New direct contact approach to evaluate soil genotoxicity using the Vicia faba micronucleus test.

A method to assess micronucleus (MN) induction in Vicia faba roots by direct contact exposure to a solid matrix was developed. The procedure comprised a 5-d germination period, as in the well-known method using aqueous extracts. However, the seeds were here sown directly into the test soil whereas a culture period is necessary before exposing seedlings to a liquid medium. One soil under forest and two contaminated soils from areas affected by industrial installations and a coke works were used. Three durations of direct exposure were tested: 2, 5 and 7 d. The optimal duration was evaluated at 2 d to observe maximal MN induction without observing toxicity symptoms. The methodology using aqueous extracts was applied to the same three soils: MN frequency was higher than in the direct contact assay but the ratios of MN frequencies from tested soils in comparison to the negative control were lower. However, for each soil, both the direct contact method and the aqueous extract exposure led to the same risk assessment diagnosis. The evaluation of a concentration range of a polycyclic aromatic hydrocarbons (PAH)-contaminated soil showed a dose-dependent MN frequency when the seeds were allowed to germinate before sowing in the soil: the soil genotoxicity was the highest at intermediate doses. The direct contact method was found to be rapid, sensitive and well suited to the evaluation of soil qualit

Etude de la génotoxicité de matrices complexes à l'aide de plantes supérieures

Complex matrices were investigated for genotoxicity in a series of experiments with higher plants : 2 spiked soils, one with metals (SI) and the other one with organics (SII), 2 contaminated soils and 2 activated sludges. Three different plant species were chosen : an herbaceous plant (Tradescantia, commonly named spiderwort), the broad bean (Vicia faba) and the small and white onion (Allium cepa). DNA strand breakages (detected with the micronucleus assay and with the comet assay) and somatic mutations were mainly studied. The genotoxicity tests with plants were carried out immersing the roots in the aqueous extract of each complex matrix (indirect procedure). Moreover, the results obtained with the Vicial/Allium assays were compared with those obtained with a direct procedure (in that case onion bulbs and broad bean seeds were directly put to germinate in each of the four soils) and an intermediate procedure (with root immersion in a mixture of soil and nutrient solution). Results showed the feasibility and the rapidity of the comet assay, the higher sensitivity of Vicia when compared to other species. A good correlation was found between the intermediate and the direct procedures, but the indirect procedure (with aqueous extract of soil) remained the most efficient way of exposure to detect the genotoxic potential of contaminated soils. Finally, the SI and SIII contaminated soils were shown to be highly genotoxic, while the SII and SIV soils appeared to be weakly genotoxic. The activated sludges were found to be very weakly genotoxic, specially when they are compostedLa présente étude concerne principalement les effets génotoxiques de différentes matrices complexes sur des plantes supérieures : 2 sols artificiellement contaminés, l'un avec des métaux (SI) et l'autre avec des polluants organiques (SII), 2 sols prélevés sur sites contaminés (SIII et SIV) et 2 boues : une boue digérée de station d'épuration urbaine (B1) et la même boue compostée (B3). Nous avons sélectionné 3 plantes supérieures : tradescantia (une plante herbacée), Vicia faba (la fève) et Allium cepa (l'oignon blanc). Le génome peut être altéré de diverses façons, mais nous nous sommes intéressés aux cassures de brins d'ADN (qui peuvent être détectées par le test des micronoyaux ou par le test des comètes) et aux mutations somatiques. Parallèlement à ces travaux, l'élongation racinaire et l'indice mitotique ont été déterminés sur Vicia et Allium. Tous ces critères ont été systématiquement réalisés sur les lixiviats (rapport solide/liquide = 1/10) des matrices testées. En outre, nous avons comparé 3 modes d'exposition en utilisant Vicia et Allium : un mode direct (phase solide), un mode indirect (lixiviat) et un mode intermédiaire où les olnates ont été mises en contact avec le sol mélangé à un milieu nutritif. Les résultats ont permis de mettre clairement en évidence les avantages de certains tests : la rapidité du test des comètes dont l'applicabilité aux cellules végétales a été démontrée, la plus grande sensibilité de Vicia par rapport aux autres espèces. Une bonne corrélation a été démontrée entre les deux modes d'exposition "alternatifs" à la lixiviation, mais ce procédé demeure le plus efficace pour détecter le potentiel génotoxique des sols contaminés. Enfin, nous avons mis en évidence une génotoxicité des sols SI et SIII et dans une moindre mesure, des sols SII et SIV. Quant à la boue de station d'épuration, elle a induit très peu d'effets génotoxiques sur les plantes étudiées. Ces effets sont d'ailleurs encore moins apparents après compostag

