Arbuscular mycorrhizal fungi (AMF) play an important role in crop productivity, but their response to different fertilization regimes is variable. Understanding the mechanisms governing mycorrhizal responses under various fertilization regimes is key to maximizing the mycorrhizal contribution to ecosystem functioning. Indigenous AMF communities and soil were collected from long-term field experiments with various fertilization regimes. A greenhouse bioassay was carried out to identify the key regulators of the mycorrhizal response to inorganic and organic fertilization. Different fertilization regimes generated continuous gradients for most soil properties and a full spectrum of mycorrhizal phenotypes. Mycorrhizal growth response (MGR) in particular showed complex shifts from positive to neutral to negative, while mycorrhizal phosphorus (P) response was consistently positive and mycorrhizal nitrogen (N) response was consistently negative in fertilized treatments. Soil available P and available N to P (N:P) ratio appeared to be key soil predictors of the mycorrhizal response. Also, the nutrient status of non-mycorrhizal (NM) plants, namely shoot N concentration, shoot P concentration and shoot N:P ratio, were plant predictors of mycorrhizal response. A positive MGR occurred when NM plants were P-limited, and neutral and negative MGR occurred when NM plants were N-limited or co-limited by N and P. Further, the thresholds of soil available P (c. 13 mg kg), NM shoot N concentration (c. 14 g kg), NM shoot P concentration (c. 0.7 g kg) and NM shoot N:P ratio (c. 18), respectively, were estimated to predict mycorrhizal response. We conclude that the relative availability of N and P in soil and NM plants are good predictors of mycorrhizal response in different fertilization regimes. The existing nutrient thresholds combining soil and plant allowed more accurate prediction of mycorrhizal response and this has important implications for optimizing the mycorrhizal association in some important crops by managing soil nutrients.

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确定多种受精方案下菌根反应的预测因子

丛枝菌根真菌（AMF）在作物生产力中发挥着重要作用，但它们对不同施肥方式的反应各不相同。了解各种施肥方案下控制菌根反应的机制是最大限度地发挥菌根对生态系统功能的贡献的关键。土著 AMF 群落和土壤是通过各种施肥方案的长期田间实验收集的。进行了温室生物测定，以确定菌根对无机和有机肥料反应的关键调节因子。不同的施肥方案对大多数土壤特性和全谱菌根表型产生连续梯度。菌根生长反应（MGR）尤其表现出从阳性到中性再到阴性的复杂转变，而在受精处理中，菌根磷（P）反应始终为阳性，而菌根氮（N）反应始终为阴性。土壤有效磷和有效氮与磷 (N:P) 的比率似乎是菌根反应的关键土壤预测因子。此外，非菌根 (NM) 植物的营养状况，即地上部 N 浓度、地上部 P 浓度和地上部 N:P 比率，是菌根反应的植物预测因子。当 NM 植物受到 P 限制时，会出现正 MGR；当 NM 植物受到 N 限制或 N 和 P 共同限制时，会出现中性和负 MGR。此外，土壤有效磷的阈值（约 13 mg kg），分别估计 NM 芽 N 浓度（约 14 g kg）、NM 芽 P 浓度（约 0.7 g kg）和 NM 芽 N:P 比率（约 18）来预测菌根反应。我们的结论是，土壤和 NM 植物中 N 和 P 的相对有效性是不同施肥方案中菌根反应的良好预测因子。结合土壤和植物的现有养分阈值可以更准确地预测菌根反应，这对于通过管理土壤养分来优化一些重要作物的菌根关联具有重要意义。