Cooperation between arbuscular mycorrhizal fungi and earthworms promotes the physiological adaptation of maize under a high salt stress

The potential independent and combined effects of arbuscular mycorrhizal fungi and earthworms on maize salt tolerance were studied in a high salinity soil. This experiment was a 2 x 2 factorial design representing all the combinations of arbuscular mycorrhizal (AM) fungi with earthworms in a high coastal saline soil. Maize biomass, physiological adaptation, ion transportation, soil aggregates, and soil bacterial community from illumina MiSeq sequence were measured at harvest. The results indicated that the earthworms and AM fungi increased the maize salt tolerance by decreasing the salt concentrations, increasing the soil macroaggregate proportions, soil bacterial diversity, maize mineral uptake, and photosynthesis. Earthworms primarily increased the soil macroaggregate proportions, root Na content, and shoot nutrient uptakes and proline content. The AM fungi enhanced K selected transportation from the root to the shoot and reduced the shoot malondialdehyde content to promote maize photosynthesis and transpiration. Illumina MiSeq sequencing analysis showed that earthworms and AM fungi decreased the relative abundance of Bacteroidetes and Fibrobacteres, which was negatively correlated with the soil organic matter. The structural equation model suggests that the soil salt concentration and soil macroaggregate proportions largely contributed to the maize biomass, followed by the shoot K content. Earthworms and AM fungi enhanced maize salt tolerance by ameliorating the soil chemical, physical and biological characteristics and, subsequently, promoting maize growth in high salinity soil.