Bacterial plant diseases present a serious threat to global agriculture, underscoring the need for sustainable biocontrol solutions. Quorum quenching (QQ), which disrupts quorum sensing (QS) to reduce virulence without promoting resistance, offers a promising approach. This study established enrichment cultures with 3-hydroxy palmitic acid methyl ester (3-OH PAME) as the sole carbon source to isolate QQ bacteria against Ralstonia solanacearum. Two novel species, Pseudomonas procumbens sp. nov. (QE6) and P. polia sp. nov. (QL9), exhibited robust and broad-spectrum QQ activity against multiple QS signals, including 3-OH PAME, 3-hydroxy myristic acid methyl ester (3-OH MAME), diffusible signal factor (DSF), and N-acyl homoserine lactones (AHLs). Phylogenetic analysis placed both strains within the P. aeruginosa group and identified functional genes associated with DSF, AHL, and putative 3-OH PAME/MAME degradation, validated via gene deletion and heterologous expression. Both strains effectively controlled plant bacterial diseases mediated by these QS signals, highlighting their potential as eco-friendly, multifunctional QQ-based biocontrol agents.

Ralstonia solanacearum poses a severe threat to global agriculture due to its broad host range, high dispersal capacity, and limited chemical control options. Plant immune inducers provide an effective strategy for controlling bacterial wilt disease. This study demonstrated a natural-derived compound esculetin (ES) serves as a novel plant immune inducer against tobacco bacterial wilt. Foliar application of ES exhibits considerable control effect on tobacco bacterial wilt, with control efficacy is high as 45.41%-68.69%, significantly higher than positive control treatment-benzothiadiazole (BTH). ES activates systemic acquired resistance (SAR) by upregulating transcriptional level of pathogenesis-related (PR) genes, inducing reactive oxygen species (ROS) burst, enhancing defense-related enzyme activity and salicylic acid (SA) accumulation. Transcriptomic analyses reveal that ES induces expression of mitogen-activated protein kinase (MAPK) signaling pathways, SA biosynthesis, phenylpropanoid pathway and brassinosteroid biosynthesis pathway. Furthermore, ES confers broad-spectrum resistance against other diseases like tobacco target spot, tobacco mosaic virus (TMV), wildfire disease and tobacco black shank. The study reveals a novel plant immunity inducer ES that confers broad-spectrum resistance against R. solanacearum by activating the SA-mediated SAR pathway, which provides a sustainable application of ES on bacterial wilt and other plant diseases in the future. © 2026 Society of Chemical Industry.

S-adenosyl-L-methionine synthetase (SAMS) catalyzes the synthesis of S-adenosylmethionine (SAM), a universal methyl donor, and regulate plant growth, development, and stress responses. Although SAMS genes have been functionally characterized in several plant species, their roles in peanut (Arachis hypogaea L.) remain unclear. Here, we conducted a genome-wide identification and characterization of the SAMS gene family in peanut. Phylogenetic analysis clustered these genes into five groups, revealing close evolutionary relationships with soybean SAMS homologs. Conserved domain and motif analyses indicated that all AhSAMS proteins share highly conserved functional features. Expression profiling revealed tissue-specific patterns, AhFJ1AK4 was highly expressed, while AhRG5YED and AhPNM9T4 were preferentially expressed in reproductive organs. Promoter analysis identified abundant cis-regulatory elements related to stress and hormone responses. Upon Ralstonia solanacearum infection and treatments with salicylic acid (SA), abscisic acid (ABA), and methyl jasmonate (MeJA), AhRG5YED and Ah6Q1KS5 were significantly induced in the resistant cultivar H108. Functional validation demonstrated that overexpression of Ah6Q1KS5 in peanut and tobacco reduced cell death, and significantly inhibited bacterial growth, confirming its role in positively regulating bacterial wilt resistance responses. This study presents the first comprehensive genome-wide analysis of the AhSAMS gene family in peanut, providing insights into their functional diversification. In particular, Ah6Q1KS5 is highlighted as a candidate gene contributing to resistance responses, providing a genetic resource and theoretical foundation for future molecular breeding aimed at enhancing disease resistance in peanut.

