Remediation of copper in vineyards--a mini review

Adverse effects of the Bordeaux mixture copper-based fungicide on the non-target vineyard pest Lobesia botrana

BACKGROUND

Bordeaux mixture is a copper-based fungicide commonly used in vineyards to prevent fungal and bacterial infections in grapevines. However, this fungicide may adversely affect the entomological component, including insect pests. Understanding the impacts of Bordeaux mixture on the vineyard pest Lobesia botrana is an increasing concern in the viticultural production.

RESULTS

Bordeaux mixture had detrimental effects on the development and reproductive performance of L. botrana. Several physiological traits were adversely affected by copper-based fungicide exposure, including a decrease in larval survival and a delayed larval development to moth emergence, as well as a reduced reproductive performance through a decrease in female fecundity and fertility and male sperm quality. However, we did not detect any effect of Bordeaux mixture on the measured reproductive behaviors (mating success, pre-mating latency and mating duration).

CONCLUSION

Ingestion by larvae of food contaminated with Bordeaux mixture had a negative effect on the reproductive performance of the pest L. botrana, which could affect its population dynamics in vineyards. Although this study highlighted collateral damage of Bordeaux mixture on L. botrana, the potential impact of copper-based fungicides on vineyard diversity, including natural predators is discussed and needs to be taken in consideration in integrated pest management. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of CUP1 copy number and pH on copper resistance of Saccharomyces cerevisiae enological strains

The widespread use of copper-based pesticides in winemaking can affect wine fermentation. Therefore, it is crucial to assess the resistance levels of Saccharomyces cerevisiae wine strains in enological growth conditions. In the context of winemaking, grape juice is a complex environment capable of chelating copper and is characterized by a distinctly acidic pH. In this work, the effects of copper concentration on the growth of 10 S. cerevisiae strains, isolated from an enological environment, and one commercial starter were tested in YNB minimal medium and synthetic must, mimicking enological conditions. In minimal medium, resistance to copper varied among yeasts (50-600 μM), revealing the presence of three resistance levels (high, intermediate, and low). Representative strains of the three groups were tested at a pH range from 5.2 to 3.0 at the copper concentration that showed a 20-25 % growth reduction. At pH range 5.2-4.5, a growth reduction was observed, while, conversely, a strain-specific recovery was observed at pH range 3.2-3.0. In synthetic must, the strains showed higher copper resistance levels than in minimal medium (50-4000 μM). In both synthetic must and minimal medium, a significant logarithmic correlation was found between copper resistance and CUP1 gene copy number. The copy number tended to better explain resistance in minimal medium compared to synthetic must. The results shed light on the role of CUP1 copy number within an enological environment.

Pest management facing warming and chemical stresses: Multi-stress effects on the biological agent Trichogramma oleae

Global change is affecting plant-insect interactions in agroecosystems and can have dramatic consequences on yields when causing non-targeted pest outbreaks and threatening the use of pest natural enemies for biocontrol. The vineyard agroecosystem is an interesting system to study multi-stress conditions: on the one hand, agricultural intensification comes with high inputs of copper-based fungicides and, on the other hand, temperatures are rising due to climate change. We investigated interactive and bottom-up effects of both temperature increase and copper-based fungicides exposure on the important Lepidopteran vineyard pest Lobesia botrana and its natural enemy, the oophagous parasitoid Trichogramma oleae. We exposed L. botrana larvae to three increasing copper sulfate concentrations under two fluctuating thermal regimes, one current and one future. Eggs produced by L. botrana were then exposed to T. oleae. Our results showed that the survival of L. botrana, was only reduced by the highest copper sulfate concentration and improved under the warmer regime. The development time of L. botrana was strongly reduced by the warmer regime but increased with increasing copper sulfate concentrations, whereas pupal mass was reduced by both thermal regime and copper sulfate. T. oleae F1 emergence rate was reduced and their development time increased by combined effects of the warmer regime and increasing copper sulfate concentrations. Size, longevity and fecundity of T. oleae F1 decreased with high copper sulfate concentrations. These effects on the moth pest and its natural enemy are probably the result of trade-offs between the survival and the development of L. botrana facing multi-stress conditions and implicate potential consequences for future biological pest control. Our study supplies valuable data on how the interaction between pests and biological control agents is affected by multi-stress conditions.

Assessment of heavy metals in soil, leaf litter, and their bioaccumulation in terrestrial macroinvertebrates in Sohag Governorate, Egypt

The presence of elevated levels of heavy metals in soil poses a significant environmental concern with implications for human health and other organisms. The main objective of our study was to reduce the gap information of seasonal abundance, distribution of heavy metals in soil, leaf litter, and some macroinvertebrates in a citrus orchard (Citrus sinensis) in Sohag Governorate, Egypt. The heavy metals copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) were determined by atomic absorption spectrometry. Degree of contamination (DC) was determined for both soil and leaf litter contamination. However, the bioaccumulation factor (BAF) was estimated to determine metal accumulation in the macroinvertebrates including earwigs Anisolabis maritima, chilopoda Scolopendra moristans, spider Dysdera crocata, and earthworm Aporrectodea caliginosa. The study area had clay-loam with varying organic matter, salinity, and pH levels. The degree of contamination varied among seasons, with the highest levels typically observed in autumn in both soil and leaf litter. The soil ranged from low contamination (1.82) to high contamination levels (4.4), while the leaf litter showed extremely high (30.03) to ultra-high (85.92) contamination levels. The mean ecological risk index results indicated that the sampling area had moderate ecological risk levels for Cd (44.3), Zn (42.17), and Pb (80.05), and extremely high levels for Cu (342.5). Heavy metal concentrations in the selected fauna were the highest in autumn, and the bioaccumulation factor varied among species and seasons with some species classified as e-concentrators, micro-concentrators, and macro-concentrators of certain heavy metals. Scolopendra moristans exhibited the highest mean metal concentrations (Cd, Pb, and Zn), while Aporrectodea caliginosa had the lowest. Thus, the differences in heavy metal concentrations found in different soil taxa highlight the significance of taxing a holistic understanding of feeding mechanisms into account when evaluating the potential risk for animals that consume invertebrates.

The distribution of beneficial mutational effects between two sister yeast species poorly explains natural outcomes of vineyard adaptation

Domesticated strains of Saccharomyces cerevisiae have adapted to resist copper and sulfite, two chemical stressors commonly used in winemaking. S. paradoxus, has not adapted to these chemicals despite being consistently present in sympatry with S. cerevisiae in vineyards. This contrast represents a case of apparent evolutionary constraints favoring greater adaptive capacity in S. cerevisiae. In this study, we used a comparative mutagenesis approach to test whether S. paradoxus is mutationally constrained with respect to acquiring greater copper and sulfite resistance. For both species, we assayed the rate, effect size, and pleiotropic costs of resistance mutations and sequenced a subset of 150 mutants isolated from our screen. We found that the distributions of mutational effects displayed by the two species were very similar and poorly explained the natural pattern. We also found that chromosome VIII aneuploidy and loss of function mutations in PMA1 confer copper resistance in both species, whereas loss of function mutations in REG1 were only a viable route to copper resistance in S. cerevisiae. We also observed a single de novo duplication of the CUP1 gene in S. paradoxus but none in S. cerevisiae. For sulfite, loss of function mutations in RTS1 and KSP1 confer resistance in both species, but mutations in RTS1 have larger average effects in S. paradoxus. Our results show that even when the distributions of mutational effects are largely similar, species can differ in the adaptive paths available to them. They also demonstrate that assays of the distribution of mutational effects may lack predictive insight concerning adaptive outcomes.

Modeling pesticides and ecotoxicological risk assessment in an intermittent river using SWAT

The present work aimed to predict the fate of two pesticides, copper (Cu) and glyphosate in a Mediterranean basin with an intermittent river and to assess the ecotoxicological risk related to their presence in water bodies coupling field measurements of streamflow and pesticide concentrations, and an eco-hydrological model. The Soil and Water Assessment Tool (SWAT) model was calibrated and, subsequently used to assess predicted environmental concentrations of pesticides in surface waters. The ecotoxicological risk related to the presence of Cu and glyphosate in surface water was assessed at the reach scale by using the Toxicity to Exposure Ratio approach (TER). Measurements of glyphosate concentrations (< 0.5 μg l-1) exceeded the maximum European threshold of environmental quality standards for pesticides (EQS) of 0.1 μg l-1. High concentrations of glyphosate were predicted in the wet season and in September, when glyphosate is mostly used in vineyards and olive grove productions. Acute risk (TER < 100) associated with the presence of glyphosate was detected for several reaches. High concentrations of Cu (< 6.5 μg l-1), mainly used as a fungicide in vineyards, were predicted in several river reaches. The results of the ecotoxicological risk assessment revealed that November and January were the critical months during which most of the river reaches showed a chronic risk associated with the presence of Cu.

