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Using Green Vaccination to Brighten the Agronomic Future: Ingenta Connect

Using Green Vaccination to Brighten the Agronomic Future: Ingenta Connect | Action des stimulateurs des défenses des plantes | Scoop.it
Crop plants host a variety of pests and diseases that can ultimately reduce agricultural productivity. Current methods of pest and disease control depend largely on pesticides. However, the use of chemicals alone is increasingly regarded as unsustainable due to the development of resistance and the introduction of stricter European regulation. There is a need, therefore, to reduce their use and to pursue the development of new Integrated Pest (and disease) Management (IPM) strategies. Research that focuses on the role that the plant's immune system can play against these biological threats provides another potential source for future IPM strategies. Plants have sophisticated ways to defend themselves effectively and some stimuli can augment their innate immune capacity to resist future diseases. This phenomenon is known as priming of defence. Studies, mainly in the model plant Arabidopsis thaliana, have unravelled the molecular and physiological mechanisms of this apparent plant 'vaccination'. This article describes recent findings and provides the ingredients for the “right formulation” in order to integrate green vaccination as a tool for the second green revolution.
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Bioassimilable sulphur provides effective control of Oidium neolycopersici in tomato, enhancing the plant immune system - Llorens - 2016 - Pest Management Science - Wiley Online Library

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
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The Protein Elicitor PevD1 Enhances Resistance to Pathogens and Promotes Growth in Arabidopsis

The Protein Elicitor PevD1 Enhances Resistance to Pathogens and Promotes Growth in Arabidopsis | Action des stimulateurs des défenses des plantes | Scoop.it
The protein elicitor PevD1, isolated from Verticillium dahlia, could enhance resistance to TMV in tobacco and Verticillium wilt in cotton. Here, the pevd1 gene was over-expressed in wild type (WT) Arabidopsis, and its biological functions were investigated. Our results showed that the transgenic lines were more resistant to Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000 than the WT line was. In transgenic plants, both the germination time and bolting time required were significantly shorter and fresh weights and plant heights were significantly higher than those in the WT line. A transcriptomics study using digital gene expression profiling (DGE) was performed in transgenic and WT Arabidopsis. One hundred and thirty-six differentially expressed genes were identified. In transgenic Arabidopsis, three critical regulators of JA biosynthesis were up-regulated and JA levels were slightly increased. Three important repressors of the ABA-responsive pathway were up-regulated, indicating that ABA signal transduction may be suppressed. One CML and two WRKY TFs involved in Ca2+-responsive pathways were up-regulated, indicating that this pathway may have been triggered. In conclusion, we show that PevD1 is involved in regulating several plant endogenous signal transduction pathways and regulatory networks to enhance resistance and promote growth and development in Arabidopsis.
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Induction of Resistance with Benzothiadiazole in Sunflower: a Comparison of Biotrophic vs. Necrotrophic Pathosystems: Acta Phytopathologica et Entomologica Hungarica: Vol 51, No 1

In the present work we aimed at comparing the effect of benzothiadiazole (BTH) treatment on defence reactions of sunflower plants to downy mildew and white rot diseases. BTH treatment resulted in reduced disease symptoms in biotrophic and in the early stage of the necrotrophic interactions. To get a better insight into the effect of BTH, changes in the activities of polyphenol oxidase and peroxidase enzymes, as well as the expression of the host response-associated sunflower genes were examined in the plants. Inoculation with Plasmopara halstedii enhanced the polyphenol oxidase and peroxidase enzyme activities, while inoculation with Sclerotinia sclerotiorum did it only at 4 dpi. However, most importantly, in each case extracts from BTH pretreated and inoculated plants showed the highest polyphenol oxidase and peroxidase enzyme activities. Similarly, the accumulation of GST and PDF transcripts was detected following inoculations with both biotrophic and necrotrophic pathogens, and again, BTH pre-treatment enhanced GST and defensine gene activities in the inoculated plants. We suggest that induction of enzyme activities, as well as of the elevated expression of GST, PDF and PR5 genes by BTH pre-treatment may be a significant part of the induced resistance of sunflower to downy mildew and white rot (white mold).
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Possible induction of potato plant defences against Potato virus Y by mineral oil application

