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
A seed blend refuge has been implemented in the U.S.Corn Belt for Bt maize resistance management.The fall armyworm,Spodoptera frugiperda(J.E.Smith),is a target pest of Bt maize in the Americas.The larvae of this pest ...A seed blend refuge has been implemented in the U.S.Corn Belt for Bt maize resistance management.The fall armyworm,Spodoptera frugiperda(J.E.Smith),is a target pest of Bt maize in the Americas.The larvae of this pest are mobile,which may affect the efficacy of seed blend refuges.In this study,field and greenhouse trials were conducted to determine the performance of Bt-susceptible(aabb)and-heterozygous dual-gene-resistant(AaBb)genotypes of S.frugiperda in seed blends of non-Bt and pyramided Bt maize.Three field trials evaluated larval survival,larval growth,and plant injury with aabb in seed blends of Bt maize expressing Cry1A.105/Cry2Ab2/Vip3A with 0–30%non-Bt seeds.Greenhouse tests investigated the performance of aabb and AaBb in seed blends of Cry1A.105/Cry2Ab2 with 0–30% non-Bt seeds.In pure non-Bt maize plots,after 9–13 d of neonates being released on the plants,0.39 and 0.65 larvae/plant survived with leaf injury ratings of 4.7 and 5.9(Davis's 1–9 scale)in the field and greenhouse,respectively.In contrast,live larvae and plant injury were virtually not observed on Bt plants across all planting patterns.Larval occurrence and plant injury by aabb on non-Bt plants were similar between seed blends and pure non-Bt plantings,suggesting that the blended refuges could provide an equivalent susceptible population as structured refuge under the test conditions.In the greenhouse,the two insect genotypes in seed blends performed similarly,indicating that the seed blends did not provide more favorable conditions for AaBb over aabb.The information generated from this study should be useful in managing S.frugiperda and evaluating if send blends could be suitable refuge options for Bt resistance management in the regions where the insect is a primary target pest.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This article is published with the approval of the Director of the Louisiana Agri-cultural Experiment Station as manuscript No.2020-234-34595This project represents work 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A seed blend refuge has been implemented in the U.S.Corn Belt for Bt maize resistance management.The fall armyworm,Spodoptera frugiperda(J.E.Smith),is a target pest of Bt maize in the Americas.The larvae of this pest are mobile,which may affect the efficacy of seed blend refuges.In this study,field and greenhouse trials were conducted to determine the performance of Bt-susceptible(aabb)and-heterozygous dual-gene-resistant(AaBb)genotypes of S.frugiperda in seed blends of non-Bt and pyramided Bt maize.Three field trials evaluated larval survival,larval growth,and plant injury with aabb in seed blends of Bt maize expressing Cry1A.105/Cry2Ab2/Vip3A with 0–30%non-Bt seeds.Greenhouse tests investigated the performance of aabb and AaBb in seed blends of Cry1A.105/Cry2Ab2 with 0–30% non-Bt seeds.In pure non-Bt maize plots,after 9–13 d of neonates being released on the plants,0.39 and 0.65 larvae/plant survived with leaf injury ratings of 4.7 and 5.9(Davis's 1–9 scale)in the field and greenhouse,respectively.In contrast,live larvae and plant injury were virtually not observed on Bt plants across all planting patterns.Larval occurrence and plant injury by aabb on non-Bt plants were similar between seed blends and pure non-Bt plantings,suggesting that the blended refuges could provide an equivalent susceptible population as structured refuge under the test conditions.In the greenhouse,the two insect genotypes in seed blends performed similarly,indicating that the seed blends did not provide more favorable conditions for AaBb over aabb.The information generated from this study should be useful in managing S.frugiperda and evaluating if send blends could be suitable refuge options for Bt resistance management in the regions where the insect is a primary target pest.
