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The effectiveness of some plant extracts to protect crops against pests enhancing the natural defensive responses of the plant has been previously reported. Plant extract of Mimosa tenuiflora and Quercus robur has promising potential to reduce the incidence of a wide range of phytopathogenic fungi due to its antimicrobial compounds. In this study, we aimed to elucidate the effectiveness and the mode of action of this mix extract in Lactuca sativa against Sclerotinia sclerotiorum. To achieve this objective, 4 weeks old lettuce plants of cv. Romana were treated with 2 cc l−1 of the plant extract either by soil drench or foliar applications 72 h before the inoculation. The treatments were able to significantly reduce the progression of the pathogen, decreasing the diameter of the infection by 32% and 17% in foliar and soil drench application, respectively. Moreover, the results showed significantly higher levels of hydrogen peroxide (H2O2) as well as callose deposition in plants treated and inoculated, compared with non-treated plants. However, no direct effect on the fungus growth was observed in vitro suggesting that foliar and soil drench treatments with M. tenuiflora and Q. robur extract significantly reduce the infection of S. sclerotiorum in leaves of lettuce, through the strengthening of the wall mediated by the deposition of callose and the release of H2O2. The fact that the treatment enhances different processes involved in plant innate defense may indicate that this treatment is acting as a resistant inducer, and could be effective against different microorganisms.

Background Phytopathogenic problems caused by the bacterial pathogen Pseudomonas syringae in tomato are becoming more serious due to the emergence of strains resistant to classical pesticides. This has led to research into new formulations with lower environmental problems. One of the most promising alternatives to the use of classical pesticides is the induction of natural plant defences. New formulations based on Cu complexed with heptagluconic acid induce plant innate defences and could be an alternative to classical treatments based on inorganic Cu against bacterial speck. To study the efficacy of this compound in tomato against P. syringae, we tested its systemic effect Applying the treatments via radicular. Results Treated plants showed less infection development and lower number of viable bacteria in leaves. We also observed better performance of parameters involved in plant resistance such as the antioxidant response and the accumulation of phenolic compounds. Conclusion Results showed that soil drench applications can be highly effective for the prevention and control of bacterial speck in tomato plants, showing a reduction in symptoms of ∼ 50%. Moreover, application of Cu heptagluconate induced accumulation of the plant polyphenols caffeic and chlorogenic acids, and reduced the amount of reactive oxygen species in infected plants. © 2018 Society of Chemical Industry.

BACKGROUND Developments of alternatives to the use of chemical pesticides to control pests are focused on the induction of natural plant defences. The study of new compounds based on liquid bioassimilable sulphur and its effect as an inductor of the immune system of plants would provide an alternative option to farmers to enhance plant resistance against pathogen attacks such as powdery mildew. In order to elucidate the efficacy of this compound in tomato against powdery mildew, we tested several treatments: curative foliar, preventive foliar, preventive in soil drench and combining preventive in soil drench and curative foliar. RESULTS In all cases, treated plants showed lower infection development, better physiological parameters and a higher level of chlorophyll. We also observed better performance in parameters involved in plant resistance such as antioxidant response, callose deposition and hormonal levels. CONCLUSION The results indicate that preventive and curative treatments can be highly effective for the prevention and control of powdery mildew in tomato plants. Foliar treatments are able to stop the pathogen development when they are applied as curative. Soil drench treatments induce immune response mechanisms of plants, increasing significantly callose deposition and promoting plant development. © 2016 Society of Chemical Industry

Phytopathogenic problems caused by the bacterial pathogen Pseudomonas syringae in tomato are becoming more serious due to the emergence of strains resistant to classical pesticides. This has led to research into new formulations with lower environmental problems. One of the most promising alternatives to the use of classical pesticides is the induction of natural plant defences. New formulations based on Cu complexed with heptagluconic acid induce plant innate defences and could be an alternative to classical treatments based on inorganic Cu against bacterial speck. To study the efficacy of this compound in tomato against P. syringae, we tested its systemic effect Applying the treatments via radicular.Treated plants showed less infection development and lower number of viable bacteria in leaves. We also observed better performance of parameters involved in plant resistance such as the antioxidant response and the accumulation of phenolic compounds.Results showed that soil drench applications can be highly effective for the prevention and control of bacterial speck in tomato plants, showing a reduction in symptoms of ∼ 50%. Moreover, application of Cu heptagluconate induced accumulation of the plant polyphenols caffeic and chlorogenic acids, and reduced the amount of reactive oxygen species in infected plants. © 2018 Society of Chemical Industry.

