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The destructive bacterial wilt disease caused by Ralstonia solanacearum leads to substantial losses in tomato production worldwide. RNA‐seq is a powerful technology to decipher various biological processes of host–pathogen interactions by analysing differentially expressed genes (DEGs). In the current study, we used RNA‐seq to analyse the transcriptome changes during the interaction of R. solanacearum and susceptible tomato leaves at the time point of 24 h. Gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were used to annotate functions of DEGs in tomato plants. DEGs related to plant and pathogen interaction pathways, photosynthesis pathways and hormone signalling pathways were further analysed. Our results revealed that R. solanacearum inoculation activated plant defence response pathways to induce a number of core defence genes against bacterial invasion, inhibited expression of genes related to photosynthesis processes and activated the salicylic acid (SA) signalling pathway to induce defence responses. We quantified SA and jasmonic acid (JA) contents after bacterial inoculation. SA treatment alleviated plant disease symptoms and induced immune‐related reactive oxygen species (ROS) bursts in tomato leaves. The extent of disease symptoms was much greater in SlNPR1‐silenced plants than wild‐type plants. Together, our results will provide a better understanding of the mechanisms of plant induced defences against bacterial invasion and provide a theoretical basis for breeding resistance of tomato against R. solanacearum in future. [ABSTRACT FROM AUTHOR]

Lignin, a major plant cell wall component, has an important role in plant-defense mechanisms against pathogens and is a promising renewable carbon source to produce bio-based chemicals. However, our understanding of microbial metabolism is incomplete regarding certain lignin-related compounds like p-coumaryl and sinapyl alcohols. Here, we reveal peripheral pathways for the catabolism of the three main lignin precursors (p-coumaryl, coniferyl, and sinapyl alcohols) in the plant pathogen Xanthomonas citri. Our study demonstrates all the necessary enzymatic steps for funneling these monolignols into the tricarboxylic acid cycle, concurrently uncovering aryl aldehyde reductases that likely protect the pathogen from aldehydes toxicity. It also shows that lignin-related aromatic compounds activate transcriptional responses related to chemotaxis and flagellar-dependent motility, which might play an important role during plant infection. Together our findings provide foundational knowledge to support biotechnological advances for both plant diseases treatments and conversion of lignin-derived compounds into bio-based chemicals. Plants strengthen their cell walls with lignin to prevent pathogen colonization. Here, Martim et al show how Xanthomonas citri degrades lignin precursors and detoxifies lignin-derived molecules to overcome this plant defense. [ABSTRACT FROM AUTHOR]

Concerning sustainable agriculture, plant growth promoting rhizobacteria (PGPR), which are a subgroup of "fluorescent Pseudomonads," are crucial. They are widely known for supporting plant health through a variety of methods. The use of fluorescent Pseudomonads in agri-biotechnology has gained traction due to their potential for safeguarding plants from a variety of phytopathogens. Fluorescent pseudomonads being commercialized as bioinoculants for the treatment of various plant diseases is currently regarded as highly successful on a global scale. Fluorescent Pseudomonads are being employed as efficient bio-control agents (BCAs) against an array of phytopathogens. Due to their capacity to generate a wide range of secondary metabolites, they offer enormous promise as BCA. Thus, this review's goal is to outline and evaluate the functions of fluorescent Pseudomonads' secondary metabolites in reducing phytopathogens and improving plant health. Prominent secondary metabolites linked to biocontrol through fluorescent Pseudomonads include phenazines (PHZ), 2, 4-diacetylphloroglucinol (DAPG), pyoluteorin (PLT), pyrrolnitrin (PRN), cyclic lipopeptides (CLPs), and volatile organic compounds (VOCs), including hydrogen cyanide (HCN). The antifungal, antibacterial, antiviral, antitumor, and antinematicidal effects of these metabolites are well-established. [ABSTRACT FROM AUTHOR]

Food loss due to pathogens is a major concern in agriculture, requiring the need for advanced disease detection and prevention measures to minimize pathogen damage to plants. Novel bioinformatic tools have opened doors for the low-cost rapid identification of pathogens and prevention of disease. The number of these tools is growing fast and a comprehensive and comparative summary of these resources is currently lacking. Here, we review all current bioinformatic tools used to identify the mechanisms of pathogen pathogenicity, plant resistance protein identification, and the detection and treatment of plant disease. We compare functionality, data volume, data sources, performance, and applicability of all tools to provide a comprehensive toolbox for researchers in plant disease management. Appropriate bioinformatic tools supply clues on mechanisms of pathogen pathogenicity and plant immunity as well as strategies on the diagnosis and treatment of plant disease. Analysis tools for plant pathogen genomes, effector proteins, and plant–pathogen interactions can be used to explore pathogen pathogenicity. Homology- and feature-based prediction tools accelerate the identification of new plant resistance proteins. Image-based tools improve the precision of disease detection and disease severity estimation. Agrochemical, biological control, and biopesticide databases facilitate finding active ingredients for plant disease treatment. [ABSTRACT FROM AUTHOR]