Genotoxicity of active compounds mesotrione and s-metolachlor and their commercial formulations in Vicia faba L

International audienceGenotoxicity of active compounds mesotrione and s-metolachlor and their commercial formulations in Vicia faba

Using Vicia-micronucleus test to assess soil genotoxicity potential

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Effets du pH du sol sur le test de génotoxicité Vicia-micronoyaux

International audienceFace à la multiplication des sites et sols contaminés, il est nécessaire d’apporter une solution technique pour évaluer le potentiel génotoxique des sols. En effet, il n’existe actuellement aucun test normalisé au niveau international pour mesurer la génotoxicité (toxicité vis-à-vis du matériel génétique) des matrices solides par exposition directe. La normalisation ISO du test Vicia-micronoyaux nous a amenés à travailler sur l’effet du pH sur la fréquence des micronoyaux ainsi que la gamme de pH dans laquelle le test est réalisable. Deux approches ont été envisagées: la modification artificielle du pH d’un sol et l’exposition à des sols de pH naturellement différents. Les résultats montrent que le test peut être réalisé en respectant les critères de validité dans une gamme de pH allant de 3,1 à 9,0 sans observer d’augmentation de la fréquence des micronoyaux. Les tests réalisés avec les sols naturels de pH différents confirment ces résultats

Genotoxic effects and induction of phytochelatins in the presence of cadmium in Vicia faba roots

International audienceThis study investigates different effects in roots of Vicia faba (broad bean) after exposure to cadmium. Genotoxic effects were assessed by use of the well-known Vicia root tip micronucleus assay. Cytotoxic effects were evaluated by determining the mitotic index in root tip cells. Finally, molecular induction mechanisms were evaluated by measuring phytochelatins with HPLC. After hydroponical exposure of V. faba roots to a range of cadmium concentrations and during different exposure times, the results of this approach showed large variations, according to the endpoint measured: after 48 h of exposure, genotoxic effects were found between 7.5 × 10−8 and 5 × 10−7 M CdCl2, and cytotoxic effects were observed between 2.5 × 10−7 and 5 × 10−7 M CdCl2. Statistically significant phytochelatin (PC) concentrations were measured at ≥10−6 M CdCl2 for PC2, and at ≥10−5 M CdCl2 for PC3 and PC4

Decrease in the genotoxicity of metal-contaminated soils with biochar amendments

International audienceBiochar amendments, i.e., the solid product of biomass pyrolysis, reduce soil metal availability, which may lower the toxicity of metal-contaminated soils.A direct link between the decrease in soil metal availability and improved plant development is however often difficult to establish, as biochar may induce undesirable side effects on plant growth, e.g., a modification to plant nutrition. In order to investigate toxicity processes at a cellular level, roots of Vicia faba were exposed for 7 days to three metal-contaminated substrates and one control soil, amended with a 0 or 5% (w/w) addition of a wood-derived biochar.Exposure to pure biochar was also tested. Root tip cells were then observed to count the number of micronuclei as an estimation of DNA damage and the number of cells at mitosis stage. Results showed that biochar amendments led to a significant decrease in soil metal availability (Cd, Cu, Ni, Pb, and Zn) and to enhance root development on acidic substrates. The micronucleus frequency in root tip cells was positively correlated and the number of mitotic cells negatively, to the extractability of Zn in soils and to the concentration of Zn in secondary roots.Exposure to pure biochar caused a lower production of roots than most soil substrates, but led to the lowest number of observed micronuclei. In conclusion, biochar amendments can reduce the genotoxicity associated with the presence of metallic contaminants in soils, thereby potentially improving plant growth

Transfert et écotoxicité des produits de traitement du hêtre

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Vicia-micronucleus test as a tool to assess soil genotoxicity potential

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Determination of doses of dimethyl sulfoxide to be applied as solvent for the active compounds mesotrione, s-metolachlor and nicosulfuron: effects on Pseudokirchneriella subcapitata and Daphnia magna

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