The use of copper as plant protection product contributes to environmental contamination and resulting impacts on terrestrial and aquatic biodiversity and ecosystem functions

Copper-based plant protection products (PPPs) are widely used in both conventional and organic farming, and to a lesser extent for non-agricultural maintenance of gardens, greenspaces, and infrastructures. The use of copper PPPs adds to environmental contamination by this trace element. This paper aims to review the contribution of these PPPs to the contamination of soils and waters by copper in the context of France (which can be extrapolated to most of the European countries), and the resulting impacts on terrestrial and aquatic biodiversity, as well as on ecosystem functions. It was produced in the framework of a collective scientific assessment on the impacts of PPPs on biodiversity and ecosystem services in France. Current science shows that copper, which persists in soils, can partially transfer to adjacent aquatic environments (surface water and sediment) and ultimately to the marine environment. This widespread contamination impacts biodiversity and ecosystem functions, chiefly through its effects on phototrophic and heterotrophic microbial communities, and terrestrial and aquatic invertebrates. Its effects on other biological groups and biotic interactions remain relatively under-documented.

Changes over time in organic matter dynamics and copper solubility in a vineyard soil after incorporation of cover crop residues: Insights from a batch experiment

Cover crops (CCs) are increasingly used in viticulture because they benefit the soil and the environment in many ways. This study investigated the extent to which the incorporation of CC residues altered organic matter (OM) and Cu dynamics in a Cu-contaminated vineyard topsoil. A 92-day incubation period was used to monitor changes over time in carbon mineralization, carbon hydrolytic enzyme activity, concentration and optical properties of dissolved organic matter (DOM), and Cu solubility after the addition (or not) of two CC residues, oat or faba bean. The results revealed that adding CCs transitorily increased the concentration of DOM in soil solution, as well as the activity of C hydrolytic enzymes and C mineralization rates. DOM content was approximately two orders of magnitude higher in CC-amended soils than in the control soil on day 0, after which it gradually decreased to reach concentrations similar to those measured in the control soil on day 92. Analyses of DOM optical properties showed that its molecular weight and degree of humification increased over time with a decrease in its concentration. The close relationship between DOM and Cu concentrations in the soil solution suggests that degradation of CCs releases soluble forms of C capable of complexing and solubilizing Cu, and hence that incorporating CC residues can transitorily increase the solubility of Cu in vineyard topsoils. Despite their different C:N ratios, oat and faba bean had almost the same effect on Cu dynamics, implying that C inputs played a prominent role in explaining the interactions between OM and Cu within the timeframe of our experiment. In conclusion, this study enabled recommendations on how to mitigate the risk of Cu ecotoxicity associated with incorporating CCs in Cu-contaminated vineyard soils.

Further Limitations of Synthetic Fungicide Use and Expansion of Organic Agriculture in Europe Will Increase the Environmental and Health Risks of Chemical Crop Protection Caused by Copper-Containing Fungicides

Copper-containing fungicides have been used in agriculture since 1885. The divalent copper ion is a nonbiodegradable multisite inhibitor that has a strictly protective, nonsystemic effect on plants. Copper-containing plant protection products currently approved in Germany contain copper oxychloride, copper hydroxide, and tribasic copper sulfate. Copper is primarily used to control oomycete pathogens in grapevine, hop, potato, and fungal diseases in fruit production. In the environment, copper is highly persistent and toxic to nontarget organisms. The latter applies for terrestric and aquatic organisms such as earthworms, insects, birds, fish, Daphnia, and algae. Hence, copper fungicides are currently classified in the European Union as candidates for substitution. Pertinently, copper also exhibits significant mammalian toxicity (median lethal dose oral = 300-2500 mg/kg body wt in rats). To date, organic production still profoundly relies on the use of copper fungicides. Attempts to reduce doses of copper applications and the search for copper substitutes have not been successful. Copper compounds compared with modern synthetic fungicides with similar areas of use display significantly higher risks for honey bees (3- to 20-fold), beneficial insects (6- to 2000-fold), birds (2- to 13-fold), and mammals (up to 17-fold). These data contradict current views that crop protection in organic farming is associated with lower environmental or health risks. Further limitations in the range and use of modern single-site fungicides may force conventional production to fill the gaps with copper fungicides to counteract fungicide resistance. In contrast to the European Union Green Deal goals, the intended expansion of organic farming in Europe would further enhance the use of copper fungicides and hence increase the overall risks of chemical crop protection in Europe. Environ Toxicol Chem 2024;43:19-30. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Metal speciation in sediments and bioaccumulation in edible bivalves to assess metal toxicity in a sand mining impacted tropical (Aghanashini) estuary, southern India

The study aims to understand the metal toxicity through the relationship between bioavailability in sediments and bioaccumulation in edible bivalves in an estuary subjected to extensive sand mining. The higher deposition of total Fe, Mn, Ni and Zn in the middle region (core M) was ascribed to estuarine processes and proximity to anthropogenic sources. EF revealed moderate to severe enrichment of Ni and Cu in sediments. Igeo showed moderate degree of pollution from Co, moderate to strong pollution from Ni and strong to extreme level of pollution from Cu. In core N, the average bioavailable concentration of Fe, Mn, Zn, Cu, Co and Ni was 1.76 %, 43.18 %, 59.14 %, 62.11 %, 60.42 % and 27.33 % respectively. The average bioavailable concentration of Fe (61.23 %), Mn (56.87 %), Cu (67.98 %), Co (69.77 %) and Ni (40.99 %) was higher in the core M as compared to core N except for Zn (56.98 %). The significant (>25.00 %) proportion of metals in bioavailable fractions in cores N and M construed their non-natural sources. Metal speciation study indicated bioavailability to fauna that likely to enhance by extensive sand mining. The level of Fe, Mn, Zn, Cu and Ni in Saccostrea cucullate, Meretrix casta and Villorita cyprinoides revealed toxicity to bivalves and probably to humans.

Copper-uptake mediated by an ecofriendly zwitterionic ionic liquid: A new challenge for a cleaner bioeconomy

This study aims to investigate the ability of an imidazolium biobased Zwitterionic Ionic Liquids (ZILs) in enhancing the phytoavailability of copper from garden (G) and vineyard (V) soils using the model plant ryegrass. Uncontaminated and artificially contaminated CuSO₄ soils, unamended and ZIL-amended soil modalities were designed. The copper/ZIL molar ratio (1/4) introduced was rationally established based on molecular modeling and on the maximal copper concentration in artificially contaminated soil. Higher accumulation of copper in the shoots was detected for the uncontaminated and copper contaminated ZIL amended V soils (18.9 and 23.3 mg/kg, respectively) contrary to G soils together with a ZIL concentration of around 3% (W/W) detected by LC-MS analyses. These data evidenced a Cu-accumulation improvement of 38% and 66% compared to non-amended V soils (13.6 and 13.9 mg/kg respectively). ZIL would be mainly present under Cu(II)-ZIL₄ complexes in the shoots. The impact on the chemical composition of shoot was also studied. The results show that depending on the soils modalitity, the presence of free copper and/or ZIL led to different chemical compositions in lignin and monomeric sugar contents. In the biorefinery context, performances of enzymatic hydrolysis of shoots were also related to the presence of both ZIL and copper under free or complex forms. Ecotoxicity assessment of the vineyard soil samples indicated that the quantity of copper and ZIL remaining in the soils had no significant toxicity. ZIL amendment in a copper-contaminated soil was demonstrated as being a promising way to promote the valorization of phytoremediation plants.

Development and validation of an eco-compatible UV-Vis spectrophotometric method for the determination of Cu2+ in aqueous matrices

Cu2+ are ubiquitous ions in the ecosystem and are responsible of serious environmental pollution. Indeed, the development of sensitive methods for Cu2+ detection is an urgent demand. In this work, we proposed a new spectrophotometric method for Cu2+ determination in different water matrices (distilled water, drinking water, wastewater, and river water). The method employs a bio-based organic ligand namely tetrasodium iminodisuccinate (IDS) able to form a stable complex with the analyte with a maximum absorption at 710 nm. Within the linear range of 6.3-381 mg L-1, the limit of detection (LOD) was determined to be as 1.43 mg L-1. Moreover, the recovery data of the spiked analysis of drinking/river/wastewater water samples were also satisfactory and verified the feasibility of the method for the analysis of Cu2+ in natural conditions. Finally, the AGREE assessment tool was used for a quantitative evaluation of the proposed method and reference method, in agreement with the green analytical chemistry principles. The results showed the lower environmental impact of the proposed method and the suitability of this novel approach for Cu2+ in water matrices.