Heat treatment has been applied in previous studies to treat diseased plants and trees affected by heat-sensitive pathogens. Huanglongbing (HLB) is a heat-sensitive pathogen and the optimal temperature-time for treating HLB-affected citrus trees was estimated to be 54 °C for 60 to 120 s from indoor experimental studies. However, utilizing this method in orchards is difficult due to technical difficulties to effectively apply heat. Recently, a mobile thermotherapy system (MTS) was developed to in-field treat HLB-affected trees. This mobile device includes a canopy cover that covers the diseased tree and a system to supply steam under the cover to treat the tree. It was proven that the temperature inside the canopy cover can reach the desired one (i.e., 54 °C) to kill bacteria. However, for HLB, the heat should penetrate the tree's phloem where the bacteria live. Therefore, measuring the heat penetration inside the tree is very critical to evaluate the performance of the MTS. In this study, a heat transfer model was developed to simulate the heat penetration inside the tree and predict the temperature in the phloem of the diseased tree during the in-field heat treatment. The simulation results were compared with in-field experimental measurements. The heat transfer model was developed by a comparative analysis of the experimental data using the ANSYS software. Results showed that the temperature in the phloem was 10-40% lower than the temperature near the surface of the bark. Simulation results were consistent with experimental results, with an average relative error of less than 5%. [ABSTRACT FROM AUTHOR]

Study of pheromones of insects could give knowledge not only about ways of their communication and spreading information but also could be powerful tool to biologically control population of harmful insects that damage economy by destroying harvest. Colorado potato beetle Lepinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) is one of those insects that need to be controlled. Alarm and sex pheromones of the beetles were well studied by numbers of scientists around the world and even synthetic forms of them were synthesized. Meanwhile, alarm pheromones of Colorado potato beetles that are liberated during traumatic or stressful situations were not deeply studied and covered in relevant literature. This article describes experiments involving the beetles and attempts to collect alarm pheromones. Purpose of experiments were checking the effect of the pheromones on the beetles that are not under stressful conditions and running NMR-spectroscopy in order to compare results with spectrogram of aggregation pheromone that is described in the literature. The results showed that Colrado potato beetles responded with escape behavior when exposed to the extracted pheromones. NMR-spectroscopy analysis showed more signals and resemblance between the extract from abdominal parts of the beetles and aggregation pheromone. [ABSTRACT FROM AUTHOR]

Traditional Malagasy farmers have developed a range of biological methods to restrict plant diseases without reliance on external or synthetic inputs. Five common Malagasy traditional practices demonstrated to be efficient against potato crop bacterial disease in experimental fields have been investigated for their antibacterial (i.e. bacteriostatic and bactericidal effects) and anti-virulence (i.e. antiquorum sensing and anti-biofilm) activities against two phytopathogens, Pseudomonas aeruginosa and Ralstonia solanacearum. Results show that polar (methanolic) extracts of recipes exert anti-virulence activities rather than bacteriostatic and/or bactericidal activities. Indeed, three recipes (R5, R7 and R9) reduce the expression of QS-dependent virulence factors whereas only recipe (R5) exhibit antibiofilm activities without affecting bacterial growth. R4 and R6 were not active, suggesting other bacterial targets and/or other bioactivity properties. Innovative approaches, inspired from ancestral practices, should be considered in the struggle against infectious diseases to limit the overuse of antibiotics for controlling infectious plant diseases and to reduce the overspread of multidrug resistant bacteria. [ABSTRACT FROM AUTHOR]

Tomato suffers a huge loss every year because of early blight disease. This study focuses on efficient inhibition of Alternaria solani, the causative agent of early blight disease in tomato in vitro and in vivo. Foliar spray of 5 μg/mL of biosynthesized silver nanoparticles in A. solani infected plants resulted in significant increase of 32.58% in fresh weight and 23.52% in total chlorophyll content of tomato as compared to A. solani infected plants. A decrease of 48.57, 30, 39.59 and 28.57% was observed in fungal spore count, lipid peroxidation, proline content and superoxide dismutase respectively in infected tomato plants after treatment with synthesized silver nanoparticles as compared to A. solani infected plants. No significant variation in terms of soil pH, cultured population, carbon source utilization pattern and soil enzymes including dehydrogenase, urease, protenase and β-glucosidase was observed after foliar spray of nanoparticles. It was revealed that direct killing of pathogens, increased photosynthetic efficiencies, increased plant resistance and decrease in stress parameters and stress enzymes are the mechanisms employed by plants and nanoparticles simultaneously to combat the biotic stress. Biosynthesized silver nanoparticles bear the potential to revolutionize plant disease management, though the molecular aspects of increased resistance must be looked upon. [ABSTRACT FROM AUTHOR]

