Bacterial Plant Diseases Research Articles

Effect of Acetic Acid on Biofilm Formation in Paracidovorax citrulli, Causal Agent of Bacterial Fruit Blotch.

The unique tissue structure of pathogenic bacteria biofilm plays an important role in its pathogenicity and bactericide resistance. Inhibition or destruction of biofilm formation of pathogenic bacteria is of great significance for the control of plant bacterial diseases. In this study, Paracidovorax citrulli was inoculated into KB medium containing acetic acid, and after shaking at 28°C and 55 r/min for 48 h, it was found that the content of extracellular polysaccharide, extracellular protein and extracellular DNA (eDNA) decreased with the increase of acetic acid concentration, which resulted in the decrease of biofilm formation, it is not even possible to form biofilms on plastic slides. When the final concentration of acetic acid in the culture medium was greater than or equal to 0.5 mg/mL, there was no biofilm on the plastic slides. Therefore, the use of acetic acid as an inhibitor of P. citrulli has a good potential for control of bacterial fruit blotch.

Endophyte Bacillus vallismortis BL01 to Control Fungal and Bacterial Phytopathogens of Tomato (Solanum lycopersicum L.) Plants

Some strains of Bacillus vallismortis have been reported to be efficient biocontrol agents against tomato pathogens. The aim of our study was to assess the biocontrol ability of the endophytic strain BL01 Bacillus vallismortis through in vitro and field trials, as well as to verify its plant colonization ability and analyze the bacterial genome in order to find genes responsible for the biocontrol activity. We demonstrated in a gnotobiotic system and by confocal laser microscopy that the endophytic strain BL01 was able to colonize the endosphere and rhizosphere of tomato, winter wheat and oilseed rape. In vitro experiments demonstrated the inhibition activity of BL01 against a wide range of phytopathogenic fungi and bacteria. BL01 showed biological efficacy in two-year field experiments with tomato plants against black bacterial spotting by 40–70.8% and against late blight by 47.1% and increased tomato harvest by 24.9% or 10.9 tons per hectare compared to the control. Genome analysis revealed the presence of genes that are responsible for the synthesis of biologically active secondary metabolites, which could be responsible for the biocontrol action. Strain BL01 B. vallismortis can be considered an effective biocontrol agent to control both fungal and bacterial diseases in tomato plants.

New emerging Pseudomonads as causal agents of bean blight disease

Common bean (Phaseolus vulgaris) production is negatively affected by several bacterial plant diseases. A severe outbreak of bean blight was observed in the nine major bean-producing provinces of Iran during 2021–2022. Necrotic spots were observed on leaves which become necrotic with chlorosis beyond it. One hundred-sixty bacterial strains with a greyish-white colony appearance were consistently isolated from the one-hundred eighteen symptomatic bean leaf, pod, seed and root samples on nutrient agar. All strains were screened for their ability to cause disease bean leaves among which 134 strains induced chlorosis three days after inoculation on bean leaves of cv. Yaghoot followed by necrotic spots on the inoculated sites one week after inoculation. The pathogenic strains clustered in three groups based on phenotypic characters and multilocus sequencing analyses. Three housekeeping genes including gyrB, rpoB, and rpoD of representative strains were partially sequenced. In the phylogenetic tree based on concatenated sequences of these three genes or each gene individually, the strains were divided into three clusters each with high bootstrap support. The first group of the strains clustered with Pseudomonas simiae CCUG 50988T. This is the first report of this species as causal agent of bean blight. The second group clustered close to Pseudomonas alloputida NMI5768T which apparently belong to a new species. The third group clustered in a separate clade in Pseudomonas chlororaphis species which belongs to a new subspecies based on pathogenicity on bean, phenotypic characters, sequences of five housekeeping genes which named as subsp. phaseoli subsp. nov. with the type strain UT-M315.

Entrapment of antimicrobial compounds in a metal matrix for crop protection.

Agricultural yields are often limited by damage caused by pathogenic microorganisms, including plant-pathogenic bacteria. The chemical control options to cope with bacterial diseases in agriculture are limited, predominantly relying on copper-based products. These compounds, however, possess limited efficacy. Therefore, there is an urgent need to develop novel technologies to manage bacterial plant diseases and reduce food loss. In this study, a new antimicrobial agent was developed using a doping method that entraps small bioactive organic molecules inside copper as the metal matrix. The food preservative agent lauroyl arginate ethyl ester (ethyl lauroyl arginate; LAE) was chosen as the doped organic compound. The new composites were termed LAE@[Cu]. Bactericidal assays against Acidovorax citrulli, a severe plant pathogen, revealed that LAE and copper in the composites possess a synergistic interaction as compared with each component individually. LAE@[Cu] composites were further characterised in terms of chemical properties and in planta assays demonstrated their potential for further development as crop protection agents.

