Endophytic fungi promote peanut fitness by re-establishing rhizosphere nematode communities under continuous monocropping conditions

Background and aims

Plant endophytes assist in plant adaptation to adverse conditions by altering the host plant’s physiology and regulating the rhizosphere microenvironment. As one of the important members of soil biosphere, nematodes play an important role in soil element cycling and physical structure. However, it is still unclear whether soil nematodes were associated with endophyte-mediated adaptations of host plants to an unfavorable environment.

Methods

The rhizosphere nematode communities were analyzed after inoculating a fungal endophyte, Phomopsis liquidambaris, under continuous monocropping conditions with high-throughput sequencing. Nematode chemotaxis experiments were carried out to verify the effect of Ph. liquidambaris-induced root exudates on nematode movement behavior. Root defence enzyme activities and plant growth parameters were analysed after introducing Ph. liquidambaris-enriched nematode communities to the rhizosphere under continuous monocropping conditions.

Results

Ph. liquidambaris increased peanut growth under continuous cropping conditions. Ph. liquidambaris inoculation changed the composition of rhizosphere nematode communities by regulating root exudates, which led to an increase in free-living nematodes and a reduction in plant parasitic nematodes, Mesocriconema, at different periods of plant developmental stages. The application of the insecticide abamectin, which is similar to endophyte fungal treatment, decreased nematode populations and diversity. In addition, a nematode transplant experiment revealed that the soil nematodes induced by Ph. liquidambaris inoculation led to a rise in peanut root defence enzyme activities to improve plant growth under continuous monocropping conditions.

Conclusion

Peanut inoculated with endophyte fungi can increase plant fitness by changing the soil nematode community through root exudates under continuous monocropping conditions.