小菜蛾对杀虫双和杀螟丹抗性的现实遗传力

Realized heritability of resistance to dimehypo and cartap in diamondback moth, Plutella xylostella

利用室内选育 119代的小菜蛾Plutellaxylostella抗性品系 ,分析了小菜蛾对杀虫双和杀螟丹抗药性的现实遗传力 ,并对遗传力和杀虫剂的杀死率对抗性发展速率的影响进行了预测。结果表明 ,室内继代药剂选择 119代后 ,小菜蛾对杀虫双和杀螟丹抗性的遗传力很低 (h2 =0 0 3)。因此 ,小菜蛾对这两种药剂产生更高水平抗性的潜力不大。在选择的前半段 (F30 ) ,杀虫双和杀螟丹的抗性遗传力 (分别为 0 14和 0 11)高于选择后半段 (F80 )的遗传力 (均为 0 0 5) ,选择前、后半段的选择差数没有明显差别。即使在室内选择条件下 ,假如斜率 =2 0 (δP=0 5) ,h2 =0 0 5,群体中 70 %个体致死时要获得 10倍的抗性 ,约需 34代。田间条件下 ,由于等位基因频率的变化、环境变异等因素的影响 ,抗性增长 10倍则需要更长的时间 。

Using the larvae of the diamondback moth Plutella xylostella reared in laboratory for 119 generations as resistant strains,the realized heritability ( h 2)of resistance to dimehypo (DR) and cartap (CR)was analysed.The results demonstrated that realized heritability of DR and CR was lower. The index h 2 was higher for the first half generations (F 30 =0 14 for DR and 0 11 for CR)than for the second half ( F 80 =0 05 for DR and 0 05 for CR).Selection differential did not differ significantly between the halves.These results suggest that substantial additive genetic variation was present initially and then declined as selection proceeded.Assuming that slope=2 0(δ p =0 5), h 2=0 05,and selection killing 70% of the population,34 generations are required for a 10 fold increase in resistance.The number of generations required for a 10 fold increase would be even more in field due to the changes in allele frequency and environmental variation or both.The index h 2 was 0 03 after 119 generations selected by either dimehypo or cartap.In this case,the resistant allele frequencies had become stable. Thus,the potential for developing higher level resistance was very lower.