Harnessing phages as biocontrol agents against common bacterial blight diseases in plants

Bacterial blight diseases in plants are caused by various bacterial pathogens such as Dickeya, Pectobacterium, Xanthomonas, and others. They infect a wide range of crops including potatoes, tomatoes, apples, and citrus. The impact of these diseases includes reduced crop yields, lower quality produce, and economic losses for farmers. Traditional control methods like antibiotics and copper-based compounds are becoming less effective due to the development of resistance and environmental concerns. As a result, there is growing interest in alternative strategies such as biocontrol agents (BCAs), particularly bacteriophages. Bacteriophages are viruses that infect bacteria, they offer a promising solution to agricultural disease management. Their specificity and ability to target pathogenic bacteria make them an environmentally friendly alternative to chemical interventions. By optimizing phage formulations and application protocols, bacteriophages have the potential to contribute to healthier crops, increased yields, and a more sustainable agricultural system.

Antagonistic Strain Bacillus velezensis JZ Mediates the Biocontrol of Bacillus altitudinis m-1, a Cause of Leaf Spot Disease in Strawberry.

Biofertilizers are environmentally friendly compounds that can enhance plant growth and substitute for chemically synthesized products. In this research, a new strain of the bacterium Bacillus velezensis, designated JZ, was isolated from the roots of strawberry plants and exhibited potent antagonistic properties against Bacillus altitudinis m-1, a pathogen responsible for leaf spot disease in strawberry. The fermentation broth of JZ exerted an inhibition rate of 47.43% against this pathogen. Using an optimized acid precipitation method, crude extracts of lipopeptides from the JZ fermentation broth were obtained. The crude extract of B. velezensis JZ fermentation broth did not significantly disrupt the cell permeability of B. altitudinis m-1, whereas it notably reduced the Ca2+-ATPase activity on the cell membrane and markedly elevated the intracellular reactive oxygen species (ROS) concentration. To identify the active compounds within the crude extract, QTOF-MS/MS was employed, revealing four antimicrobial compounds: fengycin, iturin, surfactin, and a polyene antibiotic known as bacillaene. The strain JZ also produced various plant-growth-promoting substances, such as protease, IAA, and siderophore, which assists plants to survive under pathogen infection. These findings suggest that the JZ strain holds significant potential as a biological control agent against B. altitudinis, providing a promising avenue for the management of plant bacterial disease.

Acyl hydrazone derivatives with trifluoromethylpyridine as potential agrochemical for controlling plant diseases.

Crops are consistently under siege by a multitude of pathogens. These pathogenic microorganisms, including viruses and bacteria, result in substantial reductions in quality and yield globally by inducing detrimental crop diseases, thus posing a significant challenge to global food security. However, the biological activity sepectrumof commercially available pesticides is limitedand the pesticide efficacy is poor, necessitating the urgent development of broad-spectrum and efficient strategies for crop disease prevention and control. The bioassay results revealed that certain target compounds demonstrated outstanding in vivo antiviral efficacy against cucumber mosaic virus and tobacco mosaic virus. In particular, compound D6 showed remarkable antiviral activity against CMV, significantly higher than that of the control agent ningnanmycin. Mechanism of action studies have shown that compound D6 could enhance the activity of defense enzymes and upregulate the expression of genes related to disease resistance, thereby enhancing the antiviral effects in plants. In addition, these compounds displayed superior inhibitory activity against plant bacterial diseases. For Xoo, compound D10 showed an excellent inhibitory effect that was better than that of the control agent bismerthiazol. Scanning electron microscopy and fluorescence double-staining experiments revealed that compound D10 effectively inhibited bacterial growth by disrupting the cell membrane. A series of trifluoromethyl hydrazone derivatives were designed and synthesized, and it was found that they have control effects on plant viruses and bacterial diseases. In addition, this study revealed the mechanism of action of the active compounds and demonstrated their potential as multifunctional crop protectants. © 2024 Society of Chemical Industry.

