Several species of the family Orchidaceae have limited distribution and small populations, in which the probability of extinction is much higher than in broadly distributed species. As orchid seeds are very small and lack energy reserves, they require association with compatible mycorrhizal fungi that provide nutrients and carbon needed for germination and early development. Therefore, identification of putative orchid mycorrhizal partners is essential for the design of conservation strategies for these species. We investigated the mycorrhizal associations of two endangered rare species of orchids, Bipinnula apinnula and B. volckmannii, and compared our results with the mycorrhizal associations of two broadly distributed species of Bipinnula. We isolated mycorrhizal fungi and directly amplified DNA from colonized root segments and found an extremely low diversity of mycorrhizal fungi. The rarefaction curves of rare species populations saturated at a single OTU, showing a highly specialized association and considerably lower diversity than the other two species of Bipinnula. Nevertheless, symbiotic germination experiments with fungal strains of this specific fungal OTU only reached the stage of seed coat rupture in both orchid species, without formation of protocorms. Our results suggest that seeds may require additional treatment for successful germination and that fungal partners isolated from adult plants may not be the same that support the germination of seeds. Further studies are needed to improve germination of thiese orchid species and to contribute to their conservation.

中文翻译：

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智利中部濒危珍稀兰花Bipinnula volckmannii和B. apinnula的菌根多样性低

兰科的几种物种分布有限且种群较少，其中灭绝的可能性比广泛分布的物种高得多。由于兰花种子非常小且缺乏能量储备，因此它们需要与相容的菌根真菌结合使用，该真菌可提供发芽和早期发育所需的营养和碳。因此，鉴定推定的兰花菌根伴侣对于这些物种的保护策略设计至关重要。我们调查了两种濒危珍稀兰花Bipinnula apinnula和B. volckmannii的菌根协会，并将我们的结果与Bipinnula的两种广泛分布物种的菌根协会进行了比较。。我们分离了菌根真菌，并直接从定殖的根段扩增了DNA，发现菌根真菌的多样性极低。与Bipinnula的其他两个物种相比，在一个OTU处饱和的稀有物种种群的稀疏曲线显示出高度专业化的关联性和较低的多样性。然而，使用该特定真菌OTU的真菌菌株进行的共生发芽实验仅在两种兰花物种中都达到了种皮破裂的阶段，而没有形成原球茎。我们的结果表明，种子可能需要额外的处理才能成功发芽，而从成年植物中分离出来的真菌伴侣可能与支持种子发芽的种子不同。需要进一步的研究来改善噻兰属兰花的发芽，并为它们的保护做出贡献。