Interactions between halotolerant nitrogen-fixing bacteria and arbuscular mycorrhizal fungi under saline stress

Chao Ji; Yuhan Ge; Hua Zhang; Yingxiang Zhang; Zhiwen Xin; Jian Li; Jinghe Zheng; Zengwen Liang; Hui Cao; Kun Li

doi:10.3389/fmicb.2024.1288865

Interactions between halotolerant nitrogen-fixing bacteria and arbuscular mycorrhizal fungi under saline stress

Front Microbiol. 2024 Mar 13:15:1288865. doi: 10.3389/fmicb.2024.1288865. eCollection 2024.

Authors

Chao Ji^{1

2

3

4}, Yuhan Ge⁵, Hua Zhang^{1

2}, Yingxiang Zhang^{1

2}, Zhiwen Xin^{1

2}, Jian Li⁶, Jinghe Zheng⁵, Zengwen Liang^{1

2}, Hui Cao^{1

2}, Kun Li^{3

4

7

8}

Affiliations

¹ College of Seed and Facility Agricultural Engineering, Weifang University, Weifang, China.
² Key Laboratory of Biochemistry and Molecular Biology in University of Shandong Province, Weifang University, Weifang, China.
³ Mountain Tai Forest Ecosystem Research Station of State Forestry and Grassland Administration, Shandong Agricultural University, Tai'an, China.
⁴ State Forestry and Grassland Administration Key Laboratory of Silviculture in Downstream Areas of the Yellow River, Shandong Agricultural University, Tai'an, China.
⁵ College of Biology and Oceanography, Weifang University, Weifang, China.
⁶ Shandong Institute of Pomology, Tai'an, China.
⁷ Research Center for Forest Carbon Neutrality Engineering of Shandong Higher Education Institutions, Tai'an, Shandong, China.
⁸ Key Laboratory of Ecological Protection and Security Control of the Lower Yellow River of Shandong Higher Education Institutions, Tai'an, Shandong, China.

Abstract

Background and aims: Soil 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.

Methods: We 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)].

Results: HNFB 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.

Conclusion: The 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.

Keywords: arbuscular mycorrhizal fungi; halotolerant nitrogen-fixing bacteria; nitrogen fertilization; plant growth-promoting rhizobacteria; salt stress.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by the Shandong Provincial Natural Science Foundation (ZR2022QC155), Weifang Science and Technology Development Plan Project (2022GX002), Key technologies and Products for Prevention and Control of Pine Wilt Disease in Taishan (2022TSGS001-5-2), Weifang University Doctor Initiation Fund Project (208–44121013), Horizontal Topic (208-40121141), National Natural Science Foundation of China (32072518), Shandong Academy of Agricultural Sciences International Science and Technology Cooperation Project (CXGC2023G37), Shandong Academy of Agricultural Sciences High-level Talent Introduction Project (CXGC2021B34).