In recent decades, mineral oil spray has been considered an effective means to reduce aphid-mediated spread of non-persistent viruses such as Potato virus Y (PVY). However, the mechanism by which mineral oil prevents viral outbreaks is not well-characterized. Despite the fact that several studies have investigated the effects of mineral oil on aphid feeding behaviour, vector fitness and virus attachment to vector mouthparts, the effect of oil treatment on the plant response has not been studied. To address this need, the current study has assessed the impact of Vazyl-Y mineral oil on the plant-vector-virus (i.e. potato-aphid-PVY) pathosystem in potato, with a particular focus on the plant response. These results show for the first time that oil treatment induces the expression of plant-virus interaction related genes in both local and systemic non-infected tissues, as well as in PVY-infected plants. Finally, the oil’s elicitation properties in reducing viral infectivity are discussed.
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Benzoylsalicylic acid isolated from seed coats of Givotia rottleriformis induces systemic acquired resistance in tobacco and Arabidopsis

Benzoylsalicylic acid isolated from seed coats of Givotia rottleriformis induces systemic acquired resistance in tobacco and Arabidopsis | Action des stimulateurs des défenses des plantes | Scoop.it
Systemic acquired resistance (SAR), a whole plant defense response to a broad spectrum of pathogens, is characterized by a coordinated expression of a large number of defense genes. Plants synthesize a variety of secondary metabolites to protect themselves from the invading microbial pathogens. Several studies have shown that salicylic acid (SA) is a key endogenous component of local and systemic disease resistance in plants. Although SA is a critical signal for SAR, accumulation of endogenous SA levels alone is insufficient to establish SAR. Here, we have identified a new acyl derivative of SA, the benzoylsalicylic acid (BzSA) also known as 2-(benzoyloxy) benzoic acid from the seed coats of Givotia rottleriformis and investigated its role in inducing SAR in tobacco and Arabidopsis. Interestingly, exogenous BzSA treatment induced the expression of NPR1 (Non-expressor of pathogenesis-related gene-1) and pathogenesis related (PR) genes. BzSA enhanced the expression of hypersensitivity related (HSR), mitogen activated protein kinase (MAPK) and WRKY genes in tobacco. Moreover, Arabidopsis NahG plants that were treated with BzSA showed enhanced resistance to tobacco mosaic virus (TMV) as evidenced by reduced leaf necrosis and TMV-coat protein levels in systemic leaves. We, therefore, conclude that BzSA, hitherto unknown natural plant product, is a new SAR inducer in plants.
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Integration of acibenzolar-S-methyl with antibiotics for protection of pear and apple from fire blight caused by Erwinia amylovora

Orchard experiments on integration of acibenzolar-S-methyl (ASM) with antibiotics for protection of pear and apple from fire blight were conducted in the west coast region of the United States over a period of 5 years. In 11 pathogen-inoculated trials, a single treatment of streptomycin or oxytetracycline provided an average of 84 and 60% disease control, respectively. The addition of one or two treatments of acibenzolar-S-methyl (ASM) to the single antibiotic program contributed an additional 6 and 11% disease control, respectively, for both antibiotic materials. Among trials, ASM treatment timings were varied from early to late bloom but an effect of timing on disease control could not be determined. In mature commercial pear orchards, ASM treatments at full bloom and petal fall were superimposed onto the grower’s antibiotic program used in each orchard. For the 15 orchards with fire blight, the ASM-treated plots showed 38% fewer infections than adjoining plots that received antibiotic program only. When integrated with antibiotics, ASM provides added disease suppression to fire blight control programs, but the modest degree of protection provided will likely limit its use to high disease risk situations, which includes orchards with a previous disease history, and those planted recently to highly susceptible cultivars.
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Biological Control of Rice Bakanae by an Endophytic Bacillus oryzicola YC7007