Trojan Horse virus delivering CRISPR-AsCas12f1 controls plant bacterial wilt caused by Ralstonia solanacearum.

Plant bacterial wilt caused by Ralstonia solanacearum results in huge losses. Accordingly, developing an effective control method for this disease is urgently required. Filamentous phages, which do not lyse host bacteria and exert minimal burden, offer a potential biocontrol solution. A filamentous phage RSCq that infects R. solanacearum was isolated in this study through genome mining. We constructed engineered filamentous phages based on RSCq by employing our proposed approach with wide applicability to non-model phages, enabling the exogenous genes delivery into bacterial cells. CRISPR-AsCas12f1 is a miniature class 2 type V-F CRISPR-Cas system. A CRISPR-AsCas12f1-based gene editing system that targets the key virulence regulator gene hrpB was developed, generating the engineered phage RSCqCRISPR-Cas. Similar to the Greek soldiers in the Trojan Horse, our findings demonstrated that the engineered phage-delivered CRISPR-Cas system could disarm the key "weapon," hrpB, of R. solanacearum, in medium and plants. Remarkably, pretreatment with RSCqCRISPR-Cas significantly controlled tobacco bacterial wilt, highlighting the potential of engineered filamentous phages as promising biocontrol agents against plant bacterial diseases.IMPORTANCEBacterial disease, one of the major plant diseases, causes huge food and economic losses. Phage therapy, an environmentally friendly control strategy, has been frequently reported in plant bacterial disease control. However, host specificity, sensitivity to ultraviolet light and certain conditions, and bacterial resistance to phage impede the widespread application of phage therapy in crop production. Filamentous phages, which do not lyse host bacteria and exert minimal burden, offer a potential solution to overcome the limitations of lytic phage biocontrol. This study developed a genetic engineering approach with wide applicability to non-model filamentous phages and proved the application possibility of engineered phage-based gene delivery in plant bacterial disease biocontrol for the first.

Bacillus velezensis HN-2: a potent antiviral agent against pepper veinal mottle virus.

Pepper veinal mottle virus (PVMV) belongs to the genus Potyvirus within the family Potyviridae and is a major threat to pepper production, causing reduction in yield and fruit quality; however, efficient pesticides and chemical treatments for plant protection against viral infections are lacking. Hence, there is a critical need to discover highly active and environment-friendly antiviral agents derived from natural sources. Bacillus spp. are widely utilized as biocontrol agents to manage fungal, bacterial, and viral plant diseases. Particularly, Bacillus velezensis HN-2 exhibits a strong antibiotic activity against plant pathogens and can also induce plant resistance. The experimental subjects employed in this study were Bacillus velezensis HN-2, benzothiadiazole, and dufulin, aiming to evaluate their impact on antioxidant activity, levels of reactive oxygen species, activity of defense enzymes, and expression of defense-related genes in Nicotiana benthamiana. Furthermore, the colonization ability of Bacillus velezensis HN-2 in Capsicum chinense was investigated. The results of bioassays revealed the robust colonization capability of Bacillus velezensis HN-2, particularly in intercellular spaces, leading to delayed infection and enhanced protection against PVMV through multiple plant defense mechanisms, thereby promoting plant growth. Furthermore, Bacillus velezensis HN-2 increased the activities of antioxidant enzymes, thereby mitigating the PVMV-induced ROS production in Nicotiana benthamiana. Moreover, the application of Bacillus velezensis HN-2 at 5 dpi significantly increased the expression of JA-responsive genes, whereas the expression of salicylic acid-responsive genes remained unchanged, implying the activation of the JA signaling pathway as a crucial mechanism underlying Bacillus velezensis HN-2-induced anti-PVMV activity. Immunoblot analysis revealed that HN-2 treatment delayed PVMV infection at 15 dpi, further highlighting its role in inducing plant resistance and promoting growth and development. These findings underscore the potential of Bacillus velezensis HN-2 for field application in managing viral plant diseases effectively.

