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Ralstonia solanacearum species complex (RSSC) is a serious soilborne phytopathogen affecting over 310 plant species. R. pseudosolanacearum is one clade of RSSC, which infects the important oil crop peanut. A variety of virulence factors are employed by RSSC to promote disease, among which type III effectors (T3Es) are prominent. How T3Es manipulate the interaction between R. pseudosolanacearum and peanut is unclear. A T3E RipBB was previously found specifically in a more virulent peanut R. pseudosolanacearum PeaFJ1 strain. In the present study, the function of RipBB was analysed. Loss of RipBB from PeaFJ1 strain resulted in attenuated pathogenicity to peanut, and complementation with RipBB recovered the virulence of the mutant strain. Transient expression of RipBB induced cell death and inhibited flg22‐triggered reactive oxygen species (ROS) burst in the leaves of Nicotiana benthamiana. The expression of pattern‐triggered immunity (PTI)‐related genes were also suppressed by RipBB transient expression. Among the available sequenced 639 RSSC strains, RipBB is an infrequent T3E that is only present in eight strains. Two ankyrin (ANK) repeats were identified in RipBB, which play an important role in localizing the protein to the cytomembrane and nucleus. Altogether, we verified that RipBB contributes to infecting peanut by acting as a virulence T3E, and causes cell death and suppresses immunity in N. benthamiana. These results enhance the study of ANK‐containing effectors. Further elucidation of the molecular mechanisms underlying RipBB effect on immunity may reveal ANK‐containing effector functions in host cells, helping to understanding the mechanism of R. pseudosolanacearum–peanut interaction. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) play a crucial role in regulating numerous functions in organisms. Among the key regulators of ROS production are NADPH oxidases, primarily referred to as respiratory burst oxidase homologues (RBOHs). However, our understanding of whether and how pathogens directly target RBOHs has been limited. In this study, we revealed that the effector protein RipBJ, originating from the phytopathogenic bacterium Ralstonia solanacearum, was present in low‐ to medium‐virulence strains but absent in high‐virulence strains. Functional genetic assays demonstrated that the expression of ripBJ led to a reduction in bacterial infection. In the plant, RipBJ expression triggered plant cell death and the accumulation of H2O2, while also enhancing host defence against R. solanacearum by modulating multiple defence signalling pathways. Through protein interaction and functional studies, we demonstrated that RipBJ was associated with the plant's plasma membrane and interacted with the tomato RBOH known as SlWfi1, which contributed positively to RipBJ's effects on plants. Importantly, SlWfi1 expression was induced during the early stages following R. solanacearum infection and played a key role in defence against this bacterium. This research uncovers the plant RBOH as an interacting target of a pathogen's effector, providing valuable insights into the mechanisms of plant defence. Summary Statement: This study demonstrates that a tomato plasma membrane‐bound NADPH oxidase is a direct interactor of a bacterial effector protein to mediate plant defence, providing important new information on the interplay between this devastating pathogen and its host plant. [ABSTRACT FROM AUTHOR]

Bacterial wilt caused by Ralstonia solanacearum, is one of the most notorious plant diseases of potato and causes severe yield losses globally. R. solanacearum produces fluidal white coloured colonies with a light pink centre on casamino acid-peptone-glucose medium. Bacterial wilt pathogen is soil as well as tuber borne, so early detection of bacterial wilt pathogen is necessary to take up timely management practices. Traditional methods used for detection of R. solanacearum are labour-intensive, expensive, time-consuming and can be carried out only in well-equipped laboratories. Hence, the present study was aimed to develop a loop-mediated isothermal amplification (LAMP) assay for R. solanacearum, as an alternative approach for quick and efficient detection of the bacterial wilt. LAMP reaction mix was optimized by adjusting the concentrations of MgSO4, dNTPs, betaine, and time, temperature etc. The optimum temperature and time for the detection of R. solanacearum were 65 °C and 50 min, respectively. The positive samples showed colour change from violet and were reconfirmed in 2% agarose gel electrophoresis which produced ladder like bands. The LAMP assay developed was highly specific to detect R. solanacearum from other bacteria and sensitive with a lowest detection limit of 10 pg/µl of template DNA. The developed LAMP assay was validated with R. solanacearum isolates, infected stems, tubers and soil, and also, it was capable of detecting latent infection of R. solanacearum in seed tubers. Hence, the LAMP assay protocol provides a rapid, specific and sensitive tool for the latent detection of R. solanacearum in seed potato tubers. [ABSTRACT FROM AUTHOR]

Growers may adopt a tomato hybrid if it is high yielder with good fruit quality and can withstand the bacterial wilt (BW) disease. A line × tester mating design was used to determine heterobeltiosis, combining ability and gene action for 15 characters in tomato. Most traits under study exhibited additive and non-additive gene action except days to 50% flowering, polar diameter of fruit, pH of fruit and lycopene content of fruit which were controlled by additive gene effect. Two genotypes, ‘Utkal Kumari’ and ‘CLN-2460E’ were identified as potential donors. The maximum, significant, heterobeltiosis was for disease incidence of BW followed by fruit yield per plant, fruit firmness, and fruits per plant. In the tropical tomato growing zones, two potential hybrids, ‘Utkal Kumari × CLN-2460E' and ‘Utkal Deepti × CLN-2460E', may fulfil significant horticultural requirements since they exhibited resistance against virulent biovars 3 and 6. More testing in a variety of edapho-climatic conditions is required to confirm the stability of the developed resistance and the hybrids’ resilience. Partial- to over-dominance reactions of fruit yield and other economic traits were reflected. Isolating pure lines from the segregating generation of heterotic F1s is another method to improve fruit yield and quality as well as disease resistance against bacterial wilt. [ABSTRACT FROM AUTHOR]

Background: Bacterial wilt (BW), caused by Ralstonia solanacearum (Ral), results in substantial yield losses in pepper crops. Developing resistant pepper varieties through breeding is the most effective strategy for managing BW. To achieve this, a thorough understanding of the genetic information connected with resistance traits is essential. Despite identifying three major QTLs for bacterial wilt resistance in pepper, Bw1 on chromosome 8, qRRs-10.1 on chromosome 10, and pBWR-1 on chromosome 1, the genetic information of related BW pepper varieties has not been sufficiently studied. Here, we resequenced two pepper inbred lines, C. annuum 'MC4' (resistant) and C. annuum 'Subicho' (susceptible), and analyzed genomic variations through SNPs and Indels to identify candidate genes for BW resistance. Results: An average of 139.5 Gb was generated among the two cultivars, with coverage ranging from 44.94X to 46.13X. A total of 8,815,889 SNPs was obtained between 'MC4' and 'Subicho'. Among them, 31,190 (0.35%) were non-synonymous SNPs (nsSNPs) corresponding to 10,926 genes, and these genes were assigned to 142 Gene Ontology (GO) terms across the two cultivars. We focused on three known BW QTL regions by identifying genes with sequence variants through gene set enrichment analysis and securing those belonging to high significant GO terms. Additionally, we found 310 NLR genes with nsSNP variants between 'MC4' (R) and 'Subicho' (S) within these regions. Also, we performed an Indel analysis on these genes. By integrating all this data, we identified eight candidate BW resistance genes, including two NLR genes with nsSNPs variations in qRRs-10.1 on chromosome 10. Conclusion: We identified genomic variations in the form of SNPs and Indels by re-sequencing two pepper cultivars with contrasting traits for bacterial wilt. Specifically, the four genes associated with pBWR-1 and Bw1 that exhibit both nsSNP and Indel variations simultaneously in 'Subicho', along with the two NLR genes linked to qRRs-10.1, which are known for their direct involvement in immune responses, are identified as most likely BW resistance genes. These variants in leading candidate genes associated with BW resistance can be used as important markers for breeding pepper varieties. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum and R. pseudosolanacearum are well-known bacterial plant pathogens that cause significant losses to both ornamental and agricultural plants. It has been suggested that they are not the primary cause of bacterial wilt in Eucalyptus species, but rather are opportunistic, taking advantage of trees predisposed to infection by abiotic and biotic factors. To test this hypothesis, the bacterial community within the vascular tissue of asymptomatic Eucalyptus grandis x E. urophylla trees, and those displaying varying stages of infection in China and Indonesia were compared using 16S rRNA profiling. Asymptomatic trees growing in areas where bacterial infections had never previously been reported to occur were included as controls. Ralstonia species were found within the vascular tissue of both asymptomatic and symptomatic trees, in high abundance. In the control samples, bacterial diversity within the vascular tissue was high with a low abundance of Ralstonia species. The presence of Ralstonia species in asymptomatic and control samples supports the hypothesis that these species are latent and/or opportunistic pathogens in E. grandis x E. urophylla trees. [ABSTRACT FROM AUTHOR]

