Early Warning of Resistance to Bt Toxin Vip3Aa in Helicoverpa zea.

Fei Yang,José C Santiago González,Nathan S Little,Bruce E Tabashnik,David L Kerns

doi:10.3390/toxins13090618

Fei Yang, José C Santiago González + Show 3 more

Open Access

https://doi.org/10.3390/toxins13090618

Copy DOI

Abstract

Evolution of resistance by pests can reduce the benefits of crops genetically engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt). Because of the widespread resistance of Helicoverpa zea to crystalline (Cry) Bt toxins in the United States, the vegetative insecticidal protein Vip3Aa is the only Bt toxin produced by Bt corn and cotton that remains effective against some populations of this polyphagous lepidopteran pest. Here we evaluated H. zea resistance to Vip3Aa using diet bioassays to test 42,218 larvae from three lab strains and 71 strains derived from the field during 2016 to 2020 in Arkansas, Louisiana, Mississippi, Tennessee, and Texas. Relative to the least susceptible of the three lab strains tested (BZ), susceptibility to Vip3Aa of the field-derived strains decreased significantly from 2016 to 2020. Relative to another lab strain (TM), 7 of 16 strains derived from the field in 2019 were significantly resistant to Vip3Aa, with up to 13-fold resistance. Susceptibility to Vip3Aa was significantly lower for strains derived from Vip3Aa plants than non-Vip3Aa plants, providing direct evidence of resistance evolving in response to selection by Vip3Aa plants in the field. Together with previously reported data, the results here convey an early warning of field-evolved resistance to Vip3Aa in H. zea that supports calls for urgent action to preserve the efficacy of this toxin.

Highlights

Transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) can provide safe and effective control of some key pests [1,2,3,4]
10 field-derived strains were tested at the Southern Insect Management Research Unit (SIMRU), USDA-ARS in Stoneville, MS (Table 3)
H. zea to Cry toxins, Vip3Aa is the only Bt toxin in transgenic corn and cotton that remains effective against some populations of this pest in the United States [22]

Summary

Introduction

Transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) can provide safe and effective control of some key pests [1,2,3,4]. The benefits of Bt crops are diminished when pests adapt to Bt toxins [6,7,8,9,10]. In this context, field-evolved resistance is defined as a genetically based decrease in susceptibility of an insect population to a Bt toxin caused by selection in the field [7]. Practical resistance is field-evolved resistance that decreases the efficacy of the Bt crop in the field and has practical consequences for pest control [8]. Warning of resistance includes all cases of field-evolved resistance that do not meet the additional criteria for practical resistance [6]

Methods

Results

Conclusion