title: Cry3Bb1-Resistant Western Corn Rootworm, Diabrotica virgifera virgifera (LeConte) Does Not Exhibit Cross-Resistance to DvSnf7 dsRNA.
abstract: METHODS
  There is a continuing need to express new insect control compounds in transgenic maize against western corn rootworm, Diabrotica virgifera virgifera (LeConte) (WCR). In this study three experiments were conducted to determine cross-resistance between the new insecticidal DvSnf7 dsRNA, and Bacillus thuringiensis (Bt) Cry3Bb1; used to control WCR since 2003, with field-evolved resistance being reported. Laboratory susceptible and Cry3Bb1-resistant WCR were evaluated against DvSnf7 dsRNA in larval diet-incorporation bioassays. Additionally, the susceptibility of seven field and one field-derived WCR populations to DvSnf7 (and Cry3Bb1) was assessed in larval diet-overlay bioassays. Finally, beetle emergence of laboratory susceptible and Cry3Bb1-resistant WCR was evaluated with maize plants in the greenhouse expressing Cry3Bb1, Cry34Ab1/Cry35Ab1, or DvSnf7 dsRNA singly, or in combination.
  
  
  CONCLUSIONS
  The Cry3Bb1-resistant colony had slight but significantly (2.7-fold; P<0.05) decreased susceptibility to DvSnf7 compared to the susceptible colony, but when repeated using a field-derived WCR population selected for reduced Cry3Bb1 susceptibility, there was no significant difference (P<0.05) in DvSnf7 susceptibility compared to that same susceptible population. Additionally, this 2.7-fold difference in susceptibility falls within the range of DvSnf7 susceptibility among the seven field populations tested. Additionally, there was no correlation between susceptibility to DvSnf7 and Cry3Bb1 for all populations evaluated. In greenhouse studies, there were no significant differences (P<0.05) between beetle emergence of susceptible and Cry3Bb1-resistant colonies on DvSnf7 and Cry34Ab1/Cry35Ab1, and between DvSnf7 and MON 87411 (DvSnf7 + Cry3Bb1) for the Cry3Bb1-resistant colony. These results demonstrate no cross-resistance between DvSnf7 and Cry3Bb1 against WCR. Therefore, pyramiding DvSnf7 with Bt proteins such as Cry3Bb1 and Cry34Ab1/Cry35Ab1 will provide a valuable IRM tool against WCR that will increase the durability of these Bt proteins. These results also illustrate the importance of using appropriate bioassay methods when characterizing field-evolved resistant WCR populations.
authors.affiliation: Monsanto Co., St. Louis, Missouri, United States of America.
authors.forename: William
authors.identifier: http://orcid.org/0000-0002-8396-3034
authors.initials: W
authors.lastname: Moar
authors.affiliation: Monsanto Co., St. Louis, Missouri, United States of America.
authors.forename: Chitvan
authors.initials: C
authors.lastname: Khajuria
authors.affiliation: Monsanto Co., St. Louis, Missouri, United States of America.
authors.forename: Michael
authors.initials: M
authors.lastname: Pleau
authors.affiliation: Monsanto Co., St. Louis, Missouri, United States of America.
authors.forename: Oliver
authors.initials: O
authors.lastname: Ilagan
authors.affiliation: Monsanto Co., St. Louis, Missouri, United States of America.
authors.forename: Mao
authors.initials: M
authors.lastname: Chen
authors.affiliation: Monsanto Co., St. Louis, Missouri, United States of America.
authors.forename: Changjian
authors.initials: C
authors.lastname: Jiang
authors.affiliation: Monsanto Co., St. Louis, Missouri, United States of America.
authors.forename: Paula
authors.initials: P
authors.lastname: Price
authors.affiliation: Monsanto Co., St. Louis, Missouri, United States of America.
authors.forename: Brian
authors.initials: B
authors.lastname: McNulty
authors.affiliation: Monsanto Co., St. Louis, Missouri, United States of America.
authors.forename: Thomas
authors.initials: T
authors.lastname: Clark
authors.affiliation: Monsanto Co., St. Louis, Missouri, United States of America.
authors.forename: Graham
authors.initials: G
authors.lastname: Head
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics / Q000378:metabolism; D001681:Biological Assay; D001517:Coleoptera / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity*; D004731:Endotoxins / Q000494:pharmacology*; D007305:Insecticide Resistance / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified / Q000469:parasitology*; D012330:RNA, Double-Stranded / Q000235:genetics / Q000502:physiology*; D003313:Zea mays / Q000469:parasitology*
chemical_list: D004731:Endotoxins; D012330:RNA, Double-Stranded