Soil acidification represents a severe threat to tobacco cultivation regions in South China, exacerbating bacterial wilt caused by Ralstonia solanacearum. The comprehension of the underlying mechanisms that facilitate the restoration of rhizosphere microbial communities in “healthy soils” is imperative for ecologically managing tobacco bacterial wilt. This study focuses on acidified tobacco soils that have been subjected to continuous cultivation for 20 years. The experimental treatments included lime (L), biochar (B), and a combination of lime and biochar (L+B), in addition to a control group (CK). Utilizing rhizosphere biology and niche theory, we assessed disease suppression effects, changes in soil properties, and the co-evolution of the rhizosphere bacterial community. Each treatment significantly reduced tobacco bacterial wilt by 16.67% to 20.14% compared to the control group (CK) (p < 0.05) and increased yield by 7.86% to 27.46% (p < 0.05). The biochar treatment (B) proved to be the most effective, followed by the lime-biochar combination (L+B). The key factors controlling wilt were identified through random forest regression analysis as an increase in soil pH and exchangeable bases, along with a decrease in exchangeable acidity. However, lime treatment alone led to an increase in soil bulk density and a decrease in available nutrients, whereas both biochar and lime-biochar treatments significantly improved these parameters (p < 0.05). No significant correlation was found between the abundance of Ralstonia and wilt incidence. Nonetheless, all treatments significantly expanded the ecological niche breadth and average variation degree (AVD), enhanced positive interactions and cohesion within the community, and intensified negative interactions involving Ralstonia. This study suggests that optimizing community niches and enhancing pathogen antagonism are key mechanisms for mitigating tobacco wilt in acidified soils. It recommends using lime-biochar mixtures as soil amendments due to their potential ecological and economic benefits. This study offers valuable insights for disease control strategies and presents a novel perspective for research on Solanaceous crops. [ABSTRACT FROM AUTHOR]

Bacterial wilt (BW) is caused by Ralstonia solanacearum species complex (RSSC) and can lead to severe losses in a wide range of crops, including many traditional African vegetables (TAV). Given the critical role of TAV in African food security, investigations of BW incidence, distribution, and effective breeding strategies are needed to support public and private TAV breeding programs. In this review, we address key questions related to the diversity of BW pathogens, susceptible TAV hosts, distribution, incidence, breeding strategies, sources of resistance, and gaps in the development of resistant TAV varieties in Africa. We also discuss the potential of multiomics integration to enhance our understanding of the host plant defense system against BW in Solanaceae crops. We curated BW strain databases obtained from several online platforms, representing a total of 948 BW strains. Using a refined database, we highlighted the diversity of RSSC and TAV crops affected by RSSC in different regions of Africa. Out of 29 species documented to be affected by BW in Africa, ten are TAV, including widely consumed TAV such as Amaranths and nightshades. In addition, phylotypes I and III are reported to affect TAV, and the incidence can reach up to 72.4% in farmers' fields. An overview of the first reports revealed that the disease has become a serious threat to TAV in the past decade. Finally, this review proposes a schematic map of possible avenues for successful breeding of BW-resistant TAV using Gboma eggplant as a case study. [ABSTRACT FROM AUTHOR]

Pepper (Capsicum spp.) is widely cultivated throughout the globe due to its diversified use in food (vegetable, spice, paprika, oleoresin) as well as non-food (industrial, pharmaceutical) sectors. Despite its economic value, pepper cultivation faces significant challenges due to bacterial diseases such as bacterial wilt, bacterial spot, bacterial canker, and bacterial soft rot globally. Existing chemical, and biological control strategies have numerous limitations such as the emergence of new resistant strains, negative environmental impact, and lack of user-friendly formulations. Hence, host plant resistance offers a sustainable solution restricting the use of harmful chemicals. Although significant progress has been achieved in the identification and utilization of bacterial wilt and bacterial spot-resistant genotypes, newly emerging threats in pepper like bacterial canker and bacterial soft rot require immediate attention. This article focuses on genetic resources, inheritance patterns, and molecular markers associated with resistance to bacterial diseases in pepper to develop resistant pepper varieties, hybrids, or rootstocks. [ABSTRACT FROM AUTHOR]

Abstract Background Bacterial wilt (BW), caused by Ralstonia solanacearum (Ral), results in substantial yield losses in pepper crops. Developing resistant pepper varieties through breeding is the most effective strategy for managing BW. To achieve this, a thorough understanding of the genetic information connected with resistance traits is essential. Despite identifying three major QTLs for bacterial wilt resistance in pepper, Bw1 on chromosome 8, qRRs-10.1 on chromosome 10, and pBWR-1 on chromosome 1, the genetic information of related BW pepper varieties has not been sufficiently studied. Here, we resequenced two pepper inbred lines, C. annuum ‘MC4’ (resistant) and C. annuum ‘Subicho’ (susceptible), and analyzed genomic variations through SNPs and Indels to identify candidate genes for BW resistance. Results An average of 139.5 Gb was generated among the two cultivars, with coverage ranging from 44.94X to 46.13X. A total of 8,815,889 SNPs was obtained between ‘MC4’ and ‘Subicho’. Among them, 31,190 (0.35%) were non-synonymous SNPs (nsSNPs) corresponding to 10,926 genes, and these genes were assigned to 142 Gene Ontology (GO) terms across the two cultivars. We focused on three known BW QTL regions by identifying genes with sequence variants through gene set enrichment analysis and securing those belonging to high significant GO terms. Additionally, we found 310 NLR genes with nsSNP variants between ‘MC4’ (R) and ‘Subicho’ (S) within these regions. Also, we performed an Indel analysis on these genes. By integrating all this data, we identified eight candidate BW resistance genes, including two NLR genes with nsSNPs variations in qRRs-10.1 on chromosome 10. Conclusion We identified genomic variations in the form of SNPs and Indels by re-sequencing two pepper cultivars with contrasting traits for bacterial wilt. Specifically, the four genes associated with pBWR-1 and Bw1 that exhibit both nsSNP and Indel variations simultaneously in ‘Subicho’, along with the two NLR genes linked to qRRs-10.1, which are known for their direct involvement in immune responses, are identified as most likely BW resistance genes. These variants in leading candidate genes associated with BW resistance can be used as important markers for breeding pepper varieties.

