Bacterial Wilt Research Articles

Ralstonia solanacearum infection induces tobacco root to secrete chemoattractants to recruit antagonistic bacteria and defensive compounds to inhibit pathogen.

Plant root exudates play crucial roles in maintaining the structure and function of the whole belowground ecosystem and regulating the interactions between roots and soil microorganisms. Ralstonia solanacearum causes bacterial wilt disease in many plants, while root exudate-mediated inhibition of pathogen infection is poorly understood. Here, we characterize the chemical divergence between root exudates of healthy and diseased tobacco plants and the effects of that variability on the rhizosphere microbial community and the occurrence of bacterial wilt. Compared with the healthy plants, root exudates in diseased plants showed distinct exudation patterns and metabolite profiles including increased amounts of flavonoids, phenylpropanoids, terpenoids and defense-related hormones, as well as distinct bacterial community composition, as illustrated by an increased abundance of Ralstonia and decreased abundances of Bacillus and Streptomyces in diseased plants rhizosphere. Pathogen infection stimulated roots to secrete more defensive compounds to inhibit pathogen growth. Change of root exudates modulated rhizosphere microbial community. Specific root exudates could benefit plants by attracting antagonistic Bacillus amyloliquefaciens and inhibiting pathogens. Bacillus amyloliquefaciens could utilize specific root exudates as carbon sources. Benzyl cinnamatel promoted the biofilm formation and colonization of B. amyloliquefaciens on roots. To defend against pathogen invasion, tobacco plants recruited antagonistic and plant growth-promoting rhizobacteria to the rhizosphere by modifying root exudate profiles. Specific signal molecules are recommended to recruit beneficial microorganisms for controlling bacterial wilt. The results provide insights concerning the metabolic divergence of root exudates integral to understanding root-microorganism interaction. © 2024 Society of Chemical Industry.

Impacts of copper hydroxide on leaf biochemical changes and on induction of resistance in chilli plants against bacterial wilt

This study investigated the biochemical changes in chilli plants resistant or susceptible to bacterial wilt, caused by Ralstonia solanacearum, following inoculation and treatment with copper hydroxide. Treated inoculated plants exhibited significant increases in ionic contents, including phosphorus (3.25%), nitrogen (8.98%), and micronutrients such as potassium, magnesium, zinc, calcium, and copper. Enhanced biochemical parameters were observed, including chlorophyll (80.78 µmol), peroxidase (2.22 µg/g), catalase (4.10 µg/g), hydrogen peroxide (3.30 µg/g), total phenolic compounds (14156.61 µg/g), superoxide dismutase (4.13 µg/g), total soluble proteins (3.87 µg/g), and total soluble sugars (3.17 µg/g), compared to untreated inoculated plants. These results highlight the biochemical alterations linked to disease resistance and offer insights for developing effective formulations to combat bacterial wilt in chilli.

Managing tomato bacterial wilt through pathogen suppression and host resistance augmentation using microbial peptide.

The increasing health and environmental risks associated with synthetic chemical pesticides necessitate the exploration of safer, sustainable alternatives for plant protection. This study investigates a novel biosynthesized antimicrobial peptide (AMP) from Lactiplantibacillus argentoratensis strain IT, identified as the amino acid chain PRKGSVAKDVLPDPVYNSKLVTRLINHLMIDGKRG, for its efficacy in controlling bacterial wilt (BW) disease in tomato (Solanum lycopersicum) caused by Ralstonia solanacearum. Our research demonstrates that foliar application of this AMP at a concentration of 200 ppm significantly reduces disease incidence by 49.3% and disease severity by 45.8%. Scanning electron microscopy revealed severe morphological disruptions in the bacterial cells upon exposure to the AMP. Additionally, the AMP enhanced host resistance by elevating defense enzyme activities, leading to notable improvements in plant morphology, including a 95.5% increase in plant length, a 20.1% increase in biomass, and a 96.69% increase in root length. This bifunctional AMP provides dual protection by exerting direct antimicrobial activity against the pathogen and eliciting plant defense mechanisms. These findings underscore the potential of this biologically sourced AMP as a natural agent for combating plant diseases and promoting growth in tomato crops. To the best of our knowledge, this is the first study to demonstrate the use of a foliar spray application of a biosynthesized microbial peptide as biocontrol agent against R. solanacearum. This interaction not only highlights its biocontrol efficacy but also its role in promoting the growth of Solanum lycopersicum thereby increasing overall agricultural yield.