In our previous study, we reported that a novel endophytic bacterium Bacillus oryzicola YC7007 has suppressed bacterial diseases of rice via induced systemic resistance and antibiotic production. This endophytic strain, B. oryzicola YC7007 was used as a biological control agent against bakanae disease of rice caused by Fusarium fujikuroi, and its mechanism of interaction with the pathogen and the rice was further elucidated. Root drenching with B. oryzicola YC7007 suspension reduced the disease severity of bakanae significantly when compared with the untreated controls. The treatments of B. oryzicola YC7007 suspension () to the rice rhizosphere reduced bakanae severity by 46-78% in pots and nursery box tests containing autoclaved and non-autoclaved soils. Moreover, in the detached rice leaves bioassay, the development of necrotic lesion and mycelial expansion of F. fujikuroi were inhibited significantly by spraying the culture filtrate of B. oryzicola YC7007. Drenching of ethyl acetate extracts of the culture filtrate to the rhizosphere of rice seedlings also reduced the bakanae disease severity in the plant culture dish tests. With the root drenching of B. oryzicola YC7007 suspension, the accumulation of hydrogen peroxide was observed at an early stage of rice seedlings, and a hormonal defense was elicited with and without pathogen inoculation. Our results showed that the strain B. oryzicola YC7007 had a good biocontrol activity against the bakanae disease of rice by direct inhibition, and was also capable of inducing systemic resistance against the pathogen via primed induction of the jasmonic acid pathway.
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GRP-3 and KAPP, encoding interactors of WAK1, negatively affect defense responses induced by oligogalacturonides and local response to wounding

Conserved microbe-associated molecular patterns (MAMPs) and damage-associated molecular patterns (DAMPs) act as danger signals to activate the plant immune response. These molecules are recognized by surface receptors that are referred to as pattern recognition receptors. Oligogalacturonides (OGs), DAMPs released from the plant cell wall homogalacturonan, have also been proposed to act as local signals in the response to wounding. The Arabidopsis Wall-Associated Kinase 1 (WAK1), a receptor of OGs, has been described to form a complex with a cytoplasmic plasma membrane-localized kinase-associated protein phosphatase (KAPP) and a glycine-rich protein (GRP-3) that we find localized mainly in the cell wall and, in a small part, on the plasma membrane. By using Arabidopsis plants overexpressing WAK1, and both grp-3 and kapp null insertional mutant and overexpressing plants, we demonstrate a positive function of WAK1 and a negative function of GRP-3 and KAPP in the OG-triggered expression of defence genes and the production of an oxidative burst. The three proteins also affect the local response to wounding and the basal resistance against the necrotrophic pathogen Botrytis cinerea. GRP-3 and KAPP are likely to function in the phasing out of the plant immune response.
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Evaluation of the short term effect of nursery treatments with phosphite-based products, acibenzolar-S-methyl, pelleted Brassica carinata and biocontrol agents, against lettuce and cultivated rocke...

Experimental trials have been carried out in order to evaluate the efficacy of preventative treatments based on plant defense activator products, biocontrol agents, a microbial complex with arbuscular mycorrhizal fungi, and Brassica carinata pellets against Fusarium oxysporum f. sp. lactucae race 1 on lettuce and Fusarium oxysporum f. sp. raphani on cultivated rocket under greenhouse conditions. These products were compared with fungicides known for their ability to induce host resistance (phosethyl-Al and acibenzolar-S-methyl), and with azoxystrobin. Three and four applications of the tested products were carried out on lettuce and rocket seedlings grown in nursery conditions. Treated and untreated plants were transplanted into soil infested with Fusarium wilt agents to obtain an average disease severity (DS) of 65.6–69.2 and of 56.9–62.1 on the untreated lettuce and rocket plants, respectively. The best Fusarium wilt biocontrol was obtained after four applications of Bacillus subtilis Qst713 and with the Glomas microbial complex (42 and 46.7%, efficacy, respectively). B. carinata pellets provided a consistent control when applied 14 days before the rocket and lettuce were transplanted into the infested soil. Acibenzolar-S-methyl, applied at 0.025 g/Liter, showed a DS reduction in F. oxysporum f. sp. lactucae from 36 to 61% and of F. oxysporum f. sp. raphani from 54 to 73%, thus showing statistically similar results to those of azoxystrobin, which was used as a reference (DS reduction from 59 to 65%). Although the Fusarium wilt control provided by such products was not complete in the present experimental conditions, these products can be considered interesting components for an integrated pest management of the Fusarium wilt of leafy vegetables, starting from nursey applications. Moreover, the tested BCAs could become potentially useful, especially for plant monocultures. This study has been produced new information on the effects of potassium phosphite, applied at the nursery level, on reducing lettuce and rocket fusarium wilt. An average efficacy of 69.5% was observed for lettuce, while an average efficacy of 65.2% was observed for cultivated rocket. The good fungicidal activity of the phosphite-based product, coupled with the positive effect on plant biomass, is of special interest.
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Apple scab control and activation of plant defence responses using potassium phosphite and chitosan

