Spatial variation in western corn rootworm (Coleoptera: Chrysomelidae) susceptibility to Cry3 toxins in Nebraska

PLoS One. 2018 Nov 29;13(11):e0208266. doi: 10.1371/journal.pone.0208266. eCollection 2018.

Abstract

Repeated use of field corn (Zea mays L.) hybrids expressing the Cry3Bb1 and mCry3A traits in Nebraska has selected for field-evolved resistance in some western corn rootworm (WCR; Diabrotica virgifera virgifera LeConte) populations. Therefore, this study was conducted to characterize spatial variation in local WCR susceptibility to Cry3Bb1 and mCry3A traits in Keith and Buffalo counties, Nebraska, and determine the relationship between past management practices and current WCR susceptibility. Adult WCR populations were collected from sampling grids during 2015 and 2016 and single-plant larval bioassays conducted with F1 progeny documented significant variation in WCR susceptibility to Cry3Bb1 and mCry3A on different spatial scales in both sampling grids. At the local level, results revealed that neighboring cornfields may support WCR populations with very different susceptibility levels, indicating that gene flow of resistant alleles from high trait survival sites is not inundating large areas. A field history index, comprised of additive and weighted variables including past WCR management tactics and agronomic practices, was developed to quantify relative selection pressure in individual fields. The field history index-Cry3 trait survivorship relationship from year 1 data was highly predictive of year 2 Cry3 trait survivorship when year 2 field history indices were inserted into the year 1 base model. Sensitivity analyses indicated years of trait use and associated selection pressure at the local level were the key drivers of WCR susceptibility to Cry3 traits in this system. Retrospective case histories from this study will inform development of optimal resistance management programs and increase understanding of plant-insect interactions that may occur when transgenic corn is deployed in the landscape. Results from this study also support current recommendations to slow or mitigate the evolution of resistance by using a multi-tactic approach to manage WCR densities in individual fields within an integrated pest management framework.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Bacillus thuringiensis Toxins
  • Bacterial Proteins / genetics*
  • Coleoptera / physiology*
  • Disease Susceptibility
  • Endotoxins / genetics*
  • Hemolysin Proteins / genetics*
  • Nebraska
  • Pest Control, Biological
  • Plant Diseases / parasitology*
  • Plants, Genetically Modified / genetics*
  • Plants, Genetically Modified / parasitology
  • Zea mays / genetics*
  • Zea mays / parasitology

Substances

  • Bacillus thuringiensis Toxins
  • Bacterial Proteins
  • Cry3Bbl endotoxin, Bacillus thuringiensis
  • Endotoxins
  • Hemolysin Proteins
  • insecticidal crystal protein, Bacillus Thuringiensis

Grants and funding

This was partially supported by The Nebraska Agricultural Experiment Station with funding from the Hatch Act (Accession Number 1007272) through the USDA National Institute of Food and Agriculture, and the USDA National Institute of Food and Agriculture, Biotechnology Risk Assessment Grant Program Competitive Grant 2012-33522-20010 (https://nifa.usda.gov/program/biotechnology-risk-assessment-research-grants-brag-program), sub-award from Iowa State University. LJM was the recipient of the funding. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.