Developments of alternatives to the use of chemical pesticides to control pests are focused on the induction of natural plant defences. The study of new compounds based on liquid bioassimilable sulphur and its effect as an inductor of the immune system of plants would provide an alternative option to farmers to enhance plant resistance against pathogen attacks such as powdery mildew. In order to elucidate the efficacy of this compound in tomato against powdery mildew, we tested several treatments: curative foliar, preventive foliar, preventive in soil drench and combining preventive in soil drench and curative foliar.In all cases, treated plants showed lower infection development, better physiological parameters and a higher level of chlorophyll. We also observed better performance in parameters involved in plant resistance such as antioxidant response, callose deposition and hormonal levels.The results indicate that preventive and curative treatments can be highly effective for the prevention and control of powdery mildew in tomato plants. Foliar treatments are able to stop the pathogen development when they are applied as curative. Soil drench treatments induce immune response mechanisms of plants, increasing significantly callose deposition and promoting plant development. © 2016 Society of Chemical Industry.

Summary Hexanoic acid-induced resistance (Hx-IR) is effective against several pathogens in tomato plants. Our study of the mechanisms implicated in Hx-IR against Pseudomonas syringae pv. tomato DC3000 suggests that hexanoic acid (Hx) treatment counteracts the negative effect of coronatine (COR) and jasmonyl-isoleucine (JA-Ile) on the salicylic acid (SA) pathway. In Hx-treated plants, an increase in the expression of jasmonic acid carboxyl methyltransferase (JMT) and the SA marker genes PR1 and PR5 indicates a boost in this signalling pathway at the expense of a decrease in JA-Ile. Moreover, Hx treatment potentiates 12-oxo-phytodienoic acid accumulation, which suggests that this molecule might play a role per se in Hx-IR. These results support a positive relationship between the SA and JA pathways in Hx-primed plants. Furthermore, one of the mechanisms of virulence mediated by COR is stomatal re-opening on infection with P. syringae. In this work, we observed that Hx seems to inhibit stomatal opening in planta in the presence of COR, which suggests that, on infection in tomato, this treatment suppresses effector action to prevent bacterial entry into the mesophyll.

Poster presentado en el 28th International Horticultural Congress celebrado en Lisboa del 22 al 27 de agosto de 2010

The overall pollution in the planet is reaching unbearable limits for humanity. Never before mankind had come to adopt measures agreed between countries in the magnitude of current ones. Among the measures taken to alleviate the problem are increasing green alternatives. This paper aims reporting how green alternative using Genetically Modified Organisms (GMOs) which have proven over last decade to be by far the best overall tool for combating pollution, operate in more detail. A kinetic study of heavy metals (Ni, Cu, Zn, Cd, Pb, and Hg) and B accumulation by plants grown in sludge collected from a treatment plant of industrial sewage is carried out. Summarizing: the results investigated in this work confirm again the capacity and usefulness of this tool as a solution to global pollution problems, studying another specific case which is particularly interesting since provides a real solution for a common problem: industrial water sludge. In this manner, substantiating the strategy designed in a scientific project (triggered by Doñana's disaster) granted by UE funds in 2000, and presented in Hanover’s Universal Exposition. Glossing and discussing its positive implementation during years to check out the so called superplants against pollution., global pollution, decontamination, Nicotiana glauca, mining, Cd, Pb, industrial sewage sludge

Citrus canker, caused by Xanthomonas citri subsp. citri, is a serious and wide-spread disease of citrus, causing losses in fruit yield and quality. There are no highly effective citrus canker disease control measures. Repeated spray applications of copper are often employed to protect fruit from bacterial infection with consequences for copper phytotoxicity and accumulation in the soil. Alternatively, innate plant defense mechanisms can be enhanced by plant treatments with specific natural and synthetic inducers for control of bacterial diseases. In this study, hexanoic acid applied as a soil drench or foliar spray on 9-month-old potted citrus trees reduced lesions on leaves by 50% compared with control plants. Disease-reducing activity lasted up to 50 days after application. Induction of resistance mediated by hexanoic acid was demonstrated by enhanced expression of Pathogenesis-related (PR) genes and callose deposition in treated and infected plants. These findings indicated that hexanoic acid applications trigger a defensive response in the plants. The application of this natural compound may have potential for management of citrus canker in conjunction with other disease control measures and may reduce the frequency or rate of copper bactericides. This work has been supported by the “Programa de mobilitat del personal investigador” of the Fundació Caixa Castelló-Bancaixa, the Spanish National R&D Plan (AGL2010-22300-C03-01 and AGL2010-22300-C03-02) and Prometeo2012/066. The authors are grateful to the IVIA and CREC.

