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Effect of Different Concentrations of Ozone on in Vitro Plant Pathogens Development, Tomato Yield and Quality, Photosynthetic Activity and Enzymatic Activities
Abstract
As an effective alternative to traditional pesticides, ozonated water has been used for direct immersion and spraying applications, respectively, against the pathogenic bacterium Ralstonia solanacearum (R. solanacearum) and fungus Alternaria solani (A. solani) that are pathogens of tomato. Immersing R. solanacearum in 0.8 mg/L ozonated water resulted in complete inactivation, while the growth-inhibition rates of the A. solani radial mycelia gradually increased with a 67.0% decrease compared to those of the control at an ozonated water concentration of 7.5 mg/L. This indicated that ozonated water was effective at restraining pathogens in the tomato plant. In addition, spraying wild tomato species (Solanum lycopersicum) plants with ozonated water at concentrations below 10 mg/L for 25 d had no negative effects after treatment compared to those of the control. Photosynthetic activities and the antioxidant system response in the untreated and ozonated water-treated plant leaves had no observable changes. To determine the optimal ozonated water concentration for the pathogen and its host plant, we examined a variety of modes of action, and then, below 10 mg/L of ozonated water. Thus, ozonated water not only inhibits the proliferation of plant pathogens, but is an effective alternative to the pesticides traditionally used to prevent disease in agricultural production.
... Ozone has been applied for irrigation water disinfection and to control nematodes that reduce crop yield of tomato (Guo et al., 2019;Landa Fernández et al., 2019). It is also used to residual pesticides decomposition following the overuse of chemicals in agricultural fields (Mitsugi et al., 2017). ...
... An additional positive effect of ozonisation is the inactivation of pathogenic bacteria, such as Escherichia coli, Enterococcus and Staphylococcus strains (Heß & Gallert, 2015) which raise crop protection and prevents infection with plant pathogens, It is also used to disinfect irrigation water and as an alternative to pesticides (Guo et al., 2019;Landa Fernández et al., 2019). ...
p>This article focuses on the study of the influence of ozonised water irrigation on the morphological, bacteriological and sensory characteristics of ‘Saint-Pierre’ tomatoes grown in Algeria. The results were compared with those irrigated with non-ozonised tap water called control of the same varietal type and grown under the same conditions. The work was carried out on seedlings of tomatoes grown and irrigated with ozonised water at different ozonisation times: 10- seconds, 20- seconds and 30-seconds, corresponding to lot I (tomato at 10-s), lot II (tomato at 20-s) and lot III (tomato at 30-s), respectively. Irrigation with ozonised water does not cause defects in shape, skin or colour of the fruits. They are, distinguished by a round shape, very red in colour, consistent and slightly acidic in taste. With good microbiological stability in accordance with the standard and good organoleptic quality except for the taste character of tomatoes at 30-seconds where a majority of evaluators estimated that ‘they were bland and no big difference for the other criteria analysed. In general, our results showed that the ozonisation of irrigation water improves the growth, development, vigour and yield of tomato plants without altering the marketability of the fruits. This process encourages the use of ozonised water in agriculture since it has a high added value from an environmental and economic point of view and it can be generalized to other crops.</p
... For instance, in tomato cultivation, applying ozone concentrations of 3.0 mg·L −1 in irrigation and 0.6 mg·L −1 in spraying significantly enhances the activity of antioxidant enzymes in tomato leaves [32]. Spraying ozonated water at concentrations below 10 mg·L −1 has been shown to bolster tomato defenses against plant pathogens [33]. Furthermore, ozone concentrations ranging from 10 to 40 mg·L −1 have been found to enhance pepper germination and seedling growth under low-temperature stress [34]. ...
As living standards rise, enhancing quality has become a central objective for many researchers. Soilless cultivation, known for its efficient use of resources, is increasingly used in vegetable production. It is critical to develop effective water and fertilizer management strategies to achieve high-quality yields and promote sustainable development in modern agriculture. This study employed an orthogonal experimental design to assess the impact of varying nutrient solution concentrations (50%, 75%, 100%, and 125% of Hoagland’s), lower irrigation thresholds (40%, 55%, 70%, and 85% field capacity (FC)), and ozone concentrations (0, 1, 2, and 4 mg·L−1) on lettuce growth, yield, quality, and water–fertilizer use efficiency. The results indicated that fixed nutrient solution concentrations and lower irrigation thresholds enhanced growth metrics for lettuce. Similarly, increasing ozone concentrations initially improved, then reduced growth metrics when the lower irrigation threshold was constant. Furthermore, maintaining stable ozone concentrations while raising the nutrient solution concentration initially boosted, then diminished, growth indicators. Optimal conditions for water and fertilizer management were identified at a nutrient solution concentration of 75% to 100% and an ozone concentration of 0 to 1 mg·L−1. Variance analysis highlighted the significant effects of nutrient solution concentration, lower irrigation thresholds, and ozone concentrations on lettuce yield, quality, and water and fertilizer use efficiency. Range analysis revealed the optimal management combination to be a nutrient solution concentration of 100%, an 85% lower FC irrigation threshold, and an ozone concentration of 1 mg·L−1, yielding 16.82 t·ha−1 of lettuce and a water use efficiency of 40.14 kg·m−3. These findings provide theoretical support for the sustainable advancement of soilless cultivation in contemporary agriculture.
... The application of OW treatments led to an increase in Chl levels in tomatoes when compared to the control. Notably, the treatment with 6 mg/L OW showed a 20.7% increase over the control [61]. OW treatment resulted in a substantial elevation of Chl a, Chl b, and total Chl levels in tomatoes when compared to the control group [62]. ...
Ozonated water (OW) is now being recognized as an innovative and eco-friendly solution for managing plant growth while also promoting the production of bioactive compounds and essential plant metabolites. This study aimed to identify the most effective duration of OW treatment to promote plant growth and accumulation of antioxidant activity and bioactive compounds in Agastache rugosa in a plant factory. Whole plants were subjected to OW soaking treatments for varying durations (0, 1, 10, 20, 40, and 80 s) at a concentration of 1 µmol·mol⁻¹, once per week, at 0, 1, 2, 3, and 4 weeks after transplantation. Five weeks after transplantation, plant samples were collected for the analysis of their plant growth parameters, photosynthetic pigments and parameters, total flavonoid, antioxidant activity, and bioactive compounds. Stem length was decreased in all OW treatments, while the number of flower branches, the flower fresh and dry weights were significantly increased under 20, 40, and 80 s OW treatments than in the control group. The net photosynthetic rate decreased significantly in 20, 40, and 80 s OW treatments compared with the control. Chlorophyll a concentration was the highest in the 20-s OW treatment, and chlorophyll b concentration was the highest in the 10-s OW treatment. Total flavonoid levels in plants increased significantly under 20-, 40-, and 80-s OW treatments, and their antioxidant activity (superoxide dismutase, catalase, and peroxidase) were significantly higher under 40- and 80-s OW treatments than in the control. Rosmarinic acid content increased significantly under the 10- and 40-s OW treatments, whereas the tilianin and acacetin contents increased significantly under the 20-, 40-, and 80-s OW treatments compared to those in the control. Our results suggest that soaking whole plants in OW for 20–80 s enhances the flower growth and bioactive compounds in A. rugosa for medicinal use.
Graphical Abstract
... In agriculture, ozone has been used for crop protection against pests that cause bacterial plant wilt and reduce yields, thus causing significant economic losses, it has also been used for foliar treatment, for the decomposition of pesticide residues in soils and to improve the microbiological quality of irrigation water (Díaz-López et al., 2021;Guo et al., 2019;Landa Fernández et al., 2019;Mitsugi et al., 2017). Indeed, ozone (O 3 ) is an unstable triatomic allotrope of oxygen, its half-life in water at room temperature is about 20 minutes, it is characterized by a high oxidation potential (2.07 volts) higher than that of chlorine (1.36 volts) (Holah et al., 2016). ...
p class="042abstractstekst"> This study presents the results of an experimental work carried out on tomato seedlings of the same varietal type, grown under a Mediterranean climate and irrigated with ozonised water at different ozonisation durations that vary from zero to 30 seconds. In order to assess the impact of aqueous ozone on the agronomic performances and the physicochemical characteristics of fruits. The tomatoes responded differently between themselves and the control batch. The results obtained showed precocity of germination, an increase in growth, development, and vigour in the experimental plants compared to the controls. The yield is proportional to the increase in the ozonisation time of irrigation water. During the reproductive phase of the plants, no negative effects were observed. The physicochemical characteristics of fruits could be evaluated; they are distinguished from higher sugar contents in the experimental tomatoes compared to controls, no great difference for the other criteria analysed, the latter were generally in accordance with the standardized values of the literature as well as with the applicable national regulations. Ozonisation of irrigation water is an effective and promising alternative method, which improves germination time and increases fruit yield without negatively affecting their marketability. </p
... The action of ROS during pathogenesis is variable and is able to act directly by killing the pathogen from H 2 O 2 reactions with transition metals, and releasing hydroxyl radicals (OH − ) in the medium, which are lethal to biomolecules. The presence of H 2 O 2 has already been shown to be capable of signaling a stiffening of the tissue walls, making it difficult for the infection to spread [56,64]. ...
