Long-term selection for resistance ot transgenic cotton expressing Bacillus thuringiensis toxin in Helicoverpa armigera (Hubner) (Lepidoptera:Noctuidae)

摘要

Selection experiments for resistance to transgenic Bt cotton expressing Cry1Ac toxin in Helicoverpa armigera (Hubner) were conducted suing a leaf-feeding method with 42 selection episodes over 5 generations.The cotton bollworm developed resistance to transgenic Bt cotton after 12 generations (F_(12)) of selection.The survival rate of F_(12) neonates feeding on leaves of seedling stage for 4 days and boll-opening stage for 5 days of R_(19) line were ca 34 and 72%,respectively,compared with ca 0 and 40% for a non-selected sister strain (NYCS),but lower than or similar to that of F_(12) feeding on leaves of non-Bt cotton,Sumian 12 (ca 87 or 76%).Resistance of B thuringiensis HD-1 Dipel in neonates (F_(12)) was ca 6-fold.After 42 generations of selection,the strain developed a very high level of resistance to CrylAc protoxin,210 g kg~(-1) MVPII wettable powder and 200 g litre~(-1) MVPII liquid formulation,the resistance ratios being 1680-,1780-and ca 1200-fold,respectively,comparedw ith a laboratory susceptible strain (HZS).When compared with the non-selected NYCS,the resistance ratios to the above toxins were ca 540-,580-and 510-fold,respectivley,but to Dipel only ca 16-fold.The results indicated that it is very important to develop and implement effective resistance-management strategies and to detect early resistance to Bt cotton in field populations.