Peanut (Arachis hypogaea. L) is an important oil seed crop. Both arbuscular mycorrhizal fungi (AMF) symbiosis and calcium (Ca²⁺) application can ameliorate the impact of saline soil on peanut production, and the rhizosphere bacterial communities are also closely correlated with peanut salt tolerance; however, whether AMF and Ca²⁺ can withstand high-salinity through or partially through modulating rhizosphere bacterial communities is unclear. Here, we used the rhizosphere bacterial DNA from saline alkali soil treated with AMF and Ca²⁺ alone or together to perform high-throughput sequencing of 16S rRNA genes. Taxonomic analysis revealed that AMF and Ca²⁺ treatment increased the abundance of Proteobacteria and Firmicutes at the phylum level. The nitrogen-fixing bacterium Sphingomonas was the dominant genus in these soils at the genus level, and the soil invertase and urease activities were also increased after AMF and Ca²⁺ treatment, implying that AMF and Ca²⁺ effectively improved the living environment of plants under salt stress. Moreover, AMF combined with Ca²⁺ was better than AMF or Ca²⁺ alone at altering the bacterial structure and improving peanut growth in saline alkali soil. Together, AMF and Ca²⁺ applications are conducive to peanut salt adaption by regulating the bacterial community in saline alkali soil.

Peanut (Arachis hypogaea L.) is an important oil and cash crop. An efficient utilization of saline–alkali soil resources, the development of peanut planting in saline–alkali soil, and obtaining high and stable yield have become urgent needs to ensure peanut production. Arbuscular mycorrhizal fungi (AMF) have been reported to develop the potential productivity of host plants and improve their salt resistance and tolerance. However, there is still limited research on promoting the growth and morphology of peanut roots. Therefore, in this study, seeds of salt-tolerant peanut variety “HY 25” were coated with commercial AMF inoculant before being planted in saline–alkali and normal soils to investigate the effects of AMF on peanut root growth and rhizosphere soil. The results showed that root morphological characteristics were significantly increased by the use of AMF at the podding stage in saline–alkali soil and from the flowering and pegging stage to the maturity stage in normal soil. Of note, the total root volume of peanut inoculated with AMF significantly increased by 31.57% during the podding stage in saline–alkali soil. Meanwhile, AMF significantly increased the phosphatase and invertase activities in the peanut rhizosphere of saline–alkali soil from the flowering stage to maturity stage and soil CAT activity at the maturity stage (41.16~48.82%). In normal soil, soil phosphatase and urease activities were enhanced by AMF at the flowering stage and the podding stage, respectively. AMF also increased the contents of soil organic matter, available phosphorus, and hydrolysable nitrogen, but decreased soil EC in saline–alkali soil. In addition to the significant increase in soil available phosphorus content, AMF had no significant effect on the physical and chemical properties of the soil and other soil nutrients in normal soil. AMF significantly increased pod biomass and yield in saline–alkali soil and normal soil, and improved their agronomic characteristics. In conclusion, peanut seeds coated with AMF improved the root morphological characteristics of peanuts and improved the physical and chemical properties in peanut rhizosphere, especially in saline–alkali soil. The process of rhizosphere soil nutrient transformation was also enhanced. Finally, AMF improved plant agronomic traits to increase the pod yield (16.5~21.9%). This study provides the theoretical basis and technical support for the application of AMF in peanut production in saline–alkali soil.

Polyethylene (PE) microplastics (MPs) from residual mulch films are prevalent in peanut-cultivated soils, yet their specific effects on peanut nodulation remain unclear. This study investigated the impacts of PE-MPs at concentrations of 0.2%, 0.6%, and 1.0% on peanut nodulation. Results indicated that PE-MPs significantly reduced peanut nodule number. Transcriptome analysis revealed that all three concentrations of PE-MPs down-regulated nodulation-related flavonoids, promoted lignin deposition in cell walls, disrupted antioxidant system, and enhanced the accumulation of antimicrobial substances, collectively impairing peanut nodulation efficiency. These findings indicate that PE-MPs substantially compromise the symbiosis between peanut and rhizobia, and provide insights into their interference with plant–beneficial microbe interactions in contaminated soils.