Pyoluteorin-deficient Pseudomonas protegens improves cooperation with Bacillus velezensis, biofilm formation, co-colonizing, and reshapes rhizosphere microbiome

Plant-beneficial Pseudomonas and Bacillus have been extensively studied and applied in biocontrol of plant diseases. However, there is less known about their interaction within two-strain synthetic communities (SynCom). Our study revealed that Pseudomonas protegens Pf-5 inhibits the growth of several Bacillus species, including Bacillus velezensis. We established a two-strain combination of Pf-5 and DMW1 to elucidate the interaction. In this combination, pyoluteorin conferred the competitive advantage of Pf-5. Noteworthy, pyoluteorin-deficient Pf-5 cooperated with DMW1 in biofilm formation, production of metabolites, root colonization, tomato bacterial wilt disease control, as well as in cooperation with beneficial bacteria in tomato rhizosphere, such as Bacillus spp. RNA-seq analysis and RT-qPCR also proved the pyoluteorin-deficient Pf-5 mutant improved cell motility and metabolite production. This study suggests that the cooperative effect of Bacillus–Pseudomonas consortia depends on the balance of pyoluteorin. Our finding needs to be considered in developing efficient SynCom in sustainable agriculture.

Reduced content of gamma-aminobutyric acid enhances resistance to bacterial wilt disease in tomato.

Bacteria within the Ralstonia solanacearum species complex cause devastating diseases in numerous crops, causing important losses in food production and industrial supply. Despite extensive efforts to enhance plant tolerance to disease caused by Ralstonia, efficient and sustainable approaches are still missing. Before, we found that Ralstonia promotes the production of gamma-aminobutyric acid (GABA) in plant cells; GABA can be used as a nutrient by Ralstonia to sustain the massive bacterial replication during plant colonization. In this work, we used CRISPR-Cas9-mediated genome editing to mutate SlGAD2, which encodes the major glutamate decarboxylase responsible for GABA production in tomato, a major crop affected by Ralstonia. The resulting Slgad2 mutant plants show reduced GABA content, and enhanced tolerance to bacterial wilt disease upon Ralstonia inoculation. Slgad2 mutant plants did not show altered susceptibility to other tested biotic and abiotic stresses, including drought and heat. Interestingly, Slgad2 mutant plants showed altered microbiome composition in roots and soil. We reveal a strategy to enhance plant resistance to Ralstonia by the manipulation of plant metabolism leading to an impairment of bacterial fitness. This approach could be particularly efficient in combination with other strategies based on the manipulation of the plant immune system, paving the way to a sustainable solution to Ralstonia in agricultural systems.

Genotypic and Phenotypic Analyses Show Ralstonia solanacearum Cool Virulence Is a Quantitative Trait Not Restricted to "Race 3 Biovar 2".

Most Ralstonia solanacearum species complex strains cause bacterial wilts in tropical or subtropical zones, but the group known as race 3 biovar 2 (R3bv2) is cool virulent and causes potato brown rot at lower temperatures. R3bv2 has invaded potato-growing regions around the world but is not established in the United States. Phylogenetically, R3bv2 corresponds to a subset of the R. solanacearum phylotype IIB clade, but little is known about the distribution of the cool virulence phenotype within phylotype IIB. Therefore, genomes of 76 potentially cool virulent phylotype IIB strains and 30 public genomes were phylogenetically analyzed. A single clonal lineage within the sequevar 1 subclade of phylotype IIB that originated in South America has caused nearly all brown rot outbreaks worldwide. To correlate genotypes with relevant phenotypes, we quantified virulence of 10 Ralstonia strains on tomato and potato at both 22 and 28°C. Cool virulence on tomato did not predict cool virulence on potato. We found that cool virulence is a quantitative trait. Strains in the sequevar 1 pandemic clonal lineage caused the most disease, whereas other R3bv2 strains were only moderately cool virulent. However, some non-R3bv2 strains were highly cool virulent and aggressively colonized potato tubers. Thus, cool virulence is not consistently correlated with strains historically classified as the R3bv2 group. To aid in the detection of sequevar 1 strains, this group was genomically delimited in the LINbase web server, and a sequevar 1 diagnostic primer pair was developed and validated. We discuss implications of these results for the R3bv2 definition.

