Table_1_Interactions between halotolerant nitrogen-fixing bacteria and arbuscular mycorrhizal fungi under saline stress.xlsx

Background and aimsSoil salinity negatively affects crop development. Halotolerant nitrogen-fixing bacteria (HNFB) and arbuscular mycorrhizal fungi (AMF) are essential microorganisms that enhance crop nutrient availability and salt tolerance in saline soils. Studying the impact of HNFB on AMF communities and using HNFB in biofertilizers can help in selecting the optimal HNFB-AMF combinations to improve crop productivity in saline soils. MethodsWe established three experimental groups comprising apple plants treated with low-nitrogen (0 mg N/kg, N0), normal-nitrogen (200 mg N/kg, N1), and high-nitrogen (300 mg N/kg, N2) fertilizer under salt stress without bacteria (CK, with the addition of 1,500 mL sterile water +2 g sterile diatomite), or with bacteria [BIO, with the addition of 1,500 mL sterile water +2 g mixed bacterial preparation (including Bacillus subtilis HG-15 and Bacillus velezensis JC-K3)]. ResultsHNFB inoculation significantly increased microbial biomass and the relative abundance of beta-glucosidase-related genes in the rhizosphere soil under identical nitrogen application levels (p < 0.05). High-nitrogen treatment significantly reduced AMF diversity and the relative abundance of beta-glucosidase, acid phosphatase, and urea-related genes. A two-way analysis of variance showed that combined nitrogen application and HNFB treatment could significantly affect soil physicochemical properties and rhizosphere AMF abundance (p < 0.05). Specifically, HNFB application resulted in a significantly higher relative abundance of Glomus-MO-G17-VTX00114 compared to that in the CK group at equal nitrogen levels. ConclusionThe impact of HNFB on the AMF community in apple rhizospheres is influenced by soil nitrogen levels. The study reveals how varying nitrogen levels mediate the relationship between exogenous HNFB, soil properties, and rhizosphere microbes.研究背景与目的 土壤盐胁迫会对作物生长发育产生负面影响。耐盐固氮菌（Halotolerant nitrogen-fixing bacteria, HNFB）与丛枝菌根真菌（Arbuscular Mycorrhizal Fungi, AMF）是两类可提升盐渍土壤中作物养分有效性与耐盐性的关键微生物。探究耐盐固氮菌对丛枝菌根真菌群落的影响，并将其应用于生物肥料中，有助于筛选最优的耐盐固氮菌-丛枝菌根真菌组合，以提升盐渍土壤中的作物生产力。 试验方法 本研究设置了三组施氮梯度处理：以盐胁迫下的苹果植株为试验材料，分别施加低氮（0 mg N/kg，N0）、正常氮（200 mg N/kg，N1）与高氮（300 mg N/kg，N2）肥料；每个施氮梯度下均设置两个亚处理组：无菌对照组（CK，添加1500 mL无菌水+2 g无菌硅藻土）以及接菌组（BIO，添加1500 mL无菌水+2 g混合菌剂，该菌剂包含枯草芽孢杆菌（Bacillus subtilis）HG-15与贝莱斯芽孢杆菌（Bacillus velezensis）JC-K3）。 试验结果 在相同施氮水平下，接种耐盐固氮菌可显著提升根际土壤的微生物生物量以及β-葡萄糖苷酶（beta-glucosidase）相关基因的相对丰度（p < 0.05）。高氮处理则显著降低了丛枝菌根真菌的群落多样性，以及β-葡萄糖苷酶、酸性磷酸酶与脲酶相关基因的相对丰度。双因素方差分析结果显示，施氮水平与耐盐固氮菌接种的交互作用可显著影响土壤理化性质与根际丛枝菌根真菌的丰度（p < 0.05）。具体而言，在相同施氮水平下，接种耐盐固氮菌可使球囊霉属（Glomus）MO-G17-VTX00114的相对丰度显著高于无菌对照组。 研究结论 耐盐固氮菌对苹果根际丛枝菌根真菌群落的影响受土壤氮素水平调控。本研究阐明了不同施氮水平如何介导外源耐盐固氮菌、土壤特性与根际微生物之间的相互关系。