Background: The detection and characterization of resistance reactions of crop plants against fungal pathogens are essential to select resistant genotypes. In breeding practice phenotyping of plant genotypes is realized by time consuming and expensive visual rating. In this context hyperspectral imaging (HSI) is a promising non-invasive sensor technique in order to accelerate and to automate classical phenotyping methods. A hyperspectral microscope was established to determine spectral changes on the leaf and cellular level of barley (Hordeum vulgare) during resistance reactions against powdery mildew (Blumeria graminis f.sp. hordei, isolate K1). Experiments were conducted with near isogenic barley lines of cv. Ingrid, including the susceptible wild type (WT), mildew locus a 12 (Mla12 based resistance) and the resistant mildew locus o 3 (mlo3 based resistance), respectively. The reflection of inoculated and non-inoculated leaves was recorded daily with a hyperspectral linescanner in the visual (400 - 700 nm) and near infrared (700 - 1000 nm) range 3 to 14 days after inoculation. Results: Data analysis showed no significant differences in spectral signatures between non-inoculated genotypes. Barley leaves of the near-isogenic genotypes, inoculated with B. graminis f.sp. hordei differed in the spectral reflectance over time, respectively. The susceptible genotypes (WT, Mla12) showed an increase in reflectance in the visible range according to symptom development. However, the spectral signature of the resistant mlo-genotype did not show significant changes over the experimental period. In addition, a recent data driven approach for automated discovery of disease specific signatures, which is based on a new representation of the data using Simplex Volume Maximization (SiVM) was applied. The automated approach - evaluated in only a fraction of time revealed results similar to the time and labor intensive manually assessed hyperspectral signatures. The new representation determined by SiVM was also used to generate intuitive and easy to interpretable summaries, e.g. fingerprints or traces of hyperspectral dynamics of the different genotypes. Conclusion: With this HSI based and data driven phenotyping approach an evaluation of host-pathogen interactions over time and a discrimination of barley genotypes differing in susceptibility to powdery mildew is possible. [ABSTRACT FROM AUTHOR]

Plants and their pathogens are engaged in continuous evolutionary battles and sustainable disease management requires novel systems to create environments conducive for short-term and long-term disease control. In this opinion article, we argue that knowledge of the fundamental factors that drive host–pathogen coevolution in wild systems can provide new insights into disease development in agriculture. Such evolutionary principles can be used to guide the formulation of sustainable disease management strategies which can minimize disease epidemics while simultaneously reducing pressure on pathogens to evolve increased infectivity and aggressiveness. To ensure agricultural sustainability, disease management programs that reflect the dynamism of pathogen population structure are essential and evolutionary biologists should play an increasing role in their design. [ABSTRACT FROM AUTHOR]

The use of bacteriophages as an effective phage therapy strategy faces significant challenges for controlling plant diseases in the phyllosphere. A number of factors must be taken into account when considering phage therapy for bacterial plant pathogens. Given that effective mitigation requires high populations of phage be present in close proximity to the pathogen at critical times in the disease cycle, the single biggest impediment that affects the efficacy of bacteriophages is their inability to persist on plant surfaces over time due to environmental factors. inactivation by UV light is the biggest factor reducing bacteriophage persistence on plant surfaces. Therefore, designing strategies that minimize this effect are critical. For instance, application timing can be altered: instead of morning or afternoon application, phages can be applied late in the day to minimize the adverse effects of Uv and extend the time high populations of phage persist on leaf surfaces. Protective formulations have been identified which prolong phage viability on the leaf surface, however, Uv inactivation continues to be the major limiting factor in developing more effective bacteriophage treatments for bacterial plant pathogens. Other strategies, which have been developed to potentially increase persistence of phages on leaf surfaces, rely on establishing non-pathogenic or attenuated bacterial strains in the phyllosphere that are sensitive to the phage(s) specific to the target bacterium. we have also learned that selecting the correct phages for disease control is critical. This requires careful monitoring of bacterial strains in the field to minimize development of bacterial strains with resistance to the deployed bacteriophages. we also have data that indicate that selecting the phages based on in vivo assays may also be important when developing use for field application. Although bacteriophages have potential in biological control for plant disease control, there are major obstacles, which must be considered. [ABSTRACT FROM AUTHOR]