The disordered effector RipAO of Ralstonia solanacearum destabilizes microtubule networks in Nicotiana benthamiana cells.

Ralstonia solanacearum causes bacterial wilt, a devastating disease in solanaceous crops. The pathogenicity of R. solanacearum depends on its type III secretion system, which delivers a suite of type III effectors into plant cells. The disordered core effector RipAO is conserved across R. solanacearum species and affects plant immune responses when transiently expressed in Nicotiana benthamiana. Specifically, RipAO impairs pathogen-associated molecular pattern-triggered reactive oxygen species production, an essential plant defense mechanism. RipAO fused to yellow fluorescent protein initially localizes to filamentous structures, resembling the cytoskeleton, before forming large punctate aggregates around the nucleus. Consistent with these findings, tubulin alpha 6 (TUA6) and tubulin beta-1, building blocks of microtubules, were identified as putative targets of RipAO in immunoprecipitation and mass spectrometry analyses. In the presence of RipAO, TUA6-labeled microtubules fragmented into puncta, mimicking the effects of oryzalin, a microtubule polymerization inhibitor. These effects were corroborated in a N. benthamiana transgenic line constitutively expressing green fluorescent protein-labeled TUA6, where RipAO reduced microtubule density and stability at an accumulation level that did not induce aggregation. Moreover, oryzalin treatment further enhanced RipAO's impairment of reactive oxygen species production, suggesting that RipAO disrupts microtubule networks via its association with tubulins, leading to immune suppression. Further research into RipAO's interaction with the microtubule network will enhance our understanding of bacterial strategies to subvert plant immunity.

Evaluation of the antibacterial activity of some plant essential oils against Ralstonia solanacearum and the molecular diagnosis of the bacterium

Background Evaluation of the antibacterial activity of some essential oils for controlling potato bacterial wilt. Objective In vitro and planta trials, five essential oils, lemongrass, eucalyptus, thyme, ginger, and peppermint, were evaluated for their aptitude to impede the progress of Ralstonia solanacearum. Materials and methods Five essential oils were assessed for their activity to inhibit R. solanacearum growth using the disc diffusion method. Certain volumes of each tested plant essential oil were added on filter paper discs using tetrazolium chloride agar medium, which contained the tested bacterium to obtain the proposed concentrations used to evaluate the most efficient oil for controlling potato bacterial wilt. Serological and molecular identification was also conducted. Results and conclusion R. solanacearum was characterized using cultural characteristics on the selective medium South Africa, “which is the most effective in suppressing the growth of contaminating microorganisms, and the highest recovery rate of the tested bacterium,” immunofluorescence antibody staining tomato bioassay test and molecular identification via real-time PCR (Taq-man) assay. In-vitro studies showed that all tested plant essential oils (lemongrass, eucalyptus, thyme, ginger, and peppermint) significantly reduced R. solanacearum progress. Eucalyptus (Eucalyptus globulus) and peppermint (Mentha piperita) essential oils were the most efficient in suppressing R. solanacearum growth, where it showed the highest mean inhibition zone, followed by thyme oil (Thymus vulgaris), lemongrass oil (Comybogen citratus), and ginger oil (Zingiber officinale), respectively. Phenotypic variances in bacterial cell construction have been noticed via a transmission electron microscope. Eucalyptus oil led to cell wall lysis, cell laceration, bubble-like structures, and degraded cellular components in bacterial cells.

Gatifloxacin hydrochloride confers broad-spectrum antibacterial activity against phytopathogenic bacteria.