Biotechnological potential of Bacillus sp. S26 for alleviation of abiotic and biotic stresses in vine

Grapevine (Vitis spp.) is one of the most cultivated fruit plants in the world. Vineyard growers apply copper-based products in these crops to prevent fungal diseases, generating worries about Cu contamination in soils and food. In this context, this study identifies prokaryotic communities associated with grapevine plants grown under different levels of Cu-contaminated soils. Moreover, the study isolates new bacteria to improve Cu resistance in plants. Soil Cu content correlated inversely with operational taxonomic units (OTUs) belonging to the groups Acidobacteria (SubGroup 2), Latescibacteria, Pedosphaeraceae, and Candidatus Udaeobacter. A total of 14 new bacterial isolates were obtained from copper-contaminated soils. These isolates produced Indolic Compounds (IC) in a range of 25 to 96 µg mL^- 1, highlighting bacterial strains S20 and S26 as the highest producers. These new bacteria also produced siderophores, highlighting strains S19 and S26, which removed 58 and 59% of Fe ions from the CAS complex, respectively. From the in vitro antagonistic activity against Colletotrichum spp. strains, the authors identified some bacterial strains that inhibited phytopathogen growth. Bacterial strain Bacillus sp. S26 was chosen for inoculation experiments in grapevine plants. This bacterial isolate improved the growth of grapevine plants in Cu-contaminated soils. However, growth promotion did not occur in unstressed plants. More studies are necessary for developing a new bioinoculant containing S26 cells aiming to reduce biotic and abiotic stresses in grapevine.

Study of the competition between Colletotrichum godetiae and C. nymphaeae, two pathogenic species in olive

Olive anthracnose, a critical olive fruit disease that adversely impacts oil quality, is caused by Colletotrichum species. A dominant Colletotrichum species and several secondary species have been identified in each olive-growing region. This study surveys the interspecific competition between C. godetiae, dominant in Spain, and C. nymphaeae, prevalent in Portugal, to shed light on the cause of this disparity. When Petri-dishes of Potato Dextrose Agar (PDA) and diluted PDA were co-inoculated with spore mixes produced by both species, C. godetiae displaced C. nymphaeae, even if the percentage of spores in the initial spore mix inoculation was just 5 and 95%, respectively. The C. godetiae and C. nymphaeae species showed similar fruit virulence in separate inoculations in both cultivars, the Portuguese cv. Galega Vulgar and the Spanish cv. Hojiblanca, and no cultivar specialization was observed. However, when olive fruits were co-inoculated, the C. godetiae species showed a higher competitive ability and partially displaced the C. nymphaeae species. Furthermore, both Colletotrichum species showed a similar leaf survival rate. Lastly, C. godetiae was more resistant to metallic copper than C. nymphaeae. The work developed here allows a deeper understanding of the competition between C. godetiae and C. nymphaeae, which could lead to developing strategies for more efficient disease risk assessment.

Spatial and Seasonal Structure of Bacterial Communities Within Alpine Vineyards: Trentino as a Case Study

Bacteria have a fundamental role in determining the fitness of grapevine, the composition of grapes and the features of wines but at present, little information is available. In this work, the bacteria colonizing the different portions of grapevine (bark, leaves and grapes) were explored in the vineyards of the Alpine region of Trentino, considering the impact of different environmental and agronomical variables. The vineyards included in the work were selected based on their different geographical positions (altitude) and grapevine training systems in order to explore the whole variability of the grapevine ecosystem. Moreover, the surface amount of copper was measured on grapes and leaves during the vegetative growth. Bacterial analysis, performed using plate counts and Illumina MiSeq, revealed an increase in the concentration of grape bacteria proportional to the progress of the ripening stage. Conversely, the peak of bacterial concentration onto leaf and bark samples occurred in August, probably due to the more favourable environmental conditions. In bark samples, the bacterial microbiota reached the 7 log CFU/cm², while 6 log UFC/g were measured in grape samples. A remarkable biodiversity was observed, with 13 phyla, 35 classes, 55 orders, 78 families and 95 genera of bacteria present. The presence of some taxa (Alphaproteobacteria, Desulfovibrionaceae, Clostriadiales, Oscillospira, Lachnospiraceae and Bacteroidales) was ubiquitous in all vineyards, but differences in terms of relative abundance were observed according to the vegetative stage, altitude of the vineyard and training system. Bacteria having oenological implication (Lactobacillus, Pediococcus and Oenococcus) were detected in grape samples collected in August, in low abundance. The data revealed a complex bacterial ecosystem inside the vineyard that, while maintaining common traits, evolves according to environmental and agronomical inputs. This study contributes to define the role of bacteria in the complex balance established in each vineyard between human actions and agricultural environment, known as terroir.

Identifying candidates for the phytoremediation of copper in viticultural soils: A systematic review

For many years, copper-based fungicides have been used in viticulture and have contributed to increasing concentrations in soils. Today, it is not uncommon to find vineyard soils with total copper topsoil concentrations above 100 mg kg^-1, which may have consequences for both the environment and human health. Phytoremediation, the use of plants to remove heavy metals from soils, is a promising and environmentally-friendly method to extract copper from soils. The objectives of this study were to review and synthesise the current knowledge on copper phytoremediation in vineyard soils and identify future applications. A systematic literature search in Web of Science was conducted on 19 July 2022 and resulted in twenty-seven papers meeting the inclusion criteria. Approximately one third of the papers were from Brazil and most of the experiments had been carried out in pots. In some studies, the addition of bacteria or chelators was also evaluated. Some species, such as Plantago lanceolata L. or Ricinus communis L., can accumulate copper in their tissues at concentrations above 1000 mg kg^-1. Addition of bacteria and chelators to the soil can also increase the copper uptake capacity by plants. However, most of the species evaluated accumulate copper in the roots, rather than in the shoots, thus limiting the implementation of this method in practice. Further studies are thus needed to find other hyperaccumulator plants. Future research should focus primarily on the ability of plants to accumulate copper in their aerial parts, their ability to transfer copper from roots to shoots, and their biomass production under high soil copper concentrations. Longer-term experiments and more in situ testing are also needed to evaluate the potential for development and use of copper phytoremediation in vineyards. To conclude, species of the Poaceae and Lamiaceae families are the most promising so far for phytoremediation. Identifying plants able to translocate copper from the roots to the aerial parts will be an important factor in the success of this method.

Use of cover crops in vineyards to prevent groundwater pollution by copper and organic fungicides. Soil column studies

Several fungicides, such as copper and organic products (synthetic or natural), are currently being used in vineyards to control downy mildew (Plasmopara viticola) resulting in soil, surface water, and groundwater pollution. This study aims to assess the effectiveness of using cover crops as an agricultural practice in vineyards to protect soil and groundwater pollution. For that purpose, we performed different soil column studies to quantify soil leaching of selected fungicides (copper, dimethomorph, oxathiapiprolin, zoxamide, acibenzolar-s-methyl, and laminarin) following a rainfall event after a conventional fungicide vineyard application. Two types of vineyard soils (loam and sandy-loam soil textures) and three ground covers (bare ground, monoculture cover, and polyculture cover) were assessed. These studies were completed with hydroponic assays to check the effectiveness of cover roots in the fungicide degradation. Mass balance results show that whereas 3 fungicides (Cu, zoxamide, and dimethomorph) were leached through sandy soil columns, only copper was leached from loam soil columns. The effect of cover crops was only significant for Cu and zoxamide when fungicides were applied 24 h before the rain event, reducing the fungicide leaching by 30%. Hydroponic studies showed that cover roots enhanced the kinetic rates of almost all tested fungicides by 5-467%, suggesting that they are relevant to improving the degradation of fungicides in the soil column. These results are relevant to drawing up recommendations on the use of cover crops to protect soil and groundwater pollution by fungicides.

Silicon-based additive on heavy metal remediation in soils: Toxicological effects, remediation techniques, and perspectives

Chemical fertilizer is gaining increasing attention and has been the center of much research which indicating complex beneficial and harmful effects. Chemical fertilizer might cause some environmental hazards to the biosphere, especially in the agricultural ecosystem. The application of silicon (Si) fertilizer in agriculture has been proved to be able to create good economic and environmental benefits. Si is the second most abundant earth crust element. Si fertilizer improves soil quality and alleviates biotic and abiotic crop stress. It is of great significance to understand the function of Si fertilizer in agricultural utilization and environmental remediation. This paper reviews the Si-based fertilizer in farmland use and summarizes prior research relevant with characterization, soil quality improvement, and pollution remediation effects. Its use in agriculture enhances plant silicon uptake, mediates plant salt and drought stress and remediates heavy metals such as Al, As, Cd, Cu, Zn and Cr. This article also summarizes the detoxification mechanism of silicon and its effects on plant physiological activity such as photosynthesis and transpiration. Fertilizer materials and crop fertilizer management were also considered. Foliar spraying is an effective method to improve crop growth and yield and reduce biotic or abiotic stress. Silicon nanoparticle material provides potential with great potential and prospects. More investigation and research are prospected to better understand how silicon impacts the environment and whether it is a beneficial additive.