Alternaria brown spot disease is a serious disease in mandarins and their hybrids without effective disease control measures. In recent years, induced plant resistance has been studied as an alternative to classical pesticides, but few studies on the effectiveness of these products and their long-lasting effects in woody crops have been performed. After two inoculations with Alternaria alternata, citrus plants that were treated with hexanoic acid showed enhanced resistance, displaying lower levels of disease incidence associated with an activation of the jasmonic acid pathway, the accumulation of phenolic compounds and the expression of defensive genes, such as polygalacturonase-inhibiting proteins. This work was supported by the “Programa de formació del personal investigador (PREDOC/2009/24)” of the Universitat Jaume I, the Spanish National R&D Plan (AGL2010-22300-C03-01 and AGL2010-22300-C03-02), and Generalitat Valenciana Grupos de Excelencia (PROMETEO/2012-7066). The authors are grateful to the SCIC at the Universitat Jaume I.

The use of wastewater as an alternative water resource for irrigation needs specific studies to evaluate its effect on different soils and crops. Young Citrus trees have been irrigated with wastewater from a sewage treatment plant during three consecutive seasons and the growth, leaf mineral status and fruit quality measured. Some differences have been found between groundwater and wastewater composition. Sodium ion, chloride ion, organic matter and boron concentrations were always higher in wastewater. In contrast, high nitrate levels were found in groundwater, probably due to aquifer contamination. In all seasons the values of soil-analysed elements were within the optimal ranges for this kind of crop and soil. Levels of sodium, chloride and boron in leaf tissue were below the toxic levels for Citrus. Leaf nitrogen content was in the optimal nutrition range and no significant difference was observed between samples from trees irrigated with wastewater and groundwater. Both growth and fruit quality parameters were unaffected by the high levels of sodium, chloride and boron in wastewater. Collectively our data show that no detrimental effects are found after using wastewater for irrigation of young Citrus trees. More importantly, fertiliser rates could be lowered significantly without reducing yields or affecting leaf nutrient levels when using reclaimed wastewater. Thus reclaimed wastewater appears to be a suitable alternative water resource for irrigation of Citrus trees. © 2000 Society of Chemical Industry

Hexanoic acid‐induced resistance (Hx‐IR) is effective against several pathogens in tomato plants. Our study of the mechanisms implicated in Hx‐IR against Pseudomonas syringae pv. tomato DC3000 suggests that hexanoic acid (Hx) treatment counteracts the negative effect of coronatine (COR) and jasmonyl‐isoleucine (JA‐Ile) on the salicylic acid (SA) pathway. In Hx‐treated plants, an increase in the expression of jasmonic acid carboxyl methyltransferase (JMT) and the SA marker genes PR1 and PR5 indicates a boost in this signalling pathway at the expense of a decrease in JA‐Ile. Moreover, Hx treatment potentiates 12‐oxo‐phytodienoic acid accumulation, which suggests that this molecule might play a role per se in Hx‐IR. These results support a positive relationship between the SA and JA pathways in Hx‐primed plants. Furthermore, one of the mechanisms of virulence mediated by COR is stomatal re‐opening on infection with P. syringae. In this work, we observed that Hx seems to inhibit stomatal opening in planta in the presence of COR, which suggests that, on infection in tomato, this treatment suppresses effector action to prevent bacterial entry into the mesophyll.

In addition to basal defense mechanisms, plants are able to develop enhanced defense mechanisms such as induced resistance (IR) upon appropriate stimulation. We recently described the means by which several carboxylic acids protect Arabidopsis and tomato plants against fungi. In this work, we demonstrate the effectiveness of hexanoic acid (Hx) in the control of Alternaria brown spot (ABS) disease via enhancement of the immune system of Fortune mandarin. The application of 1 mM Hx in irrigation water to 2-year-old Fortune plants clearly reduced the incidence of the disease and led to smaller lesions. We observed that several of the most important mechanisms involved in induced resistance were affected by Hx application. Our results demonstrate enhanced callose deposition in infected plants treated with Hx, which suggests an Hx priming mechanism. Plants treated with the callose inhibitor 2-DDG were more susceptible to the fungus. Moreover, polygalacturonase-inhibiting protein (PGIP) gene expression was rapidly and significantly upregulated in treated plants. However, treatment with Hx decreased the levels of reactive oxygen species (ROS) in infected plants. Hormonal and gene analyses revealed that the jasmonic acid (JA) pathway was activated due to a greater accumulation of 12-oxo-phytodienoic acid (OPDA) and JA along with a rapid accumulation of JA-isoleucine (JA-Ile). Furthermore, we observed a more rapid accumulation of abscisic acid (ABA), which could act as a positive regulator of callose deposition. Thus, our results support the hypothesis that both enhanced physical barriers and the JA signaling pathway are involved in hexanoic acid-induced resistance (Hx-IR) to Alternaria alternata. This work was supported by the National R&D Plan (AGL2010-22300-C03-01 and AGL2010-22300-C03-02). The authors are grateful to the SCIC at the Universitat Jaume I.