Growth-promoting bacteria are already used in sustainable agricultural systems in Brazil. The market is dominated by inoculants and biological pesticides, which do not reach the full potential of this tool in the agricultural sector. This study aimed to evaluate four bacterial strains for the presence of growth promotion mechanisms, as well as the reduction of Asian rust severity in soybean plants and its effects on three antioxidant enzymes during pathogenesis. The plants were treated using the bacterial cells and/or their biosurfactants before inoculation of the pathogen (IOP). Severity was measured based on a diagrammatic scale at 14, 18 and 21 days after IOP, and the activities of the enzymes SOD, CAT, and APX were evaluated 21 days after IOP. Treatments containing only bacterial cells were not efficient in reducing the severity, with losses of leaf area reaching 15%, while the addition of biosurfactants led to a result that is similar to the biofungicide, based on Bacillus subtilis (Serenade®). The presence of direct growth promotion mechanisms can be observed in all isolates, as well as the role of bacterial metabolites, especially lipopeptides, in the biological control of diseases and the modulation of the plant’s immune response.
... Post ozone treatment, the SOD activities in the tomato leaves were 18.7%, 35.4%, 33.0%, 37.0% and 27.4%, respectively, under 2-8 mg/L of ozonated water concentration. Further, the change in the activity of CAT matched with that of SOD (Fig. 5) (Guo et al., 2019). A positive correlation between the activities of SOD and CAT protects the plant against Meloidogyne incognita infection by controlling the oxidative stress defense during tomato development (Veronico et al., 2017;Zacheo et al., 1995). ...
Inactivation of deteriorative enzymes preserves the quality of fruits and vegetables and extends the shelf-life of fruit juices. Ozonation and cold plasma treatment are recent additions to the thermal and non-thermal methods for enzyme inactivation. However, these techniques stand out in their effectiveness and versatility for the treatment of a wide range of fruits and vegetables. This article appraises the mode of action and applications of ozone and cold plasma for the inactivation of enzymes in fruits, vegetables, and fruit juices. Further, a comprehensive discussion is presented on the influential parameters of enzyme inactivation effectiveness of ozonation and cold plasma processing. Besides, the latter sections of this article highlight the challenges that impose hurdles in the commercial applications of these unconventional techniques and the way forward in improving their efficacy and industrial applications.
... Ozone (O3) represents an affordable product widely used against several fungal and bacterial pathogens. The lethality of ozone against pathogens and insects was proved by several laboratory studies [3,4]. Moreover, ozone can be used as odour management tool in biogas plants [5]. ...
The environmental and socioeconomic constraints force the agricultural sector to find alternative plant protection solutions. As a result, several alternative plant protection products (PPP) have been developed in the last decades. Ozonated water sprayed on the vegetation proved to be a partial alternative to agricultural chemical PPP for plant diseases. The ozonated water efficacy is related to the production of reactive oxygen species (ROS). At the same time, ozonated water showed no significant phytotoxicity when the spraying was carried out under well-ventilated conditions. In the present study, a corona discharge ozonating water tool was installed on a commercial mist-blower axial sprayer then the redox potential was measured to assess the sanitizing effects on plants due to ROS concentration. First, the redox potential (ORP) was measured inside the tank, after the pump, at the nozzle level, and on a test bench that simulates the vertical wall of the plant. Next, the redox growth rate was measured at each point to assess the system's latency. Then, different nozzle types were used to measure the effect of different droplet sizes on redox potential. According to the result, redox potential decreases by 7%, 12%, and 29% after the pump, at the nozzle, and the test bench, respectively. These losses are affected by the droplet size and they increase in the case of a smaller droplet. Significant differences were found among different nozzles type.
... In the light of the aforementioned effects, some authors dared to suggest that OW applied at low doses could enhance plant protection and could prevent pathogens infection [20,24,25,29,38,39]. Moreover, numerous research studies in recent years have focused on the prospect of using OW as an abiotic stressor in order to stimulate bioactive secondary metabolites in grapevine leaves and fruits [40]. ...
To face the new emerging challenges in agriculture as the production of safe, nutritious, and sustainable food, plant priming results as a worthwhile practice. Low doses ozonated water (<10 mg L⁻¹) can be supplied through foliar spray, soil drench, seed preconditioning or through the ozonisation of nutrient solutions in hydroponic systems, without leaving chemical residues on crops. Here we review morphological, physiological, and biochemical effects of this innovative technique, emphasising stimulatory effect on plant metabolism (in particular on secondary metabolism) and providing an overview about the priming effect induced by the application of ozonated water. Overall, the literature survey unveils that ozonated water is a powerful tool to elicit plant resistance and promote plant nutraceutical value.
... In contrast to gaseous ozone, dissolved ozone decomposes faster and does not pose a toxic risk to respiratory tracts (Kim et al. 2002) or plants (Fujiwara and Fujii 2002). Therefore, recent interest developed in using ozonated water for control of plant diseases (Fujiwara and Fujii 2002;Guo et al. 2019;Zheng et al. 2020). ...
Phytonematodes cause severe yield losses in horticulture, partly because they are difficult to manage. Compact, energy-efficient generators that electrochemically produce ozonated water by utilizing diamond-coated electrodes have become available. In this study, the application of on-site generated ozonated water to inactivate soil nematodes and to mitigate nematode-mediated apple replant disease was tested. Pratylenchus penetrans was highly susceptible to dissolved ozone (LC 50 0.6 mg L ⁻¹ ). In one greenhouse experiment, treatment of P. penetrans in soil with ozonated water (0.27 mg ozone L ⁻¹ soil) reduced subsequent invasion of the nematodes into roots by 60%. Growth of apple saplings in soil that was affected by apple replant disease (ARD) was significantly improved following a treatment with 1/10 volume ozonated water compared to the control. In a second greenhouse experiment, one-time drenching of ARD soil with ozonated water was followed by improved growth of apple plants similar to that in autoclaved soil. A second application of ozonated water did not further improve plant growth. The number of active nematodes in replanted soil that moved through a Baermann filter was significantly reduced by all tested concentrations of ozone (0.12–0.75 mg L ⁻¹ soil). A fraction of 19–36% of the nematodes survived and slightly recovered after four weeks. In conclusion, on-site generated ozonated water has potential to mitigate nematode problems in horticulture and to expand management options.
... It was lower than the control value. So, it can be suggested that the best way to prevent pathogen (R. solanacearum) was to treat ozone water in tomatoes at 0.8 mg/ L-moreover, the number of bacteria, declining with the rising concentration of ozone water [72]. ...
Fruit and vegetables are horticultural products wealthy in water-soluble vitamins and other essential nutrients for human requirements. These products have, however, been shown to contribute to the transmission of various diseases caused by microbial contamination. Ozone is a strong, effective, and safe oxidizing and disinfectant in the handling of horticultural products. The use of ozone can eliminate the contamination of pesticides, bacteria, and heavy metals that stick to the surface of fruit and vegetables to be safe for human consumption. It can also maintain the products' shelf life and quality as the nutritional content is secured and not easily damaged. Due to evaporation, ozone compounds will automatically disappear. If exposed to the sun, ozone will also decompose back into oxygen molecules so that residues are not lost. This brief review discusses the effects of ozone on quality, the ability to reduce microbes, antioxidant activity, pesticides, and the sensory assessment of horticultural products.
Keywords: Antioxidant, horticultural, microbiology, nutrient, ozone, preservation.
