Ecology, Evolution, and Behavior Graduate Program, University of Minnesota, St. Paul, Minnesota 55108.
Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota 55108.
Mycologia. 2021 Sep-Oct;113(5):891-901. doi: 10.1080/00275514.2021.1921525. Epub 2021 Jul 8.
is among the best-known examples of an ectomycorrhizal (ECM) fungal genus that demonstrates a high degree of host specificity. Currently recognized host genera of include , and , which all belong to the pinoid clade of the family Pinaceae. Intriguingly, sporocarps have been sporadically collected in forests in which known hosts from these genera are locally absent. To determine the capacity of to associate with alternative hosts in both the pinoid and abietoid clades of Pinaceae, we examined the host associations of two species ( and ) through field-based root tip sampling and seedling bioassays. Root tip collections underneath sporocarps were molecularly identified (fungi: nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 [ITS barcode]; plant: L) to assess the association with multiple hosts. The bioassays contained both single- and two-species treatments, including a primary ( or ) and a secondary (, or ) host. For the bioassay, an additional treatment in which the primary host was removed after 8 mo was included to assess the effect of primary host presence on longer-term ECM colonization. The field-based results confirmed that fungi were able to associate with and hosts, representing novel host genera for this genus. In the bioassays, colonization on the primary hosts was detected in both single- and two-species treatments, but no colonization was present when and hosts were grown alone. Removal of a primary host had no effect on percent ECM colonization, suggesting that primary hosts are not necessary for sustaining colonization once they are successfully established on secondary hosts. Collectively, our results indicate that host specificity is more flexible in this genus than previously acknowledged and help to explain the presence of in forests where recognized hosts are not present.
是外生菌根（ectomycorrhizal，ECM）真菌属中最为人熟知的例子之一，表现出高度的宿主特异性。目前已识别的宿主属包括、和，它们都属于松科Pinaceae 家族的针形分支。有趣的是，在这些已知宿主局部缺失的森林中，偶尔会收集到的子实体。为了确定在 Pinaceae 的针形和松形分支中与替代宿主建立联系的能力，我们通过基于现场的根尖采样和幼苗生物测定，检查了两个物种（和）的宿主关联。在子实体下采集的根尖通过分子鉴定（真菌：核 rDNA 内转录间隔区 ITS1-5.8S-ITS2[ITS 条形码]；植物：L）来评估与多个宿主的关联。生物测定包含单种和两种物种处理，包括主要（或）和次要（、或）宿主。对于生物测定，还包括一种额外的处理，即在 8 个月后去除主要宿主，以评估主要宿主存在对长期 ECM 定殖的影响。基于现场的结果证实，真菌能够与和宿主建立联系，代表了该属的新宿主属。在生物测定中，在单种和两种物种处理中均检测到对主要宿主的定殖，但当单独种植和宿主时则不存在定殖。去除主要宿主对 ECM 定殖率没有影响，这表明一旦成功建立在次要宿主上，主要宿主对于维持的定殖并非必需。总的来说，我们的结果表明，该属的宿主特异性比以前认为的更为灵活，并有助于解释在没有公认宿主的森林中存在的原因。
