Plant Genotype Influences Physicochemical Properties of Substrate as well as Bacterial and Fungal Assemblages in the Rhizosphere of Balsam Poplar

Abstract

14Abandoned unrestored mines are an important environmental issue since they typically remain 15 unvegetated for decades, exposing vast amounts of mine waste to erosion. Several factors limit the 16 revegetation of these sites, including extreme abiotic conditions and unfavorable biotic conditions. 17However, some pioneer tree species having high level of genetic diversity, such as balsam poplar 18 (Populus balsamifera), are able to naturally colonize these sites and initiate plant succession. This 19 suggests that some tree genotypes are likely more suited for acclimation to the conditions of mine 20wastes. In this study, two contrasting mine waste storage facilities (waste rock versus tailings) from 21the Abitibi region of Quebec (Canada), on which poplars have grown naturally, were selected. First, 22we assessed in situ the impact of vegetation presence on each type of mine wastes. The presence of 23 balsam poplars improved soil health locally by improving physicochemical properties (e.g. higher 24 nutrient content and pH) of the mine wastes and causing an important shift in their bacterial and 25 fungal community compositions, going from lithotrophic communities that dominate mine waste 26 environments to heterotrophic communities involved in nutrient cycling. Next, in a greenhouse 27 experiment, ten genotypes of P. balsamifera collected on both mine sites and from a natural forest 28 nearby were grown in these mine wastes. Tree growth was monitored during two growing seasons, 29after which the effect of genotype-by-environment interactions was assessed by measuring the 30 physicochemical properties of the substrates and the changes in microbial communities, using a 31 metabarcoding approach. Although substrate type was identified as the main driver of rhizosphere 32 microbiome diversity and community structure, a significant effect of tree genotype was also 33 detected, particularly for bacterial communities. Plant genotype also influenced aboveground tree 34 growth and the physicochemical properties of the substrates. These results highlight the influence of 35 Tree Genotype Impacts Rhizosphere Microbiomes 2 balsam poplar genotype on the soil environment and the potential importance of tree genotype 36 selection in the context of mine waste revegetation.

Soil Characteristics Constrain the Response of Microbial Communities and Associated Hydrocarbon Degradation Genes during Phytoremediation

“…The plants used for the experiments were cuttings harvested from the same adult poplar tree. Cuttings were propagated following a previously described method (70). Briefly, cuttings were kept at 4°C until rooting.…”

Soil characteristics constrain the response of bacterial and fungal communities and hydrocarbon degradation genes to phenanthrene soil contamination and phytoremediation with poplars

“…The plants used for the experiments were cuttings harvested from the same adult poplar tree ( Populus balsamifera) . Cuttings were propagated following the method described in (Rheault et al 2020). Briefly, cuttings were kept at 4 °C until rooting.…”