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Peanut (Arachis hypogea L.) bacterial wilt (BW) is a devastating disease caused by Ralstonia solanacearum that results in severe yield and quality losses. Plant defensins are short cysteine-rich peptides with antimicrobial activity. The role of defensin genes (AhDef) in peanut is unclear. A genome-wide investigation of AhDef genes was undertaken, and 12 identified AhDef genes were classified into two groups containing the gamma-thionin domain formed by four disulfide pairs: Cys1-Cys8, Cys2-Cys5, Cys3-Cys6, and Cys4-Cys7. In silico analysis revealed that AhDef genes showed highly conserved architectural features and contained cis-elements associated with phytohormone signaling and defense responses. A highly resistant cultivar, H108 (R) and a susceptible accession, H107 (S) were tested by R. solanacearum inoculation. H108 (R) showed fewer symptoms than H107 (S) owing to inhibition of bacterial reproduction and spread in the vascular bundles of roots and stems. In a transcriptomic expression profile, AhDef genes, particularly AhDef1.6 and AhDef2.2, were up-regulated in H108 (R) compared with H107 (S) under R. solanacearum infection and phytohormone treatment. Subcellular localization showed that the AhDef1.6 and AhDef2.2 proteins were both expressed specifically on the plasma membrane. Overexpression of protein fusion AhDef2.2-YFP in Nicotiana benthamiana and peanut leaves increased resistance to R. solanacearum, suggesting its role in response to BW infection. AhDef2.2 may be valuable for peanut resistance breeding.

Potato plants and their tubers in Egypt are affected by one of the most renowned soil-borne pathogen, Ralstonia solanacearum, that caused brown rot in potato tubers and wilt in plants. There is no efficient therapeutic bactericide so; control of bacterial wilt is very rough. The study investigated three different concentrations of seven essential plant oils under in vitro and in vivo conditions as a result of their effects on Ralstonia solanacearum growth and their possibility use as potato seed pieces dressing for controlling bacterial wilt disease incidence. In vitro, anise oil at the three tested different concentrations (0.04, 0.07, and 0.14% vol/vol) was the most effective one inhibiting the growth of T4 and W9 isolates of Ralstonia solanacearum then pursued by thyme, lemongrass, and clove oils. On the other hand, rocket oil at the tested concentration was the least effective one followed by fennel oil. However, wheat germ oil was not completely effective. In vivo, experiment revealed that anise oil at the three concentrations significantly reduced disease incidence and severity in sponta and hermes potato cultivars and their effect was associated with increase of peroxidase, polyphenoloxidase, phenols and the foliar fresh weight of treated plants as well as the weight of tubers/plant followed by thyme and lemongrass oils compared to the infected untreated control. Morphological differences in bacterial cell structure have been observed using a transmission electron microscope (TEM). Anise oil at higher concentration caused of cell wall rupture and degraded cellular components.

Bacterial wilt is one of the main diseases of Solanum spp., which caused by Ralstonia solanacearum (RS), formerly known as Pseudomonas solanacearum. Different concentrations of chitosan nanoparticles have been evaluated as one of the alternative methods of disease management in vitro and in vivo to reduce the risks of pesticide residues. Results in vitro experiment indicated that RS5 isolate was the most virulence one compared to RS1 and RS3. Increasing concentration of nano-chitosan, lead to increase inhibition zone, and this was observed at higher concentrations (100 and 200 µg/ml). In vivo results showed the highest concentration of spraying chitosan nanoparticles increase percentage reduction of disease incidence and severity, in effected potato and tomato plants. Recorded data of disease incidence and severity in treated potato plants were 78.93 % and 71.85 %, while on tomato plants were 81.64 % and 77.63 %, respectively compared to untreated infected potato plants were recorded 15.38 %, 20.87 %, and tomato plants were 20.98 % and 28.64 %. Results also revealed that 100 µg/ml of chitosan nanoparticles the lowest treatments used as soil amended curative treatments led to incease percentage reduction of disease incidence and severity, respectively on potato and tomato plants, but less than preventive treatment. The results registered that on potato plant were 54.93 % and 52.65 %, whilst recorded on tomato plants were 59.93 % and 56.74 %. Transmission electron microscopy (TEM) micrpgraphs illustrated that morphological of healthy R. solanacearum cells were undesirably stained with uranyl. The electron-dense uranyl acetate dye was limited to the cell surface slightly than the cytoplasm, which designated the integrity of the cell film of healthy cells. While bacterial cells treated with nano-chitosan, showed modification in the external shape, such as lysis of the cell wall and loss of cell flagella. Also, the result of using Random amplified polymorphic DNA (RAPD)-PCR observed that differences in treated Ralstonia solanancearum genotype by nano-chitosan compared to the genotype of the same untreated isolate.

Blood disease in bananas caused by Ralstonia syzygii subsp. celebesensis is a bacterial wilt disease that causes major yield losses of banana in Indonesia and peninsular Malaysia. The disease has significantly increased its geographic distribution in the past decade. Diagnostic methods are an important component of disease management in vegetatively propagated crops such as banana to constrain incursions of plant pathogens. Therefore, the objectives of this study were (i) to design and rigorously validate a novel banana Blood disease (BBD) real-time PCR assay with a high level of specificity and sensitivity of detection and (ii) to validate published PCR-based diagnostic methods targeting the intergenic region in the megaplasmid (“121 assay” with primer set 121) or the phage tail protein-coding sequence in the bacterial chromosome (“Kubota assay” and “BDB2400 assay” with primer set BDB2400). Assay validation included 339 samples (174 Blood disease bacteria, 51 bacteria associated with banana plants, 51 members of the Ralstonia solanacearum species complex, and 63 samples from symptomatic and healthy plant material). Validation parameters were analytical specificity (inclusivity and exclusivity), selectivity, limit of detection, accuracy, and ruggedness. The 121 assay and our newly developed BBD real-time PCR assay detected all R. syzygii subsp. celebesensis strains with no cross-specificity during validation. Two different PCR assays using the primer set BDB2400 lacked specificity and selectivity. This study reveals that our novel BBD real-time PCR assay and the conventional PCR 121 assay are reliable methods for Blood disease diagnostics, as they comply with all tested validation parameters.

Bacterial wilt, caused by Ralstonia solanacearum, is a serious disease in pepper. However, the interaction between the pathogen and pepper remains largely unknown. This study aimed to gain insights into determinants of pepper susceptibility and R. solanacearum pathogenesis. We assembled the complete genome of R. solanacearum strain Rs-SY1 and identified 5,106 predicted genes, including 84 type III effectors (T3E). RNA-seq was used to identify differentially expressed genes (DEGs) in susceptible pepper CM334 at 1 and 5 days postinoculation (dpi) with R. solanacearum. Dual RNA-seq was used to simultaneously capture transcriptome changes in the host and pathogen at 3 and 7 dpi. A total of 1,400, 3,335, 2,878, and 4,484 DEGs of pepper (PDEGs) were identified in the CM334 hypocotyls at 1, 3, 5, and 7 dpi, respectively. Functional enrichment of the PDEGs suggests that inducing ethylene production, suppression of photosynthesis, downregulation of polysaccharide metabolism, and weakening of cell wall defenses may contribute to successful infection by R. solanacearum. When comparing in planta and nutrient agar growth of the R. solanacearum, 218 and 1,042 DEGs of R. solanacearum (RDEGs) were detected at 3 and 7 dpi, respectively. Additional analysis of the RDEGs suggested that enhanced starch and sucrose metabolism, and upregulation of virulence factors may promote R. solanacearum colonization. Strikingly, 26 R. solanacearum genes were found to have similar DEG patterns during a variety of host–R. solanacearum interactions. This study provides a foundation for a better understanding of the transcriptional changes during pepper–R. solanacearum interactions and will aid in the discovery of potential susceptibility and virulence factors.

