Yang Y-H, Yang Y-J, Gao W-Y, Guo J-J, Wu Y-H, Wu Y-D
Key Lab of Monitoring and Management of Plant Diseases and Insects, Ministry of Agriculture, College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
Bull Entomol Res. 2009 Apr;99(2):175-81. doi: 10.1017/S0007485308006226. Epub 2008 Oct 28.
A disrupted allele (r1) of a cadherin gene (Ha_BtR) is genetically associated with incompletely recessive resistance to Bacillus thuringiensis toxin Cry1Ac in a Cry1Ac-selected strain (GYBT) of Helicoverpa armigera. The r1 allele of Ha_BtR was introgressed into a susceptible SCD strain by crossing the GYBT strain to the SCD strain, followed by repeated backcrossing to the SCD strain and molecular marker assisted family selection. The introgressed strain (designated as SCD-r1, carrying homozygous r1 allele) obtained 438-fold resistance to Cry1Ac, >41-fold resistance to Cry1Aa and 31-fold resistance Cry1Ab compared with the SCD strain; however, there was no significant difference in susceptibility to Cry2Aa between the integrated and parent strains. It confirms that the loss of function mutation of Ha_BtR alone can confer medium to high levels of resistance to the three Cry1A toxins in H. armigera. Reciprocal crosses between the SCD and SCD-r1 strains showed that resistance to Cry1Ac in the SCD-r1 strain was completely recessive. Life tables of the SCD and SCD-r1 strains on artificial diet in the laboratory were constructed, and results showed that the net replacement rate (R0) did not differ between the strains. The toxicity of two chemical insecticides, fenvalerate and monocrotophos, against the SCD-r1 strain was not significantly different from that to the SCD strain. However, larval development time of the SCD-r1 strain was significantly longer than that of the SCD strain, indicating a fitness cost of slower larval growth is associated with Ha_BtR disruption in H. armigera.
钙黏蛋白基因（Ha_BtR）的一个 disrupted 等位基因（r1）在棉铃虫的 Cry1Ac 选择品系（GYBT）中与对苏云金芽孢杆菌毒素 Cry1Ac 的不完全隐性抗性存在遗传关联。通过将 GYBT 品系与 SCD 品系杂交，随后反复回交至 SCD 品系并进行分子标记辅助家系选择，将 Ha_BtR 的 r1 等位基因导入到敏感的 SCD 品系中。导入品系（命名为 SCD-r1，携带纯合 r1 等位基因）对 Cry1Ac 的抗性比 SCD 品系高 438 倍，对 Cry1Aa 的抗性高 41 倍以上，对 Cry1Ab 的抗性高 31 倍；然而，导入品系与亲本品系对 Cry2Aa 的敏感性没有显著差异。这证实了 Ha_BtR 的功能缺失突变单独就能赋予棉铃虫对三种 Cry1A 毒素中到高水平的抗性。SCD 品系和 SCD-r1 品系之间的正反交表明，SCD-r1 品系对 Cry1Ac 的抗性是完全隐性的。构建了 SCD 品系和 SCD-r1 品系在实验室人工饲料上的生命表，结果表明品系间的净增殖率（R0）没有差异。两种化学杀虫剂氰戊菊酯和久效磷对 SCD-r1 品系的毒性与对 SCD 品系的毒性没有显著差异。然而，SCD-r1 品系的幼虫发育时间明显长于 SCD 品系，这表明棉铃虫中 Ha_BtR 破坏与幼虫生长缓慢的适合度代价相关。
