Little is known about the soil factors influencing root-associated fungal communities in Orchidaceae. Limited evidence suggests that soil nutrients may modulate the association with orchid mycorrhizal fungi (OMF), but their influence on non-mycorrhizal fungi remains unexplored. To study how nutrient availability affects mycorrhizal and non-mycorrhizal fungi associated with the orchid Bipinnula fimbriata, we conducted a metagenomic investigation within a large population with variable soil conditions. Additionally, we tested the effect of phosphorus (P) addition on fungal communities and mycorrhizal colonization. Soil P negatively correlated with the abundance of OMF, but not with the abundance of non-mycorrhizal fungi. After fertilization, increments in soil P negatively affected mycorrhizal colonization; however, they had no effect on OMF richness or composition. The abundance and richness of pathotrophs were negatively related to mycorrhizal colonization and then, after fertilization, the decrease in mycorrhizal colonization correlated with an increase in pathogen richness. Our results suggest that OMF are affected by soil conditions differently from non-mycorrhizal fungi. B. fimbriata responds to fertilization by altering mycorrhizal colonization rather than by switching OMF partners in the short term, and the influence of nutrients on OMF is coupled with indirect effects on the whole fungal community, and potentially on plant's health.

中文翻译：

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土壤P减少了菌根定植，而有利于真菌病原体：Bipinnula（兰科）的观察和实验证据。

关于影响兰科根相关真菌群落的土壤因子知之甚少。有限的证据表明，土壤养分可以调节与兰花菌根真菌（OMF）的关联，但是它们对非菌根真菌的影响尚待探索。研究养分的可获得性如何影响与兰花Bipinnula fimbriata相关的菌根和非菌根真菌，我们在具有可变土壤条件的大量人群中进行了宏基因组研究。此外，我们测试了添加磷（P）对真菌群落和菌根定植的影响。土壤P与OMF的含量呈负相关，但与非菌根真菌的含量则不相关。施肥后，土壤P的增加会对菌根定植产生负面影响；但是，它们对OMF的丰富度或组成没有影响。病菌的丰度和丰富度与菌根定植呈负相关，然后在受精后，菌根定植的减少与病原体丰富度的增加有关。我们的结果表明，OMF受土壤条件的影响不同于非菌根真菌。炭疽芽孢杆菌 通过改变菌根定植而不是在短期内转换OMF配偶来对施肥做出反应，养分对OMF的影响与对整个真菌群落的间接影响以及对植物健康的间接影响。