Despite the strong ecological importance of ectomycorrhizal (ECM) fungi, their vertical distribution remains poorly understood. To our knowledge, ECM structures associated with trees have never been reported in depths below 2 meters. In this study, fine roots and ECM root tips were sampled down to 4-m depth during the digging of two independent pits differing by their water availability. A meta-barcoding approach based on Illumina sequencing of internal transcribed spacers (ITS1 and ITS2) was carried out on DNA extracted from root samples (fine roots and ECM root tips separately). ECM fungi dominated the root-associated fungal community, with more than 90% of sequences assigned to the genus Pisolithus. The morphological and barcoding results demonstrated, for the first time, the presence of ECM symbiosis down to 4-m. The molecular diversity of Pisolithus spp. was strongly dependent on depth, with soil pH and soil water content as primary drivers of the Pisolithus spp. structure. Altogether, our results highlight the importance to consider the ECM symbiosis in deep soil layers to improve our understanding of fine roots functioning in tropical soils.

中文翻译：

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外生菌根能走多深？以巴西桉树人工林中低至4米的Pisolithus为例。

尽管外生菌根（ECM）真菌具有很强的生态重要性，但对其垂直分布仍知之甚少。据我们所知，与树木相关的ECM结构从未在2米以下的深度报道过。在这项研究中，在挖两个独立坑的过程中，细根和ECM根尖被采样到4米深，这些坑因水的可利用性而不同。基于Illumina测序的内部转录间隔子（ITS1和ITS2）的元条形码方法是从根样品（分别为细根和ECM根尖）提取的DNA上进行的。ECM真菌主导了根相关真菌群落，其中超过90％的序列分配给了Pisolithus属。。形态学和条形码结果首次证明了ECM共生的存在（低至4-m）。Pisolithus spp的分子多样性。土壤的pH值和土壤含水量是Pisolithus spp的主要驱动力，在很大程度上取决于深度。结构体。总之，我们的结果突出了考虑深层土壤中ECM共生的重要性，以增进我们对热带土壤中细根功能的了解。