Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Mycorrhiza. 2019 Oct;29(5):541-547. doi: 10.1007/s00572-019-00907-0. Epub 2019 Jul 16.
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.
我们研究了陆生兰花 Arundina graminifolia 的幼苗和成熟共生根系的共生真菌。通过 ITS 测序对真菌进行了分离、鉴定，并测试了它们对种子萌发、原球茎形成和幼苗（第一片叶子的出现）在体外发育的影响。在所分离的六种真菌中，有四种不是标准的兰花共生真菌（茄病镰刀菌、旋孢腔菌、节菱孢霉和黄白栓菌），在 35 天的时间内，它们不能支持种子萌发超过吸胀和变绿。在此期间，从成熟共生体中分离出的一种 Tulasnella 种允许原球茎形成，但不能进一步发育。然而，从幼苗中分离出的另一种 Tulasnella 种促进了幼苗发育到高级幼苗阶段。我们的结果支持：（i）偶尔的兰花根定殖者不能支持后期种子萌发的能力；（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。在功能上，我们表明，与从成体中分离出的共生真菌相比，从幼苗中分离出的共生真菌在某些物种中支持种子萌发的效率更高，这为兰花的就地保护提供了建议。