Application of natural-products repurposing strategy to discover novel FtsZ inhibitors: Bactericidal evaluation and the structure-activity relationship of sanguinarine and its analogs

The novel bactericidal target—filamentous temperature-sensitive protein Z (FtsZ)—has drawn the attention of pharmacologists to address the emerging issues with drug/pesticide resistance caused by pathogenic bacteria. To enrich the structural diversity of FtsZ inhibitors, the antibacterial activity and structure-activity relationship (SAR) of natural sanguinarine and its analogs were investigated by using natural-products repurposing strategy. Notably, sanguinarine and chelerythrine exerted potent anti-Xanthomonas oryzae pv. oryzae (Xoo) activity, with EC50 values of 0.96 and 0.93 mg L−1, respectively, among these molecules. Furthermore, these two compounds could inhibit the GTPase activity of XooFtsZ, with IC50 values of 241.49 μM and 283.14 μM, respectively. An array of bioassays including transmission electron microscopy (TEM), fluorescence titration, and Fourier transform infrared spectroscopy (FT-IR) co-verified that sanguinarine and chelerythrine were potential XooFtsZ inhibitors that could interfere with the assembly of FtsZ filaments by inhibiting the GTPase hydrolytic ability of XooFtsZ protein. Additionally, the pot experiment suggested that chelerythrine and sanguinarine demonstrated excellent curative activity with values of 59.52% and 54.76%, respectively. Excitedly, these two natural compounds also showed outstanding druggability, validated by acceptable drug-like properties and low toxicity on rice. Overall, the results suggested that chelerythrine was a new and potential XooFtsZ inhibitor to develop new bactericide and provided important guiding values for rational drug design of FtsZ inhibitors. Notably, our findings provide a novel strategy to discover novel, promising and green bacterial compounds for the management of plant bacterial diseases.

Design, synthesis, and evaluation of novel 3-(piperazin-1-yl)propan-2-ol-modified carbazole derivatives targeting the bacterial membrane

Grain of high yield and quality is needed worldwide due to the needs of a rapidly increasing human population. However, diseases caused by some stubborn types of phytopathogenic bacteria can limit the health and yields of crops. Even worse, conventional commercial bactericides have limited efficacy against such diseases. Therefore, exploring some efficacious bactericidal alternatives is urgently needed. In this work, a new type of 3-(piperazin-1-yl)propan-2-ol modified carbazole derivatives was synthesized and assessed for their bactericidal activity. Among them, compound B16 was the optimal active molecule, giving the EC50 values of 3.11 (Xanthomonas oryzae pv. oryzae), 3.20 (Xanthomonas axonopodis pv. citri) and 3.54 μg/mL (Pseudomonas syringae pv. actinidiae). Pot experiments revealed compound B16 to be able to control rice bacterial leaf blight. Some biochemical assays illustrated that our designed compounds could destroy the integrality of bacterial cell membranes and thereby leading to leaking the intracellular protein. These findings may be regard as a reference for the design of novel membrane-targeting antimicrobial agents for managing stubborn plant bacterial diseases.

Coevolutionary analysis of Pseudomonas syringae-phage interactions to help with rational design of phage treatments.

Treating plant bacterial diseases is notoriously difficult because of the lack of available antimicrobials. Pseudomonas syringae pathovar syringae (Pss) is a major pathogen of cherry (Prunus avium) causing bacterial canker of the stem, leaf and fruit, impacting productivity and leading to a loss of trees. In an attempt to find a treatment for this disease, naturally occurring bacteriophage (phage) that specifically target Pss is being investigated as a biocontrol strategy. However, before using them as a biocontrol treatment, it is important to both understand their efficacy in reducing the bacterial population and determine if the bacterial pathogens can evolve resistance to evade phage infection. To investigate this, killing curve assays of five MR phages targeting Pss showed that phage resistance rapidly emerges invitro, even when using a cocktail of the five phages together. To gain insight to the changes occurring, Pss colonies were collected three times during a 66-h killing curve assay and separately, Pss and phage were also coevolved over 10 generations, enabling the measurement of genomic and fitness changes in bacterial populations. Pss evolved resistance to phages through modifications in lipopolysaccharide (LPS) synthesis pathways. Bacterial fitness (growth) and virulence were affected in only a few mutants. Deletion of LPS-associated genes suggested that LPS was the main target receptor for all five MR phages. Later generations of coevolved phages from the coevolution experiment were more potent at reducing the bacterial density and when used with wild-type phages could reduce the emergence of phage-resistant mutants. This study shows that understanding the genetic mechanisms of bacterial pathogen resistance to phages is important for helping to design a more effective approach to kill the bacteria while minimizing the opportunity for phage resistance to manifest.

