Seeds are involved in the transmission of microorganisms from one plant generation to the next, acting as initial inoculum for the plant microbiome, therefore provide a key source of variability in plants. This study aimed to characterize the seed bacteria and fungi communities in Elymus nutans, a dominant perennial grass growing in the Qinghai Tibet Plateau (QTP) and explore the effects of plant growth location on the seed microbiome. Seeds were collected from plants growing in four locations in the QTP. The seed microbial community was examined by Illumina MiSeq sequencing of DNA extracted from the surface sterilized seeds. The seed bacterial community was dominated by the bacteria phylum Proteobacteria (98%) and fungal phyla Ascomycota (83%) and Basidiomycota (15%). At the lower taxonomic level, the bacterial genus Pseudomonas dominated in all four locations with an average relative abundance of 83% whereas the fungal genera that dominated the seed microbiome was diverse, the most prominent being Epichloë, Pyrenophora, Mycosphaerella and Bullera. Ecologically important bacterial family Nitrosomonadaceae (nitrifiers) and fungal phylum Glomeromycota (arbuscular mycorrhizal fungi) were detected in this study for the first time as seed endophytes. The Elymus nutans seed bacterial community was not impacted by the plant growth location, in contrast, the seed fungal community varied significantly in four locations. The seeds of Elymus nutans host diverse endophytic bacteria and fungi. Unlike the bacteria, the host plant selection of seed fungal endophytes was observed to have been affected by plant growth location. Positive and negative associations in the Elymus nutans seed microbiome were observed.

中文翻译：

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青藏高原四地生长的椴树种子内生细菌和真菌的多样性

种子参与微生物从一个植物世代到下一个世代的传播，作为植物微生物组的初始接种物，因此提供了植物变异的关键来源。本研究旨在表征生长在青藏高原 (QTP) 的优势多年生牧草 Elymus nutans 的种子细菌和真菌群落，并探讨植物生长位置对种子微生物组的影响。从生长在 QTP 的四个地点的植物中收集种子。通过 Illumina MiSeq 测序从表面灭菌的种子中提取的 DNA 来检查种子微生物群落。种子细菌群落以细菌门 Proteobacteria (98%) 和真菌门子囊菌门 (83%) 和担子菌门 (15%) 为主。在较低的分类层次上，细菌属 Pseudomonas 在所有四个位置占主导地位，平均相对丰度为 83%，而在种子微生物组中占主导地位的真菌属多种多样，最突出的是 Epichloë、Pyrenophora、Mycosphaerella 和 Bullera。本研究首次检测到具有重要生态意义的细菌家族亚硝化单胞菌科（硝化菌）和真菌门球藻（丛枝菌根真菌）作为种子内生菌。Elymus nutans 种子细菌群落不受植物生长位置的影响，相反，种子真菌群落在四个位置变化显着。Elymus nutans 的种子承载着多种内生细菌和真菌。与细菌不同，观察到种子真菌内生菌的宿主植物选择受到植物生长位置的影响。