Bacterial diseases pose significant threats to agriculture and natural ecosystems, causing substantial crop losses and impacting food security. Until now, there has been a less efficient control strategy against some bacterial diseases such as bacterial wilt, caused by Ralstonia solanacearum. In this study, we screened a library of 58 microorganism-derived natural products for their antibacterial activity against R. solanacearum. Gatifloxacin hydrochloride exhibited the best inhibitory effect with an inhibition rate of 95% at 0.0625 mg/L. Further experiments demonstrate that gatifloxacin hydrochloride inhibits R. solanacearum growth in a concentration-dependent manner, with the minimum inhibitory concentration of 0.125 mg/L. Treatment with 0.5 mg/L of gatifloxacin hydrochloride killed more than 95% of bacteria. Gatifloxacin hydrochloride significantly inhibited biofilm formation by R. solanacearum. Gatifloxacin hydrochloride also shows good antibacterial activity against Pseudomonas syringae pv. tomato DC3000 and Xanthomonas campestris pv. vesicatoria. Exogenous application of gatifloxacin hydrochloride suppressed disease development caused by R. solanacearum and P. syringae. In summary, our results demonstrate the great potential of microorganism-derived compounds as broad-spectrum antibacterial compounds, providing alternative ways for the efficient control of bacterial plant diseases.

Money plant disease atlas: A comprehensive dataset for disease classification in ornamental horticulture.

Epipremnum aureum, sometimes known as the Money Plant, is a popular houseplant known for its hearts-shaped leaves and durability. Commonly referred to as Golden Pothos or Devil's Ivy, it is also appreciated for its ornamental value and air cleaning ability. They say that these plants are attractive to many people owing to their tolerance to several conditions and easy care, therefore, it is no surprise that they are found in many households and workplaces. Money Plants are hardy, but like any other plant they can also be infected by various diseases, which may render them less attractive, or even unattractive. This work encompasses bacterial wilt, manganese poisoning aspects and together with a healthy leaves aspect presents all prevalent masses and offer a comprehensive image of diseases. A dataset of 224 × 224 pixel images is utilized to accomplish this work with the intention to further enhance support in Ornamental Horticulture practices and diagnose more accurately. This work not only contributes ideas and approaches in understanding the field of plants pathology but also stresses on the fact how image processing can be beneficial in looking after plants. The dataset serves as a solid foundation for deep learning approaches into Ornamental Agriculture and provides useful insights for researchers studying the cultivation of money plants.

Ralstonia solanacearum Alters Root Developmental Programmes in Auxin-Dependent and -Independent Manners.

Microbial pathogens and other parasites can modify the development of their hosts, either as a target or a side effect of their virulence activities. The plant-pathogenic bacterium Ralstonia solanacearum, causal agent of the devastating bacterial wilt disease, is a soilborne microbe that invades host plants through their roots and later proliferates in xylem vessels. In this work, we studied the early stages of R. solanacearum infection in the model plant Arabidopsis thaliana, using an invitro infection system. In addition to the previously reported inhibition of primary root length and increase in root hair formation at the root tip, we observed an earlier xylem differentiation during R. solanacearum infection that occurs in a HrpG-dependent manner, suggesting that the pathogen actively promotes the development of the vascular system upon invasion of the root. Moreover, we found that the phytohormone auxin, of which the accumulation is promoted by the bacterial infection, is required for the R. solanacearum-triggered induction of root hair formation but not earlier xylem differentiation. Altogether, our results shed light on the capacity of R. solanacearum to induce alterations of root developmental pathways and on the role of auxin in this process.

Exploiting Bacterial Pigmentation for Non-Destructive Detection of Seed-Borne Pathogens by Using Photoacoustic Techniques.

