| Summary: | Increasing areas of artificial afforestation and poplar monoculture in China have led to serious problems with insect pests. The development of genetic engineering technology, such as transgenic modification with <i>Bacillus thuringiensis</i> (<i>Bt</i>) genes, provides novel solutions to the pest problem. We generated a <i>Bt-Cry1Ah1</i> gene incorporating codon optimization and transferred it into <i>Populus deltoides</i> × <i>P. euramericana</i> cv “Nanlin895” using an Agrobacterium-mediated method. The resulting <i>Bt-Cry1Ah1</i> transgenic poplars were planted in the field with permission from the State Forestry Administration in 2017. Field and laboratory studies were conducted in Jiangsu, China, to investigate the effects of these transgenic poplars expressing the Cry1Ah1 protein on target and non-target pests and their parasitic natural enemy. Target pests included <i>Hyphantria cunea</i> (Lepidoptera, Arctiidae), <i>Micromelalopha troglodyta</i> (Lepidoptera, Notodontidae), and <i>Clostera anachoreta</i> (Lepidoptera, Notodontidae). <i>Plagiodera versicolora</i> (Coleoptera, Chrysomelidae) served as the non-target pest. Laboratory trials showed that the six transgenic poplar lines exhibited resistance against the target insects. The corrected mortality rates of the target pest larvae fed leaves from the six lines were as high as 87.0%, significantly higher than that of the control. However, the corrected mortality rate of the non-target pest larvae was markedly lower and did not differ significantly from that of the control. Field experiments showed that transgenic poplar exhibited resistance against <i>H. cunea</i> and <i>M. troglodyta</i>. Field mortality rates were slightly higher than laboratory mortality rates. In addition, we investigated <i>Chouioia cunea</i> (Hymenoptera, Eulophidae) as a parasitoid of <i>H. cunea</i> pupae that had been fed transgenic poplar leaves. The emergence time, parasitism rate, and abundance of <i>C. cunea</i> did not differ significantly from those of the control. Therefore, <i>Bt-Cry1Ah1</i> transgenic poplar can be used to effectively control damage by target insect pests without negatively affecting non-target insects and parasitoids.
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