Ralstonia causes wilt diseases by colonizing xylem vessels and disrupting water transport. The dogma is that bacterial biomass clogs vessels and reduces the flow of xylem sap due to Ralstonia abundance. However, the physiological mechanism of xylem disruption during bacterial wilt is untested. Using a tomato and Ralstonia pseudosolanacearum GMI1000 model, we visualized and quantified spatiotemporal dynamics of xylem disruption during bacterial wilt. First, we measured stomatal conductance of leaflets on mock-inoculated and wilt-symptomatic plants. Wilted leaflets had reduced stomatal conductance, as did turgid leaflets on the same petiole as wilted leaflets. Next, we used X-ray microcomputed tomography (X-ray microCT) and light microscopy to differentiate between mechanisms of xylem disruption: blockage by bacterial biomass, blockage by vascular tyloses, or sap displacement by gas embolisms. We imaged intact plant stems to quantify embolized vessels. Embolized vessels were rare, but infected plants with low bacterial populations had a nonsignificant trend of more vessel embolisms. To test whether vessels are clogged during bacterial wilt, we imaged excised stems after brief dehydration. Most vessels in mock-infected plants emptied their contents after excision, but nonconductive clogged vessels were abundant in infected plants by 2 days post infection. At wilt onset, when bacterial populations exceeded 5 × 108CFU/g stem tissue, approximately half of the vessels were clogged with electron-dense bacterial biomass. We found no evidence of tyloses in X-ray microCT reconstructions or from light microscopy of preserved stems. Therefore, bacterial blockage of vessels appears to be the principal cause of xylem disruption during Ralstonia wilt.[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, 2022.

Made available in DSpace on 2022-04-28T19:49:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 Survival niches for phytopathogenic bacteria are important for disease management. We study the survival of Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), the causal agent of bacterial wilt in common bean and bacterial tan spot in soybean, in the soil. While Cff strains from common bean already have several studies, the ecology of soybean strains needs more information. We used the strain Feij.2628A from common bean, and CffR1, Cff2R, and Cff4R from soybean. The soils were infested with bacterial suspension (107 CFU.mL−1) from each of the strains. For experiments under laboratory conditions, they were incubated in BOD incubator (biochemical oxygen demand) at 20 °C. Under natural field conditions, pots were maintained in the field without supplementary irrigation. The survival of Cff strains was evaluated every seven days until they were not detected. The identity of the bacterium was confirmed in all treatments by PCR. Under laboratory conditions, the survival period of Feij.2628A ranged from 140 to 154 days, and between 77 to 119 days for the soybean strains. Feij.2628A and Cff1R survived for a maximum of 91 days in soil with higher clay content, under natural field conditions. Cff survival was negatively influenced by high temperatures, low soil moisture, and precipitation in some treatments. These results demonstrated the potential survival of Cff strains from common bean and soybean in the soil, being potential inoculum sources for subsequent cultivations of these crops. Fallow periods ranging from three to four months may reduce the amount of inoculum in soils under these conditions. Department of Plant Protection School of Agriculture São Paulo State University (Unesp), Avenida Universitária Department of Plant Protection School of Agriculture São Paulo State University (Unesp), Avenida Universitária

Tomato (Solanum lycopersicum L.) is one of the most important vegetables in Togo. Unfortunately, tomato is susceptible to many diseases, among which bacterial wilt caused by Ralstonia solanacearum causes major yield losses. In this study, incidence of bacterial wilt and its distribution was evaluated in the central region of Togo, the major tomato-producing area in the country. Overall, 16 localities were surveyed in four prefectures. In each locality, three fields were visited, the incidence of the disease was recorded, and diseased samples were collected for laboratory investigation. The results showed that bacterial wilt occurred in all of the fields visited, indicating a field incidence of 100%, whereas the plant incidence ranged from 10.00 ± 00 to 43.33 ± 3.33%, with an average of 20.94 ± 1.77%. The antibody-based ImmunoStrip test was positive for R. solanacearum in 100% of the visited fields. From 144 samples collected from fields, 45 R. solanacearum isolates were isolated on modified selective medium from South Africa. These survey results show that tomato bacterial wilt is a real threat to tomato production in the central region of Togo.

Bacterial pathogens in the Ralstonia solanacearum species complex (RSSC) infect the water-transporting xylem vessels of plants, causing bacterial wilt disease. Strains in RSSC phylotypes I and III can reduce nitrate to dinitrogen via complete denitrification. The four-step denitrification pathway enables bacteria to use inorganic nitrogen species as terminal electron acceptors, supporting their growth in oxygen-limited environments such as biofilms or plant xylem. Reduction of nitrate, nitrite, and nitric oxide all contribute to the virulence of a model phylotype I strain. However, little is known about the physiological role of the last denitrification step, the reduction of nitrous oxide to dinitrogen by NosZ. We found that phylotypes I and III need NosZ for full virulence. However, strains in phylotypes II and IV are highly virulent despite lacking NosZ. The ability to respire by reducing nitrate to nitrous oxide does not greatly enhance the growth of phylotype II and IV strains. These partial denitrifying strains reach high cell densities during plant infection and cause typical wilt disease. However, unlike phylotype I and III strains, partial denitrifiers cannot grow well under anaerobic conditions or form thick biofilms in culture or in tomato xylem vessels. Furthermore, aerotaxis assays show that strains from different phylotypes have different oxygen and nitrate preferences. Together, these results indicate that the RSSC contains two subgroups that occupy the same habitat but have evolved divergent energy metabolism strategies to exploit distinct metabolic niches in the xylem. IMPORTANCE Plant-pathogenic Ralstonia spp. are a heterogeneous globally distributed group of bacteria that colonize plant xylem vessels. Ralstonia cells multiply rapidly in plants and obstruct water transport, causing fatal wilting and serious economic losses of many key food security crops. The virulence of these pathogens depends on their ability to grow to high cell densities in the low-oxygen xylem environment. Plant-pathogenic Ralstonia can use denitrifying respiration to generate ATP. The last denitrification step, nitrous oxide reduction by NosZ, contributes to energy production and virulence for only one of the three phytopathogenic Ralstonia species. These complete denitrifiers form thicker biofilms in culture and in tomato xylem, suggesting they are better adapted to hypoxic niches. Strains with partial denitrification physiology form less biofilm and are more often planktonic. They are nonetheless highly virulent. Thus, these closely related bacteria have adapted their core metabolic functions to exploit distinct microniches in the same habitat.

Here, we present the complete genome sequence and annotation of Ralstonia syzygii subsp. indonesiensis strain LLRS-1, which caused bacterial wilt on flue-cured tobacco in Yunnan Province, southwest China. Strain LLRS-1 is the first R. syzygii strain identified to be pathogenic to tobacco in China. The completely assembled genome of strain LLRS-1 consists of a 3,648,314-bp circular chromosome and a 2,046,405-bp megaplasmid with 5,190 protein-coding genes, 55 transfer RNAs, 28 small RNAs, 3 structural RNAs (5S, 16S, and 23S), and a G+C content of 67.05%.