... This suggests a threshold of DOC for the application in ozone treatment, which was also reported by Graham, Zhang, and Dixon (2012) on tomato that an upper limit of DOC at 3.0 mg L −1 resulted in no adverse effect for the drip irrigation of ozonated nutrient solution, though the antioxidant capacity was not investigated in their study. Higher upper limit of the DOC at 10.0 mg L −1 for ozonated water spraying was suggested by Guo et al. (2019), which increased the SOD and CAT of tomato leaves, this is likely to be explained by the much lower residual DOC in spray droplets. Overhead watering is a much similar protocol with our study, Graham et al. (2009) suggested a safe DOC at 1.5 mg L −1 , for the cultivation of Salix integra, Weigela florida, Spiraea japonica, Hydrangea paniculata, Physocarpus opulifolius resulted in no negative effect. ...
Ozone is one of the potential high-effective oxidants for the disinfection of nutrient solution. However, ozone residue in aqueous state in the nutrient solution could be a stress factor for the crops cultivated. In order to address the effects of dissolved ozone concentration (DOC) on the growth and antioxidant profile of lettuce, nutrient solution with DOC of 2.0 and 4.0 mg L⁻¹ was applied to the two soilless cultivation methods (substrate and hydroponic cultivation). Based on our results, we conclude that the nutrient solution with DOC up to 4.0 mg L⁻¹ resulted in no negative impact on the development and root antioxidant of the lettuce, which suggest ozonation of the nutrient solution is applicable as an alternative disinfection method with the purpose of reducing the waste of water resources and chemical residual of traditional disinfectants.
... In the control treatment, the incidence of this disease reached 18% of all heads, while the treatments using ozonated water on the shoot alone (T1) or combined with the roots (T3), reduced this value to 2-3% (Fig. 1). Reflecting our results obtained in broccoli, recent studies in wild tomato species have shown that spraying plants with ozonated water results in growth-inhibition of the Alternaria solani radial mycelia (Guo et al., 2019). By contrast, the treatment with ozonated water by irrigation (T2) showed no significant differences in the incidence of the infection compared to the control. ...
The impact of pre-harvest applications of ozonated water via the shoot (T1), roots (T2) and combined (T3) on the visual and nutritional quality of broccoli was evaluated. None of the treatments produced visual damage or affected the physical quality of broccoli. Application to the shoot decreased the incidence of Alternaria from 18% to 2–3%. In addition, this treatment reduced the content of glucoraphanin and increased that of glucobrassicin, without modifying the total concentration of glucosinolates or vitamin C and phenolic compounds. Application to the roots increased the content of all the glucosinolates and main phenolic compounds. Lastly, the combined application to both plant parts had the same benefits for head quality as the root-only treatment, improving on the effects of the leaf-only treatment. The results underline the potential of using ozonated water to improve the commercial and nutritional quality of broccoli.
Background and aims: Ozone technology is utilized to inactivate enzymes, destroy microorganisms, and preserve and maintain food quality without chemicals as antimicrobial agents. Methods: As an emerging processing technology, ozone pretreatment objectives combine some selected features with low molecular weight functional components and bioactive properties of medicinal plants. Changes observed were those in physical and functional properties such as pH, sensorial attributes of aroma and texture, and bioactive compounds like polyphenols, oxidants, and non-enzymatic enzymes. Results: It has been shown through research that different reactions occur, which could be beneficial according to the mixture of plants present, given that each case has a different mechanism. Ozone’s natural behavior, improved economic viability, and enhanced environmental safety distinguish it from traditional means. Nevertheless, research on the effects of ozone on functional and bioactive compounds of food and medicinal plants is still ongoing since it will be the basis for its establishment as a new technique. Conclusion: The primary objectives achieved by applying ozone technology include maintaining and enhancing quality, improving antimicrobial efficiency, reducing chemical usage, environmental sustainability, and developing new processing methods. This study investigates the effect of ozone on the physical and functional properties, such as pH and sensory attributes, based on controlled experiments while analyzing the different reactions induced by ozone when combined with medicinal plants.
Air pollution from multiple sources causes various short-term health effects, primarily affecting the respiratory and cardiovascular systems. The main pollutants causing these effects are particulate matter, nitrogen dioxide, sulfur dioxide, ozone, and carbon monoxide. Short-term exposure to elevated levels of particulate matter consists of tiny particles in the air that can penetrate the respiratory system, causing health problems include eye and throat irritation, exacerbation of respiratory conditions, and cardiovascular abnormalities. Nitrogen dioxide can lead to lung and respiratory irritation, exacerbating bronchoconstriction and increasing respiratory symptoms, particularly in individuals with pre-existing conditions. Sulfur dioxide exposure can lead to respiratory problems such as eye and throat irritation and exacerbate asthma symptoms. Exposure to ozone can cause respiratory discomfort, exacerbate asthma symptoms, and contribute to respiratory infections, especially during outdoor activities. Carbon monoxide impairs the body’s ability to transport oxygen, leading to symptoms such as headaches, dizziness, and nausea. Elevated levels can lead to severe health complications, including loss of consciousness and fatality. Immediate strategies to tackle these impacts involve stringent regulations for emission control, public education campaigns to raise awareness about pollution sources and self-protection measures, urban development schemes to reduce traffic congestion and enhance green spaces, and swift emergency procedures for high pollution periods. Collaboration among governments, companies, and communities is necessary to ensure adherence to air quality rules. This will aid in safeguarding public health and advocating for sustainable approaches to mitigate the direct impacts of air pollution.
In recent years, the production and demand of berries in the world have gradually increased, but the infection of fungal pathogens has become one of the important factors restricting the production and sales of fresh berries. It has been found that Alternaria can cause a variety of plant diseases and fruit rot worldwide. This review introduces the effect of Alternaria infection on berry quality, including physical, chemical and physiological aspects, and discusses the possible infection mechanisms. In addition, Alternaria produces toxins during infections and seriously threatens the safety of berries and consumer health. Therefore, the prevention and control measures of Alternaria are systematically summarized. This review provides the basis for further optimization of postharvest preservation technology and fruit quality, to prolong the shelf life of berries. We can realistically expect to control plant diseases with increasing efficiency, which is conducive to improving the quality and safety of postharvest berry fruits.
The environmental and socioeconomic constraints force the agricultural sector to find alternative plant protection solutions. As a result, several alternative plant protection products (PPP) have been developed in the last decades. Ozonated water sprayed on the vegetation proved to be a partial alternative to agricultural chemical PPP for plant diseases. The ozonated water efficacy is related to the production of reactive oxygen species (ROS). At the same time, ozonated water showed no significant phytotoxicity when the spraying was carried out under well-ventilated conditions. In the present study, a corona discharge ozonating water tool was installed on a commercial mist-blower axial sprayer then the redox potential was measured to assess the sanitizing effects on plants due to ROS concentration. First, the redox potential (ORP) was measured inside the tank, after the pump, at the nozzle level, and on a test bench that simulated the vertical wall of the plant. Next, the redox growth rate was measured at each point to assess the system’s latency. Then, different nozzle types were used to measure the effect of varying droplet sizes on redox potential. The result shows potential redox decreases by 7%, 12%, and 29% after the pump, at the nozzle, and at the test bench, respectively. These losses are affected by the droplet size, and they increase in the case of a smaller droplet. Significant differences were found among different nozzle types.KeywordsIntegrated Pest ManagementOzoneSpray Droplet SizeAir Speed
Spore forming bacteria (SFB) are strongly chlorine resistant. Their presence in drinking water may cause diseases and pose threat to public health. Three SFB strains, i.e. Bacillus alvei, Bacillus cereus, and Lysinibacillus fusiformis, were isolated and identified from the finished water of a drinking water treatment plant where bacteria colonies occasionally reached the limit value. Due to their chlorine resistance, a SFB control strategy coupling pre-oxidation, coagulation sedimentation, and UV-AOPs inactivation in water treatment process was studied in lab scale. Five minutes pre-oxidation treatment by applying Cl2 and ClO2 induced remarkable spore transformation. Longer pre-oxidation exposure time didn't have apparent improvement. Cl2 and ClO2 dosages of 0.9 mg/L and 0.5 mg/L were suggested, respectively. The formed spores can be efficiently removed by the following coagulation sedimentation treatment. At a suggested dosage combination of 20 mg/L PAC and 0.08 mg/L PAM, spore removal efficiency reached about 3.15-lg. Comparing to applying sole UV irradiation, enhanced UV inactivation by adding 0.1 mM H2O2, or Cl2, or peroxymonosulfate (PMS) substantially improved the inactivation of the most chlorine resistant SFB strain, Lysinibacillus fusiformis. UV-AOPs stably achieved 2-lg inactivation rate at UV dosage of 40 mJ/cm². UV/H2O2, UV/Cl2 and UV/PMS inactivation kinetically enhanced 1.20 times, 1.36 times and 1.91 times over sole UV irradiation. Intracellular DNA and ATP leakages were detected, and remarkable damages of Lysinibacillus fusiformis cells’ surface and ultrastructure were observed. These findings evidenced cell wall and cell membrane destructions, guaranteeing substantial SFB cells inactivation. This study was carried out based on three SFB strains isolated from a finished water, and common engineering practical operations. By providing engineeringly relevant references, the outcomes obtained would be helpful for dealing with SFB outbreak risk in drinking water treatment.