Ralstonia solanacearum usually infects the vascular bundle system through the roots of host plants, causing bacterial wilt and leading to irreversible wilting and death of plants. Bacterial wilt is a devastating soil-borne bacterial disease. At present, it has been one of the main diseases restricting the production of Solanaceae crops in China. Type Ⅲ secretion system (T3SS) plays an important role in the pathogenesis of R. solanacearum, using T3SS to inject large amounts of Type Ⅲ effectors (T3Es) into host cells to interfere with the immune response of the host. Scholars at home and abroad are committed to exploring how R. solanacearum interferes with host cells and regulates host immune function by identifying target proteins in the host. Therefore, the identification of host proteins that can be targeted by T3Es is helpful to understand the biological function of R. solanacearum T3Es, the pathogenic process of R. solanacearum, and to explore the R. solanacearum resistance-related proteins and their mechanism of action in hosts. Although most of the functions of T3Es are still unknown, so far, it has been reported that R. solanacearum T3Es can regulate host resistance to bacterial wilt by interfering with plant innate immunity, inducing plant hypersensitivity response and affecting plant metabolism and hormone signal transduction through a variety of molecular mechanisms. In this review, we summarize the current research progress on the characteristics and functional identification methods of T3Es of R. solanacearum, and its research progress in participating in the regulation of pathogenicity and plant immunity mechanism of R. solanacearum, which can provide an in-depth understanding of the pathogenic mechanism of R. solanacearum and the response mechanism of the host immune system. The mechanism of interaction between R. solanacearum T3Es and the host are prospected, which will provide an effective reference for the analysis of the host resistance mechanism induced by R. solanacearum and the prevention and control of bacterial wilt.

PAMP-triggered immunity (PTI) is the first layer of plant defense response that occurs on the plant plasma membrane. Recently, the application of a rhizobacterium, Bacillus amyloliquefaciens strain PMB05, has been demonstrated to enhance flg22Pst- or harpin-triggered PTI response such as callose deposition. This PTI intensification by PMB05 further contributes to plant disease resistance to different bacterial diseases. Under the demand for rapid and large-scale screening, it has become critical to establish a non-staining technology to identify microbial strains that can enhance PTI responses. Firstly, we confirmed that the expression of the GSL5 gene, which is required for callose synthesis, can be enhanced by PMB05 during PTI activation triggered by flg22 or PopW (a harpin from Ralstonia solanacearum). The promoter region of the GSL5 gene was further cloned and fused to the coding sequence of gfp. The constructed fragments were used to generate transgenic Arabidopsis plants through a plant transformation vector. The transgenic lines of AtGSL5-GFP were obtained. The analysis was performed by infiltrating flg22Pst or PopW in one homozygous line, and the results exhibited that the green fluorescent signals were observed until after 8 h. In addition, the PopW-induced fluorescent signal was significantly enhanced in the co-treatment with PMB05 at 4 h after inoculation. Furthermore, by using AtGSL5-GFP to analyze 13 Bacillus spp. strains, the regulation of PopW-induced fluorescent signal was observed. And, the regulation of these fluorescent signals was similar to that performed by callose staining. More importantly, the Bacillus strains that enhance PopW-induced fluorescent signals would be more effective in reducing the occurrence of bacterial wilt. Taken together, the technique by using AtGSL5-GFP would be a promising platform to screen plant immunity-intensifying microbes to control bacterial wilt. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum usually infects the vascular bundle system through the roots of host plants, causing bacterial wilt and leading to irreversible wilting and death of plants. Bacterial wilt is a devastating soil-borne bacterial disease. At present, it has been one of the main diseases restricting the production of Solanaceae crops in China. Type Ⅲ secretion system (T3SS) plays an important role in the pathogenesis of R. solanacearum, using T3SS to inject large amounts of Type Ⅲ effectors (T3Es) into host cells to interfere with the immune response of the host. Scholars at home and abroad are committed to exploring how R. solanacearum interferes with host cells and regulates host immune function by identifying target proteins in the host. Therefore, the identification of host proteins that can be targeted by T3Es is helpful to understand the biological function of R. solanacearum T3Es, the pathogenic process of R. solanacearum, and to explore the R. solanacearum resistancerelated proteins and their mechanism of action in hosts. Although most of the functions of T3Es are still unknown, so far, it has been reported that R. solanacearum T3Es can regulate host resistance to bacterial wilt by interfering with plant innate immunity, inducing plant hypersensitivity response and affecting plant metabolism and hormone signal transduction through a variety of molecular mechanisms. In this review, we summarize the current research progress on the characteristics and functional identification methods of T3Es of R. solanacearum, and its research progress in participating in the regulation of pathogenicity and plant immunity mechanism of R. solanacearum, which can provide an in-depth understanding of the pathogenic mechanism of R. solanacearum and the response mechanism of the host immune system. The mechanism of interaction between R. solanacearum T3Es and the host are prospected, which will provide an effective reference for the analysis of the host resistance mechanism induced by R. solanacearum and the prevention and control of bacterial wilt. [ABSTRACT FROM AUTHOR]

Potato (Solanum tuberosum L.) seed production using the aeroponic system has been widely implemented in Indonesia. However, aeroponic systems in tropical areas such as Indonesia faced obstacles in the form of high wilt attacks caused by the bacteria Ralstonia solanacearum. This research aimed to control R. solanacearum wilt disease in an aeroponic system using various microbes. The research was carried out from September 2022 to January 2023. This research consisted of four stages, namely exploration and isolation of microorganisms, identification of microbial antagonism, testing of in vitro potential microbial antagonism and testing of selected microbial antagonism in the aeroponic system. The nutrients used in the aeroponic system contained R. solanacearum with a concentration of 104 CFU mL-1, while the concentration of the microbial solution used was 108 CFU mL-1. Pseudomonas fluorescence was consistently the best microbe both in vitro and in aeroponics, whereas Bacillus subtilis could only overcome wilt in vitro and could not overcome wilt in aeroponic system. Pseudomonas fluorescence required 5 min soaking time and could increase wilt with increasing soaking time. The consortium between B. subtilis and P. fluorescence with 10 min soaking time could overcome wilt by 85% and increase the number of tubers and tuber weight by 79% and 85%, respectively, so this prospective microbial consortium could be applied to aeroponic systems environmentally friendly in tropical areas with high R. solanacearum opportunities. [ABSTRACT FROM AUTHOR]

Within a few years of the establishment of the convict settlement at Sydney Cove, the potato became one of the staple crops of the population due to its relatively high yield and the prior experience of the convicts and free settlers with growing the crop. In 1894, Henry Tryon described a new disease in southern Queensland that caused rapid wilting of plants, a ring of slightly translucent tissue just below the surface of affected tubers, oozing of a thick, white fluid from the 'eyes', and ultimately rotting of the tubers. It soon became known as 'Tryon's disease'. He found that a microbe (bacterium) was always associated with affected tubers and stems, provided a very brief description of the bacterial cells and named the microbe Bacillus vascularum solani. A few years later the American scientist Erwin Frink Smith wrote a paper on a new disease (brown rot) of solanaceous plants including the potato and tomato, in which he called the causal agent Pseudomonas solanacearum , now known as Ralstonia solanacearum. Smith dismissed Tryon's prior claim to the discovery of the disease with some of his comments being personal and scathing. Tryon had the last word, however, cloaking his response in restrained and somewhat convoluted tones. In 1894, the Queensland government entomologist, and later vegetable pathologist, Henry Tryon (1856–1943) discovered a new disease that caused potato tubers to become rotted and putrid. He consistently found bacterial cells in a thick mucilaginous gum in the vascular tissues of wilted stems and infected tubers, and gave it the name Bacillus vascularum solani. The American bacteriologist Erwin Frink Smith would not accept Tryon's discovery, instead naming the causal agent Pseudomonas solanacearum. That bacterium, now called Ralstonia solanacearum is a significant plant pathogen worldwide. Photograph by an unknown person. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum and R. pseudosolanacearum, the causative agents of bacterial wilt, ranks as the second most devastating phytopathogens, affecting over 310 plant species and causing substantial economic losses worldwide. R. solanacearum and R. pseudosolanacearum infect plants through the underground root system, where it interacts with both the host and the surrounding microbiota and multiply in the xylem where bacteria cell and its polysaccharide product block the water transportation from root to aboveground. Currently, effective control methods are limited, as resistance genes are unavailable and antibiotics prove ineffective. In current Commentary, we review recent advancements in combating bacterial wilt, categorizing the approaches (weapons) into three distinct strategies. The physical and chemical weapons focus on leveraging sound waves to trigger crop immunity and reducing bacterial virulence signaling, respectively. The biological weapon employs predatory protists to directly consume Ralstonia cells in the root zone, while also reshaping the protective rhizosphere microbiome to fortify the plant. We believe that these novel methods hold the potential to revolutionize crop protection from bacterial wilt and inspire new era in sustainable agriculture.