Apple scab control and activation of plant defence responses using potassium phosphite and chitosan | Action des stimulateurs des défenses des plantes | Scoop.it
In this study, the effects of two elicitors (potassium phosphite and chitosan) on apple scab (Venturia inaequalis) and their ability to modulate plant defences were assessed. Potassium phosphite and chitosan were sprayed on apple seedlings 7 days before fungus inoculation, and disease intensity was evaluated 14 days after inoculation. Samples of leaves treated with phosphite or chitosan that proved to be susceptible and moderately susceptible to disease were then collected for analysis of their metabolic profile by attenuated total reflectance–Fourier transform infrared spectroscopy. The activity of the plant defence enzymes and the phenolic compound content were also determined by spectrophotometry and high performance liquid chromatography, respectively. The effect of product application on the germination of V. inaequalis was also evaluated. Moderately susceptible leaves presented higher peroxidase activity, regardless of the application of a product. Although it reduced spore germination by 45 %, chitosan did not affect the intensity of the disease. On the other hand, potassium phosphite (2 μL mL−1) reduced significantly the severity of scab by up to 62 % and it promoted the accumulation of salicylic acid, protocatechuic acid, and epicatechin in susceptible leaves, especially after the challenge with V. inaequalis. The salt did not exhibit antimicrobial activity. The resistance induced by potassium phosphite could thus play a significant role in scab control.
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Hydrogen Peroxide and Acetylsalicylic Acid Induce the Defense of Lupine Against Root Rot Disease

Abstract: Isolation of pathogenic fungi from both cultivars of diseased lupine was carried out in five districts of Dakahlia governorate. The high frequency isolated fungi presented in Temi El-Amdeed followed by Bani-Ebeed district. Fusarium solani and F. oxysporum proved to be the most dominate isolated followed by Rhizoctonia solani . In greenhouse, Giza 1 was high susceptible cultivar for infected with root rot pathogenic fungi. Sclerotium rolfsii followed by R. solani then F. solani were the most aggressive damping-off disease. In the field experiment, Giza 2 cultivar was the best in germination% and more tolerant of damping-off than Giza 1. The application of Rhizolex-T50 followed by H2O2 at low concentrate (0.50 mM) showed a highest percentage of germination within lowest percentage of damping-off. With considerable that, no significant differences between Rhizolex-T50 and low concentrate of H2O2. The high photosynthetic pigments and phenolic content were obtained from the application of acetylsalicylic acid (ASA) at moderate concentrate (15 mM) in both cultivars. Giza 2 gave the highest values in these parameters. Soaking both cultivars of lupine seeds in both tested materials increased significantly growth parameter, yield components and seed quality. The moderate concentration of ASA (15 mM) was the most effective followed by the low concentration of H2O2 (0.50 mM). The data suggested that the application of H2O2 at 0.50 mM and ASA at 15 mM as seed soaking could be considered as fungicide alternatives for controlling lupine root rot disease as well as improve growth and productivity.
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Frontiers | Editorial: Control of Plant Pathogens by Biogenic Elicitors and Possible Mechanisms of Action | Plant Biotic Interactions