From the ethyl acetate extract of solid‐state cultures of the endophytic fungus Diaporthe sp. WLM-Y1 (isolated from the leaves of Cayratia japonica (Thunb.) Gagnep.), we characterised three previously undescribed α-pyranones, wodiaporones A–C (1–3), together with eleven known metabolites (4–14). Structures were clarified by an integrated analysis of 1D/2D NMR and high-resolution MS datasets. In preliminary screening assays, all isolated metabolites (1–14) were evaluated at 50 μg/mL against the phytopathogens Ralstonia solanacearum (ATCC 11696), Fusarium oxysporum (ATCC 48112), and Alternaria alternata (ATCC 6663). Several metabolites showed measurable inhibition, with the most pronounced effect observed for compound 13 against R. solanacearum (27.74% inhibition at 50 μg/mL). Compound 11 displayed the highest activity against F. oxysporum (25.55%), whereas only compounds 1, 11–13 showed detectable inhibition towards A. alternata (3.69%–8.93%). These findings expand the α-pyranone chemical space from Diaporthe and provide leads for further evaluation of plant-pathogen control.

The Ralstonia solanacearum species complex (RSSC) comprising soil-borne Gram-negative phytopathogenic bacteria causes bacterial wilt diseases of diverse crop plants. Considering that phylotype I strain OE1-1 enters iron-rich roots from iron-deficient soil during an infection of tomato plants, the mechanisms controlling strain OE1-1 gene expression in response to extracellular iron levels should be clarified. In this study, RSSC was revealed to have two ferric uptake regulator homologs (Fur1 and Fur2). Notably, Fur1 and Fur2 cooperatively repress the expression of genes related to siderophores (Fe3+-chelating compounds) as well as the extracellular Fe3+-chelating activity in the presence of sufficient amounts of extracellular Fe2+. Additionally, Fur1 and Fur2 contribute to the virulence of strain OE1-1 in tomato plants. These findings suggest that RSSC uses two Fur proteins to modulate extracellular Fe3+-chelating activities in response to extracellular iron levels to maintain virulence in crop plants.

CRISPR/Cas-mediated polyphenol oxidase gene knockout in potato reveals divergent roles in resistance to bacterial wilt and late blight.

This study focuses on the synthesis of six novel thioether derivatives with potent antimicrobial activity against Ralstonia solanacearum, the causative agent of tobacco bacterial wilt. This disease, which has caused significant economic losses, has become increasingly resistant to traditional bactericides. In response, the study investigates the potential of thioether derivatives, known for their broad spectrum of biological activities, as eco-friendly alternatives. Through SEM observations, molecular docking, and DFT calculations, we identified DHFR as a potential target for these compounds, particularly highlighting compound R4, which showed superior activity compared to conventional controls. Additionally, toxicity predictions and ADME simulations suggest that compound R4 could be a promising, safe agricultural antimicrobial agent. This research aims to expand the range of agricultural chemical frameworks and contribute to the development of more effective and environmentally friendly solutions for pest and disease control.

Bacterial wilt is one of the most devastating soil borne disease of solanaceous crops particularly sweet pepper, chilli, tomato and brinjal in the tropics and subtropics. The present study was conducted to evaluate the best rootstock for sweet pepper variety California Wonder for bacterial wilt resistance under artificial inoculation and to assess growth, yield, quality and bacterial wilt resistance of sweet pepper grafts under field condition. Artificial inoculation of Ralstonia solanacearum was carried out by root dipping method. California Wonder grafted on Haritha rootstock found highly resistant to bacterial wilt but grafting parameters and mean performance of this graft was found poor. The graft combinations of sweet pepper on the rootstocks Capsicum chinense variety Vellayani Thejus and Capsicum annuum variety Ujwala were found superior for grafting parameters, flowering and yield parameters and were resistant to bacterial wilt under artificial inoculation and field condition. So, these rootstocks can be recommended in areas with higher bacterial wilt incidence as well as to get higher yield.

Bacterial wilt, caused by the soil-borne pathogen Ralstonia solanacearum is a major threat to solanaceous crops worldwide. The onset of this disease is frequently associated with disruptions in the rhizosphere microbial community. Quorum sensing (QS), a key mechanism for microbial communication, plays a critical role in regulating microbial interactions and maintaining community structure. However, whether and how QS is involved in reshaping the rhizosphere microbiome during R. Solanacearum infection remains poorly understood. In this study we compared QS-related genes, signaling pathways, and network structures in metagenomes of healthy and wilt-infected rhizospheres. The results show QS-related genes of the plant beneficial bacterial were significantly down-regulate, whereas QS-related genes of pathogenic R. Solanacearum were up-regulated in wilt-infected rhizosphere. The up-regulated QS genes of pathogens belong to eight QS signaling pathways (AI-1, GABA, PapR, NprX, Phr, cCF10, and DSF). Network analysis showed a simplified structure in the wilt-infected rhizosphere. It is also found the number of connectors in the QS gene co-occurrence network was reduced in wilt-infected rhizosphere network. This is due to the upregulation of QS system allows the pathogen to mediate the rhizosphere microbial ecology network, and leads to destabilization of rhizosphere community. These findings demonstrate that QS system contributes to bacterial wilt infection by suppressing the QS-based interactions among plant beneficial microbes, thereby triggering community function disruption.

