Abstract
Cover crop suppression with glyphosate-based herbicides (GBHs) represents a common agricultural practice. The objective of this study was to compare rhizospheric microbial communities of A. sativa plants treated with a GBH relative to the mechanical suppression (mowing) in order to assess their differences and the potential implications for soil processes. Samples were obtained at 4, 10, 17 and 26 days post-suppression. Soil catabolic profiling and DNA-based methods were applied. At 26 days, higher respiration responses and functional diversity indices (Shannon index and catabolic evenness) were observed under glyphosate suppression and a neat separation of catabolic profiles was detected in multivariate analysis. Sarcosine and Tween 20 showed the highest contribution to this separation. Metabarcoding revealed a non-significant effect of suppression method on either alpha-diversity metrics or beta-diversity. Conversely, differences were detected in the relative abundance of specific bacterial taxa. Mesorhizobium sequences were detected in higher relative abundance in glyphosate-treated plants at the end of the experiment while the opposite trend was observed for Gaiella. Quantitative PCR of amoA gene from ammonia-oxidizing archaea showed a lower abundance under GBH suppression again at 26 days, while ammonia-oxidizing bacteria remained lower at all sampling times. Broad host range plasmids IncP-1β and IncP-1ε were exclusively detected in the rhizosphere of glyphosate-treated plants at 10 days and at 26 days, respectively. Overall, our study demonstrates differential effects of suppression methods on the abundance of specific bacterial taxa, on the physiology and mobile genetic elements of microbial communities while no differences were detected in taxonomic diversity.
Highlights
Cover crops (CC) have gained popularity in agricultural practices as a sustainable alternative to fallow between grain crops, to incorporate carbon (C) rich residues in soils and to promote soils coverage, reducing risks of erosion, nitrogen (N) losses, and weeds proliferation [1,2,3]
Proteobacteria showed a clear dominance in the rhizosphere of A. sativa, in comparison with other phyla and in agreement with the results observed in the rhizosphere of A. fatua [72]
Our results are consistent with those reported by Vandenkoornhuyse et al [73] who demonstrated that Proteobacteria, in contrast to Actinobacteria and Acidobacteria, are the most active bacteria assimilating root exudates
Summary
Cover crops (CC) have gained popularity in agricultural practices as a sustainable alternative to fallow between grain crops, to incorporate carbon (C) rich residues in soils and to promote soils coverage, reducing risks of erosion, nitrogen (N) losses, and weeds proliferation [1,2,3]. Cover crop suppression with glyphosate-based herbicides (GBHs) represents a common agricultural practice. Considering the growing trend of CC in sustainable agriculture, thoroughly assessing the effects of suppression managements on microbial communities deserves investigation. Glyphosate may modify the quality and quantity of rhizodeposits stimulating the exudation of carbohydrates and amino acids [6,9] and promoting the turnover of dead root tissue [10], which, in turn, induce shifts in rhizospheric microbial communities [10]. As for them, no effects have been observed on bacterial communities (16S rRNA gene copy numbers) after mowing of barley [10] and on community structure of fungal/bacterial communities (assessed by denaturing gradient electrophoresis, DGGE) after defoliation of ryegrass [11]. The microbial activity and the proportion of fast and slow-growing bacteria were not affected by mowing treatment in barley [10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