Identifying molecular markers linked to tobacco bacterial wilt resistance is crucial for developing resistant tobacco varieties, thereby enhancing tobacco production and quality. In this two-year study, we evaluated the tobacco bacterial wilt disease index (TBWDI) in a mapping population of 78 tobacco accessions using SSR/InDel markers across 1377 marker loci. Two association models, GLM_Q and MLM_Q + Kinship, were used for association analysis. By considering multiple environments, selection thresholds, and phenotype values, we identified 19 reliable marker loci (P = 7.07-E05–4.98-E02) that explained 5.37–19.10 % of the phenotypic variation. Among these, we selected 11 accessions with high resistance to tobacco bacterial wilt, each containing at least one excellent locus. The models predicted five hybrid combinations whose offspring aggregated additional excellent loci. Additionally, one locus was identified during quantitative trait loci mapping, with accessions carrying this locus exhibiting significantly different TBWDI values from those without it, confirming its reliability and stability. A candidate gene (LOC107795335) was also identified downstream at 17.58 Kbp of the locus. Our study pinpointed reliable loci associated with bacterial wilt resistance, identified important materials for breeding resistant tobacco varieities, and predicted the best hybrid combinations for low disease indexes. The results of our study offer invaluable theoretical insights for breeding varieties with high and stable resistance.

Ralstonia pseudosolanacearum, a plant pathogenic bacterium that can survive for a long time in soil and water, causes lethal wilt in the Solanaceae family. Sigma S is a part of the RNA polymerase complex, which regulates gene expression during bacterial stress response or stationary phase. In this study, we investigated the role of sigma S in R. pseudosolanacearum under stress conditions using a rpoS-defective mutant strain of R. pseudosolanacearum and its wild-type strain. The phenotypes of rpoS-defective mutant were complemented by introducing the original rpoS gene. There were no differences observed in bacterial growth rate and exopolysaccharide production between the wild-type strain and the rpoS mutant. However, the wild-type strain responded more sensitively to nutrient deficiency compared to the mutant strain. Under the nutrient deficiency, the rpoS mutant maintained a high bacterial viability for a longer period, while the viability of the wild-type strain declined rapidly. Furthermore, a significant difference in pH was observed between the culture supernatant of the wild-type strain and the mutant strain. The pH of the culture supernatant for the wild-type strain decreased rapidly during bacterial growth, leading to medium acidification. The rapid decline in the wild-type strain's viability may be associated with medium acidification and bacterial sensitivity to acidity during transition to the stationary phase. Interestingly, the rpoS mutant strain cannot utilize acetic acid, D-alanine, D-trehalose, and L-histidine. These results suggest that sigma S of R. pseudosolanacearum regulates the production or utilization of organic acids and controls cell death during stationary phase under nutrient deficiency.

Abstract This study focused on developing novel pyridine-3-carboxamide analogs to treat bacterial wilt in tomatoes caused by Ralstonia solanacearum. The analogs were synthesized through a multistep process and their structures confirmed using spectroscopy. Molecular docking studies identified the most potent analog from the series. A specific analog, compound 4a, was found to significantly enhance disease resistance in tomato plants infected with R. solanacearum. The structure–activity relationship analysis showed the positions and types of substituents on the aromatic rings of compounds 4a–i strongly influenced their biological activity. Compound 4a, with a chloro group at the para position on ring C and hydroxyl group at the ortho position on ring A, was exceptionally effective against R. solanacearum. When used to treat seeds, the analogs displayed remarkable efficacy, especially compound 4a which had specific activity against bacterial wilt pathogens. Compound 4a also promoted vegetative and reproductive growth of tomato plants, increasing seed germination and seedling vigor. In plants mechanically infected with bacteria, compound 4a substantially reduced the percentage of infection, pathogen quantity in young tissue, and disease progression. The analogs were highly potent due to their amide linkage. Molecular docking identified the best compounds with strong binding affinities. Overall, the strategic design and synthesis of these pyridine-3-carboxamide analogs offers an effective approach to targeting and controlling R. solanacearum and bacterial wilt in tomatoes.

Potato (Solanum tuberosum L.) is one of the most important tuber crops in the world and it is fourth among food crops after rice, wheat and maize. Potato is widely cultivated for its cheap source of carbohydrates, vitamins as well as minerals. In Cameroon, where potato provide a livelihood for most producers, especially in the Western highland, production is challenged by unavailability of appropriate seeds of local varieties or Cameroon improve varieties. Many decades ago, Cipira was released by the Institute of Agricultural Research for Development, Bambui, North West Region, Cameroon as an improved resistant variety. The current study evaluated the performance of Cipira considering seed sizes. Four seed sizes (20mm, 25mm, 30mm and 35mm diameter) were evaluated in a randomized complete block trial in Bambili in 2022 and 2023. Green peach aphid incidence was inversely related to tuber seed sizes (P < 0.05). Aphid population abundance was higher from plants with larger diameter. Late blight and bacterial wilt incidence and disease severity index was significantly higher for plants of smaller tuber seed size. Productivity was 8.06 t ha-1, 6.2 t ha-1, 5.7 t ha-1 and 5.8 t ha-1 from 35mm, 30mm, 25mm and 20mm tuber seed sizes, respectively in 2022. The yield in 2023 was 8.9 t ha-1, 7.8 t ha-1, 7.1 t ha-1, and 6.3 t ha-1, from 35mm, 30mm, 25mm and 20mm, respectively. For improved yield and reduced pest and diseases incidences, Cipira at 30 mm and 35 mm seed sizes are recommended. [Fundam Appl Agric 2024; 9(2.000): 80-90]

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.

The bacterial wilt disease caused by Ralstonia solanacearum is a significant threat to eggplant production. Breeding and promoting resistant varieties is one of the most effective methods to manage bacterial wilt. Conducting QTL (quantitative trait locus) mapping of resistant genes can substantially enhance the breeding of plant resistance to bacterial wilt. In this study, a population of 2200 F2 individuals derived from resistant and susceptible materials was utilized to establish extreme resistance and susceptibility pools. Following resequencing analysis of the parents and extreme pools, the QTL were examined using the DEEP-BSA software and QTLseqr R package (version 0.7.5.2). The results revealed that the detection of 10 QTL sites on chromosomes 5, 8, 9, and 11 by the five algorithms of the DEEP-BSA software. Additionally, the candidate region of 62 Mb–72 Mb on chromosome 5 was identified in all five algorithms of the DEEP-BSA software, as well as by the QTLseqr R package. Subsequent gene annotation uncovered 276 genes in the candidate region of 62 Mb–72 Mb on chromosome 5. Additionally, RNA-seq results indicated that only 13 genes had altered expression levels following inoculation with R. solanacearum in the resistant materials. Based on the expression levels, SMEL4_05g015980.1 and SMEL4_05g016110.1 were identified as candidate genes. Notably, SNP annotation identified a non-synonymous mutation in the exonic region of SMEL4_05g015980.1 and a variant in the promoter region of SMEL4_05g016110.1. The research findings have practical significance for the isolation of bacterial wilt resistance genes in eggplant and the development of resistance to bacterial wilt varieties in eggplant. [ABSTRACT FROM AUTHOR]

