An Assessment of the Environmental Impacts of Transgenic Triploid Populus tomentosa in Field Condition

Abstract

Populus tomentosa grow rapidly, but are salt susceptible. To quickly and efficiently gain new poplar breeds with better salt resistance, a DREB transcription factor derived from Atriplex hortensis was transformed into triploid Populus tomentosa by our lab, which significantly improved the salt tolerance of host plants. However, environmental impacts of transgenic plants must be assessed before large-scale cultivation in China. Here, we conducted a field trial of AhDREB1 transgenic and non-transgenic triploid Populus tomentosa to assess the impact of transgenic trees on rhizospheric soil microbial communities and allelopathic activity of leaves. No significant differences in the number of soil microbes present were detected between the transgenic lines and the non-transgenic controls. The allelopathic activity of leaves from both the transgenic and non-transgenic lines varied with sampling time, but did not differ significantly between the transgenic and non-transgenic lines. These results indicate that the impact on the environment of AhDREB1 transgenic P. tomentosa did not differ significantly from that of the non-transformed controls for the variables observed in this field trial. We also investigated the persistence of AhDREB1 genes in decomposing transgenic poplar leaf on the soil under natural conditions for five months, and our data indicated that fragments of the genetically modified DNA were not detectable in the field after more than two months. We used a triphenyl tetrazolium chloride test (TTC) (or pollen germination method) and hybridization to test the pollen viability and fertility, respectively, of the transgenic and non-transgenic trees and the results showed that the pollen viability of both the transgenic and non-transgenic trees was extremely low in 2016; the receptor plant may have been sterile.

…Fell Upas Sits, the Hydra-Tree of Death †, or the Phytotoxicity of Trees

“…Supposedly, it promotes stable inheritance of functional chemical defense pathways in populations [281]. About 30 examples of clusters of genes encoding products important for secondary metabolic pathways were reviewed recently [282], but only for grass species.…”

“…Allelopathic tests on Lactuca sativa showed that the root exudates and leaf litter of field-grown transgenic Populus alba with xyloglucanase gene for increasing the cellulose content did not produce harmful substances [354]. Guo et al [282] evaluated the allelopathic activity of leaves from Populus tomentosa with the DREB transcription factor under field conditions. Sandwich and the soil-mix methods with Lactuca sativa seeds did not show significant differences between the transgenic and non-transgenic lines.…”