We studied mycobionts from advanced seedlings and adult mycorrhizal roots of the terrestrial orchid Arundina graminifolia. Fungi were isolated, identified by ITS sequencing, and tested for their impact on seed germination, protocorm formation, and development of advanced seedlings (emergence of first leaf) in vitro. Among the six fungal species isolated, four were not standard orchid mycorrhizal fungi (Fusarium solani, Cylindrocarpon sp., Acremonium sp., and Phlebiopsis flavidoalba) and did not support germination beyond imbibition and greening of the seeds during a span of 35 days. Over the same time, one Tulasnella species isolated from adult mycorrhiza allowed protocorm formation but not further development. However, another Tulasnella species isolated from advanced seedlings facilitated development to the advanced seedling stage. Our results support (i) the inability of occasional orchid root colonizers to support late seed germination, and (ii) the growing literature showing that fungal associates can change over orchid development. Functionally, we show that mycorrhizal taxa isolated from advanced seedlings can be more efficient than those from adults in supporting germination in some species, leading to recommendations for ex situ orchid conservation.

中文翻译：

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成年兰花的根真菌是否是发芽的最佳共生体？案例研究。

我们研究了来自陆地兰花Arundina graminifolia的先进幼苗和成年菌根的真菌根。分离真菌，通过ITS测序鉴定，并测试它们对种子萌发，原球茎形成和高级幼苗发育（第一片叶子出现）的影响。在分离的6种真菌中，有4种不是标准的兰花菌根真菌（Fusarium solani，Cylindrocarpon sp。，Acremonium sp。和Phlebiopsis flavidoalba），并且在35天的时间里不支持种子吸收和绿化之外的发芽。在同一时间，一棵Tulasnella从成年菌根分离出的物种允许原球茎形成，但不能进一步发育。然而，从高级幼苗中分离出的另一种风铃草属物种则促进了向高级幼苗阶段的发展。我们的研究结果支持（i）偶然的兰花根部定植者不能支持后期种子萌发，以及（ii）越来越多的文献表明真菌伴生物可以随着兰花的发育而变化。从功能上讲，我们表明，从高级幼苗中分离出的菌根类群在某些物种中支持萌发方面可能比成年的更为有效，从而为异地保护兰花提供了建议。