A Collection of 360 isolates of Bradyrhizobium japonicum was developed from soybean (Glycine max [L.] Merrill) nodules taken from 18 locations in Delaware. The isolates were characterized serologically with an enzyme-linked immunosorbent assay, morphologically by colony type on yeast extract-mannitol agar, and for production of rhizobitoxine symptoms with soybean plants. These analyses revealed 12 and 3 groups based on serology and morphology, respectively. The more common identifiable isolates were in serogroups 94, 6, 122, and 76. Nearly 33% of the isolates were rated nonreactive with all of the antisera tested. Overall, 18% of the isolates produced rhizobitoxine symptoms, and these were associated with five known serogroups (31, 46, 76, 94, and 130) and the nonreactive grouping, but with only one colony type. A subsample of 92 isolates was rated for N2-fixing ability in the greenhouse and for hydrogenase phenotype in the laboratory. The nitrogen content of plant shoots was strongly and comparably related to both the serological and morphological groupings. Rhizobitoxine and hydrogenase phenotypes were relatively poor predictors of symbiotic effectiveness. Among the serologically reactive isolates, those in serogroups 38-115, 122, and 110 fixed the most N2, whereas one colony type (that containing isolates producing rhizobitoxine) was clearly inferior to the remaining two morphological groupings. Isolates displaying hydrogenase activity (approximately 15% of the isolates tested) correlated with three serologically reactive groupings (serogroups 110 and 122 and a 122/123 cross-reactive group) and two colony types, none of which coincided with groupings containing bradyrhizobia rated positive for rhizobitoxine production.
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机译:从特拉华州18个地点采集的大豆(Glycine max [L.] Merrill)根瘤中提取了360种日本根瘤菌。通过酶联免疫吸附测定对分离株进行血清学鉴定,在酵母提取物-甘露醇琼脂上按菌落类型进行形态学鉴定,并用大豆植物产生根除毒素的症状。这些分析分别显示了基于血清学和形态的12和3组。更常见的可识别分离株是血清群94、6、122和76。近33%的分离株在所有测试的抗血清中均被定为非反应性。总体而言,有18%的分离株产生了根除毒素的症状,这些症状与5个已知的血清群(31、46、76、94和130)和非反应性群相关,但只有一种菌落类型。评估了92个分离物的子样本在温室中的N2固定能力和实验室中的氢化酶表型。植物芽中的氮含量与血清学和形态学分组均密切相关。根瘤菌毒素和氢化酶表型是共生功效相对较差的预测指标。在具有血清学反应活性的分离株中,血清群38-115、122和110中的N2固定最多,而一种菌落类型(含有产生根瘤菌毒素的分离株)明显次于其余两个形态学分组。表现出加氢酶活性的分离株(约占测试分离株的15%)与三个血清学反应性组(血清组110和122和122/123交叉反应组)和两种菌落类型相关,这些菌落类型均与含有定为根硫ox素的生产。
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