Bacterial wilt caused by Ralstonia solanacearum is a destructive plant disease, particularly in potato (Solanum tuberosum). R. solanacearum deploys a diverse and potent arsenal of type III effectors to inhibit the plant immune system. However, the understanding of individual effectors promoting susceptibility in host plants and interfering with plant immunity responses is still limited. Here, we demonstrated that the type III effector RipV1 functioned as a novel E3 ubiquitin ligase (NEL) effector and exhibited E3 ubiquitin ligase activity in vitro. Transient expression of RipV1 suppressed plant pathogen‐associated molecular pattern (PAMP)‐triggered immunity (PTI) responses in Nicotiana benthamiana, such as the expression of PTI‐related genes and the reactive oxygen species (ROS) burst. Prolonged expression of RipV1 induced cell death in N. benthamiana leaves. Notably, mutating the conserved cysteine residue of RipV1 abolished its E3 ligase activity and its ability to suppress plant PTI responses. This study also revealed the indispensability of RipV1 for R. solanacearum's full virulence in potato. Transgenic potato plants overexpressing ripV1 but not the catalytic mutant ripV1‐C444A displayed enhanced susceptibility to R. solanacearum. RipV1 was observed to localize specifically to the plant plasma membrane, with its N‐terminus being pivotal in determining this localization. These findings showcase that RipV1 acts as a NEL effector and contributes to R. solanacearum virulence by suppressing plant PTI responses through its E3 activity. [ABSTRACT FROM AUTHOR]

SUMMARY: Bacterial wilt, caused by Xanthomonas translucens pv. graminis (Xtg), is a serious disease of economically important forage grasses, including Italian ryegrass (Lolium multiflorum Lam.). A major QTL for resistance to Xtg was previously identified, but the precise location as well as the genetic factors underlying the resistance are yet to be determined. To this end, we applied a bulked segregant analysis (BSA) approach, using whole‐genome deep sequencing of pools of the most resistant and most susceptible individuals of a large (n = 7484) biparental F2 population segregating for resistance to Xtg. Using chromosome‐level genome assemblies as references, we were able to define a ~300 kb region highly associated with resistance on pseudo‐chromosome 4. Further investigation of this region revealed multiple genes with a known role in disease resistance, including genes encoding for Pik2‐like disease resistance proteins, cysteine‐rich kinases, and RGA4‐ and RGA5‐like disease resistance proteins. Investigation of allele frequencies in the pools and comparative genome analysis in the grandparents of the F2 population revealed that some of these genes contain variants with allele frequencies that correspond to the expected heterozygosity in the resistant grandparent. This study emphasizes the efficacy of combining BSA studies in very large populations with whole genome deep sequencing and high‐quality genome assemblies to pinpoint regions associated with a binary trait of interest and accurately define a small set of candidate genes. Furthermore, markers identified in this region hold significant potential for marker‐assisted breeding strategies to breed resistance to Xtg in Italian ryegrass cultivars more efficiently. Significance Statement: Elucidating the genetic control of phenotypic traits in highly heterozygous, outbreeding plant species is laborious as it requires phenotyping and genotyping of a large number of individuals. Using 7484 individuals of an Italian ryegrass population, bulked segregant analysis, and whole genome deep sequencing of pools, we identified a 300 kb genomic region harboring promising candidate genes for resistance to bacterial wilt, an important target trait in forage grass breeding. [ABSTRACT FROM AUTHOR]

The long-term application of agrochemicals, including pesticides, in intensive agricultural practices to protect crops from biotic stresses results in the emergence of resistance among phytopathogens and the ineffectiveness of chemical applications. The microbiological strategies, in contrast, minimize the reliance on chemicals and, hence, reduce environmental and human health risks. Bacterial wilt of tomato induced by Ralstonia solanacearum is one of the most destructive diseases worldwide that requires urgent attention to develop a safer and more efficient method to control the phytopathogen. The present work was conducted in the year 2022-2023. In this study, the bacterial wilt was managed by an antagonist bacterium, Pseudomonas fluorescens, exhibiting variable morphological, biochemical, and plant growth-promoting activities. The P. fluorescens inhibited the growth of R. solanacearum in plate assay at different time intervals (0-48 h). The SEM image of R. solanacearum cells cultured with P. fluorescens revealed pores, distortion, and fragmented cell envelope, while the untreated bacterial cells were uniform and smooth. Tomato plants infected with R. solanacearum showed 89% disease incidence compared to uninfected but PGPR-inoculated tomato plants. Application of P. fluorescens reduced disease incidence by 63% compared to R. solanacearum infested plants. Furthermore, plant length enhanced by 21 and 26% significantly following bacterial inoculation after three and four weeks of growth. Conclusively, this study emphasizes the effectiveness of using PGPR as a potent strategy for managing wilt disease in vegetable crops, especially tomato. [ABSTRACT FROM AUTHOR]

Soil degradation has been accelerated by the use of chemical pesticides and poor agricultural practices, which has had an impact on crop productivity. Recently, there has been a lot of interest in the use of eco-friendly biochar applications to enhance soil quality and sequester carbon in sustainable agriculture. This study aimed to determine the individual and combined effects of Leaf Waste Biochar (LWB) and the bio-control agent Trichoderma harzianum (BCA) on the development of bacterial wilt in eggplants (Solanum melongena) caused by Ralstonia solanacearum (RS). The effects of LWB and BCA on eggplant physiology and defense-related biochemistry were comprehensively examined. Inoculated (+RS) and un-inoculated (-RS) eggplants were grown in potting mixtures containing 3% and 6% (v/v) LWB, both with and without BCA. The percentage disease index was considerably reduced (90%) in plants grown in the 6% LWB+ BCA amended treatments. Moreover, the plants grown in LWB and inoculated with BCA had higher phenolics, flavonoids and peroxidase contents compared to the non-amended control. The level of NPK was significantly increased (92.74% N, 76.47% P, 53.73% K) in the eggplants cultivated in the 6% LWB + BCA composition. This study has shown that the association of T. harzianum with biochar improved plant growth and reduced R. solanacearum induced wilt. Furthermore, the combined impact of biochar and T. harzianum was greater in terms of wilt suppression and increase in plant physiological measurements when the biochar concentration was 6%. Biochar and bio-control agents triggered biochemical alterations, thus enhancing the management of disease-infested soils. [ABSTRACT FROM AUTHOR]

This study demonstrates the effect of fermented botanical product (FBP) on Ralstonia pseudosolanacearum -induced bacterial wilt disease and unravels its action mechanism. Soaking with diluted FBP solutions (0.1%-0.5%) significantly suppressed bacterial wilt in tomato plants, and FBP-treated tomato plants grew well against R. pseudosolanacearum infection. Growth assays showed that FBP had no antibacterial effect but promoted R. pseudosolanacearum growth. In contrast, few or no R. pseudosolanacearum cells were detected in aerial parts of tomato plants grown in FBP-soaked soil. Subsequent infection assays using the chemotaxis-deficient mutant (Δ cheA) or the root-dip inoculation method revealed that FBP does not affect pathogen migration to plant roots during infection. Moreover, FBP-pretreated tomato plants exhibited reduced bacterial wilt in the absence of FBP. These findings suggest that the plant, but not the pathogen, could be affected by FBP, resulting in an induced resistance against R. pseudosolanacearum , leading to a suppressive effect on bacterial wilt. [ABSTRACT FROM AUTHOR]