Pathogenic stress causes severe cellular damage and leads to plant diseases. Hydrogen cyanide (HCN)-producing plant growth-promoting rhizobacteria (PGPR) may help to manage disease and significantly improve plant growth and physiological attributes in arid and semiarid environments. This study aimed to evaluate PGPRs against pathogen Ralstonia solanacearum (the real cause of bacterial wilt disease) as biocontrol agents and their role in improving tomato (Solanum lycopersicum) yield during 2023. Twenty PGPR strains were isolated from the root rhizosphere and assessed for plant growth-promoting traits i.e. indole-3-acetic acid (IAA), phosphate, potassium and zinc solubilization, as well as HCN and siderophore production. Seven PGPR strains were analyzed using 16S rRNA gene sequencing. The disc sensitivity technique was used to evaluate PGPRs against R. solanacearum under laboratory conditions with three replicates. Completely Randomized Design (CRD) was used to evaluate the PGPRs under greenhouse conditions with 3 replicates (5 plants per replicate). Pseudomonas aeruginosa was the most effective strain, inhibiting pathogen growth by 56% and reducing disease incidence. PGPR-treated tomato seedlings showed improvement in plant growth through increased plant height, root, shoot length and fruit production. HCN-producing PGPR (P. aeruginosa and Bacillus megaterium) enhanced plant immunity by increasing superoxide dismutase, peroxidase, and catalase enzyme levels. Mineral nutrition improved through enhanced solubilization of potassium, phosphorus and zinc under biotic stress. HCN-producing PGPRs enhance tomato yield by improving nutrient availability and inducing plant defense mechanisms. These findings highlight their potential as biocontrol agents for sustainable tomato production in arid and semiarid regions.

Plants are constantly exposed to a variety of biotic stresses in their natural environment and rely on their immune systems to adapt to these challenges. Pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) constitute two complementary layers of the plant innate immune system, both of which can be activated by immune elicitors. In this study, a pFRK1-GUS reporter system was employed to screen multiple natural product libraries, leading to the identification of the animal-derived neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) and its truncated form, PACAP 6-38, as potential plant immune elicitors. Exogenous application of PACAP and PACAP 6-38 triggered multiple PTI-associated immune responses, including cytosolic calcium influx, MAPK phosphorylation, and induction of FRK1 expression under the tested conditions, while notably failing to induce a detectable reactive oxygen species (ROS) burst. Moreover, pre-treatment with PACAP or PACAP 6-38 at the tested concentrations reduced bacterial titers of Pseudomonas syringae pv. tomato DC3000 by approximately 0.3-0.7 log units under single-application conditions. Notably, both peptides also enhanced plant resistance to Ralstonia solanacearum, indicating a broader role in bacterial disease resistance. Although the molecular receptors and downstream signaling components remain to be identified, this study establishes a proof-of-concept for cross-kingdom recognition of an animal neuropeptide by plants. Together, these findings highlight PACAP-induced immunity as being uncoupled from the canonical ROS burst, underscoring the conceptual novelty of animal-derived peptides as unconventional elicitors and providing a reference for potential future applications of PACAP in plants.

Bacterial wilt, caused by Ralstonia solanacearum, is a highly destructive disease that can reduce tomato yields by 80–90%. Chromolaena odorata and Azadirachta indica extracts are rich in phenolic compounds at contents of 339.16 and 261.95 mg GAE/g, respectively, and notably contain prominent levels of chlorogenic acid (5.64–14.44 mg/g) and rutin (15.16–20.45 mg/g). These extracts effectively inhibited R. solanacearum, each with a MIC of 10 mg/mL. The extract combination exhibited an additive antibacterial effect, with a combined FIC index of 1.5. Greenhouse experiments using a combination of A. indica and C. odorata extracts after bacterial inoculation achieved the highest control efficacy of 66.4%, giving an effectiveness comparable to the Physan bactericide. Moreover, tomatoes treated with the phenolic-rich extracts exhibited improved growth, highlighting their potential as a natural and effective alternative to conventional chemical agents.

Structural basis of dinucleotide substrate recognition and catalysis by the Nudix effector RipN from Ralstonia solanacearum.

