Reduced levels of glyphosate-based herbicide residues were found to have a negative impact on endophytic microbes linked to garden strawberry. In a field study, researchers at the University of Turku, Finland, followed the standard agricultural practices of herbicide application and investigated the impact of glyphosate residues in soil on the endophytic microbial communities of garden strawberry.
‘Wealth of certain plant-beneficial endophytic microbes and the governance of potentially glyphosate resistant bacteria are concerning if they have effects on plant health in the long run.’
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Samples collected from strawberry plants that had been growing in the experimental field showed that even though the overall composition of a microbial community and the growth of garden strawberries were unaffected, certain endophytic microbes known for their plant-beneficial functions were relatively less abundant in the strawberry plants that had been exposed to herbicide residues in soil.“These plant-beneficial microbes are endophytic meaning that they live within leaves and roots of plants. They include bacteria, and fungi, and they form microbial communities within plants. These microbial communities promote nutrition, disease resistance and stress tolerance of their host plants. So, these endophytic microbes are essential partners of plants, as plants depend on them for health and survival,” explains Dr. Suni Mathew from the University of Turku Department of Biology.
Glyphosate-based herbicides are used to kill weeds in agricultural fields before sowing and are claimed to degrade quickly in the soil, so that agricultural crops planted after the two-week safety period are not exposed to the chemical. However, other studies have shown that this is not the case and low residues of glyphosate are found in the soil even after two weeks.
What Are the Long-Term Effects of Glyphosate-Based Herbicides on Soil?
In this study, the herbicide plots of experimental field were sprayed with the standard dose of glyphosate-based herbicide (glyphosate concentration: 450 g L–1, CAS: 3864-194-0, application rate: 6.4 L ha−1) and control plots with tap water. After spraying, the researchers observed the two-week long safety period before planting the strawberry plantlets.Researchers are only starting to understand the importance of endophytic microbes to plant health.
The effect of glyphosate is based on inhibition of the ‘shikimate pathway’, a metabolic pathway for the synthesis of amino acids that is found in plants but not in animals. However, this pathway is present also in many microbes.
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The study also utilized a new bioinformatics approach for finding whether the changes in microbial communities are linked to their sensitivity to glyphosate. The results showed that the microbial community in the roots of the plants in the herbicide plots had more potentially glyphosate-resistant bacteria than the roots of the plants in the control plots.
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Source-Eurekalert