Copper-based fungicide copper hydroxide accelerates the evolution of antibiotic resistance via gene mutations in Escherichia coli

The extensive use of copper-based fungicides in orchards, especially in vineyards, leads to the accumulation of copper, which has caused growing concern. However, data on the acquisition of antibiotic resistance in opportunistic pathogens under copper-based fungicides are scarce. In this study, we investigated the potential development of antibiotic resistance in Escherichia coli K12 under selective copper hydroxide pressure. The results indicated that copper hydroxide at concentrations of 100 mg/L and 200 mg/L evolved resistance against chloramphenicol and tolerance against tetracycline to 4-8 and 2.00-2.67 times than the initial minimal inhibitory concentrations (MICs), respectively. Whole-genome sequencing analysis showed that the obtained resistant strains carried gene mutations including AcrAB-TolC multidrug efflux pump (acrB and marR), outer membrane porin (evZ), and another indirect pathways. Furthermore, the expression of multidrug efflux pump genes and oxidative stress-related genes were significantly upregulated, whereas outer membrane porin genes were downregulated. Thus, our results could well explain the emergence of antibiotic resistance and resistance mechanisms selected by copper-based fungicide, and provide a basis for the management of copper-based fungicide in agriculture to avoid the spread of antibiotic resistance.

Phytoremediation of copper-contaminated soil by Artemisia absinthium: comparative effect of chelating agents

Phytoremediation is a promising method for the removal of toxic trace elements, specifically of copper, from the contaminated soil in the mining regions of Armenia. Thereby, the objectives of our study were the assessment of copper accumulation capacity and phytoremediation suitability of wormwood (Artemisia absinthium L.), a potential metal hyperaccumulator, as well as the identification of the influence of some chelating agents and their combinations on copper phytoremediation effectiveness. The results of studies have shown that A. absinthium is a relatively well-adapted plant species with the ability to grow in copper-contaminated soils collected from the surroundings of Zangezur Copper and Molybdenum Combine (south-east of Armenia). The observed decrease in plant growth in contaminated soil was possible to restore by the use of ammonium nitrate. It was revealed that for the remediation of copper-contaminated soils by phytostabilisation method, A. absinthium could be grown without the application of chelating agents, as being a perennial herb, it is able to accumulate relatively high contents of copper in its root and do not transfer this metal to the above-ground part at the same time. As opposed to the phytostabilisation method, for the cleaning of copper-contaminated soils through phytoextraction method by A. absinthium, the application of chemical amendments is needed for the enhancement of copper bioavailability and for its intensive transportation to the above-ground part of the plant. Collating the effects of various chemical agents on the plant, we concluded that the growth scheme, when the application of NH₄NO₃, a promoter of plant growth, is combined with the joint use of citric and malic acids, can be applied as the most expedient approach for remediation of copper-contaminated soils by phytoextraction method.

Advantages and limits to copper phytoextraction in vineyards

Copper (Cu) contamination of soils may alter the functioning and sustainability of vineyard ecosystems. Cultivating Cu-extracting plants in vineyard inter-rows, or phytoextraction, is one possible way currently under consideration in agroecology to reduce Cu contamination of vineyard topsoils. This option is rarely used, mainly because Cu phytoextraction yields are too low to significantly reduce contamination due to the relatively "low" phytoavailability of Cu in the soil (compared to other trace metals) and its preferential accumulation in the roots of most extracting plants. This article describes the main practices and associated constraints that could theoretically be used to maximize Cu phytoextraction at field scale, including the use of Cu-accumulating plants grown (i) with acidifying plants (e.g., leguminous plants), and/or (ii) in the presence of acidifying fertilizers (ammonium, elemental sulfur), or (iii) with soluble "biochelators" added to the soil such as natural humic substances or metabolites produced by rhizospheric bacteria such as siderophores, in the inter-rows. This discussion article also provides an overview of the possible ways to exploit Cu-enriched biomass, notably through ecocatalysis or biofortification of animal feed.

Particularities of Fungicides and Factors Affecting Their Fate and Removal Efficacy: A Review

Systemic fungicide use has increased over the last decades, despite the susceptibility of resistance development and the side effects to human health and the environment. Although herbicides and insecticides are detected more frequently in environmental samples, there are many fungicides that have the ability to enter water bodies due to their physicochemical properties and their increasing use. Key factors affecting fungicide fate in the environment have been discussed, including the non-target effects of fungicides. For instance, fungicides are associated with the steep decline in bumblebee populations. Secondary actions of certain fungicides on plants have also been reported recently. In addition, the use of alternative eco-friendly disease management approaches has been described. Constructed Wetlands (CWs) comprise an environmentally friendly, low cost, and efficient fungicide remediation technique. Fungicide removal within CWs is dependent on plant uptake and metabolism, absorption in porous media and soil, hydrolysis, photodegradation, and biodegradation. Factors related to the efficacy of CWs on the removal of fungicides, such as the type of CW, plant species, and the physicochemical parameters of fungicides, are also discussed in this paper. There are low-environmental-risk fungicides, phytohormones and other compounds, which could improve the removal performance of CW vegetation. In addition, specific parameters such as the multiple modes of action of fungicides, side effects on substrate microbial communities and endophytes, and plant physiological response were also studied. Prospects and challenges for future research are suggested under the prism of reducing the risk related to fungicides and enhancing CW performance.

Excess copper promotes catabolic activity of gram-positive bacteria and resistance of gram-negative bacteria but inhibits fungal community in soil

The extensive use of copper fungicides has resulted in significant non-target effects on soil microbial communities. However, the documented effects are often variable and contradictory, depending on the methods used to assess them. In this study, we examined the effects of copper accumulation in surface soils on microbial catabolic activity, active biomass and composition, and sensitive bacterial species. The community-level catabolic profiles (CLCPs) showed that both normal (50 mg CuSO₄ kg^-1 soil) and high dosages (tenfold rate) of CuSO₄ significantly increased the catabolic diversity of gram-positive bacteria, while the high dosage increased the overall catabolic activity of gram-negative bacteria. The phospholipid fatty acid (PLFA) analysis showed that the high dosage reduced the biomass of gram-positive bacteria by 27% but did not affect that of gram-negative bacteria. In comparison, the normal and high dosages decreased the fungal biomass by 34% and 58%, respectively. Furthermore, 16S rRNA-denaturing gradient gel electrophoresis (DGGE) fingerprint revealed that more than two-thirds of identified bands belonged to gram-negative bacteria. Some Cu-resistant gram-negative bacterial genera, such as Actinobacterium, Pseudomonas, and Proteobacterium, were detected in the soil to which the high dosage of CuSO₄ had been applied. In conclusion, an excess application of CuSO₄ increased the catabolic diversity of gram-positive bacteria and induced resistance in gram-negative bacteria, whereas the active fungal community displayed a dosage-dependent response to CuSO₄ and can thus be used as a sensitive indicator of copper contamination.

Assessment of the Effects of Heavy Metals in Soils after Removal by Nanoscale Zero-Valent Iron with Three Methods

Nanoscale zero-valent iron (nZVI) has been broadly applied in the remediation of heavy metals pollution. In this research, the toxicity characteristic leaching procedure (TCLP), the in vitro gastrointestinal (IVG) method, and the diffusive gradients in thin-films (DGT) technique were used to evaluate the effects of heavy metals in soil with remediation by nZVI. The results indicate that, compared with the dose of 0.5 g·L−1, the nZVI in the dose of 1.0 g·L−1 can remove the heavy metals in the soil. The leaching toxicities of the heavy metals (Cr, Cu, Zn, Pb) showed apparent decreases after the remediation by nZVI. In the gastric phase, the highest bioaccessibility values of the Cr, Cu, Zn, Pb were decreased by 27.2, 31.7, 11.7, and 20.1%, respectively. Moreover, in the gastric phase, the highest bioaccessibility values of the Cr, Cu, Zn, Pb were decreased by 5.5, 1.29, 8.0, and 7.3%, respectively. The availabilities of the heavy metals were also reduced. The above results show that the nZVI effectively reduced the heavy metal pollution in the soil.

Monitoring of the copper persistence on plant leaves using pulsed thermography

Copper-based fungicides are largely used in agriculture in the control of a wide range of plant diseases. Applied on plants, they remain deposited on leaf surfaces and are not absorbed into plant tissues. Because of accumulation problems and their ecotoxicological profiles in the soil, their use needs to be monitored and controlled, also by using modern technologies to better optimize the efficacy rendering minimum the amount of copper per season used. In this work, we test a novel approach based on pulsed thermography to evaluate the persistence of the copper on plant leaves so that the time between two applications should be the minimum needs. We monitored the thermal response observed on different treatments of both grapevine and tobacco plants over a 3-week period. Our experimental results demonstrate that the new methodological approach based on pulsed thermography can be an effective tool to evaluate in real time the presence of copper on differently treated plants allowing a tentative quantification and, therefore, to optimize its use in the agricultural practices, according also to the European Regulation n. 1107/2009.