Erwinia tracheiphila, the causal pathogen of bacterial wilt of cucurbit crops, is disseminated by cucumber beetles. A bacteriophage, designated FBB1 (Fu-Beattie-Beetle-1), was isolated from spotted cucumber beetles (Diabrotica undecimpunctata) that were collected from a field in which E. tracheiphila is endemic. FBB1 was classified into the Myoviridae family based on its morphology, which includes an elongated icosahedral head (106 × 82 nm) and a putatively contractile tail (120 nm). FBB1 infected all 62 E. tracheiphila strains examined and three Pantoea spp. strains. FBB1 virions were stable at 55°C for 1 h and tolerated a pH range from 3 to 12. FBB1 has a genome of 175,994 bp with 316 predicted coding sequences and a GC content of 36.5%. The genome contains genes for a major bacterial outer-membrane protein, a putative exopolysaccharide depolymerase, and 22 predicted transfer RNAs. The morphology and genome indicate that FBB1 is a T4-like virus and thus in the Tevenvirinae subfamily. FBB1 is the first virulent phage of E. tracheiphila to be reported and, to date, is one of only two bacteriophages to be isolated from insect vectors of phytopathogens. Collectively, the results support FBB1 as a promising candidate for biocontrol of E. tracheiphila based on its virulent (lytic) rather than lysogenic lifestyle, its infection of all E. tracheiphila strains examined to date, and its infection of a few nonpathogenic bacteria that could be used to support phage populations when pathogen numbers are low.

Bacterial wilt caused by Ralstonia solanacearum is a serious soilborne disease that results in severe losses to tobacco (Nicotiana tabacum) production in China. In this study, a novel RPA-LFD assay for the rapid visual detection of R. solanacearum was established using recombinase polymerase amplification (RPA) and lateral-flow dipstick (LFD). The RPA-LFD assay was performed at 37°C in 30 min without complex equipment. Targeting the sequence of the RipTALI-9 gene, we designed RPA primers (Rs-rpa-F/R) and an LF probe (Rs-LF-probe) that showed high specificity to R. solanacearum. The sensitivity of RPA-LFD assay to R. solanacearum was the same as that in conventional PCR at 1 pg genomic DNA, 103 CFU/g artificially inoculated tobacco stems, and 104 CFU/g artificially inoculated soil. The RPA-LFD assay could also detect R. solanacearum from plant and soil samples collected from naturally infested tobacco fields. These results suggest that the RPA-LFD assay developed in this study is a rapid, accurate molecular diagnostic tool with high sensitivity for the detection of R. solanacearum.

Strains of Erwinia tracheiphila, causal agent of bacterial wilt of cucurbits, are divided into distinct clades. Et-melo clade strains wilt Cucumis spp. but not Cucurbita spp., thus exhibiting host specificity, whereas Et-C1 clade strains wilt Cucurbita spp. more rapidly than Cucumis melo, thus exhibiting a host preference. This study investigated the contribution of the effector proteins Eop1 and DspE to E. tracheiphila pathogenicity and host adaptation. Loss of eop1 did not enable Et-melo strains to infect squash (Cucurbita pepo) or an Et-C1 strain to induce a more rapid wilt of muskmelon (Cucumis melo), indicating that Eop1 did not function in host specificity or preference as in the related pathogen E. amylovora. However, overexpression of eop1 from Et-melo strain MDCuke but not from Et-C1 strain BHKY increased the virulence of a BHKY eop1 deletion mutant on muskmelon, demonstrating that the Eop1 variants in the two clades are distinct in their virulence functions. Loss of dspE from Et-melo strains reduced but did not eliminate virulence on hosts muskmelon and cucumber, whereas loss of dspE from an Et-C1 strain eliminated pathogenicity on hosts squash, muskmelon, and cucumber. Thus, the centrality of DspE to virulence differs in the two clades. Et-melo mutants lacking the chaperone DspF exhibited similar virulence to mutants lacking DspE, indicating that DspF is the sole chaperone for DspE in E. tracheiphila, unlike in E. amylovora. Collectively, these results provide the first functional evaluation of effectors in E. tracheiphila and demonstrate clade-specific differences in the roles of Eop1 and DspE. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

Ralstonia solanacearum species complex (RSSC) contains a group of destructive plant pathogenic bacteria, causing bacterial wilt of >200 species of crops and trees, such as Casuarina equisetifolia, worldwide. RSSC can survive in the soil environment for a long time and start infection after activation by host plants. This study conducted a transcriptome analysis on the expression pattern of the pathogenicity-related genes of a new isolated RSSC strain YQ (Ralstonia pseudosolanacearum phylotype I-16) in response to C. equisetifolia cladophyll (a branch of a stem that resembles and functions as a leaf) and root debris under in vitro culture. The cladophyll debris induced more genes up-regulated than the root debris, including pathogenicity-related genes involved in motility, effectors, type III secretion systems, quorum sensing, and plant cell wall degradation. Besides, many differentially expressed genes were related to transcriptional regulator such as cyclic dimeric guanosine monophosphate. Moreover, the cultures with cladophyll debris induced a faster wilting in bioassays, and the cell swimming was enhanced by cladophyll exudate. C. equisetifolia cladophylls could activate the expression of pathogenicity-related genes of strain YQ and accelerate infection. Our findings suggest that litterfall management in C. equisetifolia forests, or even other plantations, should receive attention to prevent the induction of bacterial wilt disease caused by RSSC.

WIPK-NtLTP4 module improves the resistance to R. solanacearum via upregulating the expression of defense-related genes, increasing the antioxidant enzyme activity, and promoting stomatal closure in tobacco. Lipid transfer proteins (LTPs) are a class of small lipid binding proteins that play important roles in biotic and abiotic stresses. The previous study revealed that NtLTP4 positively regulates salt and drought stresses in Nicotiana tabacum. However, the role of NtLTP4 in biotic stress, especially regarding its function in disease resistance remains unclear. Here, the critical role of NtLTP4 in regulating resistance to Ralstonia solanacearum (R. solanacearum), a causal agent of bacterial wilt disease in tobacco, was reported. The NtLTP4-overexpressing lines markedly improved the resistance to R. solanacearum by upregulating the expression of defense-related genes, increasing the antioxidant enzyme activity, and promoting stomatal closure. Moreover, NtLTP4 interacted with wound-induced protein kinase (WIPK; a homolog of MAPK3 in tobacco) and acted in a genetically epistatic manner to WIPK in planta. WIPK could directly phosphorylate NtLTP4 to positively regulate its protein abundance. Taken together, these results broaden the knowledge about the functions of the WIPK-NtLTP4 module in disease resistance and may provide valuable information for improving tobacco plant tolerance to R. solanacearum.

Banana Xanthomonas Wilt (BXW), caused by Xanthomonas campestris pv. musacearum (Xcm), a devastating disease, causes up to 100% loss and affects all banana varieties. The disease is widespread in East and Central Africa region. Study objective was to evaluate the performance of single stem rouging options for rehabilitation of severely affected banana orchard. Five single stem rouging options were implemented in banana orchard with 80% BXW severity in Western Kenya. The options included rouging of infected banana plants; uprooting, cutting at the base, injecting 20 ml of glyphosate herbicide at the soil base of the pseudostem, uprooting the whole stool and control leaving the infected stools. Initial visual assesment before implementation of the orchard was over 80% infection. Later samples were collected for diagnosis of ten plants per treatment from different plant parts and were subjected to ELISA and PCR procedures for confirmion of the presence of Xcm. Rouging options was implemented for one year. During and after experimentation periodic visual assesment of BXW incidence and severity reduced. Results of ELISA assays and PCR results indicated Xanthomonas was present on banana plants. Rouging the infected banana stems by cutting at the base, uprooting and injection of herbicide reduced BXW incidence within six months. Xanthomonas, an inhibiting bacteria cannot surve without host and by killing the banana plant the Xanthomonas dies. Yields were recovered from the rehabilitated orchard within one year. Banana orchard highly infected with BXW was effectively rehabilitated.