Seed-borne pathogens pose a significant threat to global food security. This study focuses on Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), a quarantine plant pathogen causing bacterial wilt of common beans. Despite its global spread and economic impact, effective control measures are limited. Existing diagnostic methods, such as PCR, are time-consuming, destructive, and challenging for large-scale screening. This study explores the potential of photoacoustic techniques as a non-destructive, rapid, and high-throughput alternative. These techniques leverage the photoacoustic effect to measure optical absorption, offering high sensitivity and accuracy. Cff colonies exhibit distinct pigmentation, suggesting their suitability for photoacoustic detection. We characterised the optical properties of Cff and developed an in vitro model to simulate conditions within Cff-infected bean seeds. The results demonstrate the efficiency of the photoacoustic technique in detecting Cff in a mimicked-bean seed and indicate the potential discrimination of different coloured Cff strains. This study paves the way for a novel, non-invasive approach to the early detection of Cff and other seed-borne pathogens, contributing to improve crop health and food security.

Exploring Pediococcus sp. M21F004 for Biocontrol of Bacterial and Fungal Phytopathogens.

This study explores the biocontrol potential of Pediococcus sp. M21F004, a lactic acid bacteria (LAB) isolated from marine environments, against several bacterial and fungal phytopathogens. Out of 50 marine bacterial isolates, Pediococcus sp. M21F004 was selected for its exceptional antimicrobial activity. The strain, isolated from the intestine of a starry flounder, was identified as Pediococcus sp. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that oleic acid (OA) is a key antimicrobial compound produced by Pediococcus sp. M21F004. In vitro assays showed that the culture broth (CB) of Pediococcus sp. M21F004, as well as OA, exhibited significant inhibitory effects against pathogens such as Fusarium oxysporum, Clarireedia homoeocarpa, and Pectobacterium carotovorum subsp. carotovorum. In vivo tests on cucumber Fusarium wilt, creeping bentgrass dollar spot, tomato bacterial wilt, and kimchi cabbage soft rot further demonstrated the strain's efficacy in reducing disease severity. Moreover, OA had the highest control value of 74% against tomato bacterial wilt, followed by 64.1% against cucumber fusarium wilt, 42.5% against kimchi cabbage soft rot, and 16.5% against creeping bentgrass dollar spot. These findings suggest that Pediococcus sp. M21F004 and its metabolite OA offer promising alternatives to chemical pesticides, contributing to sustainable plant disease management by promoting resistance induction and providing an eco-friendly approach to agriculture.

Engineering seed microenvironment with embedded bacteriophages and plant growth promoting rhizobacteria

BackgroundEngineering the seed microenvironment with embedded bacteriophages and Plant Growth Promoting Rhizobacteria (PGPR) shows promise for enhancing germination, mitigating biotic and abiotic stressors, and improving resilience under challenging environmental conditions. This study aimed to enhance potato seed germination and control bacterial wilt caused by Ralstonia solanacearum and salinity by using novel technology to encapsulate, preserve, and deliver phage therapy and rhizobacteria.ResultsSilk fibroin and trehalose biomaterial combined with the phage P-PSG11 and Pseudomonas lalkuanensis were applied to potato seeds. A pot experiment was conducted to investigate pathogen suppression, salt tolerance, and plant growth enhancement. The combination of silk and trehalose effectively preserved both phage and bacteria for ≥ 8 weeks, maintaining both phage titers and bacterial colony counts. Seeds coated with the P-PSG11 and P. lalkuanensis mixture exhibited the highest germination rate at 93.5%, followed by P. lalkuanensis at 86.3%. In vivo evaluations showed significant increases in root length (72.7%, 61.0%, and 22.5%), plant height (71.5%, 65.1%, and 8.2%), and dry matter (129.1%, 125.7%, and 13.1%) for the P-PSG11 and P. lalkuanensis mixture, P. lalkuanensis, and P-PSG11, respectively. The incidence of wilt was significantly reduced by 88.2% and 81.2%, and salinity was mitigated by 83.3% and 79.2% for the P-PSG11 and P. lalkuanensis mixture and P. lalkuanensis treatment, respectively, compared to the control (p < 0.001). The viability of preserved P-PSG11 and P. lalkuanensis was confirmed after one year using phage titers and bacterial colonies.ConclusionThis innovative approach enhanced plant growth, promoted seed germination, controlled wilt disease, and mitigated soil salinity.