Root system structure as a criterion for the selection of grapevine genotypes that are tolerant to excess copper and the ability of phosphorus to mitigate toxicity

Using tolerant genotypes and the correct use of fertilizers can mitigate the negative effect of elevated Cu levels in the growing medium. In this context, the study aimed to evaluate the effects of excess Cu in the root system and the effectiveness of phosphorus (P) in minimizing the phytotoxicity of Cu in three genotypes: IAC 572 [(Vitis riparia x V. rupestris) x V. caribaea], Magnolia (V. rotundifolia) and Paulsen 1103 (V. berlandieri x V. rupestris). The plants were grown in nutrient solutions and were supplemented with the following treatments: 0.3 μM Cu (Control), 60 μM Cu (Cu) and 60 μM Cu and 62 mg L-1 P (Cu + P). Root samples were sectioned for microscopy analyses, and the shoot lengths, shoot and root dry matter, relative growth rates (RGR) and tissue nutrient contents were also evaluated. The roots of the genotypes that were cultivated with high Cu concentrations produced greater numbers of branches and larger diameters, except for Magnolia genotype that was cultivated in a Cu + P solution, which had an organization similar to the control. Excess Cu caused accumulations of phenolic compounds and decreased shoot lengths, dry matter and RGR in the genotypes. In the treatments with excess Cu, there were increases in this element in the tissues, but P decreased the metal concentrations in Magnolia roots. Therefore, Cu accumulations alter the root system development patterns, growth parameters and tissue nutrient contents in the studied genotypes. Magnolia has a higher tolerance and is also the only genotype for which the use of P has been shown to be effective.

Integrating transcriptomics and behavior tests reveals how the C. elegans responds to copper induced aging

Copper (Cu) pollution in water and agricultural soil has always been a worldwide concern. This research aims to investigate the health effects of copper exposure on Caenorhabditis elegans (C. elegans) under the existing environmental quality standards (1 mg/L and 2 mg/L) via lifespan, reproduction, biological markers and transcriptome analysis. The results showed that copper of these two environmental standards shorten the lifespan of nematodes, reduced the brood size, reduced the frequency of pharyngeal pumps and prolonged defecation time as aging-related behaviors, and increased the levels of aging-related markers ROS, MDA and H₂O₂. There was a certain effect trend for the two exposure concentrations. Further, the possible molecular mechanism of copper-induced aging and reproductive effects on C. elegans was explored. Differential gene expression analysis was performed, and 2332 genes (567 up- and 1765 down-regulated genes) in the 1 mg/L group, 2449 DEGs (724 up- and 1725 down-regulated genes) in the 2 mg/L group in response to copper treatment. The top 20 regulated genes were vit (vit-1, vit-3, vit-4) genes, col genes (col-35, col-72, col-114, col-123, col-164, col-183, col-185), eea-1, him-18 and grl-20, which suggested that cuticle collagen synthesis and yolk expression were disrupted by copper. Analysis of KEGG pathway showed copper exposure widely affects longevity regulation pathways, thereby promoting aging. In summary, the sequencing results extensively and deeply reveal the health hazards of environmentally relevant doses of copper exposure to C. elegans, and behavioral testing verified that copper promoted aging of C. elegans.

Copper Tolerance and Accumulation on Pelargonium graveolens L'Hér. Grown in Hydroponic Culture

Heavy metal contamination is a major health issue concerning the commercial production of medicinal and aromatic plants (MAPs) that are used for the extraction of bioactive molecules. Copper (Cu) is an anthropogenic contaminant that, at toxic levels, can accumulate in plant tissues, affecting plant growth and development. On the other hand, plant response to metal-induced stress may involve the synthesis and accumulation of beneficial secondary metabolites. In this study, hydroponically grown Pelargonium graveolens plants were exposed to different Cu concentrations in a nutrient solution (4, 25, 50, 100 μM) to evaluate the effects Cu toxicity on plant growth, mineral uptake and distribution in plants, some stress indicators, and the accumulation of bioactive secondary metabolites in leaf tissues. P. graveolens resulted in moderately tolerant Cu toxicity. At Cu concentrations up to 100 μM, biomass production was preserved and was accompanied by an increase in phenolics and antioxidant capacity. The metal contaminant was accumulated mainly in the roots. The leaf tissues of Cu-treated P. graveolens may be safely used for the extraction of bioactive molecules.

Effect of copper and zinc as sulfate or nitrate salts on soil microbiome dynamics and blaVIM-positive Pseudomonas aeruginosa survival

The exposure of soil to metals and to antibiotic resistant bacteria may lead to the progressive deterioration of soil quality. The persistence of antibiotic resistant bacteria or antibiotic resistance genes in soil can be influenced by the microbial community or by soil amendments with metal salts. This work assessed the effect of soil amendment with copper and zinc, as sulfate or nitrate salts, on the fate of a carbapenem-resistant (bla_VIM⁺) hospital effluent isolate of Pseudomonas aeruginosa (strain H1FC49) and on the variations of the microbial community composition. Microcosms with soil aged or not with copper and zinc salts (20 mM), and inoculated with P. aeruginosa H1FC49 were monitored at 0, 7, 14 and/or 30 days, for community composition (16S rRNA gene amplicon) and strain H1FC49 persistence. Data on culturable P. aeruginosa, quantitative PCR of the housekeeping gene ecf, and the presumably acquired genes bla_VIM⁺ and integrase (intI1), and community composition were interpreted based on descriptive statistics and multivariate analysis. P. aeruginosa and the presumably acquired genes, were quantifiable in soil for up to one month, in both metal-amended and non-amended soil. Metal amendments were associated with a significant decrease of bacterial community diversity and richness. The persistence of P. aeruginosa and acquired genes in soils, combined with the adverse effect of metals on the bacterial community, highlight the vulnerability of soil to both types of exogenous contamination.

Copper Content and Export in European Vineyard Soils Influenced by Climate and Soil Properties

Copper-based fungicides (Cu_f) are used in European (EU) vineyards to prevent fungal diseases. Soil physicochemical properties locally govern the variation of the total copper content (Cu_t) in EU vineyards. However, variables controlling Cu_t distribution at a larger scale are poorly known. Here, machine learning techniques were used to identify governing variables and to predict the Cu_t distribution in EU vineyards. Precipitation, aridity and soil organic carbon are key variables explaining together 45% of Cu_t distribution across EU vineyards. This underlines the effect of both climate and soil properties on Cu_t distribution. The average net export of Cu at the EU scale is 0.29 kg Cu ha^-1, which is 2 orders of magnitude less than the net accumulation of Cu (24.8 kg Cu ha^-1). Four scenarios of Cu_f application were compared. The current EU regulation with a maximum of 4 kg Cu ha^-1 year^-1 may increase by 2% of the EU vineyard area, exceeding the predicted no-effect concentration (PNEC) in soil in the next 100 years. Overall, our results highlight the vineyard areas requiring specific remediation measures and strategies of Cu_f use to manage a trade-off between pest control and soil and water contamination.

Investigating the remediation potential of iron oxide nanoparticles in Cu-polluted soil-plant systems: coupled geochemical, geophysical and biological approaches

Although the use of iron oxide nanoparticles (IONPs) has high potential in remediation and agriculture, a major hindrance to their use includes the risk of contamination of soil and water resources with underexplored effects of IONPs on biota. The fate, phytotoxicity and remediation potential of IONPs are investigated with soil column experiments using 7 nm-sized magnetite (Fe₃O₄) nanoparticles (magnNPs) and sunflower (Helianthus annuus). Control soil, magnNP-containing soil (10 g magnNPs per kg soil), copper-polluted soil (500 mg Cu per kg soil) and copper-polluted soil containing magnNPs (10 g magnNPs per kg soil and 500 mg Cu per kg soil) support sunflower growth for 57 and 95 days. In magnNP-exposed plants, the occurrence of magnNPs does not affect the growth of the vegetative aerial parts and photosynthetic efficiency. Decreased lipid peroxidation indicates an enhanced antioxidant enzymatic response of magnNP-exposed plants. In plants grown in Cu- and magnNP-Cu-soils, the physiological and biochemical impacts of excess copper are clearly identified, resulting in growth retardation, decreased pigment contents and photosynthetic efficiency, and increased lipid peroxidation and peroxidase (POD) activities. Based on magnetic susceptibility, a higher amount of magnNPs is detected after 57 days in the roots of magnNP-exposed plants (1400 mg kg^-1) than in the roots of magnNP-Cu-exposed plants (920 mg kg^-1). In the latter, magnNP internalization is likely hampered because of the plants' physiological responses to Cu toxicity. At the working Cu and magnNP concentrations, magnNPs neither decrease Cu accumulation in the plant tissues nor alleviate the overall growth retardation of sunflowers and certain phytotoxic effects induced by excess Cu. However, this study highlights several positive environmental aspects relative to magnNP use, including the harmless effects of magnNPs on sunflowers (1% magnNPs in soil) and the ability of magnNPs to influence Cu mobility in the soil (which could be even more pronounced at lower Cu concentration).

