Journal
ECOLOGICAL ENTOMOLOGY
Volume 32, Issue 4, Pages 366-375Publisher
WILEY
DOI: 10.1111/j.1365-2311.2007.00891.x
Keywords
Cry1Ac; Helicoverpa armigera; Bt cotton; resistance frequency
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Changes in the frequency of Cry1Ac resistance genes and shifts in tolerance of cotton bollworm, Helicoverpa armigera, to the Cry1Ac toxin were assessed using bioassays of F-1 and F-2 offspring of isofemale lines from Anci County of Hebei Province (a multiple-crop system including corn, soybean, peanut, and Bt cotton) and Xiajin County of Shandong Province (an intensive Bt cotton planting area) in Northern China during 2002-2005. A conservative analysis of the overall results indicated that there was a small increase in the frequency of major, non-recessive resistance genes over time. The relative average development ratings [RADR - growth rate of a line on a Bt diet in proportion to the growth rate on a non-Bt (NBT) diet] of the bollworm larvae in F-1 tests increased significantly from year to year, indicating a gradual trend towards higher tolerance to Cry1Ac in the field populations. There were also significant positive correlations between RADR of the lines in the F-1 generation and the RADR of their F-2 offspring, indicating that the tolerance was genetically based. Quantitative genetic simulation analysis showed that resistance of H. armigera to Bt cotton in Xiajin could evolve to a high level in 11-15 years if no effective resistance management measures are carried out.
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