Growth and arthropod community characteristics of transgenic poplar 741 in an experimental forest *

Use of the Bt insect-resistance gene has provided substantial economic and ecological benefits. Full utilization of transgenic poplars requires a comprehensive understanding of the growth-related phenotypic characteristics and ecological risks associated with of genetically modified trees. In the present study, we assessed the effects of transgenic poplar 741 with different insect-resistant genes on plant growth and arthropod communities in the field. Transgenic lines carrying the Cry1Ac and Cry3A genes were used as model lines, and non-transgenic poplar 741 was used as a control. Over a period of 6 years, we analyzed plant growth and transcriptomic data, and monitored arthropod richness and abundance in an experimental forest comparing transgenic and control lines. Our results indicate that the Pb29 line had a similar plant height to CK, but a significantly lower diameter at breast height (DBH) than CK. The plant height and DBH of the CC84 line were slightly higher than those of CK, but the differences were not significant. Transcriptome data analysis showed downregulated and upregulated expression of growth hormone-related genes and lignin synthesis-related genes, respectively, in the Pb29 line compared with CK and the CC84 line. The survey data obtained in this study showed that annual trends in arthropod numbers in the ecosystem were consistent among transgenic poplar 741 and control lines, gradually decreasing with time since planting. The Cry1Ac line has selective resistance to Lepidoptera and exerted strong toxic effects on Arctiidae, Tortricidae, and Notodontidae, but had no obvious effects on Lyonetiidae or Geometridae. The Cry3A line exhibited significant resistance to coleopterans only in 2016 when the abundance of coleopteran insects was high. Both lines exhibited inhibitory effects on non-target pests. The two transgenic lines were similar to the control with respect to arthropod community structure, and there were no significant differences in arthropod diversity indices between transgenic and control lines, although richness was slightly higher for the Cry3A line than for the control. The results of this study showed that the insertion of Bt genes had no apparent inhibitory effect on the growth of poplar 741. Also, there was no adverse environmental impact of transgenic poplar 741 on ecosystem arthropod communities compared with conventional poplar 741.

Automated summary

The study showed that transgenic poplar lines carrying Cry1Ac and Cry3A genes had different phenotypic characteristics compared to non-transgenic poplar 741, but did not significantly impact arthropod communities in the ecosystem.