Background Following the introduction of Bacillus thuringiensis(Bt)cotton in India,its cultivation expanded rapidly from 29000 hectares in 2002-2003 to 3353000 hectares in 2006-2007 with Bollgard I.To delay and manage...Background Following the introduction of Bacillus thuringiensis(Bt)cotton in India,its cultivation expanded rapidly from 29000 hectares in 2002-2003 to 3353000 hectares in 2006-2007 with Bollgard I.To delay and manage resistance to the Cry1Ac toxin,genotypes expressing two toxins,Cry1Ac and Cry2Ab(BollgardⅡ),were introduced in 2006.By 2010,these BollgardⅡgenotypes had gradually replaced Bollgard I to enhance resistance management.However,the widespread use of Bt cotton increased selection pressure,leading to field resistance in the pink bollworm(PBW),Pectinophora gossypiella.Conventional bioassays used to confirm resistance are time-consuming.To address this limitation,bulk segregant analysis(BSA)has been employed to identify simple sequence repeat(SSR)markers for Cry resistance,providing a quicker and more cost-effective assessment method.Results Among the 59 Pectinophora gossypiella populations analyzed across India during 2022-2023,the Nagpur population exhibited the highest resistance levels,with median lethal concentration(LC_(50))values of 7.682µg·mL^(-1)for Cry1Ac(resistance ratio=960)and 12.574µg·mL^(-1)for Cry2Ab(resistance ratio=2096).Furthermore,the Nagpur PBW strain was used in bulk segregant analysis and identified three polymorphic SSR markers(notr15F/r15allR2,164Pgcad5F/163Pgcad3R and gF47/gR47)linked to Cry1Ac resistance.The marker pair gF47/gR47 also showed polymorphism in Cry2Ab-resistant individuals.These markers were further validated during the 2023-2024 season using samples collected from 15 locations across India,including larvae,pupae,and adult males.The molecular marker results were consistent with traditional larval bioassay outcomes,confirming their association with resistance phenotypes.Conclusion Using specific SSR markers,a rapid and highly reliable technique for identifying resistance in Indian populations of pink bollworms to Cry toxins(Cry1Ac and Cry2Ab)has been found.The whole process was dependable,quick,robust,and cost-effective.展开更多
基金supported by the Department of Science&Technology(DST)—Innovation in Science Pursuit for Inspired Research(INSPIRE)Fellowship,Government of India(Grant number:DST/INSPIRE Fellowship/2021/IF210036)awarded to the first author.
文摘Background Following the introduction of Bacillus thuringiensis(Bt)cotton in India,its cultivation expanded rapidly from 29000 hectares in 2002-2003 to 3353000 hectares in 2006-2007 with Bollgard I.To delay and manage resistance to the Cry1Ac toxin,genotypes expressing two toxins,Cry1Ac and Cry2Ab(BollgardⅡ),were introduced in 2006.By 2010,these BollgardⅡgenotypes had gradually replaced Bollgard I to enhance resistance management.However,the widespread use of Bt cotton increased selection pressure,leading to field resistance in the pink bollworm(PBW),Pectinophora gossypiella.Conventional bioassays used to confirm resistance are time-consuming.To address this limitation,bulk segregant analysis(BSA)has been employed to identify simple sequence repeat(SSR)markers for Cry resistance,providing a quicker and more cost-effective assessment method.Results Among the 59 Pectinophora gossypiella populations analyzed across India during 2022-2023,the Nagpur population exhibited the highest resistance levels,with median lethal concentration(LC_(50))values of 7.682µg·mL^(-1)for Cry1Ac(resistance ratio=960)and 12.574µg·mL^(-1)for Cry2Ab(resistance ratio=2096).Furthermore,the Nagpur PBW strain was used in bulk segregant analysis and identified three polymorphic SSR markers(notr15F/r15allR2,164Pgcad5F/163Pgcad3R and gF47/gR47)linked to Cry1Ac resistance.The marker pair gF47/gR47 also showed polymorphism in Cry2Ab-resistant individuals.These markers were further validated during the 2023-2024 season using samples collected from 15 locations across India,including larvae,pupae,and adult males.The molecular marker results were consistent with traditional larval bioassay outcomes,confirming their association with resistance phenotypes.Conclusion Using specific SSR markers,a rapid and highly reliable technique for identifying resistance in Indian populations of pink bollworms to Cry toxins(Cry1Ac and Cry2Ab)has been found.The whole process was dependable,quick,robust,and cost-effective.