Bacterial wilt, caused by Ralstonia pseudosolanacearum (Rpsol) and R. solanacearum (Rsol), poses a significant challenge to solanaceous plant cultivation worldwide, particularly in tropical and subtropical regions. Even though Brazil is recognized as one of the centres of origin and diversity of Rsol, in certain regions of this large country there is an emerging prevalence of Rpsol in production fields. Therefore, this study aimed to comprehensively investigate the adaptive traits of Rpsol and Rsol using a polyphasic approach. A diverse collection of isolates from both species was assessed for their physiological, biochemical, ecological and pathogenic traits. Rsol isolates demonstrated greater adaptability to a broader range of temperature, salinity and pH. They also exhibited enhanced abilities in biofilm formation and bacteriocin production. Conversely, Rpsol isolates exhibited a broader utilization of carbon sources and displayed a wider spectrum of resistance to inhibitory substances. Moreover, they demonstrated higher infectivity towards different solanaceous hosts, showing a faster invasion and colonization process in the roots and stems of tomato plants compared to Rsol isolates. Based on our findings, we concluded that Rsol exhibited greater physiological and ecological adaptability, while Rpsol showed greater pathogenic and biochemical adaptability. These results suggest that the coexistence of both species is maintained through a balance of distinct traits within each species. [ABSTRACT FROM AUTHOR]

: In order to investigate the incidence of bacterial wilt in the solanaceae crops such as tomato, eggplant and pepper in South China, the samples were collected from the healthy plants, the plants infected bacterial wilt and their rhizosphere soil. Then, the isolation and identification of pathogenic bacteria, pathogenicity determination and distribution characteristics analysis were carried out. The results showed that: the areas with the highest incidence of bacterial wilt in tomato, eggplant and pepper were Lingshui in Hainan, Jin'an in Fujian and Shaowu in Fujian, respectively. The average incidence rates during their growth period were 20.01%, 5.24% and 23.33%, respectively. A total of 86 strains of Ralstonia solanacearum were isolated and identified from the solanaceae crops with different geographical origins. The pathogenicity of the isolated Ralstonia solanacearum was further divided by using the Attenuation index (AI). Among them, 7 strains were non-pathogenic strains (AI larger than 0.75), 13 strains were transitional-type strains (0.65≤AI≤0.75), and 66 strains were high virulent strains (AI smaller than 0.65). The distribution characteristics of Ralstonia solanacearum were studied. It was found that for different hosts, the distribution characteristics of Ralstonia solanacearum were that the distribution number of Ralstonia solanacearum in the diseased plants and their rhizosphere soil was significantly higher than that in the healthy plants and their rhizosphere soil. Moreover, the distribution number in the tissue and soils ranged in the descending order of soil > root > stem. In addition, among the solanaceae crops investigated, the distribution number of Ralstonia solanacearum in the soil where the plants infected bacterial wilt was greater than 106 cfu·g-1, and the distribution number of Ralstonia solanacearum in the roots and stems of the plants infected bacterial wilt was greater than 105 cfu·g-1. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum species complex (RSSC) is a phytopathogenic bacterial group that causes bacterial wilt in several crops, being potato (Solanum tuberosum) one of the most important hosts. The relationship between the potato plant ionome (mineral and trace elements composition) and the resistance levels to this pathogen has not been addressed until now. Mineral content of xylem sap, roots, stems and leaves of potato genotypes with different levels of resistance to bacterial wilt was assessed in this work, revealing a positive correlation between divalent calcium (Ca) cation concentrations and genotype resistance. The aim of this study was to investigate the effect of Ca on bacterial wilt resistance, and on the growth and virulence of RSSC. Ca supplementation significantly decreased the growth rate of Ralstonia pseudosolanacearum GMI1000 in minimal medium and affected several virulence traits such as biofilm formation and twitching motility. We also incorporate for the first time the use of microfluidic chambers to follow the pathogen growth and biofilm formation in conditions mimicking the plant vascular system. By using this approach, a reduction in biofilm formation was observed when both, rich and minimal media, were supplemented with Ca. Assessment of the effect of Ca amendments on bacterial wilt progress in potato genotypes revealed a significant delay in disease progress, or a complete absence of wilting symptoms in the case of partially resistant genotypes. This work contributes to the understanding of Ca effect on virulence of this important pathogen and provides new strategies for an integrated control of bacterial wilt on potato. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum, the bacterium that causes bacterial wilt, is a destructive phytopathogen that can infect over 450 different plant species. Several agriculturally significant crop plants, including eggplant, tomato, pepper, potato, and ginger, are highly susceptible to this plant disease, which has a global impact on crop quality and yield. There is currently no known preventive method that works well for bacterial wilt. Bacteria use two-component systems (TCSs) to sense their environment constantly and react appropriately. This is achieved by an extracellular sensor kinase (SK) capable of sensing a suitable signal and a cytoplasmic response regulator (RR) which gives a downstream response. Moreover, our investigation revealed that R. solanacearum GMI1000 possesses a substantial count of TCSs, specifically comprising 36 RRs and 27 SKs. While TCSs are known targets for various human pathogenic bacteria, such as Salmonella, the role of TCSs in R. solanacearum remains largely unexplored in this context. Notably, numerous inhibitors targeting TCSs have been identified, including GHL (Gyrase, Hsp, and MutL) compounds, Walk inhibitors, and anti-TCS medications like Radicicol. Consequently, the investigation into the involvement of TCSs in virulence and pathogenesis has gained traction; however, further research is imperative to ascertain whether TCSs could potentially supplant conventional anti-wilt therapies. This review delves into the prospective utilization of TCSs as an alternative anti-wilt therapy, focusing on the lethal phytopathogen R. solanacearum. [ABSTRACT FROM AUTHOR]

Summary: N6‐methyladenosine (m6A) is the most abundant mRNA modification in eukaryotes and is an important regulator of gene expression as well as many other critical biological processes. However, the characteristics and functions of m6A in peanut (Arachis hypogea L.) resistance to bacterial wilt (BW) remain unknown.Here, we analyzed the dynamic of m6A during infection of resistant (H108) and susceptible (H107) peanut accessions with Ralstonia solanacearum (R. solanacearum), the causative agent of BW. Throughout the transcriptome, we identified 'URUAY' as a highly conserved motif for m6A in peanut. The majority of differential m6A located within the 3′ untranslated region (UTR) of the transcript, with fewer in the exons.Integrative analysis of RNA‐Seq and m6A methylomes suggests the correlation between m6A and gene expression in peanut R. solanacearum infection, and functional analysis reveals that m6A‐associated genes were related to plant‐pathogen interaction.Our experimental analysis suggests that AhALKBH15 is an m6A demethylase in peanut, leading to decreased m6A levels and upregulation of the resistance gene AhCQ2G6Y. The upregulation of AhCQ2G6Y expression appears to promote BW resistance in the H108 accession. [ABSTRACT FROM AUTHOR]

Rhizosphere bacteria based biological control strategy is an eco-friendly approach to protect crops from various plant diseases. Among these, spore-forming Bacillus, abundant in the rhizosphere, provide unique advantages for plant health. This study focused on characterising two tomato rhizosphere-associated Bacillus amyloliquefaciens strains (Trb7 and Trb11), highly effective against the bacterial wilt pathogen Ralstonia pseudosolanacearum in vitro. Species identification was based on partial 16S rRNA gene sequencing, supported by phylogenetic analysis. Five antimicrobial peptide (AMP) genes (surfactin, fengycin, bacilysin, subtilin, and spore protein) were detected in both the isolates of B. amyloliquefqciens using specific molecular markers. Greenhouse trials showed that prophylactic application of these isolates led to an 83.4% reduction in tomato bacterial wilt, with only 16.6% wilt incidence compared to the 100% in the R. pseudosolanacearum-inoculated control. Moreover, these B. amyloliquefaciens isolates exhibited plant-growth-promoting traits in vitro. Interestingly, they also showed significant inhibition of mycelial growth against Sclerotium rolfsii and Alternaria alternata, major fungal pathogens in tomatoes. Overall, our findings highlight the potent bactericidal role of B. amyloliquefaciens isolates in suppressing R. pseudosolanacearum in tomatoes. Two among the 100 Bacillus displayed antibacterial activity against Ralstonia pseudosolanacearum. Antibacterial firmicutes was identified as Bacillus amyloliquefaciens through the 16S rRNA gene sequence analysis. Five AMP genes (srfAA, fenD, bacA, spas, and spoVG) were identified in the isolates. Delivery of B. amyloliquefaciens drenching on rhizosphere significantly reduced wilt. Additionally, B. amyloliquefaciens showed the antifungal activity on Sclerotium rolfsii and Alternaria alternata. [ABSTRACT FROM AUTHOR]