Frontiers | Editorial: Control of Plant Pathogens by Biogenic Elicitors and Possible Mechanisms of Action | Plant Biotic Interactions | Action des stimulateurs des défenses des plantes | Scoop.it
Editorial: Control of Plant Pathogens by Biogenic Elicitors and Possible Mechanisms of Action
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Mechanisms of action of aloe polysaccharides and xanthan gum for control of black rot in cauliflower

Black rot is the main bacterial disease of crucifers. The establishment of this disease in the field can result in significant yield losses. The objective of this study was to evaluate the potential of xanthan gum (GUM) and polysaccharides extracted from Aloe barbadensis (aloe polysaccharides—AP) for controlling black rot and eliciting defense mechanisms as well as revealing changes in the physiological behavior of cauliflower. Cauliflower plants were sprayed with distilled water, AP (0.75–6.0 mg mL−1) or GUM (0.25–1.5 mg mL−1), inoculated with Xanthomonas campestris pv. campestris 4 days later and evaluated for disease severity at 14 days after inoculation. In vitro bacterial growth in a culture medium containing AP or GUM (0.0 to 3.0 mg mL−1) was evaluated for checking the antimicrobial activity of the polymers. Defense mechanisms (hypersensitivity reaction—HR, enzyme activities, content of phenolic compounds and flavonoids) and physiological changes (photosynthetic rate, stomatal conductance and transpiration) were quantified from cauliflower plants treated with distilled water, AP (1.5 mg mL−1) or GUM (0.5 mg mL−1), inoculated or not with X. campestris. On average, AP reduced bacterial blight symptoms by 68.1% compared to the control. At 0.5 mg mL−1, GUM controlled 74.65% of the disease; however, it caused high levels of phytotoxicity on the leaf surface at 1.5 mg mL−1. There was no direct effect of polysaccharides on the in vitro growth of X. campestris. Peroxidase activity was increased significantly at 2 and 4 days after GUM application, while AP did not change the activity of this enzyme. There were no cells with HR, and no changes in polyphenol oxidase activity, phenolic compound content, flavonoid content or in the antioxidant activity in plants treated with polysaccharides. The photosynthetic rate in plants sprayed with GUM or AP was 22.55% and 39.10% lower, respectively, than the rate of plants treated with distilled water. On average, the polymers reduced conductance by 54.8%. A similar behavior was observed in the transpiration of the plants. Although GUM decreased black rot in cauliflower, it caused signs of stress and phytotoxicity on leaves. By contrast, the application of Aloe barbadensis polysaccharides can be considered as an effective alternative for controlling black rot. This paper also discusses how these polysaccharides reduced the severity of the disease.
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Chitosan and oligochitosan enhance ginger (Zingiber officinale Roscoe) resistance to rhizome rot caused by Fusarium oxysporum in storage

The ability of chitosan and oligochitosan to enhance ginger (Zingiber officinale) resistance to rhizome rot caused by Fusarium oxysporum in storage was investigated. Both chitosan and oligochitosan at 1 and 5 g/L significantly inhibited rhizome rot, with the best control at 5 g/L. Chitosan and oligochitosan applied at 5 g/L also reduced weight loss, measured as a decrease in fresh weight, but did not affect soluble solids content or titratable acidity of rhizomes. The two compounds applied at 5 g/L induced β-1,3-glucanase and phenylalanine ammonia-lyase enzyme activity and the transcript levels of their coding genes, as well as the total phenolic compounds in rhizome tissues. Therefore, the ability of chitosan and oligochitosan to reduce rot in stored rhizomes may be associated with their ability to induce defense responses in ginger. These results have practical implications for the application of chitosan and oligochitosan to harvested ginger rhizomes to reduce postharvest losses.
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 Decreased Biosynthesis of Jasmonic Acid via Lipoxygenase Pathway Compromised Caffeine-Induced Resistance to Colletotrichum gloeosporioides Under Elevated CO2 in Tea Seedlings - Phytopathology

