Effective dominance and incomplete resistance of Cry1A.105/Cry2Ab2 dual-protein resistance in Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae)

Sunday, November 13, 2022

11:12 AM – 11:24 AM PT

Location: Vancouver Convention Centre, Meeting Room 306

Presenting Author(s)

FH

Fangneng Huang

Professor
Louisiana State University Agricultural Center
Baton Rouge, Louisiana

Co-Author(s)

TS

Tiago H. Silva

M.Sc student
Louisiana State University
Baton Rouge, Louisiana
Ying Niu

Louisiana State University Agricultural Center
Baton Rouge, Louisiana
TT

Tyler Towles

Louisiana State University
Winnsboro, Louisiana
GH

Graham P. Head

Global Head of Resistance Management
Bayer Crop Science
Frontenac, Missouri
SB

Sebe Brown

Louisiana State University Agricultural Center
Alexandria, Louisiana
James M. Villegas

Research Associate
Louisiana State University
Alexandria, Louisiana
WW

Wade Walker

Louisiana State University Agricultural Center
Winnsboro, Louisiana
CS

Caroline Sakuno

Centro de Tecnologia Canavieira
Piracicaba, São Paulo, Brazil

Helicoverpa zea is a major pest targeted by both transgenic corn and cotton expressing Bacillus thuringiensis (Bt) proteins. Practical resistance to Cry1A/Cry2A corn and cotton in H. zea has widely occurred in the United States. In this study, multiple trials were preformed to evaluate the life table parameters of a Bt-susceptible, a Cry1A/Cry2A dual-protein resistant (VT2P-RR), and an F1 heterozygous (VT2P-RS) genotypes of H. zea on ears of non-Bt and five common pyramided corn traits expressing Vip3A and/or Cry (Cry1A, Cry2A, Cry1F) proteins. In the laboratory, neonates of the three insect genotypes were placed on the silks of corn ears collected from fields at R1-R2 plant stages. Larvae of all three H. zea genotypes survived well on non-Bt corn hybrids. Varied number of VT2P-RR and VT2P-RS larvae also survived on ears of hybrids expressing Cry proteins without Vip3A. However, the dual-protein resistance on ears of Cry protein corn was incomplete, and the VT2P-RR was highly susceptible to Bt corn hybrids containing Vip3A gene. Effective dominance levels of VT2P-RR on ears of Cry protein corn varied from recessive to incompletely dominant. Data generated from the study should be useful in assessing the risk of resistance evolution to Vip3A and refining IRM modeling for the sustainable use of the Bt crop technology for management of H. zea.

Key words: Corn earworm, Cry protein, Vip3A, Bt corn, effective dominance, incomplete resistance