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<p>Transgenic crops producing insecticidal <i>Bacillus thuringiensis</i> (Bt) proteins have revolutionized the control of some pests. However, the evolution of resistance by pests has reduced the efficacy of Bt crops. Pest resistance to Bt crystalline (Cry) proteins has spurred a shift to crops that produce the Bt vegetative insecticidal protein Vip3Aa together with Cry proteins. With widespread field-evolved practical resistance of the major pest <i>Helicoverpa zea</i> (corn earworm or bollworm) to Cry proteins in the United States, Vip3Aa is the only Bt protein in transgenic corn and cotton that is highly effective against many populations. We generated five strains of <i>H. zea</i> with &gt; 100-fold resistance to Vip3Aa in a susceptible genetic background using F<sub>2</sub> screens of field populations from Louisiana, Mississippi, and Texas followed by crosses to a susceptible strain and additional laboratory selection with Vip3Aa. The results from diet bioassays show that in these Vip3Aa-resistant strains, cross-resistance to Cry1Ab, Cry1Ac, Cry1A.105, Cry1Fa, and Cry2Ab was not consistent and ranged 1100-fold: from 16-fold negative cross-resistance to 65-fold positive cross-resistance. By crossing a Vip3Aa-resistant strain with a Cry-resistant strain followed by selection with both types of Bt protein, we generated a strain highly resistant to Cry1Ac, Cry2Ab, and Vip3Aa. Cry1Ac and Cry2Ab interacted synergistically with Vip3Aa against this triple-resistant strain, such that combinations of the Cry proteins and Vip3Aa caused higher mortality than expected from their individual toxicity. The observed synergy may increase the durability of Bt crops producing combinations of these proteins against <i>H. zea</i>.</p>

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Evaluating cross-resistance and synergy between Vip3Aa and Cry proteins from Bt in six strains of Helicoverpa zea derived via F2 screens

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月9日

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  • Yucheng Wang,
  • David L. Kerns,
  • Graham P. Head,
  • Dawson Kerns,
  • Bruce E. Tabashnik,
  • Fei Yang

摘要

Transgenic crops producing insecticidal Bacillus thuringiensis (Bt) proteins have revolutionized the control of some pests. However, the evolution of resistance by pests has reduced the efficacy of Bt crops. Pest resistance to Bt crystalline (Cry) proteins has spurred a shift to crops that produce the Bt vegetative insecticidal protein Vip3Aa together with Cry proteins. With widespread field-evolved practical resistance of the major pest Helicoverpa zea (corn earworm or bollworm) to Cry proteins in the United States, Vip3Aa is the only Bt protein in transgenic corn and cotton that is highly effective against many populations. We generated five strains of H. zea with > 100-fold resistance to Vip3Aa in a susceptible genetic background using F2 screens of field populations from Louisiana, Mississippi, and Texas followed by crosses to a susceptible strain and additional laboratory selection with Vip3Aa. The results from diet bioassays show that in these Vip3Aa-resistant strains, cross-resistance to Cry1Ab, Cry1Ac, Cry1A.105, Cry1Fa, and Cry2Ab was not consistent and ranged 1100-fold: from 16-fold negative cross-resistance to 65-fold positive cross-resistance. By crossing a Vip3Aa-resistant strain with a Cry-resistant strain followed by selection with both types of Bt protein, we generated a strain highly resistant to Cry1Ac, Cry2Ab, and Vip3Aa. Cry1Ac and Cry2Ab interacted synergistically with Vip3Aa against this triple-resistant strain, such that combinations of the Cry proteins and Vip3Aa caused higher mortality than expected from their individual toxicity. The observed synergy may increase the durability of Bt crops producing combinations of these proteins against H. zea.