Caffeine, the major purine alkaloid in tea has long been known for its role in plant defense. However, its effect on Colletotrichum gloeosporioides that causes brown blight disease in tea is largely unknown especially under elevated CO2. Here we show that elevated CO2 reduced endogenous caffeine content in tea leaves, but sharply increased susceptibility of tea to C. gloeosporioides. The expression of C. gloeosporioides actin gene was gradually increased during the postinoculation period. In contrast, foliar application of caffeine decreased the C. gloeosporioides-induced necrotic lesions and the expression of C. gloeosporioides actin. Analysis of endogenous jasmonic acid (JA) content revealed that exogenous caffeine could induce JA content under both CO2 conditions in absence of fungal infection; however, in presence of fungal infection, caffeine increased JA content only under elevated CO2. Furthermore, exogenous caffeine enhanced lipoxygenase (LOX) activity and its biosynthetic gene expression under both CO2 conditions, indicating that increased JA biosynthesis via LOX pathway by caffeine might strengthen plant defense only under elevated CO2, while caffeine-induced defense under ambient CO2 might be associated with JA-independent LOX pathway in tea. These results provide novel insights into caffeine-induced plant defense mechanisms that might help to develop an eco-friendly approach for disease control.
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Allyl-isothiocyanate treatment induces a complex transcriptional reprogramming including heat stress, oxidative stress and plant defence responses in Arabidopsis thaliana

Isothiocyanates (ITCs) are degradation products of the plant secondary metabolites glucosinolates (GSLs) and are known to affect human health as well as plant herbivores and pathogens. To investigate the processes engaged in plants upon exposure to isothiocyanate we performed a genome scale transcriptional profiling of Arabidopsis thaliana at different time points in response to an exogenous treatment with allyl-isothiocyanate. The treatment triggered a substantial response with the expression of 431 genes affected (P < 0.05 and log2 ≥ 1 or ≤ -1) already after 30 min and that of 3915 genes affected after 9 h of exposure, most of the affected genes being upregulated. These are involved in a considerable number of different biological processes, some of which are described in detail: glucosinolate metabolism, sulphate uptake and assimilation, heat stress response, oxidative stress response, elicitor perception, plant defence and cell death mechanisms. Exposure of Arabidopsis thaliana to vapours of allyl-isothiocyanate triggered a rapid and substantial transcriptional response affecting numerous biological processes. These include multiple stress stimuli such as heat stress response and oxidative stress response, cell death and sulphur secondary defence metabolism. Hence, effects of isothiocyanates on plants previously reported in the literature were found to be regulated at the gene expression level. This opens some avenues for further investigations to decipher the molecular mechanisms underlying the effects of isothiocyanates on plants.
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Suppression of Bacterial Blight on Mustard Greens with Host Plant Resistance and Acibenzolar-S-Methyl - Plant Disease

Bacterial blight, caused by Pseudomonas cannabina pv. alisalensis, attacks the leaves of most brassica vegetables, including mustard greens (Brassica juncea). ‘Carolina Broadleaf,’ a new mustard cultivar, is resistant to bacterial blight, whereas ‘Florida Broadleaf,’ a commonly grown cultivar, is susceptible. Acibenzolar-S-methyl (trade name Actigard) has been used to manage bacterial diseases caused by P. syringae on a variety of crops. The objective of this study was to evaluate host plant resistance and acibenzolar-S-methyl alone and in combination to manage bacterial blight. Three field experiments were done in spring and fall 2011 and fall 2014. In each experiment, acibenzolar-S-methyl was applied twice as a foliar spray, once before and once after plants were inoculated. Severity of bacterial blight was 81% less on nontreated Carolina Broadleaf than on nontreated Florida Broadleaf (P ≤ 0.0003). Acibenzolar-S-methyl applications reduced severity of bacterial blight by 55% compared with the water control treatment on susceptible Florida Broadleaf. Mean weight of diseased leaves, averaged across acibenzolar-S-methyl treatments, was 53% less with Carolina Broadleaf than with Florida Broadleaf (P < 0.0001). However, acibenzolar-S-methyl applied at the recommended rate (14.2 g/ha) significantly injured leaves of Carolina Broadleaf in two experiments and injured leaves of Florida Broadleaf in one experiment. Overall, host plant resistance was more effective than acibenzolar-S-methyl for managing bacterial blight on mustard greens.
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Exogenous proteinogenic amino acids induce systemic resistance in rice