Aims: To determine the phytochemical composition and antibacterial activity of Solanum incanum fruits against Ralstonia solanacearum. Study Design: Experimental design involving completely randomized design Place and Duration of Study: The study was conducted at department of Chemistry and Biochemistry, School of Sciences and Aerospace studies, Moi University, Kenya, between January and June 2021. Methodology: Extraction was done by maceration using ethanol as the extracting solvent. Phytochemical screening was done following standard procedures. Total Phenolic Content (TPC) and Total Flavonoid Content (TFC) were determined using the Folin–Ciocalteu colorimetric method and aluminum chloride colorimetric assay respectively. The extract was further analyzed using Gas Chromatography Mass spectroscopy (GC-MS) and Fourier transformed Infrared (FT-IR). In vitro antibacterial activity was determined using disc diffusion method while in vivo studies was done under greenhouse conditions. Results: Phytochemical analysis showed presence of alkaloids, glycosides, steroids, tannins, flavonoids, phenols, saponins and terpenoids. The TPC and TFC were found to be 84.997 ± 0.2 mg GAE/g and 20.535 ± 0.2 mg/g QE of dried sample respectively. GC-MS analysis revealed the presence of 15 compounds, (9E)-1-Methoxy-9-Octadecene (26.85%), 9-Octadecenamide (Z) (21.43%), E-15-Heptadecenal (7.28%), E-14-Hexadecenal (6.28%), 2,4-Di-tert-butylphenol (4.96%) among others. FT-IR analysis revealed presence of OH, C-H, N-H, CO functional groups at wavenumbers 3348 cm-1, 2931 cm-1, 1589 cm-1, and 1218 cm-1 respectively. The antibacterial activity for in vitro studies at concentrations 0.01, 0.05, 0.10, and 0.15 g/10 mL, the diameters of zone of inhibition were 20.75 ± 1.3, 25.75 ± 0.5, 27.25 ± 0.5, and 30.75 ± 0.5 mm respectively. This was comparable (P= .02) to that of ampicillin (positive control) which had zones of inhibition of 26.75 ± 0.5, 28.75 ± 0.5, 31.75 ± 0.4, and 35.00 ± 0.0 mm at the concentrations respectively. For the in vivo studies the plant extract and ampicillin delayed the development of the disease by eight and ten days post-inoculation respectively while symptoms of bacterial wilt for water treatment (negative control) were observed four days post-inoculation. Conclusion: The plant extract had remarkable antibacterial activity and can be used to make viable formulations to control the devastating bacterial wilt disease.

Blood disease in bananas caused by Ralstonia syzygii subsp. celebesensis is a bacterial wilt causing significant crop losses in Indonesia and Malaysia. Disease symptoms include wilting of the plant and red-brown vascular staining, internal rot, and discoloration of green banana fruit. There is no known varietal resistance to this disease in the Musa genus, although variation in susceptibility has been observed, with the popular Indonesian cooking banana variety Kepok being highly susceptible. This study established the current geographic distribution of Blood disease in Indonesia and confirmed the pathogenicity of isolates by Koch’s postulates. The long-distance distribution of the disease followed an arbitrary pattern indicative of human-assisted movement of infected banana materials. In contrast, local or short-distance spread radiated from a single infection source, indicative of dispersal by insects and possibly contaminated tools, water, or soil. The rapid expansion of its geographical range makes Blood disease an emerging threat to banana production in Southeast Asia and beyond.

Despite the substantial economic impact of Curtobacterium flaccumfaciens pv. flaccumfaciens on legume production worldwide, the genetic basis of its pathogenicity and potential host association is poorly understood. The production of high-quality reference genome assemblies of C. flaccumfaciens pv. flaccumfaciens strains associated with different hosts sheds light on the genetic basis of its pathogenic variability and host association. Moreover, the study of recent outbreaks of bacterial wilt and microevolution of the pathogen in Australia requires access to high-quality reference genomes that are sufficiently closely related to the population being studied within Australia. We provide the first genome assemblies of C. flaccumfaciens pv. flaccumfaciens strains associated with mungbean and soybean, which revealed high variability in their plasmid composition. The analysis of C. flaccumfaciens pv. flaccumfaciens genomes revealed an extensive suite of carbohydrate-active enzymes potentially associated with pathogenicity, including four carbohydrate esterases, 50 glycoside hydrolases, 23 glycosyl transferases, and a polysaccharide lyase. We also identified 11 serine peptidases, three of which were located within a linear plasmid, pCff119. These high-quality assemblies and annotations will provide a foundation for population genomics studies of C. flaccumfaciens pv. flaccumfaciens in Australia and for answering fundamental questions regarding pathogenicity factors and adaptation of C. flaccumfaciens pv. flaccumfaciens to various hosts worldwide and, at a broader scale, contribute to unraveling genomic features of gram-positive, xylem-inhabiting bacterial pathogens. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

We share whole genome sequences of six strains from the Ralstonia solanacearum species complex, a diverse group of Betaproteobacteria that cause plant vascular wilt diseases. Using single-molecule real-time technology, we sequenced and assembled full genomes of Rs5 and UW700, two phylotype IA-sequevar 7 (IIA-7) strains from the southeastern United States that are closely related to the R. solanacearum species type strain, K60, but were isolated >50 years later. Four sequenced strains from Africa include a soil isolate from Nigeria (UW386, III-23), a tomato isolate from Senegal (UW763, I-14), and two potato isolates from the Madagascar highlands (RUN2474, III-19 and RUN2279, III-60). This resource will support studies of the genetic diversity, ecology, virulence, and microevolution of this globally distributed group of high-impact plant pathogens. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Thirteen-tomato genotypes were assembled from the USA, Taiwan and Ghana for screening for bacterial wilt resistance in two environments: in a screen house at Crops Research Institute, Kumasi, Ghana and in the field at a bacterial wilt hot spot at Bechem in the Brong-Ahafo region of Ghana. The bacterium, Ralstonia solanacearum was isolated using the serial dilution method on Nutrient Agar (NA) and aseptically cultured for inoculation. The bacterium was implicated as the causal organism of the bacterial wilt disease of tomato. A local check, Petofake and H7996 were used as susceptible and resistant checks respectively. Three genotypes, H7996, LA0442 and LA0443 demonstrated significant resistance stability in both experimental environments by recording significantly low wilt incidence and severity. H7996 was obtained from the World Vegetable Centre (WVC), Taiwan while the other two genotypes were collected from the University of California, Davis, USA. Apart from the highest yielding genotype LA 0442 that recorded 50.67 t/h, the rest recorded very low yields. The lowest yielding genotype AVTO 1713, recorded (12.67 t/h). Thus, the highest yielding genotype, LA 0442 over-yielded the lowest AVTO1713 by approximately 300%. It is instructive to note that LA0442, which was identified as a stable resistant genotype also recorded the highest yield. This result supports the potential of developing a resistant, high yielding variety using LA0442 as a parent. The future of the tomato industry in Ghana therefore looks promising.

Complex interactions based on host plant, rhizosphere microorganisms and soil microenvironment are presumed to be responsible for the suppressive properties of biochar against soil-borne diseases, although the underlying mechanisms are not well understood. This study is designed to evaluate the efficacy of biochar amendment for controlling tomato bacterial wilt caused by Ralstonia solanacearum, and to explore the interactions between biochar-induced changes in rhizosphere compound composition, the pathogen and tomato growth. The results showed that biochar amendment decreased disease incidence by 61–78% and simultaneously improved plant growth. The positive ‘biochar effect’ could be associated with enhanced microbial activity and alterations in the rhizosphere organic acid and amino acid composition. Specifically, elevated rhizosphere citric acid and lysine, but reduced salicylic acid, were induced by biochar which improved microbial activity and rendered the rhizosphere unsuitable for the development of R. solanacearum. In addition, nutrients which were either made more available by the stimulated microbial activity or supplied by the biochar could improve plant vigor and potentially enhance tomato resistance to diseases. Our findings highlight that biochar's ability to control tomato bacterial wilt could be associated with the alteration of the rhizosphere organic acid and amino acid composition, however, further research is required to verify these ‘biochar effects’ in field conditions.