Novel aurone-derived piperazine sulfonamides: Development and mechanisms of action as immunostimulants against plant bacterial diseases

Bacterial diseases pose a significant threat to the sustainable production of crops. Given the unsatisfactory performance and poor eco-compatibility of conventional bactericides, here we present a series of newly structured bactericides that are inspiringly designed by aurone found in plants of the Asteraceae family. These aurone-derived compounds contain piperazine sulfonamide motifs and have shown promising in vitro performance against Xanthomonas oryzae pv. oryzae, Xanthomonas oryzae pv. oryzicola and Xanthomonas axonopodis pv. citri, in particular, compound II23 achieved minimum half-maximal effective concentrations of 1.06, 0.89, and 1.78 μg/mL, respectively. In vivo experiments conducted in a greenhouse environment further revealed that II23 offers substantial protective and curative effects ranging between 68.93 and 70.29% for rice bacterial leaf streak and 53.17–64.43% for citrus bacterial canker, which stands in activity compared with lead compound aurone and commercial thiodiazole copper. Additional physiological and biochemical analyses, coupled with transcriptomics, have verified that II23 enhances defense enzyme activities and chlorophyll levels in rice. Significantly, it also stimulates the accumulation of abscisic acid (ABA) and upregulates the expression of key genes OsPYL/RCAR5, OsBIPP2C1, and OsABF1, thereby activating the ABA signaling pathway in rice plants under biological stress from bacterial infections.

Application of inhibitors targeting the type III secretion system in phytopathogenic bacteria

Plant bacterial diseases have inflicted substantial economic losses in global crop, fruit, and vegetable production. The conventional methods for managing these diseases typically rely on the application of antibiotics. However, these antibiotics often target the growth factors of the pathogenic bacteria, leading to the accumulation and emergence of drug-resistant strains, which exacerbates antibiotic resistance. Innovative methods are urgently needed to treat and prevent the toxicity caused by these pathogenic bacteria. Targeting virulence mechanisms in pathogens is a globally recognized and effective strategy for mitigating bacterial resistance. Type III secretion system (T3SS) serves as a crucial virulence determinant in Gram-negative pathogens, and its non-essentials for pathogen growth renders it an ideal target. Targeting the T3SS holds significant potential to alleviate selective pressure for resistance mutations in pathogens. Therefore, targeting T3SS in pathogenic bacteria, while preserving their growth, has emerged as a novel avenue for the development of antimicrobial drugs. In recent years, a multitude of small molecular inhibitors targeting T3SS have been identified. This article offers a comprehensive review of T3SS inhibitors in plant pathogens, while also presenting the latest research advancements in this research direction.

Beyond the β-amino alcohols framework: identification of novel β-hydroxy pyridinium salt-decorated pterostilbene derivatives as bacterial virulence factor inhibitors.

Bacterial virulence factors are involved in various biological processes and mediate persistent bacterial infections. Focusing on virulence factors of phytopathogenic bacteria is an attractive strategy and crucial direction in pesticide discovery to prevent invasive and persistent bacterial infection. Hence, discovery and development of novel agrochemicals with high activity, low-risk, and potent anti-virulence is urgently needed to control plant bacterial diseases. A series of novel β-hydroxy pyridinium cation decorated pterostilbene derivatives were prepared and their antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo) were systematacially assessed. Among these pterostilbene derivatives, compound 4S exhibited the best antibacterial activity against Xoo in vitro, with an half maximal effective concentration (EC50) value of 0.28 μg mL-1. A series of biochemical assays including scanning electron microscopy, crystal violet staining, and analysis of biofilm formation, swimming motility, and related virulence factor gene expression levels demonstrated that compound 4S could function as a new anti-virulence factor inhibitor by interfering with the bacterial infection process. Furthermore, the pot experiments provided convinced evidence that compound 4S had the high control efficacy (curative activity: 71.4%, protective activity: 72.6%), and could be used to effectively manage rice bacterial leaf blight in vivo. Compounds 4S is an attractive virulence factor inhibitor with potential for application in treating plant bacterial diseases by suppressing production of several virulence factors. © 2024 Society of Chemical Industry.