Plant immune responses can be induced by endogenous and exogenous signaling molecules. Recently, amino acids and their metabolites have been reported to affect the plant immune system. However, how amino acids act in plant defense responses has yet to be clarified. Here, we report that treatment of rice roots with amino acids such as glutamate (Glu) induced systemic disease resistance against rice blast in leaves. Treatment of roots with Glu activated the transcription of a large variety of defense-related genes both in roots and leaves. In leaves, salicylic acid (SA)-responsive genes, rather than jasmonic acid (JA) or ethylene (ET)-responsive genes, were induced by this treatment. The Glu-induced blast resistance was partially impaired in rice plants deficient in SA signaling such as NahG plants expressing an SA hydroxylase, WRKY45-knockdown, and OsNPR1-knockdown plants. The JA-deficient mutant cpm2 exhibited full Glu-induced blast resistance. Our results indicate that the amino acid-induced blast resistance partly depends on the SA pathway but an unknown SA-independent signaling pathway is also involved.
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Chitosan-Elicited Plant Innate Immunity: Focus on Antiviral Activity - Springer

Immunity represents a trait common to all living organisms, and animals and plants share some similarities. Therefore, in susceptible host plants, a complex defence machinery may be stimulated by elicitors. Among these, chitosan deserves particular attention because of its proved efficacy. This survey deals with the antiviral activity of chitosan, focusing on its perception by the plant cell and mechanism of action. Emphasis has been paid to benefits and limitations of this strategy in crop protection, as well as to the potential of chitosan as a promising agent in virus disease control.
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Fructooligosaccharides: Effects, Mechanisms, and Applications - Springer

Fructooligosaccharide (FOS) is a generic term for a series of homologous oligosaccharides in plants, composed of linear chains of fructose units, linked by β (2 → 1) bonds. As one of the most widely commercially available prebiotics, the health benefits of dietary FOS have long been appreciated. Numerous experimental studies have demonstrated the roles of FOS in boosting immunity, reducing the risk and severity of gastrointestinal infection, inflammation, diarrhea, inflammatory bowel disease, obesity related metabolic disorders, and promoting anticancerous effect. However, little is known about their effect on inducing resistance in plants. In this chapter, we mainly introduce the induced resistance of burdock fructooligosaccharide (BFO), which is one of the most intensively studied FOS, in plants and postharvest fruits. As a potential elicitor, BFO could modulate the expression of defense-related genes and accumulation of secondary metabolites, especially salicylic acid-mediated pathway, related with multiple signaling pathways and defense components to enhance host defense responses in plants. A variety of applications in food formulations, medical treatment, and agriculture are also discussed.
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Evaluation of soil applied systemic acquired resistance inducers integrated with copper bactericide sprays for control of citrus canker on bearing grapefruit trees

Soil application of systemic neonicotinoid insecticides and the commercial systemic acquired resistance (SAR) inducer, acibenzolar-S-methyl (ASM), provides season-long control of foliar infection by Xanthomonas citri subsp. citri, the causal agent of citrus canker. Reduction in leaf disease incidence with ASM is comparable to protection with 21-day interval foliar sprays of copper hydroxide (CH). Soil applications of ASM alone, rotated with the neonicotinoids imidacloprid (IMID), thiamethoxam (THIA), and clothianidin (CLOTH), or combined with foliar sprays of CH were compared for canker disease control on fruit of 5- to 7-year-old bearing ‘Ruby Red’ grapefruit trees in Southeast Florida. All treatments significantly reduced the incidence of canker lesions on fruit compared to the untreated check. Soil drenches of ASM and season-long rotations with IMID, THIA, and CLOTH were as effective for suppressing fruit canker as season-long foliar sprays with CH. SAR inducers combined with CH sprays provided optimum control of fruit canker when initiated before the onset of the susceptible foliar flush in the spring. Additional control of canker with soil-applied SAR inducers may enable reduction in the frequency of copper sprays and reduce disease loss from copper resistant Xcc strains where they are prevalent.
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BcIEB1, a Botrytis cinerea secreted protein, elicits a defense response in plants