The phytopathogen Ralstonia solanacearum is responsible for the "bacterial wilt disease" in several crop species worldwide, viz., tomato, brinjal, chilli, potato, groundnut, etc. This results in the yellowing of host plants, wilting, and finally their death. Motility is an essential requirement of plant pathogens, which helps them to infect and navigate through the host tissues and spread inside the host plant. The phytopathogen R. solanacearum exhibits motility such as twitching and swimming, which are governed by pili and flagella, respectively. This study aims to delineate the role of pili and flagella encoding genes, such as pilY_1, fliP, and fliG, by recognising the genes and their associated pathways. Disruption of these genes led to the creation of three motility mutants of the R. solanacearum F1C1 strain. Motility assays showed that the ΔfliP and ΔfliG mutants were significantly altered in terms of swimming ability. Further, transcriptomic analysis identified the differentially expressed genes in the respective altered mutants.

The Ralstonia solanacearum species complex (RSSC) is a major soil-borne pathogen of solanaceous crops. During a field experiment originally designed to monitor rhizosphere and episphere microbiomes in two pepper cultivars, a naturally emerging and asymptomatic Ralstonia dominance event was detected in the rhizosphere without visible wilt symptoms. This unexpected occurrence provided an opportunity to characterize asymptomatic RSSC dynamics and their microbial interactions under field conditions. Full-length 16S rRNA amplicon sequencing showed that one ASV (Sq_1) was nearly absent from the episphere but increased sharply in the rhizosphere from week 3 onward, dominating 20–80% of samples during weeks 7–10. Phylogenetic comparison with 93 historical Korean RSSC isolates placed Sq_1 within a 16S-defined lineage corresponding to pepper-associated R. pseudosolanacearum biovars 3 and 4. Sq_1 abundance accounted for a large portion of β-diversity turnover in the rhizosphere. After within-plot correlations were meta-analyzed, selected taxa were evaluated using a Bayesian pairwise compositional Lotka–Volterra (pcLV) model, which identified three taxa (Sq_272, TRA3-20; Sq_178, Bradyrhizobium; and Sq_124, Bryobacter) that consistently exerted inhibitory effects on Sq_1 per-interval growth. Supported by the longitudinal design and the high accuracy of PacBio full-length 16S sequencing, these findings highlight potential microbial suppressors of RSSC and demonstrate the utility of pcLV modeling for resolving directional interactions at the ASV level.

ABSTRACTRalstonia solanacearum (RS) is a soil‐borne phytopathogen responsible for bacterial wilt disease on a wide range of crops worldwide. Bacteriophage biocontrol is a promising sustainable RS management method. However, more work is needed to design methods to store, ship and apply phage that are effective, scalable and environmentally friendly. Here, we investigate the use of wood hemicellulose excipients—glucuronoxylans (GX) and galactoglucomannans (GGM) – to encapsulate phage PYO4, which can infect the pandemic RS strain UW551. Yield and preservation efficiencies of GX and GGM were compared to the conventional excipient maltodextrin (MD). Encapsulation via spray drying was carried out at two inlet/outlet temperatures, and the resulting powders were stored at room temperature or at 4°C. Phage titers were measured after spray drying, and then weekly for 25 weeks. GX yielded the highest titre of encapsulated phage and preserved phage survival effectively at 4°C. Phages encapsulated with MD had the highest stability at room temperature. GGM had poor results, with low survival after spray drying and low long‐term stability at either temperature. In vitro experiments demonstrated that encapsulated phages inhibited RS as efficiently as unencapsulated phage. Phage encapsulated in GX and MD also reduced bacterial wilt symptoms on tomato. At low MOIs, phage encapsulated in GX and MD reduced symptoms more than unencapsulated phage, suggesting the excipients themselves could be affecting RS. We found that GX alone could inhibit RS growth in vitro and reduce disease progression in planta without phage. MD alone couldn't significantly reduce bacterial wilt symptoms or inhibit RS growth in vitro. Together, these results show that the encapsulation of phages in hemicelluloses has great promise for efficient biocontrol methods to combat plant pathogens. Not only are hemicelluloses effective in phage preservation, but also have potential to enhance the biocontrol efficacy of phages through their antimicrobial activities.

