F2 screen for resistance to Bacillus thuringiensis Cry2Ab2-maize in field populations of Spodoptera frugiperda (Lepidoptera: Noctuidae) from the southern United States

Authors: NIU, YING - Louisiana State University; QURESHI, JAWWAD - University Of Florida; Ni, Xinzhi; HEAD, GRAHAM - Monsanto Corporation; PRICE, PAULA - Monsanto Corporation; Meagher, Robert - Rob; KERNS, DAVID - Louisiana State University; LEVY, RONNIE - Louisiana State University; YANG, XIANGBING - Texas A&M University; HUANG, FANGNENG - Louisiana State University

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2016
Publication Date: 6/14/2016
Citation: Niu, Y., Qureshi, J.A., Ni, X., Head, G.P., Price, P.A., Meagher Jr, R.L., Kerns, D., Levy, R., Yang, X., Huang, F. 2016. F2 screen for resistance to Bacillus thuringiensis Cry2Ab2-maize in field populations of Spodoptera frugiperda (Lepidoptera: Noctuidae) from the southern United States. Journal of Invertebrate Pathology. 138(2016): 66-72. doi.10.1016/j.jip.2016.06.005.
DOI: https://doi.org/10.1016/j.jip.2016.06.005

Interpretive Summary: The fall armyworm, Spodoptera frugiperda, is a caterpillar pest of many row and vegetable crops in the Americas. One method of controlling populations is to use transgenic maize (corn) and cotton plants that have genes expressing Bacillus thuringiensis (Bt) proteins. Recently, fall armyworm has become resistant to one of these Bt proteins, however, others are still being tested. This report by researchers from Louisiana State University, the University of Florida, Monsanto Company, Texas A&M University, USDA-ARS Tifton, Georgia, in collaboration with scientists from the USDA, Agricultural Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, assessed the susceptibility of fall armyworm populations in the southeast U.S. to the Bt protein Cry2Ab2. Laboratory bioassays were conducted to determine the frequency of resistant alleles in these populations. After testing with Bt corn plants, results showed that one population collected in Georgia had the potential to become resistant in the field. Overall, the frequency of resistant alleles was relatively low indicating that field resistance originating from populations in the southeast, although possible, is unlikely.

Technical Abstract: The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a target of transgenic maize and cotton expressing Bacillus thuringiensis (Bt) proteins in both North and South America. In 2013 and 2014, a total of 215 F2 two-parent families of S. frugiperda were established using single-pair mating of field individuals collected from seven locations in four states of the southern U.S.: Texas, Louisiana, Georgia, and Florida. The objective of the investigation was to determine the frequency of resistance alleles in field populations to Cry2Ab2, a common Bt protein produced in transgenic maize and cotton. For each F2 family, 128 F2 neonates were screened on leaf tissue of Cry2Ab2 maize plants in the laboratory. The estimated frequency of major Cry2Ab2 resistance alleles in S. frugiperda from the four states was 0.0023 with a 95% credibility interval of 0.0003 to 0.0064. In addition, six families were identified to possess minor resistance alleles at a frequency of 0.0082 with a 95% credibility interval of 0.0033 to 0.0152. One F2 family from Georgia (GA-15) was found to possess a major resistance allele to the Cry2Ab2 protein. Larvae from this family survived well on whole maize plants expressing Cry2Ab2 protein and demonstrated a significant level (>15-fold) of resistance when fed with the same protein incorporated in a meridic diet. Overall, the estimated frequency of major Cry2Ab2 resistance alleles in the tested populations of S. frugiperda from the four states was relatively low. The detection of the major resistance allele along with the relatively abundant minor resistance alleles revealed in this study may have important implications for resistance management.