Department of Mycorrhizal Symbioses, Institute of Botany, Czech Academy of Sciences, Lesní 322, Průhonice, 252 43, Czechia.
Department of Taxonomy, Institute of Botany, Czech Academy of Sciences, Zámek 1, Průhonice, 252 43, Czechia.
Mycorrhiza. 2023 Mar;33(1-2):69-86. doi: 10.1007/s00572-023-01101-z. Epub 2023 Jan 26.
Most of our knowledge on the ericoid mycorrhizal (ErM) symbiosis comes from temperate heathlands characterized by acidic peaty soils and many experiments with a few ascomycetous fungi. However, ericaceous plants thrive in many other ecosystems and in temperate coniferous forests, their seedlings often prosper on decomposing wood. While wood is typically exploited by basidiomycetous ectomycorrhizal (EcM) and saprobic fungi, the role of ErM fungi (ErMF) is much less clear. We explored the cultivable mycobiota of surface sterilized hair roots of Vaccinium spp. growing on decomposing wood in two coniferous forests in Mid-Norway (Scandinavia) and Northern Bohemia (Central Europe). Obtained isolates were identified using molecular tools and their symbiotic potential was tested in vitro. While the detected community lacked the archetypal ErMF Hyaloscypha hepaticicola and the incidence of dark septate endophytes and EcM fungi was negligible, it comprised other frequent asexual ascomycetous ErMF, namely H. variabilis and Oidiodendron maius, together with several isolates displaying affinities to sexual saprobic H. daedaleae and H. fuckelii. Ascomycete-suppressing media revealed representatives of the saprobic basidiomycetous genera Coprinellus, Gymnopilus, Mycena (Agaricales), and Hypochnicium (Polyporales). In the resyntheses, the tested basidiomycetes occasionally penetrated the rhizodermal cells of their hosts but never formed ericoid mycorrhizae and in many cases overgrew and killed the inoculated seedlings. In contrast, a representative of the H. daedaleae/H. fuckelii-related isolates repeatedly formed what morphologically appears as the ErM symbiosis and supported host's growth. In conclusion, while basidiomycetous saprobic fungi have a potential to colonize healthy-looking ericaceous hair roots, the mode(-s) of their functioning remain obscure. For the first time, a lineage in Hyaloscypha s. str. (corresponding to the former Hymenoscyphus ericae aggregate) where sexual saprobes are intermingled with root symbionts has been revealed, shedding new light on the ecology and evolution of these prominent ascomycetous ErMF.
我们对共生菌（ErM）共生关系的大部分了解来自于以酸性泥炭土壤为特征的温带石南荒原，并且许多实验都是用少数几种子囊菌进行的。然而，石南科植物在许多其他生态系统和温带针叶林中茁壮成长，其幼苗通常在分解的木材上繁茂生长。虽然木材通常是由担子菌外生菌根（EcM）和腐生真菌利用的，但共生菌（ErMF）的作用却不太清楚。我们探索了在挪威中部（斯堪的纳维亚）和北波希米亚（中欧）的两片针叶林中，生长在分解木材上的 Vaccinium spp.的表面消毒根毛的可培养真菌群。使用分子工具鉴定获得的分离株，并在体外测试其共生潜能。虽然检测到的群落缺乏典型的共生菌 Hyaloscypha hepaticicola 和深色隔丝内生真菌的发病率可以忽略不计，但它包含了其他常见的无性子囊菌 ErMF，即 H. variabilis 和 Oidiodendron maius，以及几个与有性腐生菌 H. daedaleae 和 H. fuckelii 亲缘关系密切的分离株。抑制子囊菌的培养基显示出腐生担子菌属 Coprinellus、Gymnopilus、Mycena（伞菌目）和 Hypochnicium（多孔菌目）的代表。在重新合成中，测试的担子菌偶尔会穿透其宿主的根皮层细胞，但从未形成共生菌，并且在许多情况下会过度生长并杀死接种的幼苗。相比之下，H. daedaleae/H. fuckelii 相关分离株的代表多次形成形态上似乎是共生菌共生的形态，并支持宿主的生长。总之，虽然担子菌腐生真菌有可能定殖外观健康的石南科毛发根，但它们的作用模式仍然不清楚。首次揭示了 Hyaloscypha s. str.（对应于前 Hymenoscyphus ericae 聚集体）中的一个谱系，其中有性腐生菌与根共生体混在一起，这为这些突出的子囊菌共生菌的生态学和进化提供了新的认识。
