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International audience; β-triketone herbicides are among the most used herbicides in corn crop. These herbicides inhibit the 4-hydroxyphenylpyruvate dioxygenase (4-HPPD), lead to bleaching and prevent the growth of broadleaf weeds. This enzyme is not only found in plants but in all living organisms, including microorganisms where it plays a role in the tyrosine degradation pathway. Thus, microorganisms classified as “non-target organisms” by current EU regulation for pesticide authorization, might be impacted by β-triketones, with consequences on microbial function supporting soil ecosystem services. Since microorganisms have been proposed by EFSA as key-drivers to protect soil ecosystem services, we suggest a novel approach consisting in considering the hppd bacterial community as a biomarker sensitive to the exposure to β-triketone residues. With this objective, we developed a toolbox to monitor the abundance, the composition, the diversity and the activity of the hppd bacterial community. Each method was tested in a lab-tofield experimental design following the tiered-approach recommended by EFSA to conduct pesticide environmental risk assessment (ERA). Under lab conditions, soil microcosms not exposed (control) or exposed to x1 or x10 the agronomical dose of sulcotrione (active ingredient) or Decano® (one of the commercial formulation of sulcotrione) were studied. Under field conditions, samples were collected in corn crop exposed to β-triketones. Soil samples were also collected from a non-treated corn field (not exposed control). Analytical chemistry was applied to all samples to search for β-triketone residues and to estimate the scenario of exposure of soil microorganisms. Nucleic acids (DNA/RNA) were extracted from soil samples to measure the abundance (quantitative PCR), the expression (quantitative RT-qPCR), the composition (α-diversity) and the diversity (β-diversity) (NGS) of the hppd bacterial community. Our results will be presented to the audience with the aim to identify the better proxy of the hppd bacterial community that could be used as a biomarker to reflect the exposure of soil microbial community to β-triketone residues. This explanatory work might be extended to other pesticides targeting other enzymes that are also present in so call non-target organisms such as sulfonylureas inhibiting acetohydroxy acid synthase (AHAS).

International audience; β-triketone herbicides are among the most used herbicides in corn crop. These herbicides inhibit the 4-hydroxyphenylpyruvate dioxygenase (4-HPPD), lead to bleaching and prevent the growth of broadleaf weeds. This enzyme is not only found in plants but in all living organisms, including microorganisms where it plays a role in the tyrosine degradation pathway. Thus, microorganisms classified as “non-target organisms” by current EU regulation for pesticide authorization, might be impacted by β-triketones, with consequences on microbial function supporting soil ecosystem services. Since microorganisms have been proposed by EFSA as key-drivers to protect soil ecosystem services, we suggest a novel approach consisting in considering the hppd bacterial community as a biomarker sensitive to the exposure to β-triketone residues.With this objective, we developed a toolbox to monitor the abundance, the composition, the diversity and the activity of the hppd bacterial community. Each method was tested in a lab-to-field experimental design following the tiered-approach recommended by EFSA to conduct pesticide environmental risk assessment (ERA). Under lab conditions, soil microcosms not exposed (control) or exposed to x1 or x10 the agronomical dose of sulcotrione (active ingredient) or Decano® (one of the commercial formulation of sulcotrione) were studied. Under field conditions, samples were collected in corn crop exposed to β-triketones. Soil samples were also collected from a non-treated corn field (not exposed control). Analytical chemistry was applied to all samples to search for β-triketone residues and to estimate the scenario of exposure of soil microorganisms. Nucleic acids (DNA/RNA) were extracted from soil samples to measure the abundance (quantitative PCR), the expression (quantitative RT-qPCR), the composition (α-diversity) and the diversity (β-diversity) (NGS) of the hppd bacterial community. Our results will be presented to the audience with the aim to identify the better proxy of the hppd bacterial community that could be used as a biomarker to reflect the exposure of soil microbial community to β-triketone residues.This explanatory work might be extended to other pesticides targeting other enzymes that are also present in so call non-target organisms such as sulfonylureas inhibiting acetohydroxy acid synthase (AHAS).