Japanese mustard spinach with 4–5 unfolded leaves were transplanted in a nutrient film technique hydroponic system to investigate the effects of washing roots intermittently with ozonated water (OW) on plant growth. The high concentration of OW generated electrolytically was mixed in the nutrient solution tank, showed 5.8 mg.L⁻¹, and circulated through the culture beds for 1 h every week. After washing the roots with OW or tap water (TW) as a control for 1 h, Otsuka house A solution (NO3-N: 16.8 me.L⁻¹, NH4-N: 1.8 me.L⁻¹, P: 5.1 me.L⁻¹, K: 8.6 me.L⁻¹, Ca: 8.2 me.L⁻¹, Mg: 3.0 me.L⁻¹) at 1.2 dS.m–1 was provided for plant cultivation in hydroponic culture systems. The OW or TW was replaced every week. The fresh and dry weights of the leaves, number of leaves, leaf length, and leaf width of plants treated with OW were significantly higher than those of the plants treated with TW at 1, 2, and 3 weeks after transplanting (WAT). The ratio of the shoot and root dry weights at 1, 2, and 3 WAT was significantly higher in plants grown in the OW flushing treatment compared with the control treatment. However, the roots dry weights were not significantly different between the OW- and TW-treated plants. Moreover, the number of coliform bacteria and aerobic plate count (APC) in the solution and plants were not significantly different between the two treatments. These results indicate that washing roots intermittently with 5.8 mg.L⁻¹ dissolved ozone concentration of OW for 1 h per week promotes aerial plant growth without physiological disorder and is not accompanied by a decrease in the number of coliform bacteria and APC in the solution and plants.
Root-knot nematodes (Meloidogyne incognita) are plant parasitic worms that widely influence the agricultural production including soilless cultivation. In this study, we investigated the inactivating effect of ozonated nutrient solution on the root-knot nematode juveniles in both nutrient solution and substrate, as well as the in vitro egg hatching. The results showed that twice ozonation treatments with dissolved ozone concentration (DOC) at 0.5 mg/L resulted in a mortality at 90.8% for in vitro study. DOC of 4.0 mg/L with three treatment repeats in the substrate experiment resulted in a mortality at 88.3%. Our results imply that the application of ozonated nutrient solution might be a feasible method in soilless cultivation for the control of root-knot nematodes. In practical application, ozonation treatment should be conducted with appropriate DOC and treatment repeats.
Fungal contamination of drinking water sources is increasingly threatening the environment and human health. In this study, the inactivation of three genera of dominant fungi in drinking water sources using ozone was first reported. The inactivation of the fungal spores by ozone could be divided into two distinct stages: first a rapid reduction in survival, and then the inactivation at a slower rate. The secondary stage inactivation fitted the Chick–Watson model well, and there was no significant difference in the second-order inactivation rate constants of the three fungal spores (0.199–0.209 L mg⁻¹ min⁻¹). The inactivation rate constants of fungal spores by molecular ozone were much lower than those of viruses, which were equivalent to that of Cryptosporidium. The increase in pH and temperature showed a positive effect on the inactivation rate. Damage to cell membranes, leakage of intracellular compounds, and changes of reactive oxygen species and esterase activity in the spores were detected after inactivation. The results indicated that ozone inactivated fungal spores by firstly destroying cell walls and membranes and then causing the release of intracellular compounds. The fungicidal efficiency of ozone was superior to those of chlorine and chlorine dioxide. In addition, the inactivation efficiency of ozone on fungal spores in real water matrices was reduced to 50.7–91.2% of the efficiency in phosphate buffer. In conclusion, ozone showed high efficiency in the inactivation of fungal spores and could be used as an alternative disinfectant for fungi contamination in drinking water sources.
The effects of different levels of water stress on oxidative parameters (H2O2 and MDA), the total pool sizes of ascorbate, the activities of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), as well as the activities and relative transcript levels of the enzymes of ascorbate-glutathione cycle ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were studied in the fruit of tomato (Solanum lycopersicum L. cv. Micro-Tom). Plants were subjected to three levels of water stress (S50, S25 and S0) and fruits at different development stages were harvested after 3, 6 and 10 days of stress. Changes in H2O2 and MDA contents indicated that water stress induced oxidative stress in fruits. The concentrations of ascorbate (AsA) and dehydroascorbate (DHA) generally modified with water stress treatments. Moreover, changes in SOD and CAT activities and DHAR, MDHAR, APX and GR activities and relative transcript levels were dependent on the fruit development stage and the intensity and the duration of water stress. These results suggest that the response of antioxidant systems of tomato fruits to oxidative stress induced by water stress treatments was different depending on the fruit development stage.
Ozone, a powerful oxidant, is effective against various kinds of microorganisms on fruits and vegetables. Promising results have been revealed in solving the problems of the food industry like mycotoxin and pesticide residues by ozone application. Spontaneous decomposition without forming hazardous residues in the treatment medium makes ozone safe in food applications. If improperly used, ozone can cause some deleterious effects on products, such as losses in sensory quality. Treatment conditions should be specifically determined for all kinds of products for effective and safe use of ozone.
Ralstonia solanacearum was ranked in a recent survey the second most important bacterial plant pathogen, following the widely used research model Pseudomonas syringae (Mansfield et al., 2012). The main reason is that bacterial wilt caused by R. solanacearum is the world's most devastating bacterial plant disease (http://faostat. fao.org), threatening food safety in tropical and subtropical agriculture, especially in China, Bangladesh, Bolivia and Uganda (Martin and French, 1985). This is due to the unusually wide host range of the bacterium, its high persistence and because resistant crop varieties are unavailable. In addition, R. solanacearum has been established as a model bacterium for plant pathology thanks to pioneering molecular and genomic studies (Boucher et al., 1985; Salanoubat et al., 2002; Cunnac et al., 2004b; Occhialini et al., 2005; Mukaihara et al., 2010). As for many bacterial pathogens, the main virulence determinant in R. solanacearum is the type III secretion system (T3SS) (Boucher et al., 1985; 1994), which injects a number of effector proteins into plant cells causing disease in hosts or a hypersensitive response in resistant plants. In this article we discuss the current state in the study of the R. solanacearum T3SS, stressing the latest findings and future perspectives. © 2013 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.
The phytotoxic threshold of five woody perennial nursery crops to applications of aqueous ne was investigated to determine if aqueous ozone could be used forremediation of recycled y irrigation water and for pathogen control. The perennial nursery crops [Salix integra Thunb. akura Nishiki'; Weigela florida Thunb. ;Alexandra'; Spiraea japonica L.f. ;Goldmound'; paniculata Seib. ;Grandiflora'; Physocarpus opulifolius L. Maxim. ;Summer Wine'] were evaluated or aqueous ozone hytotoxicity after 6 weeks of overhead spray irrigation in which five aqueous ozone treatments (0, 10.4, 31.2, 62.5, 125.0 μmolL-1) were applied on a daily basis. The concentrations applied represent levels useful for irrigation system maintenance (pathogen and biofilm control) with the highest levels selected to clearly demonstrate phytotoxicity. Aqueous ozone solutions were prepared and injected in-line during irrigation for 7.5 min every day for 6 weeks, after which growth parameters (leaf area, shoot dry weig ,root dry weight, height, flower number) were measured and leaf injury was evaluated. High residual aqueous ozone (62.5 μmolL-1 or greater at emitter discharge; 0.3 m from canopy) in the irrigation water was shown to negatively affect the growth parameters measured; however, low residual ozone concentrations (31.2 μmolL-1 or less at emitter discharge; 0.3mfrom canopy) did not present any measurable risk to plant growth. Furthermore, even at higher dose levels, leaves produced during the treatment period showed reduced damage levels. It is concluded that ozone residuals of 31.2 μmolL-1 (at emitter discharge) can remain in overhead irrigation water without negatively affecting the crop species examined under the application protocols used. At the ozone concentrations demonstrated to be tolerable by the crop species examined, it is reasonable to surmise that control of pathogens at all points within the irrigation system will be achievable using aqueous ozone as part of an irrigation management strate .The use of aqueous ozone in this fashion could also aid in dramatically reducing chemical residuals on crops by reducing the input requirements of traditional chemical controls.