Soil tillage affects soybean growth and promotes heavy metal accumulation in seeds

When soybean is grown in soils with high heavy metal concentrations, it may introduce those contaminants into the human food chain, posing risks to human health. This study evaluated the effect of tilling the soil with high Cu, Zn, and Mn levels on soybean physiology and metal accumulation in seeds. Disturbed and undisturbed soil samples were collected in two different sites: a vineyard with high heavy metal concentration and a grassland area, containing natural vegetation. Two soybean cultivars were sown and grown in the greenhouse. Photosynthetic parameters and biochemical analysis of oxidative stress were performed. Cu, Zn, and Mn in leaves and seeds, dry mass, and weight of seeds were evaluated. Soil structure had a high influence on plant growth and physiology, while soil site had a high impact on heavy metal accumulation in leaves and seeds. Soybean plants that grown in vineyard soils with high heavy metal concentrations, accumulated 50% more Zn in leaves and seeds, 70% more Cu in leaves, and 90% more Cu in seeds, than those plants grown in grassland soils. Besides, Zn concentration in seeds was higher than the permissible limit. Moreover, the disturbance of both vineyard soil and grassland soil was not good for plant growth and physiology, which have increased TBARS and H2O2 concentration in plants, transpiration rate, metal concentration in leaves and seeds. Soil disturbance may have caused organic matter oxidation and changes in the composition and quantity of soil microorganisms and it affects the availability of other nutrients in the soil.

Kiwifruit bacterial canker: an integrative view focused on biocontrol strategies

Phage-based biocontrol strategies can be an effective alternative to control Psa-induced bacterial canker of kiwifruit. The global production of kiwifruit has been seriously affected by Pseudomonas syringae pv. actinidiae (Psa) over the last decade. Psa damages both Actinidia chinensis var. deliciosa (green kiwifruit) but specially the susceptible Actinidia chinensis var. chinensis (gold kiwifruit), resulting in severe economic losses. Treatments for Psa infections currently available are scarce, involving frequent spraying of the kiwifruit plant orchards with copper products. However, copper products should be avoided since they are highly toxic and lead to the development of bacterial resistance to this metal. Antibiotics are also used in some countries, but bacterial resistance to antibiotics is a serious worldwide problem. Therefore, it is essential to develop new approaches for sustainable agriculture production, avoiding the emergence of resistant Psa bacterial strains. Attempts to develop and establish highly accurate approaches to combat and prevent the occurrence of bacterial canker in kiwifruit plants are currently under study, using specific viruses of bacteria (bacteriophages, or phages) to eliminate the Psa. This review discusses the characteristics of Psa-induced kiwifruit canker, Psa transmission pathways, prevention and control, phage-based biocontrol strategies as a new approach to control Psa in kiwifruit orchards and its advantages over other therapies, together with potential ways to bypass phage inactivation by abiotic factors.

A Smart and Sustainable Future for Viticulture Is Rooted in Soil: How to Face Cu Toxicity

In recent decades, agriculture has faced the fundamental challenge of needing to increase food production and quality in order to meet the requirements of a growing global population. Similarly, viticulture has also been undergoing change. Several countries are reducing their vineyard areas, and several others are increasing them. In addition, viticulture is moving towards higher altitudes and latitudes due to climate change. Furthermore, global warming is also exacerbating the incidence of fungal diseases in vineyards, forcing farmers to apply agrochemicals to preserve production yields and quality. The repeated application of copper (Cu)-based fungicides in conventional and organic farming has caused a stepwise accumulation of Cu in vineyard soils, posing environmental and toxicological threats. High Cu concentrations in soils can have multiple impacts on agricultural systems. In fact, it can (i) alter the chemical-physical properties of soils, thus compromising their fertility; (ii) induce toxicity phenomena in plants, producing detrimental effects on growth and productivity; and (iii) affect the microbial biodiversity of soils, thereby influencing some microbial-driven soil processes. However, several indirect (e.g., management of rhizosphere processes through intercropping and/or fertilization strategies) and direct (e.g., exploitation of vine resistant genotypes) strategies have been proposed to restrain Cu accumulation in soils. Furthermore, the application of precision and smart viticulture paradigms and their related technologies could allow a timely, localized and balanced distribution of agrochemicals to achieve the required goals. The present review highlights the necessity of applying multidisciplinary approaches to meet the requisites of sustainability demanded of modern viticulture.

Chemical speciation of metals from marine sediments: Assessment of potential pollution risk while dredging, a case study in southern Sweden

Contamination associated with metals is a critical concern related to their toxicity, persistence, and bio-accumulation. Trace elements are partitioned into several chemical forms, which some are more labile during fluctuations in the environment. Studying the distribution of metals between the different chemical fractions contributes to assess their bioavailability and to identify their potential risk of contamination to surrounding environments. This study concerns the speciation of metals (Pb, Cr, Ni, Zn and Fe) from sediments coming out from Malmfjärden bay, Sweden. The aim was to assess the potential risk of metal pollution during present and future dredging as well as while using dredged sediments in beneficial uses. The Tessier speciation procedure was chosen, and the results showed that low concentrations of metals were associated with the exchangeable fraction. In contrast, the major concentrations were linked to the residual part. The risk indexes (contamination factor and risk assessment code) showed that, during dredging activities, there is a low concern of pollution for Cr, Ni and Fe and a medium risk for Pb and Zn. Additionally, in all elements, the sum of non-residual concentrations was below the Swedish limits for using dredged sediments in sensitive lands. The findings suggested that the investigated metals in Malmfjärden sediments are related to low risks of spreading during using in beneficial uses.

Identification of Type III Secretion Inhibitors for Plant Disease Management

Bacterial plant pathogens are among the most devastating threats to agriculture. To date, there are no effective means to control bacterial plant diseases due to the restrictions in the use of antibiotics in agriculture. A novel strategy under study is the use of chemical compounds that inhibit the expression of key bacterial virulence determinants. The type III secretion system is essential for virulence of many Gram-negative bacteria because it injects into the plant host cells bacterial proteins that interfere with their immune system. Here, we describe the methodology to identify bacterial type III secretion inhibitors, including a series of protocols that combine in planta and in vitro experiments. We use Ralstonia solanacearum as a model because of the number of genetic tools available in this organism and because it causes bacterial wilt, one of the most threatening plant diseases worldwide. The procedures presented can be used to evaluate the effect of different chemical compounds on bacterial growth and virulence.

Cotyledonary leaves effectively shield the true leaves in Ricinus communis L. from copper toxicity

The stress-buffering effects of cotyledonary leaves of Ricinus communis and the protection thus offered to the true leaves upon exposure to copper stress was performed by analyzing bioaccumulation of Cu and associated metabolic processes in the presence and absence of cotyledonary leaves. One-month-old seedlings of R. communis were treated with various concentrations of CuSO₄ for 6 d under hydroponics with quarter strength modified Hoagland medium. Even though the photosynthetic pigments showed a decreasing trend with an increase in CuSO₄ concentration and days of exposure in cotyledonary and true leaves, it was significant in true leaves with excised cotyledonary leaves. The results of chlorophyll a fluorescence parameters indicated that toxic levels of CuSO₄ do not impart any major negative effect on the photochemistry of true leaves along with cotyledonary leaves. The analysis of osmolality, malondialdehyde, and metabolites showed a significantly increasing trend in true leaves with excised cotyledonary leaves. The above observations were strongly supported by higher Cu bioaccumulation in true leaves with excised cotyledonary leaves. The results suggest that the cotyledonary leaves have got the potential to evade Cu toxicity and thereby R. communis can be effectively used for the phytoremediation of Cu contaminated lands.

The arbuscular mycorrhizal fungus Rhizophagus intraradices and other microbial groups affect plant species in a copper-contaminated post-mining soil

BACKGROUND AND AIM

Arbuscular mycorrhizal fungi (AMF) have an important role in plant-microbe interactions. But, there are few studies in which the combined effect of AMF with a stress factor, such as the presence of a metal, on plant species were assessed. This study investigated the effect of arbuscular mycorrhizal (AM) fungus Rhizophagus intraradices and other soil microbial groups in the presence of copper on three plant species in a microcosm experiment.

METHODS

Two grass species Poa compressa and Festuca rubra and one herb species Centaurea jacea were selected as model plants in a pot-design test in which soils were artificially contaminated with copper. Treatments were bacteria (control), saprophytic fungi, protists, and a combined treatment of saprophytic fungi and protists, all in the presence or absence of the AM fungal species. After sixty days, plants were harvested and the biomass of grass and herb species and microbial respiration were measured.

RESULTS

The results showed almost equal above- and belowground plant biomass and microbial respiration in the treatments in the presence or absence of R. intraradices. The herb species C. jecea responded significantly to the soil inoculation with AM fungus, while grass species showed inconsistent patterns. Significant effect of AMF and copper and their interactions was observed on plant biomass when comparing contaminated vs. non-contaminated soils.

CONCLUSION

Strong effect of AMF on the biomass of herb species and slight changes in plant growth with the presence of this fungal species in copper-spiked test soils indicates the importance of mycorrhizal fungi compared to other soil microorganisms in our experimental microcosms.