Biopesticide potential of Anisomeles indica Kuntze leaf essential oil and its nanoemulsion against bacterial blight - Xanthomonas strains

The objective of this study was to examine the chemical composition of essential oil A. indica leaves and its nanoemulsion, and evaluation of potential for use as a biopesticide. Essential oil of A. indica extracted from fresh leaves was found to be 99.97% composed of 59 components, according to GC-MS analysis. A non-ionic surfactant Tween 80 and the essential oil of A. indica were combined to create a stable nanoemulsion using sonication method. A long durable stable nanoemulsion was obtained after thirty minutes of sonication, and it was examined using TEM (Transmission electron microscopy), DLS (Dynamic light scattering), and FTIR (Fourier transform infrared spectroscopy) analyses. To consider its practical applications, other factors such as stability, viscosity, pH, turbidity, and creaming index were also investigated. Antibacterial properties of essential oil and nanoemulsion were evaluated against bacterial blight plant pathogens Xanthomonas oryzae and Xanthomonas citri. The MIC (Minimum inhibitory concentration) was determined using the broth microdilution method, and the anti-Xanthomonas activity was assessed utilizing by agar disc diffusion method. Using the crystal violet (CV) technique, inhibition of biofilm formation and development were evaluated. Disturbance of bacterial membrane permeability was confirmed by estimating the proteins and nucleic acids (DNA, and RNA) leakage from the cell membrane. Greenhouse studies using rice/paddy plants were conducted to demonstrate the antibacterial potential of essential oil and nanoemulsion, using RNR-15048 rice cultivar by seed treatment and foliar spray groups. Results of the investigations suggest that, when the essential oil was transformed into a nanoemulsion, its antibacterial effect against bacteria was significantly increased, that might be attributed to the essential oil enhanced ability to penetrate the bacterial cells. Essential oil of A. indica and its nanoemulsion reduced rice bacterial blight disease by 84%and pathogen-virulence by 92%, and promoted the growth and development of rice/paddy seedlings. These results confirm that A. indica essential oil and its nanoemulsion possess anti-bacterial blight properties, without affecting growth and development of host plants. Essential oil of A. indica and its nanoemulsion could be used as biopesticide to control Xanthomonas induced bacterial blight diseases in crop plants either by using for seed treatment or as a foliar spray.

Cross amplification of 16S rRNA bacterial primer 27F/1492R on horticultural crop chloroplast genome

Molecular techniques have been applied as fast and accurate detection methods of plant pathogenic bacteria. Bacteria-specific primer 27F paired with the universal primer 1492R was used in PCR to detect plant pathogenic bacteria in symptomatic leaves of tomato (Solanum lycopersicum L.), chili pepper (Capsicum annum L.), napa cabbage (Brassica rapa subsp. pekinensis L.), cabbage (Brassica oleracea var. capitata L.), and longan (Dimocarpus longan Lour.). The targeted single bands with length of 1400 bp were obtained but bidirectional sequencing of the PCR products recovered partial sequence of chloroplast instead of bacterial genomes. Thus, this result confirmed cross amplification of 27F/1492R primer pair against chloroplast genome of plants. Phylogenetic tree was constructed to separate the tested isolates according to their taxonomic relations: Order Sapindales, Solanales, and Brassicales. In-silico analysis on the new five and nineteen selected sequences in NCBI GenBank detected at least seven conserved regions with some single nucleotide polymorphisms. This report might be a cautionary advice for other researchers to avoid false positive results which could lead to misdiagnosis of bacterial plant diseases.

Phage-Dependent Alteration of Rhizosphere Microbiota in Tomato Plants

Bacteriophages (phages) that infect bacterial pathogens are an alternative means of controlling bacterial diseases in humans, animals, and plants. However, the effects of targeted phage therapy on indigenous microbial communities are not fully understood. In this study, we hypothesized that phages infecting plant pathogenic bacteria play a role in modulating the microbial community in the plant rhizosphere. To explore this, we used the soil-borne plant bacterial pathogen Ralstonia pseudosolanacearum as the host bacterium and its phages as a model system in the tomato rhizosphere. The effect of phages on the microbiota was examined using a narrow host range phage RpY1 and a combination of two phages (RpY2 and RpT1, termed the phage combo) with a broad host range under the natural rhizosphere microbiota of tomato plants. Both RpY1 and the phage combo altered the tomato rhizosphere microbiota. The phage combo displayed phage effects mostly in the presence of R. pseudosolanacearum. However, RpY1 affected the rhizosphere microbiota even in the absence of the host bacterium. The effect of phage RpY1 on the microbiota was further investigated in the tomato rhizosphere using a synthetic community (SynCom) mimicking the natural tomato rhizosphere microbiota. Phage RpY1 affected the microbial community structure of the SynCom in the tomato rhizosphere in the absence of the host bacterium. Analyses of the natural microbiota and SynCom in the tomato rhizosphere indicated an indirect effect of phage RpY1 on the microbiota. This study suggests that phage application modulates the indigenous microbiota through unknown interactions with nonhost bacterial members in the plant rhizosphere. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Plant Disease Diagnosis Based on Hyperspectral Sensing: Comparative Analysis of Parametric Spectral Vegetation Indices and Nonparametric Gaussian Process Classification Approaches