In recent years, plastic greenhouse vegetable cultivation (PGVC) has expanded worldwide, particularly in
China, where it accounts for more than 90% of all global PGVC operations. As compared with conventional
agricultural methods, PGVC has doubled crop yields by extending growing seasons and intensifying agriculture.
PGVC also offers more ecosystem services relative to conventional approaches, including greater soil
carbon sequestration, lower water consumption, and improved soil protection at regional scales. The economic
benefits of this easily implemented agricultural method are attractive to small-holder farmers.
However, greater environmental impacts (eg greenhouse-gas emissions, generation of large amounts of plastic
waste) are associated with PGVC than with conventional approaches. Here, we review what is currently
known about PGVC and identify future research priorities that will comprehensively assess the ecosystem services
offered by this method of cultivation, as well as its environmental impacts and socioeconomic benefits.
We report two cases of occupational asthma caused by sensitisation to powdered fungicides fluazinam and chlorothalonil, from the same fungicide formulation plant. Both developed work related lower respiratory symptoms after a latent interval of asymptomatic exposure. The diagnosis in each case was confirmed with a serial peak flow record in the workplace followed by specific inhalation tests. These fungicides are known to cause dermatitis; this report indicates that these compounds can induce specific immunological reactions in the airways as well as skin.
Abiotic stresses, such as drought, salinity, extreme temperatures, chemical toxicity and oxidative stress are serious threats to agriculture and the natural status of the environment. Increased salinization of arable land is expected to have devastating global effects, resulting in 30% land loss within the next 25 years, and up to 50% by the year 2050. Therefore, breeding for drought and salinity stress tolerance in crop plants (for food supply) and in forest trees (a central component of the global ecosystem) should be given high research priority in plant biotechnology programs. Molecular control mechanisms for abiotic stress tolerance are based on the activation and regulation of specific stress-related genes. These genes are involved in the whole sequence of stress responses, such as signaling, transcriptional control, protection of membranes and proteins, and free-radical and toxic-compound scavenging. Recently, research into the molecular mechanisms of stress responses has started to bear fruit and, in parallel, genetic modification of stress tolerance has also shown promising results that may ultimately apply to agriculturally and ecologically important plants. The present review summarizes the recent advances in elucidating stress-response mechanisms and their biotechnological applications. Emphasis is placed on transgenic plants that have been engineered based on different stress-response mechanisms. The review examines the following aspects: regulatory controls, metabolite engineering, ion transport, antioxidants and detoxification, late embryogenesis abundant (LEA) and heat-shock proteins.
The differences in pigment levels and photosynthetic activity of green sun and shade leaves of ginkgo (Ginkgo biloba L.) and beech (Fagus sylvatica L.) are described. Sun leaves of both tree species possessed higher levels in chlorophylls (Chl) and carotenoids on a leaf area basis, higher values for the ratio Chl a/b and lower values for the ratio Chl/carotenoids (a+b)/(x+c) in comparison to shade leaves. The higher photosynthetic rates P(N) of sun leaves (ginkgo 5.4+/-0.9 and beech 8.5+/-2.1 micromol m(-2)s(-1)) were also reflected by higher values for the Chl fluorescence decrease ratios R(F)(d) 690 and R(F)(d) 735. In contrast, the shade leaves had lower P(N) rates (ginkgo 2.4+/-0.3 and beech 1.8+/-1.2 micromol m(-2)s(-1)). In both tree species the stomatal conductance G(s) was significantly higher in sun (range: 70-19 1 mmol m(-2)s(-1)) as compared to shade leaves (range: 5-55 mmol m(-2)s(-1)). In fact, at saturating light conditions there existed a close correlation between G(s) values and P(N) rates. Differences between sun and shade leaves also existed in several other Chl fluorescence ratios (F(v)/F(m), F(v)/F(o), and the stress adaptation index Ap). The results clearly demonstrate that the fan-shaped gymnosperm ginkgo leaves show the same high and low irradiance adaptation response as the angiosperm beech leaves.
Erwinia carotovora subsp. carotovora (Ecc) is a bacterial pathogen that causes decay of vegetables and is found in a wide range of Brassica crops in the Shanghai area, particularly in non-heading Chinese cabbage (NHCC). In this study, aqueous ozone was used as an antimicrobial agent to prevent the growth of Ecc bacterial colonies. Ecc that were treated with aqueous ozone were completely inactivated after the bacteria had been exposed to 0.5 mg/L ozone at 28°C. Furthermore, a susceptible NHCC cultivar was directly sprayed with different concentrations of dissolved ozonated water as a pesticide substitute. The effects of the treatments on morphology were analyzed, and some treatments were characterized by induction of visible symptoms of senescence. No negative effects were observed after treatment by spraying ozonated water compared with the control at concentrations below 8 mg/L. However, visible damage to leaves was observed after the plants were exposed to 10 mg/L ozonated water via spraying for 15 days during the plant reproductive stage. Additionally, enzyme activities and antioxidant responses gradually increased to a certain degree and then decreased in the untreated and ozonated water-treated plants. These results showed that ozonated water was effective in restraining pathogens and potentially defending against disease in growing NHCC plants within a certain concentration range. These results provide a theoretical basis for preventing disease by applying ozonated water to vegetables as an alternative to pesticides.
Few studies have been carried out on the effect that ozonated water (O3 wat) has on the oxidative stress of root systems and particularly in combination with biotic stress. The aim of this study was to determine if aqueous ozone can be effective in the control of root-knot nematode (RKN) infection and to investigate concomitant changes in the basal defence system. A tomato cultivar susceptible to Meloidogyne incognita was treated with O3 wat as a soil drench. No negative effects were seen following ozone application in comparison to the control under the exposure conditions used. The treatment significantly reduced nematode infection rate and induced changes in the morphology of nematode feeding sites, some of which were characterized by visible symptoms of senescence. The antioxidant response, as well as parameters of oxidative damage, were examined in untreated and O3 wat-treated galls at 2, 4 and 7 days after inoculation and compared to uninfected roots. High levels of ROS, H2 O2 and malondialdeyde were generated in galls in response to combined abiotic and biotic stresses. Throughout the experimental period, activities and relative transcript levels of the antioxidant enzymes catalase, superoxide dismutase and ascorbate peroxidase produced different responses in response to ozone treatment and/or infection. The results demonstrate how O3 wat protects tomato against the RKN M. incognita through the modulation of basal defence mechanisms. This article is protected by copyright. All rights reserved.
IntroductionOzone as a sanitising agentHealth and safety issuesUsing ozone in industrial cleaning proceduresOzone applications in food processingReferences
Tolerance of antibiotic susceptible and antibiotic resistant Escherichia coli, Enterococcus and Staphylococcus strains from clinical and wastewater samples against ozone was tested to investigate if ozone, a strong oxidant applied for advanced wastewater treatment, will affect the release of antibiotic resistant bacteria into the aquatic environment. For this purpose, the resistance pattern against antibiotics of the mentioned isolates and their survival after exposure to 4 mg/L ozone was determined. Antibiotic resistance (AR) of the isolates was not correlating with higher tolerance against ozone. Except for ampicillin resistant E. coli strains, which showed a trend towards increased resistance, E. coli strains that were also resistant against cotrimoxazol, ciprofloxacin or a combination of the three antibiotics were similarly or less resistant against ozone than antibiotic sensitive strains. Pigment-producing Enterococcus casseliflavus and Staphylococcus aureus seemed to be more resistant against ozone than non-pigmented species of these genera. Furthermore, aggregation or biofilm formation apparently protected bacteria in subsurface layers from inactivation by ozone. The relatively large variance of tolerance against ozone may indicate that resistance to ozone inactivation most probably depends on several factors, where AR, if at all, does not play a major role.
This research combined micro/nano bubble techniques with ozone disinfection to determine feasibility of applying micro/nano bubble ozonated water in preventing tomato airborne disease. Results indicated that dissolving ozone in micro/nano bubbles is more efficient than using a mixing pump. In our in vitro studies, when dissolved ozone concentration was 1.6 mg/L, a 5.2 to 3.3 log reduction in Alternaria solani Sorauer conidia was observed; with concentration of 1.8 mg/L, there was a 5.0 to 3.7 log reduction in Cladosporium fulvum conidia. Furthermore, spraying ozonated water in a certain concentration range (0.6–1.8 mg/L) had no significant negative effects on tomato growth.