Highlights • Traditional and modern methods of diagnosing bacterial wilt disease of potato. • Evaluate the susceptibility of some Egyptian potato cultivars against to R. solanacearum. • Differentiate potato cultivars using molecular genetics methods such as SDS-PAGE profile by protein content., Bacterial wilt caused by Ralstonia solanacearum (Smith), is one of the chief severe diseases of potato in warm temperate regions, tropics and subtropics of the world. The study was conducted to isolate and identify bacterial pathogens and select the most resistant cultivars and avoid the decrease in the total value of Egyptian potato exports to the European Union (EU) due to the quarantine restrictions imposed by the EU on potato tubers exported from Egypt affected by bacterial wilt. The results of traditional identification through morphological and serological studies showed that the five isolates were isolated and identified as Ralstonia solanacearum. Furthermore, the results illustrated that RS5 isolate showed the lowest percentage of disease incidence reduction on the three tested potatoes cultivar Bellini, Spunta and Mondial recorded 9.64%, 15.41% and 34.12%, respectively. While, RS8 isolate exhibited the highest effective one the percentage of disease reduction on all tested potato cultivars. This isolate reduced disease incidence 60.60%, 63.21% and 71.66%, compering to the healthy control treatment. The result of molecular identification represent that the probe used in Taq-man (PCR) was of the type (B2) capable to detect only biovar 2 of R. solanacearum bacterial wilt. Furthermore, primer and probe are specific for detection of the race 3 biovar 2 strain. Positive results were obtained in all assays used including IFAS, protein content and SDS-PAGE with all five isolates. So the isolate (RS5) was the most virulence one, followed by RS1, RS3, RS2 and RS8, registered that the tested isolates were R. solanacearum race 3, biovar 2. Also, studies focused on the form of genetic distances and similarities based on pathogenic and plant growth parameters. The results illustrate that the highest genetic similarity (0.998) was found between Bellini and Spunta cultivars as the closest but the lowest value (0.946) was found between Mondial and Bellini as most distant. These results were similarity with genetic distances and SDS-PAGE profile of the three tested potato cultivars.

Bacterial wilt caused byR. solanacearumis a constraint that limits the production of solanaceous in Côte d'Ivoire. The genetic control, which is more widely used, comes up against the genetic and phenotypic variability of the strains. The objective of this study was to screen commercial and traditional varieties of Solanaceae against Ivorian strains of different phylotypes to assess their spectrum of resistance to the disease. The level of virulence of the five strains ofR. solanacearumwas evaluated in semi-controlled conditions against eight varieties of Solanaceae (pepper, eggplant and tomato). Four groups of strains were identified according to the level of virulence. Group 4, composed of strains (RUN 1794 and RUN 1854) of phylotype III and I, respectively, and originating from the localities of Kondoukro and Yamoussoukro, was very virulent. The resistant varieties were for the F1 kalenda eggplant, for the yellow chilli from Burkina and for the F1 Lindo tomato. These varieties could be used in the fight against bacterial wilt in Côte d'Ivoire.

Konsumsi kentang di Indonesia terus meningkat namun belum sepenuhnya diperoleh dari dalam negeri. Hal ini disebabkan produktivitas kentang nasional masih rendah akibat kultivar impor yang tidak adaptif. Perakitan kultivar yang berpotensi hasil tinggi dan tahan penyakit layu bakteri merupakan upaya untuk meningkatkan produksi kentang. Penelitian ini bertujuan untuk mengetahui tingkat ketahanan penyakit layu bakteri secara in vitro dan potensi hasil genotipe kentang IPB. Penelitian dilakukan di laboratorium Pusat Kajian Hortikultura Tropika (PKHT) IPB untuk uji ketahanan penyakit dan di lahan pertanaman kentang milik petani di Pangalengan, Kabupaten Bandung untuk uji daya hasil pada bulan Januari sampai Juni 2018. Sebanyak tujuh genotipe uji yang terdiri dari terdiri dari PKHT 4, PKHT 6, PKHT 9, PKHT 10, PKHT 12, Intan, dan Medians, serta dua pembanding yaitu Atlantik dan Granola digunakan dalam penelitian ini. Uji ketahanan penyakit layu menggunakan metode in vitro dengan cara menginokulasi plantlet dengan metode gunting pucuk dilanjutkan dengan mengamati periode inkubasi, tingkat kejadian penyakit dan derajat ketahanan. Adapun uji daya hasil dilakukan dengan cara membandingkan pertumbuhan tanaman dan produksi umbi di lapangan. Hasil uji ketahanan menunjukkan genotipe PKHT 4 dan PKHT 9 mempunyai tingkat ketahanan, yaitu agak tahan, yang lebih baik dibandingkan Atlantik dan Granola sebagai kultivar pembanding. Uji daya hasil menunjukkan terdapat dua genotipe yang memiliki potensi hasil tinggi yaitu PKHT 6 (38.91 ton ha-1) PKHT 10 (28.75 ton ha-1) yang melebihi Atlantik dan Granola sebagai pembanding. Kata kunci: kultivar, produktivitas, Ralstonia solanacearum, seleksi in vitro, Solanum tuberosum

Ralstonia solanacearum causes bacterial wilt disease in solanaceous crops. Identification of avirulence type III-secreted effectors recognized by specific disease resistance proteins in host plant species is an important step toward developing durable resistance in crops. In the present study, we show that R. solanacearum effector RipJ functions as an avirulence determinant in Solanum pimpinellifolium LA2093. In all, 10 candidate avirulence effectors were shortlisted based on the effector repertoire comparison between avirulent Pe_9 and virulent Pe_1 strains. Infection assays with transgenic strain Pe_1 individually carrying a candidate avirulence effector from Pe_9 revealed that only RipJ elicits strong bacterial wilt resistance in S. pimpinellifolium LA2093. Furthermore, we identified that several RipJ natural variants do not induce bacterial wilt resistance in S. pimpinellifolium LA2093. RipJ belongs to the YopJ family of acetyltransferases. Our sequence analysis indicated the presence of partially conserved putative catalytic residues. Interestingly, the conserved amino acid residues in the acetyltransferase catalytic triad are not required for effector-triggered immunity. In addition, we show that RipJ does not autoacetylate its lysine residues. Our study reports the identification of the first R. solanacearum avirulence protein that triggers bacterial wilt resistance in tomato. We expect that our discovery of RipJ as an avirulence protein will accelerate the development of bacterial wilt-resistant tomato varieties in the future. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

Background Understanding the specific inhibitory effects of different Brassica seed meals (BSMs) on soilborne pathogens is important for their application as biocontrol agents for controlling plant disease. In this study, the seed meals of Brassica napus L. (BnSM), Brassica campestris L. (BcSM), and Brassica juncea L. (BjSM), and the combined seed meal of BcSM and BjSM (CSM, 1:1), were selected for investigation. The inhibitory effects of these seed meals on the plant pathogen Ralstonia solanacearum (Smith) and tomato bacterial wilt, were assessed and compared. Results All the BSMs significantly inhibited the growth of R. solanacearum in vitro. Furthermore, the BSMs could effectively suppress R. solanacearum virulence traits, including motility, exopolysaccharide production, dehydrogenase activity, virulence-related gene expression, and colonization in the soil. Among them, BjSM showed the best inhibiting effects, and CSM displayed synergic toxicity against R. solanacearum. In addition, the predominant antibacterial compounds in BcSM and BjSM were identified as the volatile compounds, 3-butenyl isothiocyanate and allyl isothiocyanate, respectively. Finally, pot experiment verified that the control effects of BjSM and CSM on tomato wilt reached more than 90%. Conclusion This is the first study to report on the ability of different kinds of BSMs to suppress the virulence of R. solanacearum and biocontrol efficiencies against bacterial wilt in tomato plants. Furtherly, the main antibacterial compounds in the BSMs were identified. The results demonstrated that CSM may possess potential for controlling bacterial wilt caused by R. solanacearum. The results provide a fresh perspective for comprehending the mechanism underlying BSM suppression of pathogens and plant disease. This article is protected by copyright. All rights reserved.

