Growth and dynamic monitoring of target insect resistance of Bt-transgenic Populus × euramericana cv. “74/76” underlying field stands

The stability and sustained expression of superior traits in transgenic forest trees under long-term field cultivation are crucial criteria for assessing the safety and effectiveness of transgenic materials. However, continuous evaluation of the insect resistance of Bacillus thuringiensis ( Bt ) transgenic poplar during their field growth is still rare. Populus × euramericana cv. “74/76” (poplar 107), a fast-growing but lowly pest-resistant timber tree species in China, was selected as the transgenic receptor for this study. The exogenous insect-resistant gene ( Bt ) was transferred into poplar 107 by the Agrobacterium -mediated method. Herein, we present a study on a long-term field experiment of 10-year-old Bt -transgenic poplar 107. Based on Next-Generation Sequencing (NGS), 14 insertion sites were detected in three transgenic lines, among which 7 insertion sites were verified. The insertion of the exogenous gene had a certain negative impact on the growth of poplar 107. The transgenic poplar 107 exhibited sustained and significant inhibitory effects against target insects, with an overall inhibition rate exceeding 65 %. The suppression effect on Hyphantria cunea Drury during outbreak years is the most obvious. The inhibition rate of H. cunea exceeded 90 % in 2016, 2018, 2019 and 2020. This research demonstrates the long-term insect resistance of Bt -transgenic poplar 107, and offered a data basis for the cultivation and application of insect-resistant transgenic forest trees. • Multiple copies of T-DNA were found in transgenic lines. • The growth of transgenic line PB3 and PB9 was weaker than control. • Bt transcripts were higher in juvenile leaves, but Bt toxin protein was higher in mature leaves. • Transgenic poplar 107 has consistently suppressed target insects for a decade. • Year factors affect target insect numbers more than transgenic events.