Abstract:

Levels of resistance to Cry1Aa, Cry1Ab, Cry1Ac，Cry2Aa and Bt formulation (Bacillus thuringiensis subsp. kurstaki, Btk) in four field populations of Plutella xylostella collected respectively from Huizhou of Guangdong Province (GD-HZ), Fuzhou of Fujian Province (FJ-FZ), Hangzhou of Zhejiang Province (ZJ-HZ) and Nanjing of Jiangsu Province (JS-NJ) during the autumn of 2003 and the spring of 2004 were investigated. Compared with the susceptible PHI-S strain, the GD-HZ population exhibited high level resistance to Cry1Ab and Cry1Ac (168 and 120_fold respectively), middle level resistance to Btk (47-fold) and low level resistance to Cry1Aa and Cry2Aa (5.8 and 5.6-fold, respectively). The FJ-FZ, ZJ-HZ and JS-NJ populations showed similar resistance levels, with middle level resistance to Cry1Ab and Cry1Ac (8 to 28-fold), low level resistance to Btk (3.5 to 7-fold) and no resistance to Cry1Aa and Cry2Aa. So, it was proposed that the rotations of Btk with other Bt subspecies or other kinds of bioinsecticides should be encouraged in order to delay resistance development of P. xylostella in southeastern China.

Key words: Plutella xylostella, Bacillus thringiensis subsp. kurstaki, Bt δ-endotoxins, resistance