Abstract: Tea gray blight, caused by the fungus Pestalotiopsis theae, is one of the most destructive diseases in tea plants. In this study, we evaluated the individual and synergistic antifungal activities of tea saponin (TS) and mancozeb against P. theae, as well as the mechanisms underlying their activity. The results indicated that TS significantly inhibited both the mycelial growth of P. theae, at an EC50 value of 1.03 mg mL−1, and its spore germination, at an EC50 value of 3.68 mg mL−1. TS also significantly enhanced the antifungal activity of mancozeb, and the cotoxicity factor (CTF) assays revealed that there was a synergistic interaction between TP and mancozeb (3:7) against mycelial growth and spore germination, with CTC values exceeding 100. Our results also revealed that TS and mancozeb treatments damaged the cell membranes of P. theae, leading to a significant leakage of soluble protein, reduction of sugar and induction of a significant increase of chitinase activity in the mycelial cells; the combination treatment significantly enhanced the observed damage, leakage and induction. These findings suggested that TS had antifungal activity and a synergistic effect with mancozeb and that the mechanism of this activity might be membrane damage and the consequent cytoplasm leakage. [Copyright &y& Elsevier]

Abstract: Elicitors of systemic acquired resistance are well known to reduce severity of several plant pathogenic diseases caused by fungi, bacteria and viruses. Their field applications for management of plant diseases are, however, limited because of yield penalties. Our studies on affect of Benzo (1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), an elicitor of systemic acquired resistance, on chickpea blight caused by a fungal pathogen Didymella rabiei showed that multiple foliar applications of the chemical were effective in management of the disease under economic threshold levels. Multiple applications, however, affected chickpea grain yield adversely. The BTH induced yield penalties could be prevented by foliar spray schedule comprised of BTH and a contact fungicide mancozeb. One spray of BTH (50 ppm) followed by another of mancozeb (0.2%) was less effective (8.3% severity) than three sprays of BTH (4.2% severity) in blight control, however, this treatment enhanced grain yield significantly (1.241 t ha−1) over three sprays of BTH (0.922 t ha−1). [Copyright &y& Elsevier]

Abstract: In this paper we report the synthesis of a new family of sterol analogues that have two amidic bonds on the side chain. These azasterols were obtained by a straightforward procedure including an Ugi condensation that allows the facile attachment of a polyfunctionalized side chain into the steroidal framework. Some of the new compounds showed an interesting inhibitory effect on the growth of two pathogenic fungi involved in plant diseases. [Copyright &y& Elsevier]

Culture filtrates of five strains of Clitocybe nuda displayed various degrees of antimicrobial activity against plant pathogenic fungi and/or bacteria tested. The culture filtrate of C. nuda strain LA82 was very effective in reducing the incidence of Phytophthora blight of pepper caused by Phytophthora capsici and the incidence of leaf spot on pepper caused by Xanthomonas axonopodis pv. vesicatoria. The inhibitory substance in the C. nuda strain LA82 culture filtrate was stable at low and high pH. It was also stable at high temperature. The inhibitory substance was dialyzable in the membrane tubing with molecular weight cut-off of 1000 but not 500 or 100. It was also exchangeable by anion but not cation exchange resins, indicating that the inhibitor has a molecular weight between 1000 and 500, and negative charge on its molecule. The inhibitor is a hydrophilic compound, but not a protein. [Copyright &y& Elsevier]

Aims: The aim of this study was to evaluate the influence of environmental conditions on the antifungal activity of the Bacillus sp. CCMI 1053 cultures. Methods and Results: The electrospray ionization mass spectra (ESI-MS) analysis was used to detect the active peptides produced by Bacillus amyloliquefaciens CCMI 1051 cultures in a glucose-containing medium to which four different nitrogen sources were added. The cultures produced different patterns of Bacillus sporulation and distinct antifungal activity of the cell-free culture broths. Conclusions: The highest sporulation obtained corresponds to higher antifungal activity when it is formed after 3 days of microbial growth. The antifungal activity against Trichoderma harzianum CCMI 783 is more influenced by the concentration on the nitrogen source than the culture time of incubation. The association of nitrogen concentration and the time of incubation is particularly relevant in the expression of the antifungal activity. Significance and Impact of the Study: The present findings allow the reduction of the use of chemical pesticides and to limit some plant diseases. The association of the nitrogen source and the time of incubation is a novelty, which would improve the production of secondary metabolites. Both economical and environmental benefits arise from the study. [ABSTRACT FROM AUTHOR]

The article offers insights into bacterial leaf scorch, a disease of landscape trees. Xylella fastidiosa has been identified as a pathogen of landscape trees for over 25 years. The economic effects of the disease is estimated at between $0.7 and $1.6 million over the next 10 years. The author also presents many unanswered questions regarding host range, transmission, pathogeneses, disease management and individual tree therapy.