Humic-like acids from hydrochars: Study of the metal complexation properties compared with humic acids from anthropogenic soils using PARAFAC and time-resolved fluorescence

Humic acids (HA) play an important role in the distribution, toxicity, and bioavailability of metals in the environment. Humic-like acids (HLA) that simulate geochemical processes can be prepared by NaOH aqueous extraction from hydrochars produced by hydrothermal carbonization (HTC). HLA can exhibit properties such as those found in HA from soils, which are known for their ability to interact with inorganic and organic compounds. The molecular characteristics of HLA and HA help to explain the relationship between their molecular features and their interaction with metallic species. The aim of this study is to assess the molecular features of HA extracted from Terra Mulata (TM) and HLA from hydrochars as well as their interaction with metals by using Cu(II) ions as a model. The results from ¹³C NMR, elemental analysis, FTIR, and UV-Vis showed that HA are composed mostly of aromatic structures and oxygenated functional groups, whereas HLA showed a mutual contribution of aromatic and aliphatic structures as main constituents. The interactions of HA and HLA with Cu(II) ions were evaluated through fluorescence quenching, in which the density of complexing sites per gram of carbon for interaction was higher for HLA than for HA. Furthermore, the HLA showed similar values for stability constants, and higher than those found for other types of HA in the literature. In addition, the average lifetime in both humic extracts appeared to be independent of the copper addition, indicating that the main mechanism of interaction was static quenching with a non-fluorescent ground-state complex formation. Therefore, the HLA showed the ability to interact with Cu(II) ions, which suggests that their application can provide a new approach for remediation of contaminated areas.

Soil accumulation and chemical fractions of Cu in a large and long-term coastal apple orchard, North China

PURPOSE

Coastal orchards, with greater humidity and precipitation, are favorable for fruit production, as well as mildew fungi development, thus becoming hot spots of Cu concentrations in soils due to the use of copper-based fungicides. However, little is known on the variation tendencies of Cu availability and mobility from these soils. This study aims to investigate the accumulation, spatial-temporal distribution, and chemical fractions of soil Cu in one of the largest coastal apple-producing area with over 40-year intensive cultivation in China.

MATERIALS AND METHODS

A total of 104 orchard and 31 farmland topsoil samples were collected from Jiaodong Peninsula, Shandong Province. The total Cu concentration (T-Cu) and major element components (MnO, TiO₂, SiO₂, Fe₂O₃, and Al₂O₃) in the soil were determined by X-ray fluorescence spectroscopy. Available Cu concentration (A-Cu) was extracted with HCl or DTPA. Chemical fractionations of Cu were determined via sequential extraction method. The variation tendencies of T-Cu, A-Cu, Cu available ratio (AR), and chemical fractions with planting duration in the orchards were explored while a cokriging method was selected to predict their spatial distributions. Moreover, Pearson's correlation and multiple linear stepwise regressions were constructed to distinguish the vital factors in controlling Cu availability and mobility from these soils.

RESULTS AND DISCUSSION

The results showed that long-term application of Cu-containing fungicides had increased Cu concentrations in orchard soils (85.77 mg kg^-1) 3.5 times higher than the background value (24.0 mg kg^-1) of local agricultural soils, in which 23.8% existed in the available form. Cu in the weak acid-soluble fraction (F1, 5.0 ± 3.5 %), reducible fraction (F2, 24.7 ± 6.6%), and oxidizable fraction (F3, 18.5 ± 7.8%) in orchard soils increased significantly with increasing planting durations whereas the residual fraction (F4, 51.7 ± 15.4%) exhibited a reverse trend. Total content, available content, and chemical fractions of Cu showed strong spatial heterogeneity. The availability and mobility of Cu in orchard soils were mainly controlled by total Cu content, pH, and soil organic carbon.

CONCLUSIONS

Coastal orchards under warm and humid climate condition in China exhibited higher Cu input, along with acidification and rapid organic carbon turnover in the soils, eventually leading to large accumulation and high mobility of Cu in the soils.

The impact of CUP1 gene copy-number and XVI-VIII/XV-XVI translocations on copper and sulfite tolerance in vineyard Saccharomyces cerevisiae strain populations

In wine production, sulfites are widely used as antimicrobials and antioxidants, whereas copper is associated with fungicides and wine fining treatments. Therefore, wine yeasts are constantly exposed to these agents. Copper tolerance is related to the copy number of the CUP1 gene, encoding for a metallothionein involved in copper detoxification. In wine yeasts, sulfite resistance mainly depends on the presence of the translocation t(XVI;VIII) in the promoter region of the SSU1 gene. This gene encodes for a plasma membrane sulfite pump involved in sulfite metabolism and detoxification. Recently, a new translocation, t(XVI;VIII), was identified. In this work, 253 Saccharomyces cerevisiae strains, representing three vineyard populations from two different continents, were analyzed, along with 20 industrial starters. Copper and sulfites tolerance as well as distribution of CUP1 gene copy-number, t(XVI;VIII)and t(XVI;XV) of SSU1 gene were studied to evaluate the impact of these genomic variations on population phenotypes. The CUP1 gene copy-number was found to be highly variable, ranging from zero to 79 per strain. Moreover it differently impacted the copper tolerance in the populations of the two continents. The diffusion of t(XVI;VIII) and, for the first time, t(XVI;XV) was determined in the three vineyard populations. The correlation between the presence of the translocation and strain sulfite tolerance levels was significant only for the t(XVI;VIII).

Status of copper accumulation in agricultural soils across China (1985-2016)

The first national-scale assessment of Cu contamination of agricultural soils covering 1731 sites in China was performed based on 1837 published papers. The temporal and spatial variations from 1985 to 2016 in the Cu concentrations and the ecological and health risks associated with Cu exposure were analyzed. Approximately, 21.02% of the sampling sites revealed Cu concentrations that exceeded the screening value (50.00 mg/kg; GB15618-2018). The Cu concentrations differed among five geographical regions in the decreasing order of South China > West China > East China > Northeast China > North China. Notably, concentration of Cu in agricultural soils have begun to diminish since 2011 due to reduced heavy metal inputs. Cu mainly originated from anthropogenic activities such as mining and agricultural activities. Linear correlations were observed between the amounts of fungicides and fertilizers applied and the Cu concentrations in the soils, which suggested that the application of fungicides and fertilizers is an important contributor to the accumulation of Cu in soils. Additionally, the geoaccumulation index (I_geo) and ecological risk index (E_fⁱ) values implied that pollution and ecological risk resulting from soil Cu concentration were in low levels. The hazard index (HI) values were higher for children than for adults. Therefore, children should be prioritized for protection from heavy metal pollution. Overall, this study details the status of Cu contamination of agricultural soils in China, and thus provides insights for policymakers regarding the preventive measures.

Iron fertilization to enhance tolerance mechanisms to copper toxicity of ryegrass plants used as cover crop in vineyards

Ryegrass (Lolium perenne L.) is a plant species that can express mechanisms of tolerance to copper (Cu) toxicity. Therefore, the agronomical approach of intercropping system with ryegrass may represent a promising tool to limit the onset of Cu toxicity symptoms in the other intercropped plants species, particularly when an inadequate nutrient availability like iron (Fe) shortage is also concurrently present. This study aimed at assessing the mechanisms involved in the mitigation of Cu phytotoxicity and the stress effects on plant growth, root morphology and nutrition of ryegrass fertilized with two different Fe sources. To this purpose, seedlings of ryegrass were hydroponically grown for 14 days in controlled conditions with 4 different levels of Cu (0.2, 5.0, 25 and 50 μM) and with either 100 μM Fe-EDDHA or Fe-EDTA. Results show that high levels of Cu availability enhanced the root content of organic anions as well as the root exudation. Different Fe fertilizations at the condition of 50 μM Cu induced changes in root phenolic compounds, citrate and fumarate contents and the exudation pattern of phenolic compounds. Differences in plant growth were not observed between the two Fe sources, although Cu concentration in plant tissue fed with Fe-EDTA was lower in the condition of 50 μM Cu. The enhanced root exudation of Cu-complexing organic compounds (including phenolics) in ryegrass plants when exposed to excessive Cu availability could be at the basis of the ameliorated edaphic rhizosphere conditions (lower Cu availability). For this reason, from the agronomical point of view ryegrass plants used in intercropping systems with crops like vine plants could represent a promising strategy to control Cu toxicity in vineyard soils. Further studies under the field conditions must be taken to support present findings.

