The Efficacy of a <i>cry</i> 1Ac9 Gene Conferring Insect Resistance Is Influenced by the Target Plant Species

The efficacy of cry genes in different plant species is critical for the design and implementation of stewardship plans targeting resistance to polyphagous insects in multiple crops. Transgenic plants of three solanaceous species: Nicotiana tabacum L. (tobacco), Solanum aethiopicum L. (scarlet eggplant), and Solanum tuberosum L. (potato) were therefore transformed using the same binary vector with a cry 1Ac9 gene and assessed in bioassays against the same population of potato tuber moth (PTM; Phthorimaea operculella ). The insect resistance conferred by the cry 1Ac9 gene differed markedly among the three plant species. The cry 1Ac9 gene was most effective in scarlet eggplant, with all four transgenic lines exhibiting high mortality of neonate PTM larvae (60%–100% mortality) and very low mean larval growth index. All 24 transgenic lines of tobacco produced significantly reduced mean larval growth indices, with 50% of the lines exhibiting 7%–33% mortality. Among the 119 transgenic potato lines from six cultivars the mean larval growth indices were substantially higher, with only 85% exhibiting significant growth inhibition. No larval mortality was observed on the transgenic potato lines. The findings have important implications for managing polyphagous insect pests when the same cry gene is deployed in multiple crops.