Effects of earthworms addition on population dynamics of inoculated wheat aphids

Studies on interactions between plants and belowground organisms, or between plants and aboveground organisms are numerous. However, there is limited research on the impact of belowground organisms on aboveground organisms through plant mediation. Soil organisms can influence interactions between plants and herbivores by changing plant growth and chemistry). Four treatments including adding 0, 1, 2 and 4 Metaphire guillelmi individuals per pot were set, and wheat aphids were inoculated to investigate the effects of earthworms and aphids on the content of primary, secondary metabolisms of wheat and the population dynamics of 3 aphid species (Schizaphis graminum, Sitobion graminum , and Rhopalosiphum padi) in wheat through an indoor potted experiments, in order to provide the theoretical support for the interactions between soil biota earthworms, wheat, and aphids in agricultural ecosystems. . The results indicated that earthworm addition at different densities increased biomass, total nitrogen, and total nitrogen of wheat shoot and root, but decreased root total carbon, the ratio of total carbon to total nitrogen of wheat shoot and root, but increased total flavonoid and total phenol of wheat shoot. Aphid inoculation reduced biomass, total carbon, total nitrogen of wheat shoot, and total nitrogen of wheat root, but increased total flavonoid and total phenol of wheat shoot. The population dynamics of three wheat aphid species all exhibited logistic S-shaped curves, and population density of three wheat aphid species and the environmental capacity (K) both increased with the enhancing of earthworm density. The correlation analysis results indicated that biomass, total flavonoid and total phenol of wheat shoot were positively correlated with the population density of three wheat aphid species, respectively. As the adding densities of earthworms increases, the increase quantity in biomass, total carbon, and total nitrogen of wheat shoot all show an increasing trend. Redundancy analysis (RDA) results showed primary metabolites (soluble sugar, total carbon, and total nitrogen of wheat shoot) explained 48.83% of the changes in aphid population size, and secondary metabolites (total flavonoids and total phenols of wheat shoot), and soil physicochemical properties explained 11.91%, 31.90% of the changes in aphid population, respectively. After aphids were inoculated, earthworm addition, retarded the negative effect of aphids on biomass and total carbon of wheat shoot. The research results provide an important basis for understanding the interaction mechanisms between soil, plant and pests.