The levels of pattern-triggered immunity in the root and stembase of tomato cultivars positively correlate with the resistance to Ralstonia solanacearum

BackgroundBacterial wilt (BW), caused by Ralstonia solanacearum (Rs), is one of the most destructive diseases impacting a wide range of crops globally. The infection process is complex involving intricate interactions between the plant and Rs. Managing BW is challenging, and crop breeding remains the most effective strategy for disease control. Resistance to BW in crops is primarily associated with quantitative trait loci (QTLs), which are believed to correlate with the simultaneous activation of multiple defense mechanisms against pathogens. This study aimed to clarify the nature of BW resistance and determine whether pattern-triggered immunity (PTI) plays a role in this resistance.ResultsPTI can be triggered in tomato roots and stembases by an Rs hrpG− mutant and by the cell wall extract (PiCWE) from the root-infected beneficial fungus Piriformospora indica (Pi). Among tomato plants with varying resistance levels to Rs, BW-resistant (BWR) and moderate-resistant (BWMR) cultivars exhibited higher levels of root and stembase PTI in response to Rs hrpG− inoculation and PiCWE treatment than in BW-susceptible (BWS) cultivars. Additionally, BWR and BWMR cultivars showed enhanced leaf PTI after inoculation with a Pseudomonas syringae pv. tomato (Pst) hrcC− mutant. The BWR cultivar Hawaii 7996 (H7996) also demonstrated high tolerance to several leaf pathogens.ConclusionsEfficient systems for the analyses of PTI responses in tomato roots, stembases and leaves in response to patterns derived from root-infected pathogenic and beneficial microorganisms have been established. The levels of PTI in roots, stembases, and leaves are positively correlated with BW resistance in tomato plants. The BWR cultivar H7996 also shows tolerance to various leaf pathogens. This study reveals a significant correlation between tomato PTI and resistance to Rs, provides valuable insights into the nature of BW resistance, and offers critical information for tomato breeding.

Identification and genomic insights into Bacillus siamensis strains with host colonization potential and activity against tomato bacterial wilt.

Bacterial wilt (BW), caused by Ralstonia solanacearum species complex (RSSC), is considered as one of the most destructive plant diseases worldwide. In this study, two strains of Bacillus siamensis, BB605-1 and BB653, were screened and identified from endophytes in healthy tomato and mangrove plants, respectively. Both strains demonstrated antagonistic activities against all 16 RSSC strains, representing eight sequevars from various hosts. The growth of RSSC was suppressed by the crude antimicrobial extracts produced by two strains. The pot inoculation experiment revealed the control efficiencies of two strains against tomato bacterial wilt as 59.63% and 63.98%, respectively. After imparting rifampicin resistance to the strains and applying them to tomato plants, both strains successfully established stable colonization in the rhizosphere, roots, stems, and leaves of tomato plants. Additionally, our study demonstrated that both strains exhibited significant plant growth-promoting properties. Complete genome sequencing revealed genome size of 3.868 M bp with 3594 protein-coding genes for BB605-1, and 3.857 M bp with 3600 protein-coding genes for BB653. Genome analysis of both strains identified seven secondary metabolite clusters with known antimicrobial properties and predicted three unknown compounds with potentially novel properties. Genome mining revealed several key genes associated with plant growth regulation, colonization, and biofilm formation, and we also detected these corresponding substances. These findings provide a compelling case for the application of B. siamensis in agricultural practices. The isolates' multiple capacities to colonize, enhance plant growth, and exert antagonistic effects against BW positions them as highly promising candidates for an integrated biological solution. © 2024 Society of Chemical Industry.