Bacterial wilt (BW) disease caused by Ralstonia solanacearum is a major constraint in eggplant (Solanum melongena L.) cultivation, resulting in economic loss in tropics, sub-tropics and temperate r...

Biological control of phytopathogen is a promising approach when compared to the use of chemical agents. In the present study, seven Streptomyces cultures showing promising anti biofilm activity against Ralstonia solanacearum was mixed individually with farmyard manure. All the Streptomyces fortified farmyard manure (SFYM) were screened for plant growth promotion and control of bacterial wilt caused by R. solanacearum on tomato. Further, the ability of SFYM on stimulating the production of defense-related enzymes in R. solanacearum-inoculated tomato plants was investigated. When compared to the control tomato plants, the SFYM-treated plants had longer shoot and root length along with higher fresh and dry weight. The maximum level of chlorophyll was observed in the plants treated with strain UP1A-1 (2.21 ± 0.18 mg g−1). Strain UP1A-1 also showed maximum of 96.8 ± 1.4% biocontrol efficacy in tomato plants challenged with R. solanacearum. In addition, the UP1A-1 treated tomato plants showed maximum accumulation of total phenolics (3.02 ± 0.09 mg g−1) after 6 days of pathogen inoculation (DPI). Similarly, tomato plants treated with UP1A-1 showed highest level of peroxides, polyphenol oxidase and phenylalanine ammonia lyase during 1–9 DPI. Findings of present study revealed that the Streptomyces culture UP1A-1 fortified farm yard manure could be applied as an eco-friendly alternative to synthetic agents for controlling bacterial wilt in tomato plants.

Turmeric (Curcuma longa L. (Zingiberaceae)) is a rich source of medicinally important chemical compounds obtained from both pseudostem (aboveground part) and rhizome (underground part). However, the availability of disease-free elite varieties of the plant is highly restricted. Leaf spot caused by Colletotrichum curcumae Butler & Bisby and bacterial wilt caused by Ralstonia pseudosolanacearum Safni have been reported as major diseases responsible for reduced rhizome productivity in the turmeric plant. Meristem culture is a well-known alternative for production of disease-free mother rhizome. The aim of this investigation was to eradicate bacterial and fungal disease instances through culturing of meristematic tissue pretreated with 1.44 to −2.88 μM GA (gibberellic acid) followed by detection of disease contamination using PCR amplification and chemical assay. Meristem (0.5 to 2.0 mm) was identified as a good material for initiating tissue culture, as it exhibited 100% survival rate and absence of R. pseudosolanacearum and C. curcumae when tested with SPA (sucrose peptone agar), TZC (Kelman’s tripheny tetrazolium chloride), and PDA (potato dextrose agar) selective media. Plantlets derived from meristematic tissues of size 2.0 mm were healthy and displayed rapid recovery and uniformity in size. Disease-free status of plantlets (derived from meristem culture) was confirmed by PCR products of specific primers, RP1F/RP1R and RP3F/RP3R for R. pseudosolanacearum and CCactF/CCactR and CChisF/CChisR for C. curcumae. Moreover, shoot elongation using supplemented GA in the culture medium was successfully induced for meristem cutting. All meristem cultures pretreated with GA were confirmed to be contamination-free through TZC, SPA, and PDA media as well as PCR amplification. Based on this study, the 1.0 to 2.0 mm in size of meristem cutting and pretreatment with 1.44 to 2.88 μM GA for shoot elongation were successfully identified in addition to confirming the disease-free status of the plantlets using chemical assay and PCR products.

An easy, rapid method has been needed to test the pathogenicity of strains of Ralstonia pseudosolanacearum, the cause of serious bacterial wilt on ginger (Zingiber officinale). When ginger leaves were clip-inoculated with race 4 strains, yellowing and V-shaped lesions developed on leaves, but no lesions formed after inoculation with race 1 strain or on mock-inoculated leaves. Tests of different bacterial concentrations as inoculum showed that the optimal concentration was greater than or equal to 106 cfu/ml. This simple, high-throughput leaf clipping inoculation method provides an efficient, easy method to evaluate pathogenicity of R. pseudosolanacearum race 4 on ginger.

Twelve F1 hybrids developed through line × tester design along with seven parents were evaluated for fruit yield, quality, incidence of bacterial wilt disease and anatomical features of root and stem to study the manifestation of heterobeltiosis, and to understand the implication of anatomical characters towards tolerance against bacterial wilt disease. Two hybrids (Utkal Deepti × CLN-2764A and Utkal Kumari × CLN-2777G) registering substantial tolerance against bacterial wilt exhibited marked heterobeltiosis for fruit yield per plant and other component traits. Hypocotyls of the highly tolerant hybrid did not show any bacterial colonization in xylem tissues under light microscope even at 8 days of inoculation with native bacterial isolate. The potted seedlings of tolerant hybrid showed mean disease index of 1.16 even at 20 days of inoculation with bacterial isolate which indicated promise for its utilization in bacterial wilt prone areas. Establishment of significant negative correlations between the incidence of bacterial wilt disease and the ratio of large vessels/small vessels in stem, diameter of large vessels in stem, and diameter of large vessels in roots suggested that these anatomical characters might be considered as important indices for selection of hybrid tolerant to bacterial wilt disease. Significant heterobeltiosis was also manifested for three anatomical traits. This study justified the scope of utilizing the anatomical features of stem and root in breeding tomato cultivars tolerant to bacterial wilt disease. Overwhelming response of non-additive genetic control for these anatomical traits also exposed the evidence of heterosis breeding for their improvement.

Beneficial host-associated bacteria can assist plant protection against pathogens. In particular, specific microbes are able to induce plant systemic resistance. However, it remains largely elusive which specific microbial taxa and functions trigger plant immune responses associated with disease suppression. Here, we experimentally studied this by setting up two independent microcosm experiments that differed in the time at which plants were exposed to the pathogen and the soil legacy (i.e., soils with historically suppressive or conducive). Overall, we found soil legacy effects to have a major influence on disease suppression irrespective of the time prior to pathogen exposure. Rhizosphere bacterial communities of tomato plants were significantly different between the two soils, with potential beneficial strains occurring at higher relative abundances in the suppressive soil. Root transcriptome analysis revealed the soil legacy to induce differences in gene expression, most importantly, genes involved in the pathway of phenylpropanoid biosynthesis. Last, we found genes in the phenylpropanoid biosynthesis pathway to correlate with specific microbial taxa, including Gp6, Actinomarinicola, Niastella, Phaeodactylibacter, Longimicrobium, Bythopirellula, Brevundimonas, Ferruginivarius, Kushneria, Methylomarinovum, Pseudolabrys, Sphingobium, Sphingomonas, and Alterococcus. Taken together, our study points to the potential regulation of plant systemic resistance by specific microbial taxa, and the importance of soil legacy on disease incidence and eliciting plant-defense mechanisms.

Bacterial wilt caused by Ralstonia solanacearum is a major constraint to production of potatoes (Solanum tuberosum L). To date, there are no known conventional bactericides which provide effective control of this soil borne pathogen. This study aimed at investigating the antibacterial activity of eugenol and thymol which are the major components of thyme and clove essential oils, respectively against R. solanacearum. The pathogen was isolated from potato tubers exhibiting bacterial wilt symptoms. The inhibitory effect of these compounds was assayed by disc diffusion and minimal inhibition concentration (MIC) methods. Combinational test was also performed using chequerboard assay. At a concentration of 100 mg mL-1, thymol and eugenol had inhibition zones of 27 and 17 mm, respectively. The MIC of eugenol and thymol were determined as 275 and 175 µg mL-1, respectively and both had bactericidal effect against R. solanacearum. Combinational test revealed an additive effect indicating that their combined use does not significantly enhance inhibition. Both compounds have a potential to be exploited as antibiotic for the management of bacterial wilt disease albeit thymol at a lower concentration. Exploitation of these volatile compounds in vivo however faces challenges which can be overcome through nanoencapsulation by an appropriate nanocarrier. Key words: Essential oils, inhibitory effect, combinational test, chequerboard assay, bactericidal effect.

