SINGLE‐HELICOVERPA ARMIGERA TEST TO DETERMINE INSECTICIDE RESISTANCE GENOTYPE FREQUENCY*

Abstract

Abstract A sensitive technique for identifying insecticide resistance genotype frequency of the Ace gene existing in natural populations of Helicoverpa armigera in China is described. The technique is based on the comparison of acetylcholinesterase (AChE) activity in 3 equal aliquots, which are taken from the homogenate of a single H. urnzigera: 1) in absence of inhibitor (well No. 1); 2) in absence of enzyme precursor (well No. 2); and 3) in presence of a concentration of propoxur inhibiting the AChE coded by the AceSallele but not by the AceRallele (well No. 3). An intensity of same strength in wells No. 1 and No. 3 indicates that propoxur has no effect on AChE activity, and the genotype should be AceRR(when well No. 3 = well No. 1). A same weak intensity in well No. 2 and No. 3 (and a strong intensity in well No. l), indicates that propoxur completely inhibited AChE activity; and the genotype should be AceSs(when well No. 3 = well No. 2). Well No. 3 displaying an intermediate intensity between well No. 1 (strong intensity) and well No. 2 (weak intensity) indicates that AChE activity was partially inhibited by the propoxur concentration and genotype should be AceRs(when well No. 2<well No. 3<well No. 1). The genotype frequency was determined in 1995 and 1996. the AceSSis 76. 1%, 70. 6% for low resistance populations respectively whereas the AceRRis 68. 3%, 65. 3% for high resistance population respectively.