Early and accurate disease diagnosis is pivotal for effective phytosanitary management strategies in agriculture. Hyperspectral sensing has emerged as a promising tool for early disease detection, yet challenges remain in effectively harnessing its potential. This study compares parametric spectral Vegetation Indices (VIs) and a nonparametric Gaussian Process Classification based on an Automated Spectral Band Analysis Tool (GPC-BAT) for diagnosing plant bacterial diseases using hyperspectral data. The study conducted experiments on tomato plants in controlled conditions and kiwi plants in field settings to assess the performance of VIs and GPC-BAT. In the tomato experiment, the modeling processes were applied to classify the spectral data measured on the healthy class of plants (sprayed with water only) and discriminate them from the data captured on plants inoculated with the two bacterial suspensions (108 CFU mL−1). In the kiwi experiment, the standard modeling results of the spectral data collected on nonsymptomatic plants were compared to the ones obtained using symptomatic plants’ spectral data. VIs, known for their simplicity in extracting biophysical information, successfully distinguished healthy and diseased tissues in both plant species. The overall accuracy achieved was 63% and 71% for tomato and kiwi, respectively. Limitations were observed, particularly in differentiating specific disease infections accurately. On the other hand, GPC-BAT, after feature reduction, showcased enhanced accuracy in identifying healthy and diseased tissues. The overall accuracy ranged from 70% to 75% in the tomato and kiwi case studies. Despite its effectiveness, the model faced challenges in accurately predicting certain disease infections, especially in the early stages. Comparative analysis revealed commonalities and differences in the spectral bands identified by both approaches, with overlaps in critical regions across plant species. Notably, these spectral regions corresponded to the absorption regions of various photosynthetic pigments and structural components affected by bacterial infections in plant leaves. The study underscores the potential of hyperspectral sensing in disease diagnosis and highlights the strengths and limitations of VIs and GPC-BAT. The identified spectral features hold biological significance, suggesting correlations between bacterial infections and alterations in plant pigments and structural components. Future research avenues could focus on refining these approaches for improved accuracy in diagnosing diverse plant–pathogen interactions, thereby aiding disease diagnosis. Specifically, efforts could be directed towards adapting these methodologies for early detection, even before symptom manifestation, to better manage agricultural diseases.

Harnessing the bacteriophages to deal with canker infection of kiwi fruit: challenges and future perspective

The worldwide kiwifruit industry has suffered significant economic losses in recent decades as a result of the destructive bacterial plant disease Pseudomonas syringae pv. actinidiae (Psa). Existing control approaches, which depend on the use of copper bactericides and antibiotics, are facing growing challenges due to the rise of resistance to antibiotics and ecological issues. Although biocontrol techniques show promise in laboratory settings, their efficacy in real-world field situations remains unclear. In order to tackle this issue, the emergence of a phage-based biocontrol method becomes a vital alternative, considering the precise targeting of bacteriophages (phages) towards the particular bacteria and their ecologically benign characteristics. This thorough assessment commences by delineating the repercussions of Psa-induced kiwifruit canker, underscoring the need for pioneering management strategies. The text explores the many types and strengths of Psa strains, and then shifts its attention to recent progress in the identification and description of Psa phages. The main topics discussed are the physical structure of phages, the spectrum of organisms they may infect, their ability to destroy bacterial cells, the study of their genetic material, and the process by which they break down bacterial cells. The review examines biocontrol tactics and their possible obstacles in kiwifruit orchards, specifically focusing on abiotic variables such as elevated temperature, UV irradiation and severe pH. The manuscript highlights the crucial importance of phages in efficiently controlling Psa infections, providing a sustainable and focused approach for safeguarding plants.