Abstract:

Objective: This study systematically evaluated the biosafety of first-generation transgenic BtCry1Ac European black poplar (Populus nigra) and its transgenic hybrid F₁ progeny ‘Jingxing 1’ and ‘Jingxing 2’, with a focus on the stability of the exogenous gene expression and insect-resistance traits, and investigated their potential impacts on rhizosphere soil microorganisms and biodiversity within forest stands, thereby providing a scientific basis for the biosafety assessment and industrial application of BtCry1Ac transgenic insect-resistant poplar. Method: PCR and RT-qPCR techniques were used to verify the stability of the target gene in transgenic poplar. Growth performance was evaluated by measuring plant height and diameter at breast height (DBH). Insect resistance was assessed through an 18-days feeding trial with Hyphantria cunea larvae. The pH value and major nutrient contents in the rhizosphere soil of different clones were determined using standard methods. Soil microbial community composition and diversity were profiled using 16SrRNA/ITS high-throughput sequencing. Understory weed and arthropod assemblages were monitored using quadrat surveys and Malaise traps. Result: 1) PCR and RT-qPCR detection results confirmed the stable presence and expression of the BtCry1Ac gene in both the primary transgenic P. nigra and the F₁ transgenic hybrid progeny, with a specific 546 bp amplicon detected. 2) Growth assessments revealed that tree height and DBH of transgenic clone ‘Jingxing 1’ and ‘Jingxing 2’ increased by 9.62% and 7.56%, and 17.57% and 15.07%, respectively, compared to the control 108 poplar (Populus × euramericana ‘Guariento’), though these differences were not statistically significant. 3) Laboratory feeding assays demonstrated that the insect resistance of ‘Jingxing 1’and ‘Jingxing 2’ against H. cunea larvae was significantly higher than that of 108 poplar, with larval mortality rates increasing by 116.24% and 96.21% higher than the control after 18 days. 4) Analysis of the physicochemical properties of rhizosphere soil showed that there was a modest but significant rise in pH in the rhizosphere soil of transgenic clone n208, whereas organic matter, N, P, and K contents remained statistically unchanged. 5) There were no significant alterations in the composition of dominant bacterial (Proteobacteria) and fungal (Ascomycota) phyla. There was no statistically significant difference in α diversity indices of bacterial and fungal community structure among different clones. However, β diversity analysis revealed that there was significant differentiation in fungal community structure, while the bacterial community structure remained stable. 6) Understory surveys recorded 14 weed species (8 families) and 22 arthropod families (6 orders). The expression of BtCry1Ac gene did not have a significant impact on the species richness, Shannon diversity, dominance, nor evenness indices of weed communities. Target Lepidopteran pests declined markedly, yet overall arthropod community composition was highly similar to the control, with no significant changes in key diversity metrics. Conclusion: BtCry1Ac-transgenic poplar stably expresses the exogenous gene and exhibits high insect resistance, with no significant adverse effects on soil nutrient cycling, microbial α diversity, and the stability of understory biological communities. The hybrid progeny ‘Jingxing 1’ and ‘Jingxing 2’ demonstrate promising insect resistance and application potential. This study provides a scientific basis for the environmental biosafety assessment of transgenic poplar, and long-term ecological monitoring is recommended to systematically evaluate their impact on the ecological environment.

Key words: transgenic poplar, BtCry1Ac, insect resistance, biodiversity, soil microorganism, environmental risk assessment