BcIEB1, a Botrytis cinerea secreted protein, elicits a defense response in plants | Action des stimulateurs des défenses des plantes | Scoop.it
BcIEB1 is a very abundant protein in the secretome of Botrytis cinerea but it has no known function and no similarity to any characterized protein family. Previous results suggested that this protein is an elicitor of the plant defense system. In this work we have generated loss-of-function B. cinerea mutants lacking BcIEB1 and we have expressed the protein in yeast to assay its activity on plants. Analysis of the Δbcieb1 mutants did not result in any observable phenotype, including no difference in the virulence on a variety of hosts. However, when BcIEB1 was applied to plant tissues it produced necrosis as well as a whole range of symptoms: inhibition of seedling growth in Arabidopsis and tobacco, ion leakage from tobacco leaf disks, a ROS burst, cell death and autofluorescence in onion epidermis, as well as the expression of defense genes in tobacco. Moreover, tobacco plants treated with BcIEB1 showed an increased systemic resistance to B. cinerea. A small 35-amino acids peptide derived from a conserved region of BcIEB1 is almost as active on plants as the whole protein. These results clearly indicate that BcIEB1 elicits plant defenses, probably as a consequence of its recognition as a pathogen associated molecular pattern.
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Pre-treatment with salicylic acid induces phenolic responses of Norway spruce (Picea abies) bark to bark beetle (Ips typographus) attack

Conifer bark is the target of numerous organisms due to its assimilated transport and nutrient storage functions. In the presented study, 100 mM salicylic acid (SA) was applied onto Norway spruce stems prior to being infested with bark beetles (Ips typographus L.), to study the temporal gradation of changes in condensed tannins (CT) and total phenolics (tPH) and their significance for mediating stress-tolerance. A significant accumulation of CT was monitored in untreated trees in response to progressive bark beetle infestation occurring from May onwards. In SA-treated infested trees, the CT values remained at control levels until May, but after the re-treatment of infested trees in June, the concentrations of CT rose significantly in comparison to the controls. The tPH values dropped 16 days after SA-treatment, independent of infestation, and later on remained at control level until July. In contrast, tPH contents accumulated in untreated infested trees in May, eased in June and increased again in July, when the trees were affected by the second generation of bark beetles. To sum up, in May and July when the highest beetle-flight activity was monitored the metabolic shift of phenolics within untreated infested trees differed significantly from the response of SA-treated trees. In addition, on SA-treated trees less entrance holes were monitored over the whole period of sampling when compared to untreated infested trees. These results provide evidence that SA-treatment alleviates the phenolic responses, activates the synthesis of condensed tannins and inhibits bark beetle colonisation.
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Effectiveness of Postharvest Treatment with Chitosan to Control Citrus Green Mold

Control of green mold, caused by Penicillium digitatum, by fungicides raises several problems, such as emergence of resistant pathogens, as well as concerns about the environment and consumers’ health. As potential alternatives, the effects of chitosan on green mold disease and the quality attributes of citrus fruits were investigated. Fruits were wounded then treated with different concentrations of chitosan 24 h before their inoculation with P. digitatum. The results of in vitro experiment demonstrated that the antifungal activity against P. digitatum was improved in concert to the increase of chitosan concentration. In an in vivo study, green mold was significantly reduced by chitosan treatments. In parallel, chitinase and glucanase activities were enhanced in coated fruits. Evidence suggested that effects of chitosan coating on green mold of mandarin fruits might be related to its fungitoxic properties against the pathogen and/or the elicitation of biochemical defense responses in coated fruits. Further, quality attributes including fruit firmness, surface color, juice content, and total soluble solids, were not affected by chitosan during storage. Moreover, the loss of weight was even less pronounced in chitosan-coated fruit.
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