Bacterial wilt is one of the most important vascular diseases that generate high worldwide losses. The main strategy to control it involves early detection of infected plants that mitigate its spread in the field. This research characterized the spectral response of healthy plants, infected with Ralstonia solanacearum E.F. Smith race 2 and subjected to water stress, in two banana cultivars by spectroscopy reflectance. The spectral data were used to detect vascular wilt during the incubation period of the disease in Gros Michel and Cavendish banana cultivars. The reflectance data were collected from the leaves using a portable spectrometer. Both varieties of healthy plants showed a typical low reflectance in the visible range, with a peak of green of around 12% in Williams and 5% in Gros Michel. In the measured infrared range, the two varieties presented values between 60 and 70% in the latest days post-infection measurements, decreasing to ~ 50% after 12 dpi. The results obtained indicate that plants infected with R. solanacearum have no initial increase in reflectance in the visible (Vis) range, whereas decrease rapidly after 6 dpi in the 700–1000 nm range. This methodology identifies three wavelengths (710, 770, and 965 nm) that allow differentiation between ill and healthy plants after 6 days post-inoculation, with a percentage of correct classification that ranges from 96 to 100%. The spectral response characterization in healthy plants and those subjected to various types of stress is a fundamental input for the development of early disease detection systems based on spectroscopy techniques. [ABSTRACT FROM AUTHOR]

Bacterial wilt is a widespread and devastating disease that impacts the production of numerous crucial crops worldwide. The main causative agent of the disease is Ralstonia solanacearum. Due to the pathogen's broad host range and prolonged survival in the soil, it is challenging to control the disease with conventional strategies. Therefore, it is of great importance to develop effective alternative disease control strategies. In recent years, phage therapy has emerged as an environmentally friendly and sustainable biocontrol alternative, demonstrating significant potential in controlling this severe disease. This paper summarized basic information about isolated phages that infect R. solanacearum , and presented some examples of their application in the biocontrol of bacterial wilt. The risks of phage application and future prospect in this area were also discussed. Overall, R. solanacearum phages have been isolated from various regions and environments worldwide. These phages belong mainly to the Inoviridae, Autographiviridae, Peduoviridae , and Cystoviridae families, with some being unclassified. Studies on the application of these phages have demonstrated their ability to reduce pathogenicity of R. solanacearum through direct lysis or indirect alteration of the pathogen's physiological properties. These findings suggested bacteriophage is a promising tool for biocontrol of bacterial wilt in plants. [ABSTRACT FROM AUTHOR]

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Abstract Background Bacterial wilt caused by Ralstonia solanacearum severely affects peanut (Arachis hypogaea L.) yields. The breeding of resistant cultivars is an efficient means of controlling plant diseases. Therefore, identification of resistance genes effective against bacterial wilt is a matter of urgency. The lack of a reference genome for a resistant genotype severely hinders the process of identification of resistance genes in peanut. In addition, limited information is available on disease resistance-related pathways in peanut. Results Full-length transcriptome data were used to generate wilt-resistant and -susceptible transcript pools. In total, 253,869 transcripts were retained to form a reference transcriptome for RNA-sequencing data analysis. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis of differentially expressed genes revealed the plant-pathogen interaction pathway to be the main resistance-related pathway for peanut to prevent bacterial invasion and calcium plays an important role in this pathway. Glutathione metabolism was enriched in wilt-susceptible genotypes, which would promote glutathione synthesis in the early stages of pathogen invasion. Based on our previous quantitative trait locus (QTL) mapping results, the genes arahy.V6I7WA and arahy.MXY2PU, which encode nucleotide-binding site-leucine-rich repeat receptor proteins, were indicated to be associated with resistance to bacterial wilt. Conclusions This study identified several pathways associated with resistance to bacterial wilt and identified candidate genes for bacterial wilt resistance in a major QTL region. These findings lay a foundation for investigation of the mechanism of resistance to bacterial wilt in peanut.

Bacterial wilt (BW) of tomatoes, caused by Ralstonia solanacearum, is a devastating disease that results in large annual yield losses worldwide. Management of BW of tomatoes is difficult due to the soil-borne nature of the pathogen. One of the best ways to mitigate the losses is through breeding for disease resistance. Moreover, plant height (PH) is a crucial element related to plant architecture, which determines nutrient management and mechanical harvesting in tomatoes. An intraspecific F2 segregating population (NC 11212) of tomatoes was developed by crossing NC 84173 (tall, BW susceptible) × CLN1466EA (short, BW resistant). We performed quantitative trait loci (QTL) mapping using single nucleotide polymorphic (SNP) markers and the NC 11212 F2 segregating population. The QTL analysis for BW resistance revealed a total of three QTLs on chromosomes 1, 2, and 3, explaining phenotypic variation (R2) ranging from 3.6% to 14.9%, whereas the QTL analysis for PH also detected three QTLs on chromosomes 1, 8, and 11, explaining R2 ranging from 7.1% to 11%. This work thus provides information to improve BW resistance and plant architecture-related traits in tomatoes. [ABSTRACT FROM AUTHOR]

Many bacterial plant pathogens have a broad host range important for their life cycle. Alternate hosts from plant families other than the main (primary) host support the survival and dissemination of the pathogen population even in absence of main host plants. Metabolic peculiarities of main and alternative host plants can affect genetic diversity within and between the pathogen populations isolated from those plants. Strains of Gram-positive bacterium Curtobacterium flaccumfaciens were identified as being causal agents of bacterial spot and wilt diseases on leguminous plants, and other crop and weed plants, collected in different regions of Russia. Their biochemical properties and susceptibility to copper compounds have been found to be relatively uniform. According to conventional PCR assays, all of the isolates studied were categorised as pathovar Curtobacterim flaccumfaciens pv. flaccumfaciens, a pathogen of legumes. However, the strains demonstrated a substantial diversity in terms of virulence on several tested host plants and different phylogenetic relationships were revealed by BOX-PCR and alanine synthase gene (alaS) sequencing. [ABSTRACT FROM AUTHOR]

Biochar is increasingly being recognized as an effective soil amendment to enhance plant health and improve soil quality, but the complex relationships among biochar, plant resistance, and the soil microbial community are not clear. In this study, biochar derived from an invasive plant (Solidago canadensis L.) was used to investigate its impacts on bacterial wilt control, soil quality, and microbial regulation. The results reveal that the invasive plant biochar application significantly reduced the abundance of Ralstonia solanacearum in the soil (16.8–32.9%) and wilt disease index (14.0–49.2%) and promoted tomato growth. The biochar treatment increased the soil organic carbon, nutrient availability, soil chitinase, and sucrase activities under pathogen inoculation. The biochar did not influence the soil bacterial community diversity, but significantly increased the relative abundance of beneficial organisms, such as Bacillus and Sphingomonas. Biochar application increased the number of nodes, edges, and the average degree of soil microbial symbiotic network, thereby enhancing the stability and complexity of the bacterial community. These findings suggest that the invasive plant biochar produces win–win effects on plant–soil systems by suppressing soilborne wilt disease, enhancing the stability of the soil microbial community network, and promoting resource utilization, indicating its good potential in sustainable soil management. [ABSTRACT FROM AUTHOR]