[EN] The agricultural use of anaerobically digested sewage sludge (ADSS) as stable, mature compost implies knowing its total content in heavy metals and their bioavailability. This depends not only on the initial characteristics of the composted substrates but also on the organic matter transformations during composting which may influence the chemical form of the metals and their bioavailability. The objective of this work was to examine the relationships between the changes in the organic matter content and humus fractions, and the bioavailability of heavy metals. A detailed sampling at 0, 14, 84, and 140 days of the composting process was performed to measure C contents in humic acids (HAs), fulvic acids, (FAs) and humin, the total content of Zn, Pb, Cu, Ni, and Cd, and also their distribution into mobile and mobilisable (MB), and low bioavailability (LB) forms. Significant changes of C contents in HA. FA, and Humin, and in the FA/HA, HA/Humin and C-humus/TOC ratios were observed during composting. The MB and LB fractions of each metal also varied significantly during composting. The MB fraction increased for Zn, Cu, Ni, and Cd, and the LB fraction increased for Pb. Stepwise linear regressions and quadratic curve estimation conducted on the MB and LB fractions of each metal as dependent on the measured organic variables suggested that Zn bioavailability was mainly associated to percentage of C in FAs. Bioavailability of Cu, Ni and Cd during composting was associated to humin and HAs. Pb concentration increased in the LB form, and its variations followed a quadratic function with the C-humus/TOC ratio. Our results suggest that the composting process renders the metals in more available forms. The main forms of metal binding in the sludge and their availability in the final compost may be better described when metal fractionation obtained in sequential extraction and humus fractionation during composting are considered together. (C) 2011 Elsevier Ltd. All rights reserved., This work was part of the Generalitat Valenciana projects IIARCO2004-A-196, IIARCO2004-A-212, and IIARCO/2004/213, and the national project 135/2004/3 (Ministerio de Medio Ambiente). We thank FACSA Sewage Treatment Plant (Castellon, Spain), and University Jaume I of Castellon (Spain) for providing materials and technical assistance. We thank the two anonymous reviewers for their useful comments on the manuscript.

Variations of composition and consistency of the culture medium and time of exposure to growth regulators were assayed to optimize normal caulogenic response ofDigitalis obscura hypocotyls cultured in vitro. The effects of the culture conditions on physiologic changes related to vitrification of the regenerated plants were also investigated. Liquid medium increased the bud-forming capacity of the explants but induced buds failed to develop into shoots and showed symptoms of vitrification. On agar-solidified media, maximum multiplication rates were achieved with 0.7% agar. Increasing agar concentration reduced vitrification but lowered the propagation rate. Changes in the strength of the macronutrients of Murashige and Skoog did not significantly affect the bud-forming capacity of the explants. In contrast, a drastic inhibitory effect on both bud formation and shoot elongation was produced when NH4NO3 was omitted. Reduction of NH4NO3 to one-half or one-fourth of the level of the original formulation not only increased the bud-forming capacity ofD. obscura hypocotyls but also resulted in less vitrification. Modifications of time and method of exposure to growth regulators neither improved the multiplication rates nor overcame vitrification. Cardenolide content was lower in vitrified than in normal cultures and coincided with an overall reduction of photosynthetic pigments, lignin, and dry matter.

Somatic embryogenesis was induced in hypocotyls of Digitalis obscura using indoleacetic acid or 2,4-dichlorophenoxyacetic acid with different culture and subculture conditions. Indoleacetic acid-induced embryogenic cultures were used to investigate the effects of amino acids, polyamines and growth regulators on embryo differentiation and maturation. Supplementation of the media with amino acids, polyamines or abscisic acid did not influence or had an adverse effect on embryogenic response. Gibberellic acid at 1.4 μM in either culture (30 days) or subculture medium was effective in promoting both differentiation and normal embryo development. The efficiency of somatic embryogenesis was greatly enhanced when isolated indoleacetic acid-induced proembryogenic masses were subcultured in liquid medium with reduced auxin content.

Hypocotyl explants of Digitalis obscura L. were grown on Murashige and Skoog medium supplemented with 0.57 μM IAA and 4.40 μM BA. The effects of sucrose, maltose, glucose, galactose or mannitol on their growth and bud formation were investigated. None of the carbohydrate sources tested was superior to sucrose, and best results were obtained with 2.0% (w/v) of this disaccharide. Although mannitol did not support morphogenesis, it had a promotive effect on bud formation when added to 1.0 or 1.5% sucrose-supplied media to give the molar sucrose equivalent to 2.0%. The inhibitory effect of high sucrose concentrations could be duplicated by substituting mannitol for sucrose on a molar basis. Our data suggest a dual role of sucrose as osmotic and energy source in D. obscura hypocotyl cultures.