Copper Supplementation in Watering Solution Reaches the Xylem But Does Not Protect Tobacco Plants Against Xylella fastidiosa Infection

Xylella fastidiosa is a xylem-limited plant pathogenic bacterium that causes disease in many crops worldwide. Copper (Cu) is an antimicrobial agent widely used on X. fastidiosa hosts to control other diseases. Although the effects of Cu for control of foliar pathogens are well known, it is less studied on xylem-colonizing pathogens. Previous results from our group showed that low concentrations of CuSO4 increased biofilm formation, whereas high concentrations inhibited biofilm formation and growth in vitro. In this study, we conducted in planta experiments to determine the influence of Cu in X. fastidiosa infection using tobacco as a model. X. fastidiosa-infected and noninfected plants were watered with tap water or with water supplemented with 4 mM or 8 mM of CuSO4. Symptom progression was assessed, and sap and leaf ionome analysis was performed by inductively coupled plasma with optical emission spectroscopy. Cu uptake was confirmed by increased concentrations of Cu in the sap of plants treated with CuSO4-amended water. Leaf scorch symptoms in Cu-supplemented plants showed a trend toward more severe at later time points. Quantification of total and viable X. fastidiosa in planta indicated that CuSO4-amended treatments did not inhibit but slightly increased the growth of X. fastidiosa. Cu in sap was in the range of concentrations that promote X. fastidiosa biofilm formation according to our previous in vitro study. Based on these results, we proposed that the plant Cu homeostasis machinery controls the level of Cu in the xylem, preventing it from becoming elevated to a level that would lead to bacterial inhibition.

Use of a Pleurotus ostreatus Complex Cell Wall Extract as Elicitor of Plant Defenses: From Greenhouse to Field Trial

Fungi constitute an abundant source of natural polysaccharides, some of them harboring original structures which can induce responses in mammalian or plant cells. An alkaline extract from the edible mushroom Pleurotus ostreatus has been obtained and called Pleuran complex cell wall extract (CCWE). It consists of a glucan-peptide complex whose components fall in a quite broad range of molecular weights, from 30 to 80 kDa. Pleuran extract has been tested on cultivated plants in laboratory conditions and also during field trial for its capacity to stimulate plant defenses in response to pathogen attack. Following Pleuran CCWE treatment, enhanced levels of various biochemical markers associated with plant responses have been observed, including enzymatic activities (e.g., peroxidase) or expression of some pathogenesis-related genes. In addition, during field experiments, we have noticed significant reductions in disease symptom levels in relation to different plant/pathogen systems (wheat/septoria, vine/mildew). These results confirmed that Pleuran CCWE could be used as an elicitor of plant defenses and could help in reducing pesticide applications against plant pathogens.

Experimental and modeling study of proton and copper binding properties onto fulvic acid fractions using spectroscopic techniques combined with two-dimensional correlation analysis

Fulvic acid (FA) significantly influences the bioavailability and fate of heavy metals in environments, while its acid-base characters and metal binding processes are still unclear. Here, spectroscopic techniques combined with multiple models (e.g., NICA-Donnan model) and two-dimensional correlation spectroscopy (2D COS) were applied to explore the proton and copper binding properties of FA sub-fractions (FA₃-FA₁₃). The charge densities, average contents of carboxylic and phenolic groups, average dissociation constants pKa₁ and pKa₂ of sub-fractions ranged 0-16 meq∙g∙C^-1, 5.03-9.58 meq∙g∙C^-1, 2.52-4.67 meq∙g∙C^-1, 4.15-4.33 and 8.52-9.72, respectively. FA sub-fractions had a relatively narrow distribution of carboxyl group and a broad distribution of phenolic group. FA sub-fractions also exhibited roughly two phenolic hydroxyl groups per every 1-3 phenyl rings. Differential absorbance spectra (DAS) derived Gaussian bands were associated to the inter-chromophore interactions, the changes of molecular conformations and functional groups with copper addition. Differential spectra slopes (DSlope_{275-295&325-375}) were more significant with higher copper concentration and copper amounts bonded to carboxylic groups. UV-Vis and fluorescence spectra with 2D heterospectral COS revealed the copper binding heterogeneities and sequential orders of chromophores and fluorophores, quantitatively confirming by the order of conditional stability constants (log K_Cu: 4.64-5.56). Salicylic-/polyhydroxyphenolic, hydroxyl and amino groups were strongly associated to the basic units for fluorophores. Sequential changes followed the order of humic-like→fulvic-like materials for FA₃/FA₅, humic-like→fulvic-like→tryptophan-like materials for FA₇, and humic-like→tryptophan-like→fulvic-like→tyrosine-like materials for FA₉/FA₁₃. Spectroscopic techniques combined with various models (especially for 2D COS) are beneficial to elucidate the binding heterogeneity and sensitivity for metal-organic matters at the functional group level.

Amelioration of heavy metal stress by endophytic Bacillus amyloliquefaciens RWL-1 in rice by regulating metabolic changes: potential for bacterial bioremediation

This study aimed to investigate the bioremediation efficiency of phytohormone-producing endophytic Bacillus amyloliquefaciens RWL-1 isolated from rice seeds. In this study, we tested RWL-1 against various heavy metals (Cu, Cr, Pb, and Cd). Among the tested heavy metals, RWL-1 showed the highest tolerance for Cu stress and we observed alterations in growth kinetics with various Cu concentrations (1, 2.5, and 5 mM). We confirmed the biosorption potential of RWL-1 by scanning electron microscopy coupled with energy-dispersive X-ray spectrometry showing that Cu ions were adsorbed on RWL-1 cell surfaces. We further tested RWL-1 for its plant growth promoting and stress reliance efficiency in response to a dose-dependent increase in soil Cu (1, 2.5, and 5 mM). The RWL-1 inoculation significantly increased seedling biomass and growth attributes compared with non-inoculated control seedlings with and without Cu stress. Moreover, RWL-1 inoculation significantly promoted a physiochemical response in seedlings with and without Cu stress by reducing Cu uptake, improving carbohydrate levels (glucose, sucrose, fructose, and raffinose), enhancing amino acids regulation, and augmenting antioxidant levels (POD, PPO, and GHS). Levels of stress-responsive phytohormones such as abscisic acid (ABA) and jasmonic acid were significantly reduced in RWL-1-inoculated seedlings as compared with non-inoculated control seedlings under normal condition and same levels of Cu stress. In conclusion, the inoculation of B. amyloliquefaciens RWL-1 can significantly improve plant growth in Cu-contaminated soil and reduce metal accumulation, thus making plants safer for consumption. This approach could be tremendously helpful for safe and sustainable agriculture in heavy metal-contaminated areas.

The potential of two different Avena sativa L. cultivars to alleviate Cu toxicity

Agronomic strategies as intercropping might be applied to reduce plant-available copper (Cu) in Cu-contaminated soils. Thus, our aim was to characterize two different oat cultivars, Avena sativa L. cv. Fronteira and cv. Perona for their ability to tolerate and/or phytostabilize Cu. Copper toxicity reduced plant biomass of both cultivars. The exudate analysis revealed the presence of phenolic compounds and phytosiderophores, yet with a different pattern between the cultivars: cv. Fronteira showed a Cu-concentration and time-dependent release of phenolic compounds, while cv. Perona down-regulated this release during the second week of treatment. Copper concentration increased linearly in all the tissues analysed with increasing Cu concentration showing yet a different compartmentalization: cv. Fronteira and cv. Perona preferentially accumulated Cu in the apoplasm and symplast, respectively. This higher accumulation of Cu in the apoplasm strongly reduces the available binding sites, leading to a competitive absorption with other macro-and micronutrients (e.g. Ca, Mn, Zn). Furthermore, in both cultivars Cu toxicity led to a significant reduction of shoot phosphorus content. The ionomic profile and compartmentalization of Cu together with the root activities demonstrate the different tolerance mechanism towards Cu toxicity of the two oat cultivars. In particular, cv. Fronteira seems to adopt an exclusion strategy based on accumulating Cu in the apoplasm and on the exudation of phenolic compounds. Thus, this cultivar could reduce the mobility and the consequent soil bioavailability of Cu playing an important role as phytostabilizer plant in intercropping systems in Cu-contaminated vineyards or orchards.

Morphological Root Responses and Molecular Regulation of Cation Transporters Are Differently Affected by Copper Toxicity and Cropping System Depending on the Grapevine Rootstock Genotype

The high copper (Cu) concentration in vineyard soils causes the increase of Cu toxicity symptoms in young grapevines. Recently, intercropping of grapevine and oat was shown to reduce Cu toxicity effects, modulating the root ionome. On these bases, the focus of the work was to investigate the impact of Cu toxicity of either monocropped or oat-intercropped grapevine rootstocks plants (196.17 and Fercal), at both phenotypic (i.e., root architecture), and molecular (i.e., expression of transporters) levels. The results showed a different response in terms of root morphology that are both rootstock- and cropping system dependent. Moreover, the expression pattern of transporter genes (i.e., VvCTr, VvNRAMP, and VvIRT1) in monocropped grapevine might resemble a Mn deficiency response induced by the excess of Cu, especially in Fercal plants. The gene expression in intercropped grapevines suggested rootstock-specific response mechanisms, depending on Cu levels. In fact, at low Cu concentrations, Fercal enhanced both root system growth and transporter genes expression; contrarily, 196.17 increased apoplast divalent cations accumulation and transporters expression. At high Cu concentrations, Fercal increased the expression of all bivalent cation transporters and, as previously observed, enhanced the release of root exudates, whereas the 196.17 only modulated transporters. In conclusion, our results might suggest that the different adaptation strategies of the two rootstocks to Cu toxicity could be mainly ascribable to a fine-tuning of bivalent cations transporters expression at root level.