Understanding the response of soil microbial communities to pathogenic Ralstonia solanacearum is crucial for preventing bacterial wilt outbreaks. In this study, we investigated the soil physicochemical and microbial community to assess their impact on the pathogenic R.solanacearum through metagenomics. Our results revealed that certain archaeal taxa were the main contributors influencing the health of plants. Additionally, the presence of the pathogen showed a strong negative correlation with soil phosphorus levels, while soil phosphorus was significantly correlated with bacterial and archaeal communities. We found that the network of microbial interactions in healthy plant rhizosphere soils was more complex compared to diseased soils. The diseased soil network had more linkages, particularly related to the pathogen occurrence. Within the network, the family Comamonadaceae, specifically Ramlibacter&lowbar;tataouinensis, was enriched in healthy samples and showed a significantly negative correlation with the pathogen. In terms of archaea, Halorubrum, Halorussus&lowbar;halophilus (family: Halobacteriaceae), and Natronomonas&lowbar;pharaonis (family: Haloarculaceae) were enriched in healthy plant rhizosphere soils and showed negative correlations with R.solanacearum. These findings suggested that the presence of these archaea may potentially reduce the occurrence of bacterial wilt disease. On the other hand, Halostagnicola&lowbar;larseniia and Haloterrigena&lowbar;sp.&lowbar;BND6 (family: Natrialbaceae) had higher relative abundance in diseased plants and exhibited significantly positive correlations with R.solanacearum, indicating their potential contribution to the pathogen's occurrence. Moreover, we explored the possibility of functional gene sharing among the correlating bacterial pairs within the Molecular Ecological Network. Our analysis revealed 468 entries of horizontal gene transfer (HGT) events, emphasizing the significance of HGT in shaping the adaptive traits of plant-associated bacteria, particularly in relation to host colonization and pathogenicity. Overall, this work revealed key factors, patterns and response mechanisms underlying the rhizosphere soil microbial populations. The findings offer valuable guidance for effectively controlling soil-borne bacterial diseases and developing sustainable agriculture practices. [ABSTRACT FROM AUTHOR]

Bacterial wilt is a significant soil-borne disease that poses a threat to mulberry production yield and quality of agricultural production worldwide. However, the disease resistance mechanisms dependent on root exudates are not well understood. In this present study, we investigated the antibacterial mechanisms of the main active substances (erucamide, oleamide, and camphor bromide) present in mulberry root exudates (MRE) against Ralstonia pseudosolanacearum (Rp), the causal agent of bacterial wilt. Our findings revealed that these three active substances inhibited the growth activity of Rp by affecting the cell morphology and extracellular polysaccharide content, as well as triggering a burst of reactive oxygen species. The active substances induced oxidative stress, leading to a decrease in Rp growth. Additionally, the expression levels of key genes in the hrp gene cluster (hrpB, hrpX, and hrpF) and other virulence-related genes (such as ripAW, ripAE, Rs5-4819, Rs5-4374, ace, egl3, and pehB) were significantly reduced upon treatment with the active substances. Further pathogenicity experiments demonstrated that root exudates (at a concentration of 1.5 mg·mL−1) delayed or slowed down the occurrence of bacterial wilt in mulberry. These findings provide valuable insight into the antimicrobial mechanisms of MRE against Rp and lay a theoretical foundation for the development and application of biocontrol agents to control mulberry bacterial wilt. [ABSTRACT FROM AUTHOR]

CRISPR/Cas is a breakthrough genome editing system because of its precision, target specificity, and efficiency. As a speed breeding system, it is more robust than the conventional breeding and biotechnological approaches for qualitative and quantitative trait improvement. Tomato (Solanum lycopersicum L.) is an economically important crop, but its yield and productivity have been severely impacted due to different abiotic and biotic stresses. The recently identified SlHyPRP1 and SlDEA1 are two potential negative regulatory genes in response to different abiotic (drought and salinity) and biotic stress (bacterial leaf spot and bacterial wilt) conditions in S. lycopersicum L. The present study aimed to evaluate the drought, salinity, bacterial leaf spot, and bacterial wilt tolerance response in S. lycopersicum L. crop through CRISPR/Cas9 genome editing of SlHyPRP1 and SlDEA1 and their functional analysis. The transient single- and dual-gene SlHyPRP1 and SlDEA1 CRISPR-edited plants were phenotypically better responsive to multiple stress factors taken under the study. The CRISPRedited SlHyPRP1 and SlDEA1 plants showed a higher level of chlorophyll and proline content compared to wild-type (WT) plants under abiotic stress conditions. Reactive oxygen species accumulation and the cell death count per total area of leaves and roots under biotic stress were less in CRISPR-edited SlHyPRP1 and SlDEA1 plants compared to WT plants. The study reveals that the combined loss-of-function of SlHyPRP1 along with SlDEA1 is essential for imparting significant multi-stress tolerance (drought, salinity, bacterial leaf spot, and bacterial wilt) in S. lycopersicum L. The main feature of the study is the detailed genetic characterization of SlDEA1, a poorly studied 8CM family gene in multi-stress tolerance, through the CRISPR/Cas9 gene editing system. The study revealed the key negative regulatory role of SlDEA1 that function together as an anchor gene with SlHyPRP1 in imparting multi-stress tolerance in S. lycopersicum L. It was interesting that the present study also showed that transient CRISPR/Cas9 editing events of SlHyPRP1 and SlDEA1 genes were successfully replicated in stably generated parent-genome-edited line (GEd0) and genome-edited first-generation lines (GEd1) of S. lycopersicum L. With these upshots, the study's key findings demonstrate outstanding value in developing sustainable multi-stress tolerance in S. lycopersicum L. and other crops to cope with climate change. [ABSTRACT FROM AUTHOR]

The soil microbial community plays a critical role in promoting robust plant growth and serves as an effective defence mechanism against root pathogens. Current research has focused on unravelling the compositions and functions of diverse microbial taxa in plant rhizospheres invaded by Ralstonia solanacearum, however, the specific mechanisms by which key microbial groups with distinct functions exert their effects remain unclear. In this study, we employed a combination of amplicon sequencing and metabolomics analysis to investigate the principal metabolic mechanisms of key microbial taxa in plant rhizosphere soil. Compared to the healthy tobacco rhizosphere samples, the bacterial diversity and co-occurrence network of the diseased tobacco rhizosphere soil were significantly reduced. Notably, certain genera, including Gaiella, Rhodoplanes, and MND1 (Nitrosomonadaceae), were found to be significantly more abundant in the rhizosphere of healthy plants than in that of diseased plants. Eight environmental factors, including exchangeable magnesium, available phosphorus, and pH, were found to be crucial factors influencing the composition of the microbial community. Ralstonia displayed negative correlations with pH, exchangeable magnesium, and cation exchange flux, but showed a positive correlation with available iron. Furthermore, metabolomic analysis revealed that the metabolic pathways related to the synthesis of various antibacterial compounds were significantly enriched in the healthy group. The correlation analysis results indicate that the bacterial genera Polycyclovorans, Lysobacter, Pseudomonas, and Nitrosospira may participate in the synthesis of antibacterial compounds. Collectively, our findings contribute to a more in-depth understanding of disease resistance mechanisms within healthy microbial communities and provide a theoretical foundation for the development of targeted strategies using beneficial microorganisms to suppress disease occurrence. [ABSTRACT FROM AUTHOR]