Frankia Populations in Soil and Root Nodules of Sympatrically Grown Alnus Taxa
Frankia Populations in Soil and Root Nodules of Sympatrically Grown Alnus Taxa
复制标题
土壤中的 Frankia 种群和同域生长的桤木类群根瘤
作者：
A. Pokharel;Babur S. Mirza;J. Dawson;D. Hahn
利用PCR和nifH基因序列分析方法，对土壤和同域生长的桤木根瘤中Frankia菌的遗传多样性进行了研究。Rep-PCR分析未培养的Frankia种群在根瘤的12 Alnus类群（n = 10个结节）共域生长在莫顿植物园附近的芝加哥揭示了相同的模式，从每个Alnus类群的结节，包括复制树相同的主机类群，和低的多样性整体只有三个配置文件检索。从9个分类群（Alnus incana subsp. incana、日本桤木Alnus japonica、日本桤木Alnus sp. tenuifolia，Alnus incana subsp.第二种在两个植物类群的所有根瘤中均有发现（A. rugosa，Alnus rhombifolia，Alnus mandshurica，Alnus maritima，Alnus serrulata）。印加亚种hirsuta和A.红毛藻变种第三种是所有Frankia种群在A.印加亚种皱纹变种美国。nifH基因片段的比较序列分析代表这三个配置文件分配这些frankiae不同的亚组内的桤木宿主感染组的结节。然而，这些序列中没有一个代表Frankiae检测土壤中确定的73个克隆从Frankia-specific nifH基因克隆库的序列分析。对生长在不同土壤上的选定桤木的结核种群的进一步分析表明，每种土壤的结核中存在不同的Frankia种群，这些种群在同一土壤的结核中显示出相同的序列，但植物分类群之间存在差异。这些结果表明，土壤环境条件和宿主植物基因型都有一个作用，在选择Frankia菌株的宿主植物根瘤形成，这种选择不仅仅是一个函数的丰富的Frankia菌株在土壤中。
The genetic diversity of Frankia populations in soil and in root nodules of sympatrically grown Alnus taxa was evaluated by rep-polymerase chain reaction (PCR) and nifH gene sequence analyses. Rep-PCR analyses of uncultured Frankia populations in root nodules of 12 Alnus taxa (n = 10 nodules each) growing sympatrically in the Morton Arboretum near Chicago revealed identical patterns for nodules from each Alnus taxon, including replicate trees of the same host taxon, and low diversity overall with only three profiles retrieved. One profile was retrieved from all nodules of nine taxa (Alnus incana subsp. incana, Alnus japonica, Alnus glutinosa, Alnus incana subsp. tenuifolia, Alnus incana subsp. rugosa, Alnus rhombifolia, Alnus mandshurica, Alnus maritima, and Alnus serrulata), the second was found in all nodules of two plant taxa (A. incana subsp. hirsuta and A. glutinosa var. pyramidalis), and the third was unique for all Frankia populations in nodules of A. incana subsp. rugosa var. americana. Comparative sequence analyses of nifH gene fragments in nodules representing these three profiles assigned these frankiae to different subgroups within the Alnus host infection group. None of these sequences, however, represented frankiae detectable in soil as determined by sequence analysis of 73 clones from a Frankia-specific nifH gene clone library. Additional analyses of nodule populations from selected alders growing on different soils demonstrated the presence of different Frankia populations in nodules for each soil, with populations showing identical sequences in nodules from the same soil, but differences between plant taxa. These results suggest that soil environmental conditions and host plant genotype both have a role in the selection of Frankia strains by a host plant for root nodule formation, and that this selection is not merely a function of the abundance of a Frankia strain in soil.