Effectiveness of a novel developed sanitizer, stable ozone microbubble-containing water (ozone microbubble water; OMBW), on reducing 13 kinds of bacteria was evaluated in vitro. The effectiveness of dip inoculated Escherichia coli O157:H7 or naturally attached bacteria on four kinds of leafy vegetables was also evaluated. For the purpose of comparison, the effectiveness of gaseous ozone (GO), sodium hypochlorite solution (NaClO) and distilled water (DW) were also evaluated. A 5.0 to 7.4 log reduction of viable cells was observed in an in vitro study. In contrast, a 0.8 to 1.2 or 0.9 to 1.8 log CFU/g reduction in E. coli viable cells was observed after washing with OMBW or NaClO, respectively, for all tested leafy vegetables. No significant difference was observed in the effectiveness of OMBW, ozonated water (OW) and DW. No reduction of viable cells was observed after exposure of leaves to GO. Similar experimental results were observed with the naturally attached bacteria. No difference in color and appearance was observed with DW and other sanitizing treatments. These results suggest that the effectiveness of OMBW in surface decontamination of leafy vegetables is similar to that of OW.
Changes of superoxide(O) and hydrogen peroxide(H O), malondialdehyde(MDA) contents and 2 2 2 activities of enzymes involving cell defense in leaves of strawberry (Fragaria×ananassa Duch) plantlets under different time of low temperature stress were studied. With the increase of stress times, the rates of O 2 generation and contents of H O increased to a certain degree and then decreased. The MDA contents and the 2 2 relative conductivity fluctuated were increased during the treatment. The activities of antioxidant enzymes, such as superoxide dismutase(SOD), catalase(CAT), peroxidase(POD) and ascorbate peroxidase(APX) were gradually increased to a certain degree and then decreased. The results clearly suggested that low temperature stress triggered an increase of reactive oxygen species (ROS) and the early accumulation of ROS in plants might lead to the production of antioxidant defense system. If the stress were too strong, the defense system of plants could not remove the more production of ROS effectively and result in severely damage to plants or even death.
The effects of chlorine (200 μL L−1), ozonated water (1 μL L−1) and gaseous ozone (0.7 μL L−1) on physicochemical attributes and microbial quality of minimally processed red bell peppers were studied. In all the experiments, O2 continuously decreased and CO2 concentration increased, the pH augmented and a significant softening was observed in all the fruits. By day 14, L* values decreased in all the fruits, with the greatest changes found in the chlorinated samples (approximately 12 units). Peppers treated with the aqueous solutions showed greater changes in the quality attributes with increasing washing times and especially when chlorine was used. The exposure for three min to gaseous O3 reduced the mesophiles, psychrotrophes and fungal populations of the fresh-cut peppers in 2.5, 3.3 and 1.8 log units, respectively. Combined with modified atmosphere, this could be an appropriate method to maintain the quality and extend the storage period of minimally processed red bell peppers.
Fresh produce has been recognised as a healthy food, thus there is increasing consumer demand for fresh fruit and vegetables. Their shelf-life, however, is relatively short and is limited by microbial contamination or visual, textural and nutritional quality loss. There are many methods to reduce/eliminate microorganisms present in food and ozone treatment is one of them. The use of ozone by the fresh produce industry is a good alternative to chemical treatments, e.g. the use of chlorine. The effectiveness of ozone as an antimicrobial agent has previously been reviewed and has been updated here, with the latest findings. The main focus of this review is on the effects of ozone on the fresh produce quality, defined by maintenance of texture, visual quality, taste and aroma, and nutritional content. Furthermore, ozone has been found to be efficient in reducing pesticide residues from the produce. The treatments that have the ability to reduce microbial contamination of the product without having an adverse effect on its visual, textural and nutritional quality can be recommended and subsequently incorporated into the supply chain. A good understanding of all the benefits and limitations related to the use of ozone is needed, and relevant information has been reviewed in this paper.
Ozonated water washing is one of the emerging techniques to inactivate foodborne pathogens on produce, and limited information is available to optimize processing parameters (treatment time, temperature, and pH) to improve ozone efficacy on Salmonella inactivation for different produce. The efficacy of ozonated water washing for inactivation of Salmonella enterica Typhimurium on green onions, grape tomatoes and green leaf lettuces were studied in our research. Surface inoculated fresh produce were washed by ozonated water for 1, 5, or 10 min at room temperature and pH 5.60 ± 0.03. Then efficacy of ozonated water washing at mild heated (50 °C) and refrigerated (4 °C) temperature for 5 min with pH 5.60 ± 0.03 was investigated. Salmonella inactivation efficacy under pH 5.60 ± 0.03 and 2.64 ± 0.02 with 5 min washing at room temperature were also compared. Our results showed that Salmonella inactivation by ozonated water was time‐dependent for 3 fresh produce. Mild heated temperature (50 °C) and pH 2.64 ± 0.02 improved efficacy of ozonated water to inactivate Salmonella on tomatoes and lettuces, but not on green onions. It is suggested that different surface structures of fresh produce significantly impact the antimicrobial efficacy of ozonated water washing operated under various parameters (time, temperature, and pH).
Practical Application
Washing is the essential step for green onions and lettuces in the packinghouse and grape tomatoes in the restaurants and grocery stores having salad bars. Ozonated water can be used as disinfectant to reduce microbial contamination (FDA). The effectiveness of this disinfectant depends on the type of product and treatment conditions, such as water temperature, acidity, contact time. Our study showed that Salmonella inactivation by ozonated water washing was time‐dependent. Mild heat and low pH improved inactivation efficacy on tomatoes and lettuces, but not on green onions. Processors should consider adjustments that are most appropriate for their produce.
Raw vegetables are usually contaminated by a variety of microorganisms. Post-harvest microflora differs considerably, reflecting environmental and handling conditions and might compromise the safety of the product and the consumer's health.Dipping or rinsing of vegetables in bleach solution is a common practice employed by the retailers and catering companies in order to minimize the initial bacterial load on the surface of vegetables. Rinsing or dipping vegetables in water saturated with ozone could be an alternative environmental friendly and safer process since no harmful by-products or residues are formed.Lettuce (Lactuca sativa) and bell peppers (Capsicum annuum) dipped in chlorinated water (20 ppm) resulted in 1 log decrease of the total microbial count in the first 15 min. Immersing of vegetables in water pre-saturated with ozone (0.5 mg/L) did not make any difference because the total microbial count decreased approximately 0.5 log for the same time. Sanitation treatments were most effective when vegetables were dipped in continuously ozonated (0.5 mg/L) water, leading at about 2 log of microbial load decrease in the first 15 min and 3.5 log after 30 min of exposure. The best results were achieved in the case of bell pepper, as its smooth uniform surface allows higher ozone effectiveness. Bacteria reduction kinetics in continuous ozonation trials were fitted satisfactorily by a Weibull-based model allowing a better optimization of the process.
Photooxidants have been recognized since the 1950s as gaseous agents that are potentially harmful to plants (Lefohn 1992). Early observations in the Los Angeles area had established links between vegetation damage and high photooxidant levels
which were generated, in the presence of sunlight, from photochemical reactions of nitrogen oxides and organic compounds (as
released from industrial and other anthropogenic sources into the atmosphere, Middleton et al. 1950; Haagen-Smit et al. 1952). Studies on tobacco then clarified that the typical spot-like visible symptoms were due to the 03 component of photochemical smog (Heggestad and Middleton 1959). During recent decades, high 03 regimes have spread across most major urban areas around the world, and enhanced 03 concentrations are encountered even in rural regions (Stockwell et al. 1997). Towards the beginning of the twenty-first century, ozone has become a pollutant of great concern, regarding its impact
on trees and forests, although the role of this agent in forest decline of the eastern USA and Europe has remained controversial
(Matyssek and Innes 1999).
Effects of spraying ozonated water on the severity of powdery mildew infection, visible disorder/injury occurrence, and net photosynthesis in cucumbers were investigated. The severity in the ozonated water treatment was contained to almost the same level throughout the 14-day period of the experiment, while the severity steadily increased in the non-treated control and distilled water treatment. Neither visible disorder/injury on the leaves nor a large difference in net photosynthesis between before and after spraying the ozonated water was observed. The results indicate that ozonated water can be at least a partial alternative to agricultural chemical fungicides for powdery mildew on cucumber leaves.