Evaluates the efficacy of composted pine bark mix fortified with the biocontrol agent Trichoderma hamatum 382 (FCPB) against bacterial leaf spot of radish, lettuce and tomato under controlled environment conditions. Suggestion that producing vegetable seedlings in FCPB mix or compost-based substrates may provide initial protection against bacterial leaf spot pathogens; Preparation of potting mixes; Effects of potting mixes on bacterial leaf spot of radish, lettuce and tomato; Foliar pathogen population densities.

We investigated adaptation of fire blight forecasting concepts to incorporate and optimize the use of biological agents for disease suppression. The effect of temperature on growth of the bacterial antagonists, Pseudomonas fluorescens A506 and Pantoea agglomerans C9-1S, and of the pathogen Erwinia amylovora 153N, on pear and apple blossoms was evaluated in growth chamber and screenhouse experiments. New blossoms were inoculated with the strains and subsequent growth was measured over 96 h. Bacterial growth rates on blossoms were described as functions of temperature. A degree hour-based "bacterial growth index" (96-h moving total of degree hours >10°C) was created to assess conduciveness of orchard environments for antagonist colonization. A comparison of this index to a disease risk index indicated that biocontrol treatments could be timed such that the antagonists could be expected to grow to an effective population size before the disease index shifted from "low" to "moderate" risk. For six pear- and apple-production areas of Oregon and Washington, regression of actual values of the bacterial growth and disease risk indices on index values derived from 4-day temperature forecasts resulted in coefficients of determination that averaged 0.75. The "bacterial growth index" and its estimation via temperature forecasts were incorporated into a decision matrix designed to guide optimal treatment timing. [ABSTRACT FROM AUTHOR]

Discusses the use of antimicrobials for prophylactic treatment of bacterial diseases of plants in the U.S. Antimicrobials registered by the U.S. Environmental Protection Agency for use in plant agriculture; Administration of treatment for fire blight; Recommended concentrations for streptomycin; Information about the antimicrobial resistance in plant pathogens.

The effect of soil solarization on the viability of plant pathogens and disease was evaluated in Victoria. The treatment was tested in NW and S Victoria with natural soil inoculated with high inoculum levels of Fusarium oxysporum, Plasmadiophora brassicae, Sclerotium cepivorum, Sclerotinia minor, Sclerotinia sclerotiorum, Verticullium dahliae and the nematodes Meloidogyne javanica and Pratylenchus penetrans. Other experiments were established at sites with a previous history of disease. Solarization of artifically inoculated soils reduced inoculum levels to at least a depth of 10 cm and effectively controlled diseases caused by P. brassicae on brocoli, and S. minor and S. sclerotriorum on lettuce. The treatment reduced inoculum levels but not disease of carnations and watermelons affected by F. oxysporum, tomatoes affected by M. javanica, celery affected by P. penetrans, and onions affected by S. cepivorum. Results were inconclusive for tomatoes affected by V. dahliae. Experiments in naturally infested soild established that solarization reduced disease and increased yields of Chinese cabbage affected by P. brassicae, celery affected by P. penetrans, lettuce affected by S. minor and watermelon affected by root rot. Solarization reduced disease on onions affected the S. cepivorum but did not significantly increase yield. At all sites the treatment reduced the number of viable propagules of the pathogens to at least a depth of 10 cm. [ABSTRACT FROM AUTHOR]

Although the Green Revolution was a milestone in agriculture, it was accompanied by intensive use of synthetic pesticides, which has raised serious concerns due to their impact on human and environmental health. This is increasingly stimulating the search for safer and more eco-friendly alternative means to control plant diseases and prevent food spoilage. Among the proposed alternatives, pomegranate peel extracts (PPEs) are very promising because of their high efficacy. In the present review, we discuss the complex mechanisms of action that include direct antimicrobial activity and induction of resistance in treated plant tissues and highlight the importance of PPE composition in determining their activity. The broad spectrum of activity, wide range of application and high efficiency of PPEs against bacterial, fungal and viral plant pathogens suggest a potential market not only restricted to organic production but also integrated farming systems. Considering that PPEs are non-chemical by-products of the pomegranate industry, they are perceived as safe by the public and may be integrated in circular economy strategies. This will likely encourage agro-pharmaceutical industries to develop commercial formulations and speed up the costly process of registration. [ABSTRACT FROM AUTHOR]