Abstract Bacterial wilt caused by Ralstonia solanacearum is a major threat to global tomato production. Two field trials were conducted in 2023 (wet season) and 2024 (dry season) at the Federal University of Kashere, Gombe State, to evaluate the use of neem leaf powder in the management of bacterial wilt of tomato. The experiment was conducted using a randomized complete block design with three replications. Neem leaf powder ( Azadirachta indica ) was applied to two tomato cultivars, ‘Tandino’ and ‘Dan Syria’, at 15, 30, and 45 g, while untreated (0 g) and streptomycin-treated plots served as negative and positive controls, respectively. Application of streptomycin and 45 g of neem leaf powder 9 weeks after transplanting showed population densities of 1.5 and 1.4 total cfu·g −1 soil (2023) and 1.4 and 1.0 cfu·g −1 soil (2024), which were significantly lower than the population densities of 8.6 (2023) and 8.0 (2024) cfu·g −1 soil recorded in untreated plots. After application of streptomycin and 45 g of neem leaf powder, wilt severity scores of 0.7 and 1.3 (wet season) and 0.7 and 1.0 (dry season) were observed, which was significantly lower than 5.0 in each season in untreated plots. Application of 45 g neem leaf powder resulted in a yield of 432.4 and 437.4 g of fruit per plant, which was significantly higher than the 2.8 and 2.4 g on untreated plots in 2023 and 2024, respectively. It was found that application of 45 g of neem leaf powder can reduce the severity of bacterial wilt in tomatoes and thus increase fruit yield.

Induced systemic resistance (ISR) is an essential strategy in biological control. Previous research has shown that Bacillus cereus AR156 can trigger ISR to defend against multiple pathogens, though the underlying mechanisms may vary depending on the pathogen. However, the specific mechanism by which AR156 induces systemic resistance against Ralstonia solanacearum in tomatoes remains unclear. In this study, we focused on WRKY group I transcription factors and identified WRKY4, which is downregulated by AR156 induction. Further analysis confirmed that WRKY4 functions as a negative regulator in AR156-ISR against tomato bacterial wilt. Experimental results demonstrated that WRKY4 is localized in the nucleus and exhibits transcriptional regulatory activity. Subsequent screening revealed that WRKY4 directly targets the promoter region of the SSL3 (Strictosidine Synthase-Like) gene, which encodes a key synthase for metabolic precursors, and consequently suppresses its expression. Finally, we confirmed that WRKY4 negatively regulates SSL3 expression, contributing to AR156-ISR against tomato bacterial wilt as a key negative regulator. Our research enriches our understanding of the ISR network and provides a theoretical foundation for the biological control of diseases. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 "No Rights Reserved" license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2026.

Bacterial wilt, caused by Ralstonia solanacearum, is a devastating disease that limits global tobacco production. To decipher the molecular basis of resistance, we conducted an integrated multiomics analysis of a susceptible cultivar, Honghua Dajinyuan (HD), and a moderately resistant cultivar, Yanyan 97 (YY), leveraging LC‒MS-based metabolomics and RNA-seq transcriptomics. The resistant YY cultivar exhibited coordinated multitiered defense, characterized by the accumulation of resistance-related metabolites (e.g., prenol lipids and organooxygen compounds) and the enrichment of plant hormone signaling pathways. Transcriptomic analysis revealed 818 differentially expressed genes (DEGs) involved in cell wall modification and stress responses. Crucially, the integration of weighted gene coexpression network analysis (WGCNA) with prior QTL mapping pinpointed Nta17g05760 within the qBWR17b locus as a core candidate gene. Our study systematically elucidates a defense network involving hormone signaling, cell wall reinforcement, and antimicrobial synthesis and provides a key candidate gene and theoretical foundation for the molecular breeding of wilt-resistant tobacco.

Ralstonia solanacearum species complex (RSSC) pathogens cause destructive plant wilt diseases of a wide variety of crops, leading to significant agricultural losses worldwide. These bacteria rapidly spread through the water-transporting xylem where they grow prolifically and produce abundant biofilm that clogs xylem vessels. To understand RSSC biofilm behavior in planta, we examined their complex fluid mechanics. Rheological analyses revealed that unlike all previously analyzed microbial biofilms, RSSC biofilms are shear-thinning, viscoelastic fluids at physiologically relevant shear forces. To determine which factors confer these unique mechanics, we analyzed biofilms of bacterial mutants with altered biofilm components. Genetic analysis demonstrated that development of the viscous-dominant biofilms required production of EPS-I, an amphiphilic exopolysaccharide that is a major virulence factor for all RSSC pathogens. We show that EPS-I confers "biofilm mobility", which allows wild-type RSSC colonies to passively expand when deformed. Despite its high metabolic cost, bioassays demonstrated that EPS-I production conferred a net fitness benefit where biofilm mobility allowed the pathogen to spread and access more nutrients in complex environments like xylem vessels. The RSSC are a monophyletic lineage of aggressive plant wilt pathogens, and our evolutionary hypothesis testing suggests the origin of the eps biosynthetic gene cluster coincides with the emergence of wilt pathogenesis in the RSSC ancestor. Furthermore, comparative physiological assays demonstrated that biofilm mobility is unique to the RSSC within the genus Ralstonia. In summary, EPS-I production is a key evolutionary innovation that enables RSSC dispersal and virulence by conferring unique biofilm mechanics.