The growth response and antioxidant capacity of Brassica oleracea var. capitata f. alba plants treated with 70ppb of ozone was examined. Four week old cabbage seedlings were fumigated with O3 for 3 days before being transplanted into the growing field. The effect of O3 treatment was determined directly after fumigation and over the course of field cultivation. Plants subjected to O3 treatment had an increased diameter of rosettes and number of leaves after 3 and 7 weeks in agriculture, respectively. In addition, the vast majority of fumigated plants reached marketable quality faster than control plants, indicating a positive role of episodes of increased O3 concentrations during vegetation on growth and yielding. Our analysis revealed that by fumigating juvenile white cabbage plants with moderate doses of O3 the activity of catalases (CAT) and peroxidases was elevated. The activity of the examined enzymes was not affected directly after fumigation, but it increased after several weeks in the experimental field. Increased CAT activity was accompanied by changes in 2 out of the 3 CAT genes CAT1 and CAT2, where CAT2 seemed to be responsible for the induced CAT activity. The biosynthesis of low-molecular stress protectants - tocopherols and the glucosinolate (GLS) sinigrin was transiently affected by ozone. γ-Tocopherol (γ-toc) content significantly increased directly after fumigation, but after 3 weeks of vegetation in the field its concentration reached values similar to control. The biosynthesis of α-tocopherol (α-toc) and sinigrin seemed to be upregulated in fumigated plants. However, the response was delayed; no differences were registered directly after treatment, but 3 weeks after transplanting the concentration of sinigrin and α-toc was elevated.
We study levels and trends in agricultural pesticide use for a large cross-section of countries using FAO data for the period 1990–2009. Our analysis shows that a 1% increase in crop output per hectare is associated with a 1.8% increase in pesticide use per hectare but that the growth in intensity of pesticide use levels off as countries reach a higher level of economic development. However, very few high income countries have managed to significantly reduce the level of intensity of their pesticide use, because decreases in insecticide use at higher income levels are largely offset by increases in herbicide and fungicide use. The results also show very rapid growth in the intensity of pesticide use for several middle income countries such as Brazil, Mexico, Uruguay, Cameroon, Malaysia and Thailand. Complementing our analysis with data from the Rotterdam Convention on Prior Informed Consent (PIC), we show that hazardous pesticides covered in the PIC procedure are more weakly regulated in lower than in higher income countries. We discuss the policy challenges facing developing countries with a rapid growth in pesticide use and recommend a four-pronged strategy, including an environmental tax on pesticides with revenues allocated to long-term investments in awareness building, the development of integrated crop management methods and the setting of food safety standards. The interactions between these measures should help contribute to the effectiveness of the overall strategy package.
Ozone is a powerful antimicrobial agent that is suitable for application in food in the gaseous and aqueous states. Molecular ozone or its decomposition products (for example, hydroxyl radical) inactivate microorganisms rapidly by reacting with intracellular enzymes, nucleic material and components of their cell envelope, spore coats, or viral capsids. Combination of ozone with appropriate initiators (for example, UV or H2O2) results in advanced oxidation processes (AOPs) that are potentially effective against the most resistant microorganisms; however, applications of AOPs in food are yet to be developed. When applied to food, ozone is generated on-site and it decomposes quickly, leaving no residues. Ozone is suitable for decontaminating produce, equipment, food-contact surfaces, and processing environment.
Many plant bacteriologists, if not all, feel that their particular microbe should appear in any list of the most important bacterial plant pathogens. However, to our knowledge, no such list exists. The aim of this review was to survey all bacterial pathologists with an association with the journal Molecular Plant Pathology and ask them to nominate the bacterial pathogens they would place in a 'Top 10' based on scientific/economic importance. The survey generated 458 votes from the international community, and allowed the construction of a Top 10 bacterial plant pathogen list. The list includes, in rank order: (1) Pseudomonas syringae pathovars; (2) Ralstonia solanacearum; (3) Agrobacterium tumefaciens; (4) Xanthomonas oryzae pv. oryzae; (5) Xanthomonas campestris pathovars; (6) Xanthomonas axonopodis pathovars; (7) Erwinia amylovora; (8) Xylella fastidiosa; (9) Dickeya (dadantii and solani); (10) Pectobacterium carotovorum (and Pectobacterium atrosepticum). Bacteria garnering honourable mentions for just missing out on the Top 10 include Clavibacter michiganensis (michiganensis and sepedonicus), Pseudomonas savastanoi and Candidatus Liberibacter asiaticus. This review article presents a short section on each bacterium in the Top 10 list and its importance, with the intention of initiating discussion and debate amongst the plant bacteriology community, as well as laying down a benchmark. It will be interesting to see, in future years, how perceptions change and which bacterial pathogens enter and leave the Top 10.
Recently grafted plants have been used to induce resistance to different abiotic stresses. In our work, grafted plants of tomato cultivars differing in water stress tolerance (Zarina and Josefina) were grown under moderate stress, to test the roles of roots and shoots in production of foliar biomass and antioxidant response. Stress indicators and activities of selected enzymes related to antioxidant response were determined. Our results showed that when shoots are of the drought tolerant genotype Zarina, the changes in antioxidant enzyme activities were large and consistent. However, when shoots are of the drought-sensitive genotype Josefina, the antioxidant enzyme activities were more limited and the oxidative stress was evident. These results reflect that the technique of grafting using Zarina as scion can be useful and effective for improving the antioxidant response in tomato under water stress.
The effect of ultraviolet (UV-C) treatment on total phenol, flavonoid, and vitamin C content of fresh-cut honey pineapple, banana “pisang mas”, and guava was investigated. The antioxidant capacity of the fruit also was evaluated by measuring its ferric reducing/antioxidant power (FRAP) and DPPH free radical-scavenging activity. The fresh-cut fruits were exposed to UV-C for 0, 10, 20, and 30 min. Total phenol and flavonoid contents of guava and banana increased significantly with the increase in treatment time. In pineapple, the increase in total phenol content was insignificant, but the flavonoid content increased significantly after 10 min of treatment. UV-C treatment decreased the vitamin C content of all three fruits. In fresh-cut banana, longer treatment time resulted in higher FRAP and DPPH values; these values remained stable throughout the experiment for fresh-cut pineapple. For fresh-cut guava, FRAP and DPPH values were stable until 30 min, after which a significant increase in FRAP values occurred.Industrial relevanceUV irradiation processing of fresh-cut fruits leads to increase in antioxidants, polyphenols, and flavonoids. Hence, apart from the application of UV for microbial safety at industrial levels, this novel technology can also be exploited for enhancement of health promoting compounds for benefit of consumers.
Data from 25 experiments on seedlings of 43 tree species and hybrids show that ozone (O3) can reduce growth and photosynthesis at concentrations common in many areas of the USA. Seedlings have been primarily employed for such studies for logistic reasons, and will likely provide the greatest breadth of information for some time to come. However, a number of impediments limit application of seedling response studies to assessment of impacts on regional timber production. Large trees differ from seedlings in a number of ways, including C allocation and canopy structure, and methods must be developed to account for these differences if information from seedling studies is to prove useful to forest impact assessment. Understanding how competition mediates individual tree responses will require investigation of whether systematic differences of microclimate leaf morphology that exist across canopies affects foliage sensitivity to O3, and whether the maximum growth rates of genotypes are correlated with susceptibility to O3. Definitive information on these factors is necessary to assess impacts of O3 on stand development and diameter distributions in both multi- and single species stands. Of critical economic importance is whether O3 preferentially damages taller, more valuable individuals within stands and more valuable, faster growing stand types.
Contribution of the Pest Impact Assessment Technol Res. Work Unit, USDA Forest Service, Southeastern Forest Exp. Stn.
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Various abiotic stresses lead to the overproduction of reactive oxygen species (ROS) in plants which are highly reactive and toxic and cause damage to proteins, lipids, carbohydrates and DNA which ultimately results in oxidative stress. The ROS comprises both free radical (O(2)(-), superoxide radicals; OH, hydroxyl radical; HO(2), perhydroxy radical and RO, alkoxy radicals) and non-radical (molecular) forms (H(2)O(2), hydrogen peroxide and (1)O(2), singlet oxygen). In chloroplasts, photosystem I and II (PSI and PSII) are the major sites for the production of (1)O(2) and O(2)(-). In mitochondria, complex I, ubiquinone and complex III of electron transport chain (ETC) are the major sites for the generation of O(2)(-). The antioxidant defense machinery protects plants against oxidative stress damages. Plants possess very efficient enzymatic (superoxide dismutase, SOD; catalase, CAT; ascorbate peroxidase, APX; glutathione reductase, GR; monodehydroascorbate reductase, MDHAR; dehydroascorbate reductase, DHAR; glutathione peroxidase, GPX; guaicol peroxidase, GOPX and glutathione-S- transferase, GST) and non-enzymatic (ascorbic acid, ASH; glutathione, GSH; phenolic compounds, alkaloids, non-protein amino acids and α-tocopherols) antioxidant defense systems which work in concert to control the cascades of uncontrolled oxidation and protect plant cells from oxidative damage by scavenging of ROS. ROS also influence the expression of a number of genes and therefore control the many processes like growth, cell cycle, programmed cell death (PCD), abiotic stress responses, pathogen defense, systemic signaling and development. In this review, we describe the biochemistry of ROS and their production sites, and ROS scavenging antioxidant defense machinery.
