Helicoverpa zea is a major target pest of Bt corn and Bt cotton.Field-evolved resistance of H.zea to Cry1 and Cry2 proteins has been widely reported in the United States.Understanding the frequency of resistance allel...Helicoverpa zea is a major target pest of Bt corn and Bt cotton.Field-evolved resistance of H.zea to Cry1 and Cry2 proteins has been widely reported in the United States.Understanding the frequency of resistance alleles in a target insect is critical for Bt resistance management.Despite multiple cases of practical resistance to Cry proteins having been documented in H.zea,there are no data on the current status of alleles conferring resistance to Cry1Ac and Cry2Ab2 in field populations of this pest.During 2018‒2019,a total of 106 F2 families for Cry1Ac and 120 F2 families for Cry2Ab2 were established using mass mating and light trap strategy.We screened 13,568 and 15,360 neonates using a discriminatory dose of Cry1Ac and Cry2Ab2,respectively.The results showed that 93.4%and 35.0%of the F2 families could survive on the discriminatory dose of Cry1Ac and Cry2Ab2,respectively.The estimated resistance allele frequency for Cry1Ac in H.zea ranged from 0.4150 to 0.4975 and for Cry2Ab2 ranged from 0.1097 and 0.1228.These data indicate that the frequency of alleles conferring resistance to Cry1 and Cry2 proteins in H.zea in Texas are high.In addition,our data suggest the resistance to Cry1Ac and Cry2Ab2 in the screened families of H.zea varies from recessive to dominant.The information in this study provides precise estimates of Cry resistance allele frequencies in H.zea and increases our understanding of the risks to the sustainability of Bt crops.展开更多
Helicoverpa zea(Boddie)is a destructive agricultural pest species that is targeted by both Bacillus thuringiensis(Bt)maize and cotton in the United States.Cry1A.105 and Cry2Ab2 are two Bt proteins expressed in a widel...Helicoverpa zea(Boddie)is a destructive agricultural pest species that is targeted by both Bacillus thuringiensis(Bt)maize and cotton in the United States.Cry1A.105 and Cry2Ab2 are two Bt proteins expressed in a widely planted maize event MON 89034.In this study,two tests(Test-Ⅰ and Test-Ⅱ)were conducted to evaluate the relative fitness of Bt-susceptible and-resistant H.zea on non-Bt diet(Test-Ⅰ and Test-Ⅱ)and a diet containing a mix of Cry1A.105 and Cry2Ab2 at a low concentration(Test-Ⅱ only).Insect populations evaluated in Test-Ⅰ were two Bt-susceptible strains and three Bt-resistant strains(a single-protein Cry1A.105-,a single-protein Cry2Ab2-,and a dual-protein Cry1A.105/Cry2Ab2-resistant strains).Test-Ⅱ analyzed the same two susceptible strains,three backcrossed-and-reselected Cry1A.105/Cry2Ab2-single-/dual-protein-resistant strains,and three F1 heterozygous strains.Measurements of life table parameters showed that neither the single-nor dual-protein Cry1A.105/Cry2Ab2 resistance in H.zea was associated with fitness costs under the test conditions.The single Cry protein resistances at a concentration of a mix of Cry1A.105 and Cry2Ab2 that resulted in a zero net reproductive rate for the two susceptible strains were functionally incomplete recessive or codominant,and the dual-protein resistance was completely dominant.The lack of fitness costs could be a factor contributing to the rapid revolution of resistance to the Cry proteins in this species.Data generated from this study should aid our understanding of Cry protein resistance evolution and help in refining IRM programs for H.zea.展开更多
基金supported by Biotechnology Risk Assessment grant no.2017-33522-27090/project accession no.1013740 from the USDA National Institute of Food and Agriculture.
文摘Helicoverpa zea is a major target pest of Bt corn and Bt cotton.Field-evolved resistance of H.zea to Cry1 and Cry2 proteins has been widely reported in the United States.Understanding the frequency of resistance alleles in a target insect is critical for Bt resistance management.Despite multiple cases of practical resistance to Cry proteins having been documented in H.zea,there are no data on the current status of alleles conferring resistance to Cry1Ac and Cry2Ab2 in field populations of this pest.During 2018‒2019,a total of 106 F2 families for Cry1Ac and 120 F2 families for Cry2Ab2 were established using mass mating and light trap strategy.We screened 13,568 and 15,360 neonates using a discriminatory dose of Cry1Ac and Cry2Ab2,respectively.The results showed that 93.4%and 35.0%of the F2 families could survive on the discriminatory dose of Cry1Ac and Cry2Ab2,respectively.The estimated resistance allele frequency for Cry1Ac in H.zea ranged from 0.4150 to 0.4975 and for Cry2Ab2 ranged from 0.1097 and 0.1228.These data indicate that the frequency of alleles conferring resistance to Cry1 and Cry2 proteins in H.zea in Texas are high.In addition,our data suggest the resistance to Cry1Ac and Cry2Ab2 in the screened families of H.zea varies from recessive to dominant.The information in this study provides precise estimates of Cry resistance allele frequencies in H.zea and increases our understanding of the risks to the sustainability of Bt crops.
基金supported by Bayer Crop Science(St.Louis,MO,USA),USDA Regional Research Project NC-246Hatch funds from the USDA National Institute of Food and Agriculture.
文摘Helicoverpa zea(Boddie)is a destructive agricultural pest species that is targeted by both Bacillus thuringiensis(Bt)maize and cotton in the United States.Cry1A.105 and Cry2Ab2 are two Bt proteins expressed in a widely planted maize event MON 89034.In this study,two tests(Test-Ⅰ and Test-Ⅱ)were conducted to evaluate the relative fitness of Bt-susceptible and-resistant H.zea on non-Bt diet(Test-Ⅰ and Test-Ⅱ)and a diet containing a mix of Cry1A.105 and Cry2Ab2 at a low concentration(Test-Ⅱ only).Insect populations evaluated in Test-Ⅰ were two Bt-susceptible strains and three Bt-resistant strains(a single-protein Cry1A.105-,a single-protein Cry2Ab2-,and a dual-protein Cry1A.105/Cry2Ab2-resistant strains).Test-Ⅱ analyzed the same two susceptible strains,three backcrossed-and-reselected Cry1A.105/Cry2Ab2-single-/dual-protein-resistant strains,and three F1 heterozygous strains.Measurements of life table parameters showed that neither the single-nor dual-protein Cry1A.105/Cry2Ab2 resistance in H.zea was associated with fitness costs under the test conditions.The single Cry protein resistances at a concentration of a mix of Cry1A.105 and Cry2Ab2 that resulted in a zero net reproductive rate for the two susceptible strains were functionally incomplete recessive or codominant,and the dual-protein resistance was completely dominant.The lack of fitness costs could be a factor contributing to the rapid revolution of resistance to the Cry proteins in this species.Data generated from this study should aid our understanding of Cry protein resistance evolution and help in refining IRM programs for H.zea.
