Survey of bacteria associated with western corn rootworm life stages reveals no difference between insects reared in different soils

Authors: LUDWICK, DALTON - University Of Missouri; ERICSSON, AARON - University Of Missouri; MEIHLS, LISA - Evogene; Gregory, Michelle; FINKE, DEBORAH - University Of Missouri; COUDRON, THOMAS - Retired ARS Employee; Hibbard, Bruce; Shelby, Kent

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2019
Publication Date: 10/25/2019
Citation: Ludwick, D.C., Ericsson, A.C., Meihls, L.M., Gregory, M.L., Finke, D.L., Coudron, T.A., Hibbard, B.E., Shelby, K. 2019. Survey of bacteria associated with western corn rootworm life stages reveals no difference between insects reared in different soils. Scientific Reports. 9:15332. https://doi.org/10.1038/s41598-019-51870-x.
DOI: https://doi.org/10.1038/s41598-019-51870-x

Interpretive Summary: The western corn rootworm is the most serious pests of corn production in the U.S. Larvae of this beetle chew on and destroy corn roots, severely reducing yield. Our knowledge of the role that microbes associated with the beetle play in agricultural fields remains woefully incomplete. An important component is to first identify the microorganisms present in the beetles, corn, and soil that could play a role in life history, or identify targets for pest management. Additionally it is vital to determine whether associated microbes differ by locality, or are the similar in all fields. For this study, insects were reared in soil from a geographically separate locations. The microbes present in the insects, and the soil from which they emerged were surveyed using high throughput next generation DNA sequencing. We surveyed the types of bacteria present within the digestive system of eggs and all feeding immature larval stages, emerged adult beetles, and the soil from which each larval stage was feeding. Surprisingly, no differences existed between the insects reared on soils from different geographic regions. The bacteria present in immature stages and in adult males and females revealed a possible core set of microbes assembled as the larvae burrows through the soil attacking corn roots. This finding will prove important to growers and industries developing pest microbial management strategies such as plant-beneficial seed treatments.

Technical Abstract: Western corn rootworm (Diabrotica virgifera virgifera LeConte) is a serious pest of maize (Zea mays L.) in North America and parts of Europe. With most of its life cycle spent in the soil feeding on maize root tissues, this insect is likely to encounter and interact with a wide range of soil and root rhizosphere microbes. Our knowledge of the role of microbes in pests and in agricultural fields with regards to pest management and plant health remains incomplete. An important component is to know which microorganisms are present that could play a role in life history or management. For this study, insects were reared in either autoclaved soil or soil from a geographically separate location that had not been autoclaved. Insects were sampled to determine the possible core bacteriome. Additionally, soil was sampled at each life stage to determine the contribution of soil to the rootworm bacteriome. We analyzed the V4 hypervariable region of bacterial 16S rRNA genes with Illumina MiSeq to survey the different species associated with the insect and the soils. Significant differences were noted between soil and insects with principal coordinate analysis. No significant differences existed between the insects reared on soils which did or did not undergo the autoclave process, or between non-diapausing and diapausing insects. The bacteria present in immature stages and in male and female adults revealed a possible core bacteriome of approximately 16 operational taxonomic units (OTUs).