Data from: Soil pathogen-aphid interactions under differences in soil organic matter and mineral fertilizer

There is increasing evidence showing that microbes can influence
plant-insect interactions. In addition, various studies have shown that
aboveground pathogens can alter the interactions between plants and
insects. However, little is known about the role of soil-borne pathogens
in plant-insect interactions. It is also not known how environmental
conditions, that steer the performance of soil-borne pathogens, might
influence these microbe-plant-insect interactions. Here, we studied
effects of the soil-borne pathogen Rhizoctonia solani on aphids (Sitobion
avenae) using wheat (Triticum aestivum) as a host. In a greenhouse
experiment, we tested how different levels of soil organic matter (SOM)
and fertilizer addition influence the interactions between plants and
aphids. To examine the influence of the existing soil microbiome on the
pathogen effects, we used both unsterilized field soil and sterilized
field soil. In unsterilized soil with low SOM content, R. solani addition
had a negative effect on aphid biomass, whereas it enhanced aphid biomass
in soil with high SOM content. In sterilized soil, however, aphid biomass
was enhanced by R. solani addition and by high SOM content. Plant biomass
was enhanced by fertilizer addition, but only when SOM content was low, or
in the absence of R. solani. We conclude that belowground pathogens
influence aphid performance and that the effect of soil pathogens on
aphids can be more positive in the absence of a soil microbiome. This
implies that experiments studying the effect of pathogens under sterile
conditions might not represent realistic interactions. Moreover,
pathogen-plant-aphid interactions can be more positive for aphids under
high SOM conditions. We recommend that soil conditions should be taken
into account in the study of microbe-plant-insect interactions.