Kretzer A M, Bidartondo M I, Grubisha L C, Spatafora J W, Szaro T M, Bruns T D
Oregon State University, Department of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, Oregon 97331-2902 USA;
Am J Bot. 2000 Dec;87(12):1778-82.
We have sampled the mycorrhizal roots of 76 snow plants (Sarcodes sanguinea, Monotropoideae, Ericaceae) in two areas of the Sierra Nevada of California that are ∼180 km apart. To identify the fungal symbionts associated with these plants, we first analyzed restriction fragment length polymorphisms (RFLPs) of the internal transcribed spacer region (ITS) of the fungal nuclear ribosomal repeat. Fungal ITS-RFLPs were successfully produced from 57 of the 76 plants sampled, and all symbionts shared the same DNA fragment pattern. The morphology of S. sanguinea mycorrhizae was consistent with that expected from a Rhizopogon species in section Amylopogon. To confirm and refine this identification, a total of six fungal ITS sequences were determined from S. sanguinea mycorrhizae. These sequences were analyzed together with eight existing and eight newly determined ITS sequences from Rhizopogon section Amylopogon. The newly determined sequences include an ITS sequence from the fungal symbiont of pine drops (Pterospora andromedea, Monotropoideae, Ericaceae), a plant that was previously reported to be exclusively associated with the Rhizopogon subcaerulescens group. When these sequences were analyzed together, the Sarcodes symbionts grouped tightly with several collections of R. ellenae including the holotype, one collection of R. idahoensis, and one collection of R. semireticulatus. A different lineage comprised collections of R. subgelatinosus, R. subcaerulescens, another collection of R. semireticulatus, and the Pterospora symbiont. We conclude that S. sanguinea associates exclusively with a single species in the R. ellenae species complex throughout our sampling range. These results indicate a much higher level of specificity in S. sanguinea than was previously reported and confirm the emerging pattern that nonphotosynthetic, monotropoid plants generally associate very specifically with a narrow range of ectomycorrhizal fungi.
我们在加利福尼亚内华达山脉两个相距约180公里的区域采集了76株鹿蹄草（鹿蹄草属，水晶兰亚科，杜鹃花科）的菌根。为了鉴定与这些植物相关的真菌共生体，我们首先分析了真菌核糖体重复序列内部转录间隔区（ITS）的限制性片段长度多态性（RFLP）。从76株采样植物中的57株成功获得了真菌ITS-RFLP，并且所有共生体都具有相同的DNA片段模式。鹿蹄草菌根的形态与淀粉质根须组的须腹菌属物种预期的形态一致。为了确认并完善这一鉴定结果，我们从鹿蹄草菌根中总共测定了6条真菌ITS序列。这些序列与来自须腹菌属淀粉质根须组的8条现有ITS序列以及8条新测定的ITS序列一起进行了分析。新测定的序列包括来自松下兰（松下兰属，水晶兰亚科，杜鹃花科）真菌共生体的一条ITS序列，松下兰是一种先前报道仅与亚蓝灰须腹菌组相关的植物。当将这些序列一起分析时，鹿蹄草共生体与包括模式标本在内的几株埃氏须腹菌、一株爱达荷须腹菌和一株半网纹须腹菌紧密聚为一类。另一个谱系包括凝胶质须腹菌、亚蓝灰须腹菌的另一个样本、半网纹须腹菌的另一个样本以及松下兰共生体。我们得出结论，在我们的整个采样范围内，鹿蹄草仅与埃氏须腹菌种复合体中的单个物种相关联。这些结果表明鹿蹄草的专一性程度比先前报道的要高得多，并证实了新出现的数据模式，即非光合的水晶兰类植物通常与范围狭窄的外生菌根真菌非常专一性地相关联。