Bacterial wilt alters the microbial community characteristics of tobacco root and rhizosphere soil

The root-related microorganisms have good effects of stress resistance and disease resistance, and promote the healthy growth of plants. It is important to understand the characteristics of microbial communities in healthy and infected tobacco roots and rhizosphere soil for controlling tobacco bacterial wilt by using beneficial microorganisms in specific niches. In this study, the soil properties and microbial composition of the rhizosphere soil and roots of healthy and bacterial wilt-diseased tobacco plants were analyzed to evaluate their potential influence on plant health. Soil properties including total carbon and total nitrogen have show significant differences in bacterial wilt-infected tobacco. The microbial community diversity and composition are high related to the occurrence of bacterial wilt. Fungal, bacterial and actinobacterial community varied between two different health systems with the increase/decrease of beneficial microbiomes. Results of community functions of rhizosphere microbiomes have showed the differences in Metabolic pathways. This study clarified the impact of bacterial wilt caused by Ralstonia solanacearum on tobacco root and rhizosphere soil microbial communities, providing a theoretical basis for studying the relationship between rhizosphere-soil microorganisms-plant health, and offering a new perspective for utilizing beneficial microorganisms to defend against pathogen invasion in specific ecological niches.

Cladophialophora guangxiense sp. nov., a New Species of Dark Septate Endophyte, Mitigates Tomato Bacterial Wilt and Growth Promotion Activities

Cladophialophora guangxiense sp. nov., a New Species of Dark Septate Endophyte, Mitigates Tomato Bacterial Wilt and Growth Promotion Activities

(Invited) Wet Interfacing Technique for Physiological Chemical Sensing

Since the COVID-19 pandemic, the importance of simple and miniaturized chemical sensors, immunochromatographic kit that use body fluids collected with little physical pain has been increasingly recognized in daily healthcare. Users can operate the kit by themselves and understand their own physiological condition from the easily recognizable colorimetric signal. On the other hand, as there is a shortage of workers in the agricultural field, the sensing technology for digital management of the crop growth and health is also becoming increasingly important. Recently, our research has been focused on a wet-interfacing technique [1]. This technique had been proposed in the research field of analytical chemistry to enable the extraction of chemical compounds from the human skin by simply wetting the human skin surface with water. We integrated this wet interfacing technique with the conventional miniaturized chemical sensors to establish the new non-invasive or non-destructive sensors for continuous transepidermal extraction and detection of the chemical components in the human body or plant leaf. The wet interface is composed of a hydrogel or paper impregnated with water to be handled as solid materials.For the human healthcare, the sweat components derived from blood have been expected as biomarkers for indirectly understanding the physiological conditions as an alternative to the blood test. The hydrogel touchpad-based sensors for the sweat components are fabricated by embedding various miniaturized chemical sensors into a hydrogel. The users allow the chemical sensing of their sweat components only by touching the hydrogel. The sweat compounds extracted into the hydrogel was detected by the embedded sensors in situ. Since our first report on at-rest sweat lactate sensor in 2019 [2], various types of hydrogel touchpad-based sweat sensors have been proposed for many target compounds using different types of sensing materials and gels [3,4].The non-destructive plant healthcare devices have also been proposed mainly by the optical sensors based on fluorescence, Raman, Near-infrared, and X-ray spectroscopy. On the other hand, there are few reports on the chemical sensors for non-destructive in vivo sensing of the chemical components in the plant body. Now, we are applying the wet interfacing technique overcome this challenging. A thin film type of potassium sensor was contacted with the surface of plant leaf via a filter paper in phosphate buffer saline solution. As a result, potassium ions in the leaf were non-destructively and continuously extracted, followed by detecting in real time [5]. Another application was for early detection of pathogenic disease of plant. We succeeded in extracting and detecting a blue fluorescent substance, antibacterial chlorogenic acid, as an indicator of early symptom of bacterial wilt in tomatoes from infected leaves using a hydrogel touchpad [6].We think that these wet-interfacing techniques are quite important for the future advanced healthcare not only for human but also crops. In this presentation, we will introduce the recent progress of wet-interfacing technique-based chemical sensors applied for human healthcare and smart agriculture. References Nagamine, Sens. Mater. 34 (2022) 3147-3154. https://doi.org/10.18494/SAM3899Nagamine, T. Mano, A. Nomura, Y. Ichimura, R. Izawa, H. Furusawa, H. Matsui, D. Kumaki, S. Tokito, Sci. Rep. 9 (2019) 10102. https://doi.org/10.1038/s41598-019-46611-zIchimura, T. Kuritsubo, K. Nagamine, A. Nomura, I. Shitanda, S. Tokito, Anal. Bioanal. Chem. 413 (2021) 1883-1891. https://doi.org/10.1007/s00216-021-03156-3Chiba, Y. Harada, H. Matsumoto, H. Matsui, N. ito, T. Sekine, K. Nagamine, Anal. Bioanal. Chem. 416 (2024) 1635-1645. https://doi.org/10.1007/s00216-024-05165-4Nagamine, N. Kudo, H. Sasaki, A. Asano, S. Iwasa, Sens. Mater. 35 (2023) 4751-4760. https://doi.org/10.18494/SAM4431Iwasa, Y. Kobara, K. Maeda, k. Nagamine, Sci. Rep. 12 (2022) 13598. https://doi.org/10.1038/s41598-022-17785-w

