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

Authors: HUANG, FRANGNENG - Louisiana State University; QURESHI, JAWWAD - University Of Florida; Meagher, Robert - Rob; REISIG, DOMINIC - North Carolina State University; HEAD, GRAHAM - Monsanto Corporation; ANDOW, DAVID - University Of Minnesota; Ni, Xinzhi; KERNS, DAVD - Louisiana State University; BUNTIN, G - University Of Georgia; NIU, YING - Louisiana State University; YANG, FEI - Louisiana State University; DANGAL, VIKASH - Louisiana State University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2014
Publication Date: 11/17/2014
Citation: Huang, F., Qureshi, J.A., Meagher Jr, R.L., Reisig, D.D., Head, G.P., Andow, D.A., Ni, X., Kerns, D., Buntin, G.D., Niu, Y., Yang, F., Dangal, V. 2014. Cry1F resistance in fall armyworm Spodoptera frugiperda: single gene versus pyramided Bt maize. PLoS One. 9(11):e112958. doi:10.1371/journal.pone.0112958.

Interpretive Summary: The migratory pest fall armyworm (Spodoptera frugiperda) attacks corn, cotton, grasses, and rice in North and South America and in the Caribbean, and is the number one pest of sweet corn in south Florida. Corn plants have been genetically engineered with various toxins from the bacterium Bacillus thuringiensis (Bt), and these corn varieties have been grown for over 18 years in field plantings. Although resistance to Bt plants was discovered in Puerto Rico in 2007, resistance hasn’t been documented in the mainland U.S. In collaboration with University, corporate and other USDA-ARS researchers, a scientist at USDA, Agriculture Research Service, Center for Medical Agricultural and Veterinary Entomology, Gainesville, Florida, participated in testing field populations of fall armyworm to determine if resistance to Cry1F Bt plants has developed. Results showed that fall armyworm specimens in Florida and North Carolina that were collected from damaged Bt corn plants had a greater than 85-fold resistance compared to susceptible laboratory populations. These results are the first to show field resistance to Bt corn in the continental U.S. and are a predictor that alternative methods of control will be needed to suppress these migratory pest moths.

Technical 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.