|NIU, YING - LSU Agcenter|
|QURESHI, JAWWAD - University Of Florida|
|HEAD, GRAHAM - Monsanto Corporation|
|Meagher, Robert - Rob|
|KERNS, DAVID - LSU Agcenter|
|LEVY, RONNIE - LSU Agcenter|
|YANG, XIANGBIN - Texas A&M Agrilife|
|HUANG, FANGNENG - LSU Agcenter|
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., Meagher Jr, R.L., Kerns, D., Levy, R., Yang, X., Huang, F. 2016. Estimation of resistance allele frequency to maize incorporated Bacillus thuringiensis Cry2Ab2 protein in field populations of the fall army Spodoptera frugiperda (Lepidoptera: Noctuidae) from south region of the United States. Journal of Invertebrate Pathology. 138:66-72.
Interpretive Summary: The fall armyworm is a target pest of transgenic maize and cotton expressing bacterial toxins in both North and South Americas. In 2013 and 2014, a total of 215 second generation two-parent families of fall armyworm were established using single-pair mating of the field collected individuals. The insect used in the study were collected from seven locations in four states of the southern U.S., that is., Texas, Louisiana, Georgia, and Florida. The objective of the investigation was to detect resistance alleles to a common bacterial toxin (Cry2Ab2) produced in transgenic maize and cotton in the fall armyworm populations. For each second generation family of the fall armyworm, 128 newly-hatched worms were screened using leaf tissue of maize plants expressing the toxin under the laboratory conditions. A conservative estimate of the frequency of major toxin resistance alleles in the fall armyworms collected from the four states was relatively low (0.23 %). In addition, six families were considered to likely possess minor resistance alleles that were nearly three times greater (0.64 %) than the major alleles. One second-generation family from Georgia was confirmed to possess a major resistance allele to the toxin. Larvae from this family survived well on whole maize plants expressing the toxin and demonstrated a significant level (>15-fold) of resistance when they were fed with the same toxin incorporated into an artificial insect diet. 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.
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 Americas. In the falls of 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 south region of the U.S.: Texas, Louisiana, Georgia, and Florida. The objective of the current research was to determine the frequency of resistance alleles in the 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 from? 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 they were fed with the same protein incorporated into a meridic diet. The detection of the major resistance allele along with the relatively abundant minor resistance alleles may have important implications for resistance management.