Ralstonia solanacearum is regarded as one of the world's most important bacterial plant pathogens because of its aggressiveness, large host range, broad geographical distribution and long persistence in soil and water environments. This root pathogen is an attractive model to investigate the question of host adaptation as it exhibits a remarkably broad host range, being able to infect numerous plant species belonging to different botanical families. Several effector proteins transiting through the type III secretion system have been shown to restrict or extend specifically the host range of the bacterium. Recent investigations on the mechanisms that coordinate changes in gene expression during the passage between saprophytism and life within host tissues have allowed the identification of other molecular determinants implicated in the adaptation of R. solanacearum to its hosts and pathogenesis. Among these determinants are genes involved in chemotaxis, secondary metabolic pathways and the detoxification of various antimicrobial compounds, and genes directing the biosynthesis of phytohormones or adherence factors. The regulation of many of these genes is coordinated by the master pathogenicity regulator HrpG. These hrpG-dependent genes control major steps during the interaction with plant cells, and probably determine the ecological behaviour of the microorganism, being required for the establishment of pathogenesis or mutualism.
The quenching action of dibromothymoquinone on fluorescence and on primary photochemistry was examined in chloroplasts at minus 196 degrees C. Both the initial (F0) and final (FM) levels of fluorescence as well as the fluorescence of variable yield (FV equals FM minus FO) were quenched at minus 196 degrees C to a degree which depended on the concentration of dibromothymoquinone added prior to freezing. The initial rate of photoreduction of C-550 at minus 196 degrees C, which was assumed to be proportional to maximum yield for primary photochemistry, phipo, was also decreased in the presence of dibromothymoquinone. Simple theory predicts that the ratio FV/FM should equal phipo. Excellent agreement was found in a comparison of relative values of phipo with relative values of FV/FM at various degrees of quenching by dibromothymoquinone. These results are taken to indicate that FO and FV are the same type of fluorescence, both emanating from the bulk chlorophyll of Photosystem II. Dibromothymoquinone appears to create quenching centers in the bulk chlorophyll of Photosystem II which compete with the reaction centers for excitation energy. The rate constant for the quenching of excitation energy by dibromothymoquinone is directly proportional to the concentration of the quencher. Rate constants for the de-excitation of excited chlorophyll molecules by fluorescence, kF, by nonradiative decay processes, kD, by photochemistry, kP, and by the specific quenching of dibromothymoquinone, kQ, were calculated assuming the absolute yield of fluorescence at FO to be either 0.02 or 0.05.
Ozone at 0.1 ppm for 4 hr or at 1.0 ppm for 2 hr stopped elongation of conidiophores of Alternaria solani, caused their apical cells to swell, and often collapsed the cell wall at their tips. These conidiophores began to elongate again when they were removed from ozone and exposed to light to prevent sporulation. Usually the collapsed end wall was sloughed, and the new cells often grew at an angle to the original axis of the conidiophore. Sometimes breaks appeared in the pigmented layers of the walls of the swollen cells. Ozone-damaged conidiophores, given the necessary dark period, sporulated normally. If sporulating cultures were exposed to 1.0 ppm ozone for 30 min, the conidia began to germinate while still attached to the conidiophores. Conidiophores treated with a subtoxic dose of a sulfhydryl-binding reagent (..cap alpha..-iodoacetamide) became more susceptible to ozone. Exposure to pure oxygen at either 1 or 4 atm pressure for 4 hr caused no visible damage to conidiophores of A. solani.
The purpose of this study was to compare the microbicidal effect of gaseous ozone with that of ozonated water in order to determine its usefulness as a method for disinfecting dentures. Although a large number of research studies have been done on the bactericidal effect of ozone, little is known about its microbicidal effects on oral microorganisms. Therefore, we tested the effect of ozone on three standard strains of oral microorganisms: Streptococcus mutans (strain IID 973), Staphylococcus aureus (strain 209-P), and Candida albicans (strain LAM 14322). When the gaseous ozone injection method was used, the numbers of cells of all three strains decreased to 1/10(5) at 1 min, and by 3 min they were below the detection limit. Thus, the microbicidal effect of gaseous ozone was ascertained in a short time. In contrast, when ozonated water at 1 ppm and 3 ppm was used, C. albicans decreased to 1/10. A 700 mg/h ozone production level was needed to prepare 1 ppm ozonated water, whereas 20 mg/h of ozone was required by the gaseous ozone generator. These findings indicate that direct exposure to gaseous ozone seems to be a more effective microbicide compared with ozonated water, and that gaseous ozone can be clinically useful for disinfection of dentures.
Chemical pesticides have been a boon to equatorial, developing nations in their efforts to eradicate insect-borne, endemic diseases, to produce adequate food and to protect forests, plantations and fibre (wood, cotton, clothing, etc.). Controversy exists over the global dependence on such agents, given their excessive use/misuse, their volatility, long-distance transport and eventual environmental contamination in colder climates. Many developing countries are in transitional phases with migration of the agricultural workforce to urban centres in search of better-paying jobs, leaving fewer people responsible for raising traditional foods for themselves and for the new, industrialized workforce. Capable of growing two or three crops per year, these same countries are becoming "breadbaskets" for the world, exporting nontraditional agricultural produce to regions having colder climates and shorter growing seasons, thereby earning much needed international trade credits. To attain these goals, there has been increased reliance on chemical pesticides. Many older, nonpatented, more toxic, environmentally persistent and inexpensive chemicals are used extensively in developing nations, creating serious acute health problems and local and global environmental contamination. There is growing public concern in these countries that no one is aware of the extent of pesticide residue contamination on local, fresh produce purchased daily or of potential, long-term, adverse health effects on consumers. Few developing nations have a clearly expressed "philosophy" concerning pesticides. There is a lack of rigorous legislation and regulations to control pesticides as well as training programs for personnel to inspect and monitor use and to initiate training programs for pesticide consumers.
The wild tomato species Lycopersicon pimpinellifolium (currant tomato) was exposed to different O3 concentration, both in controlled environment fumigation facilities and in open-top chambers, to assess its sensitivity and to verify its potential as a bioindicator plant. Plants appeared particularly sensitive to O3 at an early stage of growth, responding with typical chlorotic spots within 24 h after exposure to a single pulse of 50 ppb for 3 h, and differentiating peculiar symptoms, such as reddish necrotic stipples, bronzing and extensive necrosis, depending on O3 concentration. Histo-cytochemical investigations with 3,3'-diaminobenzidine, to localize H2O2, and Evans blue, to detect dead cells, suggested that currant tomato sensitivity to O3 could be due to a deficiency in the anti-oxidant pools. The combination of these stainings proved to be useful, either to predict visible symptoms, early before their appearance, and to validate leaf ozone injury.
Interspecific Potato Breeding Lines Display Differential Colonization Patterns and Induced Defense Responses after Ralstonia Solanacearum Infection
- V Ferreira
- M J Pianzzola
- F L Vilaro
- G A Galvan
- M L Tondo
- M V Rodriguez
- E G Orellano
- M Valls
- M I Siri
Plant-Nematode Interactions: Histochemical, Physiological and Biochemical Interaction.” Pathogenesis and Host-Parasite Specificity in Plant Diseases: Histopathological, Biochemical, Genetic and Molecular Basis
- G Zacheo
- T Bleve-Zacheo
The Use of Transformed Plants in the Assessment of Physiological Stress Responses.” In Responses of Plant Metabolism to Air Pollution and Global Change
- C H Foyer
- A H Kingston-Smith
- J Harbinson
- A C M Arisi
- L Jouanin
- G Noctor
Part 381.66- Poultry Products; Temperatures and Chilling and Freezing Procedures
- Usda