In nature, plants interact with multiple organisms, below and aboveground. Although interactions of plants with single biotic stressors are well characterized, knowledge of how the immune system responds to multiple biotic stressors is lacking. It is known that the two most important pathways involved in the plant immune defenses are jasmonic acid (JA) and salicylic acid (SA). The crosstalk between these plant hormonal signaling pathways seems to fine-tune the plant responses to different stressors. In this study, we characterized maize (Zea mays) hormonal interactions under the attack of two economically important pests: the bacterial pathogen that causes Goss’s bacterial wilt and leaf blight (Clavibacter michiganensis subsp. nebraskensis), and the chewing insect, fall armyworm (Spodoptera frugiperda). Our results indicate that the Goss’s wilt-resistant maize plants when pretreated with bacteria became more vulnerable to the subsequent attack by the fall armyworm larvae. Furthermore, plant hormone analysis demonstrated that the antagonistic interactions of JA-Isoleucine (JA-Ile), biologically active form of JA, and SA in maize plants contributed to enhanced plant susceptibility to herbivory. Collectively, our results suggest that plant hormonal interactions may play a major role in maize defense against multiple biotic stressors. Furthermore, this study will improve our understanding and ability to predict plant-induced hormone responses in an economically important crop.

Bacterial wilt caused by Ralstonia solanacearum is the main bacterial disease in potato. Solanum commersonii Dun. (cmm; 2n = 2x = 24, 1 EBN) is a native species to southern Brazil, Uruguay and Argentina with desirable traits for introgressive hybridisation breeding into cultivated potato such as resistance to R. solanacearum. In Uruguay, successful crosses between cmm and Solanum tuberosum Group Tuberosum (tbr; 2n = 4x = 48, 4 EBN) have been carried out with this objective, resulting in backcross 1, 2 and 3 progenies. The aim of this study was to characterise one backcross 3 progeny (BC3) using cytogenetic, genetic, morphological and agronomic descriptors. Resistance to R. solanacearum showed transgressive segregation and an association with plant architecture. Fifty-two percent of individuals had chromosome numbers close to cultivated potato with no evidence of preferential loss of cmm chromosomes. All BC3 individuals showed male sterility, probably due to nuclear-cytoplasmic interactions. Although there was wide segregation in morphological traits, most individuals resembled the recurrent tbr parents. A few more backcrosses combined with screening for bacterial wilt resistance may be necessary to allow for further recombination and removal of undesirable traits from cmm. The presence of BC3 individuals with chromosome numbers close to 2n = 48, combining morphological traits from tbr with good levels of resistance, suggests the occurrence of introgression events. This points to S. commersonii as one of the most promising genetic resources for potato breeding from the Southern Atlantic region.

The soilborne pathogen Ralstonia solanacearum causes a lethal bacterial wilt disease of tomato and many other crops by infecting host roots, then colonizing the water-transporting xylem vessels. Tomato xylem sap is nutritionally limiting but it does contain some carbon sources, including sucrose, trehalose, and myo-inositol. Transcriptomic analyses revealed that R. solanacearum expresses distinct catabolic pathways at low cell density (LCD) and high cell density (HCD). To investigate the links between bacterial catabolism, infection stage, and virulence, we measured in planta fitness of bacterial mutants lacking specific carbon catabolic pathways expressed at either LCD or HCD. We hypothesized that early in disease, during root infection, the bacterium depends on carbon sources catabolized at LCD, while HCD carbon sources are only required later in disease during stem colonization. A R. solanacearum ΔiolG mutant unable to use the LCD-catabolized nutrient myo-inositol was defective in tomato root colonization, but after it reached the stem this strain colonized and caused symptoms as well as wild type. In contrast, R. solanacearum mutants unable to use the HCD-catabolized nutrients sucrose (ΔscrA), trehalose (ΔtreA), or both (ΔscrA/treA), infected roots as well as wild-type R. solanacearum but were defective in colonization and competitive fitness in midstems and had reduced virulence. Further, xylem sap from tomato plants colonized by ΔscrA, ΔtreA, or ΔscrA/treA R. solanacearum mutants contained twice as much sucrose as sap from plants colonized by wild-type R. solanacearum. Together, these findings suggest that quorum sensing specifically adapts R. solanacearum metabolism for success in the different nutritional environments of plant roots and xylem sap. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Ralstonia solanacearum causes bacterial wilt of tomato and limits the crop production, and antagonistic microorganisms use to suppress the disease, of which Trichoderma and Pseudomonas species are the most effective agents to control bacterial wilt. In the present study, attempt was made to isolate these two microorganisms to evaluate their effectiveness to control R. solanacearum, the causal agent of bacterial wilt disease of tomato under greenhouse conditions. Thus R. solanacearum, Pseudomonas and Trichoderma spp. were isolated from wilted and healthy tomato plants grown from farmer's field in Ziway and Meki, Oromia Ethiopia. The virulence of the pathogen and the antagonistic effect of the bacteria and fungi were evaluated against R. solanacearum in vitro and in vivo condition. Based on the in vitro results the best two isolates were selected to show their antagonistic effect under greenhouse condition in single and combined designs. The result showed the pathogenicity test of the isolates were evaluated under greenhouse condition, and isolate AAURS1 showed highest virulence (75%) followed by isolate APPRCRS2 with pathogenicity of 50%. With regard to antagonism test, isolates AAURB20 and AAUTR23 showed the highest inhibition against R. solanacearum with inhibition zone of 16 and 15 mm, respectively. Among the treatments co-inoculation was more effective and reduced disease incidence by 13.33% and increased the bio-control efficacy by 72.22% when compared with individual treatment and negative control. The isolates significantly increased the plant height and dry weight by 72.33 cm and 12.18 g, respectively. Thus, the combined use of the biocontrol agents significantly reduced the incidence of tomato bacterial wilt disease. However, their performance should be evaluated using other yield parameters under field conditions to produce healthy tomato seedling to minimize the use of chemicals and reduce environmental pollution. Key words: Biocontrol, Pseudomonas, Ralstonia solanacearum, Trichoderma.

Bacterial wilt caused by Ralstonia solanacearum is a major devastating soil-borne disease impeding eggplant cultivation worldwide. The present investigation was conducted to recognize and assess bacterial wilt resistant rootstocks among Solanum melongena (Haritha, Surya, SM 1, SM 2, SM 3, SM116, and SM 398), Solanum torvum (St TNAU 1 and St KAU 1), and Solanum sisymbrifolium (SS 1) for vigor, yield and qualitative traits of ‘Green Long Hybrid’ scion through grafting. The artificial inoculation method as well as the sick plot method of bacteria wilt screening were adopted. The root dip method of artificial inoculation was found to be the most reliable method as compared to media drenching and stem inoculation methods. All the rootstocks except Solanum sisymbrifolium possessed a high degree of bacterial wilt resistance (in artificial as well as sick plot conditions). Maximum plant spread, stem girth, number of primary branches, yield per plant (6.69 kg), number of fruits per plant (94.80), fruit length (22.22 cm), root length (63.65 cm), and root spread (87.05 cm) were exhibited by Green Long Hybrid scion when grafted onto Solanum melongena cv. Haritha rootstock. Taller plants with high fruit girth (10.97 cm) and average fruit weight (78.00 g) of scion were recorded on SM 116 rootstock. The highest dry matter content (11.12%) and total phenolic content (113.30 mg/100 g) of fruits were observed in scion when SM 398 and SM 3 were used as rootstocks, respectively. Overall, ‘Haritha’ cultivar was found to be the best rootstock for grafting in the current study. Thus, grafting technology can be effectively used for the control of bacterial wilt as well as for acquiring higher yield in eggplant.