First Report of Kosakonia cowanii Causing Bacterial Blight on Amorphophallus konjac in China.

Amorphophallus konjac, commonly known as konjac, has significant economic and medicinal value, particularly in Asian countries (Gao et al. 2022). In July 2024, an outbreak of leaf blight was observed in a one-hectare field in Fuyuan (25.67°N; 104.25°E), Yunnan, China. The disease manifested as brown lesions starting at the leaf tips or edges, which rapidly darkened and expanded, leading to leaf necrosis. In severe cases, the disease affected the overall plant health, reducing corm yield and quality significantly. To isolate the causal agent, six diseased leaves from six plants were surface disinfected, and the junction region of healthy and diseased tissues was excised and homogenized in a 15-ml sterile centrifuge tube with 2 ml of sterile distilled water. The resulting bacterial suspension was serially diluted to 10-5 and 200 μl of the diluted sample was spread on LB agar plates. Three pure cultures (designated MY1, MY2, and MY3) were obtained through successive streaking. The isolated colonies were light yellow, convex, and nearly round in shape. Genomic DNA from the three pure isolates was extracted and used to amplify partial sequences of 16S ribosomal RNA (16S rRNA) with primers 27F/1492R (Brady et al. 2008), the beta-subunit of RNA polymerase (rpoB) using primers CM81-F/CM32b-R (Polz and Cavanaugh 1998), and the DNA gyrase subunit B (gyrB) with primers UP-1/UP-2r (Yamamoto and Harayama 1995). The sequences for 16S rRNA (accession nos. PQ288765-PQ288767), rpoB (PQ304887-PQ304889), and gyrB (PQ304884-PQ304886) were deposited in GenBank. Nucleotide BLAST analysis showed that the rpoB, gyrB and 16S rRNA sequences of isolate MY1 shared 99.36, 98.89 and 99.86% identity with those of K. cowanii strains (EU629168, CP107077 and OR121838), respectively. Furthermore, a multigene phylogenetic analysis revealed a strongly supported clade including strain MY1, MY2, MY3 and other K. cowanii isolates. To test pathogenicity, a greenhouse experiment was conducted using five four-month-old healthy A. konjac plants grown in pots. For each plant, three leaves were inoculated with a bacterial suspension of strain MY1 (108 CFU/ml) via leaf infiltration. Another set of three leaves were infiltrated with sterile water as controls. These plants were enclosed in plastic bags for 24 hours post-inoculation. Inoculated plants initially exhibited brown lesions with a yellow halo, which subsequently developed into dark symptoms within seven days. Control plants remained symptom-free. This experiment was repeated three times with consistent results. K. cowanii was reisolated from infected leaves and identified based on Sanger sequencing of 16S rRNA, thus fulfilling Koch's postulates. In recent years, K. cowanii has been confirmed to cause fruit blotch on Trichosanthis fructus (Chen et al. 2024), stalk rot in foxtail millet (Han et al. 2023), bacterial wilt on patchouli (Zhang et al. 2022), and bacterial blight on soybean (Krawczyk and Borodynko-Filas 2020). To our knowledge, this is the first report of K. cowanii causing leaf blight on A. konjac worldwide. This study identifies a previously unrecognized disease affecting konjac production. The identification of the causal agent provides essential information for the diagnosis and management of this disease.