Cry1F resistance in fall armyworm Spodoptera frugiperda: single gene versus pyramided Bt maize.

Fangneng Huang,Robert L Meagher,Dominic D Reisig,Fei Yang,Ying Niu,Jawwad A Qureshi,Vikash Dangal,G David Buntin,Graham P Head,Xinzi Ni,David Kerns,David A Andow,Kun Yan Zhu

doi:10.1371/journal.pone.0112958

Abstract

Evolution of insect resistance to transgenic crops containing Bacillus thuringiensis (Bt) genes is a serious threat to the sustainability of this technology. However, field resistance related to the reduced efficacy of Bt maize has not been documented in any lepidopteran pest in the mainland U.S. after 18 years of intensive Bt maize planting. Here we report compelling evidence of field resistance in the fall armyworm, Spodoptera frugiperda (J.E. Smith), to Cry1F maize (TC 3507) in the southeastern region of the U.S. An F2 screen showed a surprisingly high (0.293) Cry1F resistance allele frequency in a population collected in 2011 from non-Bt maize in south Florida. Field populations from non-Bt maize in 2012–2013 exhibited 18.8-fold to >85.4-fold resistance to purified Cry1F protein and those collected from unexpectedly damaged Bt maize plants at several locations in Florida and North Carolina had >85.4-fold resistance. In addition, reduced efficacy and control failure of Cry1F maize against natural populations of S. frugiperda were documented in field trials using Cry1F-based and pyramided Bt maize products in south Florida. The Cry1F-resistant S. frugiperda also showed a low level of cross-resistance to Cry1A.105 and related maize products, but not to Cry2Ab2 or Vip3A. The occurrence of Cry1F resistance in the U.S. mainland populations of S. frugiperda likely represents migration of insects from Puerto Rico, indicating the great challenges faced in achieving effective resistance management for long-distance migratory pests like S. frugiperda.

Highlights

Diet-incorporated bioassays showed that the larvae collected from the non-Bacillus thuringiensis (Bt) maize plants had 18.8-fold (for FL-CL-NBt-2012) and 55.9-fold (FL-CLNBt-2013) resistance to Cry1F protein (Table 2)
Resistance monitoring must be addressed in insect resistance management (IRM) plans for Bacillus thuringiensis (Bt) crops [10]
The F2 screen showed that Cry1F resistance alleles were not rare in the LA and FL populations

Summary

Introduction

Diet-incorporated bioassays showed that the larvae collected from the non-Bt maize plants had 18.8-fold (for FL-CL-NBt-2012) and 55.9-fold (FL-CLNBt-2013) resistance to Cry1F protein (Table 2). The feral population of S. frugiperda at the trial site (FL-CL-nBt-13 and FLCL-Bt-13) was highly resistant to both HX1 maize (Fig. 1) and purified Cry1F protein (Table 2).

Results

Conclusion