Cultivation of brinjal in Coastal regions of India is severely affected by bacterial wilt disease caused by Ralstonia solanacearum. In this study, recombinant inbred lines were developed and screened for bacterial wilt resistance. Seventeen promising resistant lines were evaluated in the field for two years and the results indicated these lines were resistant to bacterial wilt. Lines 262-4, 5-12-1, 66-8-1, 205-1, 12-2-4 and 28-8-5 were promising among the purple types (0 to 4 % wilt and yield 0.51 to 0.93 kg/ plant). Among the green types, lines 5-8-1, 93-8-1 and 92-3-7 were promising (0 to 5 % wilt and yield 0.64 to 0.79 kg/ plant). Demonstration of eight lines in farmer’s field indicated that lines 262-4, 5-12-1, 205-1, 5-8-1 and 12-2-4 were least infected (3 to 17 %). Based on these studies, four purple lines 262-4, 5-12-1, 66-8-1 and 205-1 were released as bacterial wilt resistant brinjal varieties in the State of Goa.

Clavibacter nebraskensis causes Goss’s bacterial wilt and leaf blight, a major disease of maize. Infected crop residue is the primary inoculum source and infection can occur via wounds or natural openings, such as stomata or hydathodes. The use of resistant hybrids is the primary control method for Goss’s wilt. In this study, colonization and movement patterns of C. nebraskensis during infection were examined using green fluorescent protein (GFP)-labeled bacterial strains. We successfully introduced a plasmid to C. nebraskensis via electroporation, which resulted in GFP accumulation. Fluorescence microscopy revealed that in the absence of wounding, bacteria colonize leaf tissue via entry through the hydathodes when guttation droplets are present. Stomatal penetration was not observed under natural conditions. Bacteria initially colonize the xylem and subsequently the mesophyll, which creates the freckles that are characteristic of the disease. Bacteria infiltrated into the mesophyll did not cause disease symptoms, could not enter the vasculature, and did not spread from the initial inoculation point. Bacteria were observed exuding through stomata onto the leaf surface, resulting in the characteristic sheen of diseased leaves. Resistant maize lines exhibited decreased bacterial spread in the vasculature and the mesophyll. These tools to examine C. nebraskensis movement offer opportunities and new insights into the pathogenesis process and can form the basis for improved Goss’s wilt management through host resistance.

Tomato (Solanum lycopersicum L.) a native of South America is a source of vitamins, minerals and antioxidant lycopene, and considered as protective food. In India, the crop is grown under the area of about 0.458 M ha with production of 7.277 M mt and productivity of 15.9 mt/ha. Biotic factors play a role in low productivity of the crops in India. Among various diseases, bacterial wilt disease incited by Ralstonia solanacearum (Smith) Yabuuchi et al. (1996) is a devastating bacterium causing damage to the crop ranging from 2 to 95% depending on the seasons and cultivars. In India, majority of the isolates of R. solanacearum infecting tomato crop belonged to biovar 3, race 1 and phylotype I. However, less than 10% isolates of the bacteria belonged to biovar 4 particularly in the states of Jharkhand and Himachal Pradesh. The genetic diversity of R. solanacearum has been studied by using methods such as random amplified polymorphic DNA (RAPD), PCR—RFLP (PCR—Restriction Length Fragment Polymorphism) of hrp gene, Repetitive element palindromic-polymerase chain reaction (Rep-PCR) and multilocus sequence typing (MLST). The genetic diversity was recorded in Indian R. solanacearum isolates irrespective of their occurrence in different agro-climatic conditions.

The infection of potato with Ralstonia solanacearum UW551 gives rise to bacterial wilt disease via colonization of roots. The type III secretion system (T3SS) is a determinant factor for the pathogenicity of R. solanacearum. To fully understand perturbations in potato by R. solanacearum type III effectors(T3Es), we used proteomics to measure differences in potato root protein abundance after inoculation with R. solanacearum UW551 and the T3SS mutant (UW551△HrcV). We identified 21 differentially accumulated proteins. Compared with inoculation with UW551△HrcV, 10 proteins showed significantly lower abundance in potato roots after inoculation with UW551, indicating that those proteins were significantly downregulated by T3Es during the invasion. To identify their functions in immunity, we silenced those genes in Nicotiana benthamiana and tested the resistance of the silenced plants to the pathogen. Results showed that miraculin, HBP2, and TOM20 contribute to immunity to R. solanacearum. In contrast, PP1 contributes to susceptibility. Notably, none of four downregulated proteins (HBP2, PP1, HSP22, and TOM20) were downregulated at the transcriptional level, suggesting that they were significantly downregulated at the posttranscriptional level. We further coexpressed those four proteins with 33 core T3Es. To our surprise, multiple effectors were able to significantly decrease the studied protein abundances. In conclusion, our data showed that T3Es of R. solanacearum could subvert potato root immune-related proteins in a redundant manner. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Bacterial wilt (BW), caused by Ralstonia solanacearum species complex (RSSC), leads to substantial potato yield losses in Rwanda. Studies were conducted to (i) determine the molecular diversity of RSSC strains associated with BW of potato, (ii) generate an RSSC distribution map for epidemiological inferences, and (iii) test the pathogenicity of predominant RSSC phylotypes on six commercial potato cultivars. In surveys conducted in 2018 and 2019, tubers from wilting potato plants were collected for pathogen isolation. DNA was extracted from 95 presumptive RSSC strain colonies. The pathogen was phylotyped by multiplex PCR and typed at sequevar level. Phylotype II sequevar 1 strains were then haplotyped using multilocus tandem repeat sequence typing (TRST) schemes. Pathogenicity of one phylotype II strain and two phylotype III strains were tested on cultivars Kinigi, Kirundo, Victoria, Kazeneza, Twihaze, and Cruza. Two RSSC phylotypes were identified, phylotype II (95.79%, n = 91) and phylotype III (4.21%, n = 4). This is the first report of phylotype III strains from Rwanda. Phylotype II strains were identified as sequevar 1 and distributed across potato growing regions in the country. The TRST scheme identified 14 TRST haplotypes within the phylotype II sequevar 1 strains with moderate diversity index (HGDI = 0.55). Mapping of TRST haplotypes revealed that a single TRST ‘8-5-12-7-5’ haplotype plays an important epidemiological role in BW of potato in Rwanda. None of the cultivars had complete resistance to the tested phylotypes; the level of susceptibility varied among cultivars. Cultivar Cruza, which is less susceptible to phylotype II and III strains, is recommended when planting potatoes in the fields with history of BW. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Bacterial wilt in potato (Solanum tuberosum) is caused by Ralstonia solanacearum in the highlands of Fouta Djalon in Guinea. The disease causes 50-70% loss of potato in Guinea. The bacterium is transmitted either by imported tuber seeds or through seed exchanges between the farmers themselves from a contaminated area to bacteria-free areas or through irrigation waters along the fields. This is mainly a consequence of the informal potato seed system that prevails in Guinea. Because of the high price of seeds, farmers use several sources of supply. However, potato is an attractive cash crop in Guinea and the most important economic crop in Fouta Djalon. Most populations in the middle Guinea utilizes potato. The potato farmer's organization in Guinea, FPFD (Fédération des Producteurs du Fouta Djalon), is a model in West African sub-region because of its dynamism and organization with its 500 groups, 25 unions and more than 25,000 members. Training of potato growers in certified seed production techniques remains a major problem in Guinea that needed to be solved. This information is important for developing bacterial wilt disease management strategies through the training of farmers and state support for research.