST4.03 Computer Software. Result GMR that produced acid and grew faster with larger colonies were identified as Sinorhizobium spp. and those which produced alkali and grew slowly with smaller colonies were identified as Bradyrhizobium spp. though further genetic analysis should be performed for verification and identification of their genus and species, respectively. Two Sinorhizobium spp. (GMR120C and GMR125B) profoundly nodulated different soybean cultivars under greenhouse conditions and significantly improved grain yield (p ≤ 0.05; maximum 3.98 tons ha −1 ) compared to 2.41, 2.82 and 2.69 recorded as maximum grain yield (tons ha −1 ) for TAL379 inoculation, positive control and negative control, respectively in field trials. Higher yield was recorded when GMR125B was co-inoculated with Achromobacter sp., but when GMR120C was inoculated singly. These GMR also showed efficient utilization of numerous substrates, some PGP traits and potential adaptation to various ecological stresses. Conclusion The two Sinorhizobium spp. (GMR120C and GMR125B) are promising soybean inoculants that can be used to enhance the productivity of the crop in the country.

中文翻译：

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接种本地共生有效的中华根瘤菌属。提高埃塞俄比亚的大豆 [Glycine max (L.) Merr.] 谷物产量

背景 大豆 [ Glycine max (L) Merr.] 是一年生豆科作物，用作食物和饲料、绿肥、生物柴油和纤维的来源。它由分别属于慢生根瘤菌和中华根瘤菌属的多种缓慢生长和快速生长的根瘤菌形成根瘤。在埃塞俄比亚，它自 1950 年代开始种植，粮食产量较低。提高产量的努力更多地集中在农艺研究、外来慢生根瘤菌（包括 TAL379）的接种和/或肥料施用上。结果通常是不令人满意和不一致的。发起这项研究是为了确定可以提高该国作物产量的有前途的本土大豆根瘤菌接种剂。方法 天然大豆根瘤菌，指定为甘氨酸最大根瘤菌的 GMR，使用大豆（cv. 埃塞俄比亚-南斯拉夫）来自埃塞俄比亚农业生态系统中收集的土壤。在温室和田间水平上筛选了它们对物理化学胁迫、植物生长促进 (PGP) 特性和共生性能的体外耐受性。所有实验中都包括参考 B. japonicum (TAL379)。一种促进大豆植物生长的无色杆菌属。还包括在共同接种的田间试验中。定量数据通过方差分析 (ANOVA) 评估，采用 SAS 计算机软件包 9.3 版。在 p ≤ 0.05 时使用 Duncan 的多范围检验进行平均分离。使用 PAST4.03 计算机软件进行测试细菌的表型变异。结果产酸、菌落较大、生长较快的GMR被鉴定为中华根瘤菌属。产碱且菌落生长缓慢的菌落被鉴定为慢生根瘤菌属（Bradyrhizobium spp）。尽管应进行进一步的遗传分析以分别验证和鉴定它们的属和种。两个中华根瘤菌属。(GMR120C 和 GMR125B) 在温室条件下对不同的大豆品种进行了深刻的根瘤处理，并显着提高了谷物产量（p ≤ 0.05；最大 3.98 吨公顷 -1 ），而 TAL379 的最大谷物产量（吨公顷 -1 ）记录为 2.41、2.82 和 2.69分别在田间试验中接种、阳性对照和阴性对照。当 GMR125B 与无色杆菌共接种时记录到更高的产量，但当 GMR120C 单独接种时。这些 GMR 还显示出对大量底物的有效利用，一些 PGP 特性和对各种生态压力的潜在适应。结论 两种中华根瘤菌属。（GMR120C 和 GMR125B）是很有前途的大豆接种剂，可用于提高该国作物的生产力。