Search Results (269)

Bacterial wilt (BW) is a globally serious soil-borne disease in a wide range of plants, caused by diverse strains of Ralstonia solanacearum. However, there are few research reports on melatonin regulating plant resistance against R. solanacearum. N-acetyltransferase SlSNAT2 is a rate-limiting enzyme in plant melatonin synthesis. This study elucidates the mechanisms of SlSNAT2 modulating tomato resistance to BW. SlSNAT2 was expressed in tomato roots, stems, and leaves and induced upon R. solanacearum inoculation. Knocking out SlSNAT2 significantly decreased the melatonin content in CRISPR/Cas9 mutant slsnat2. With R. solanacearum inoculation, the morbidity and disease index value of slsnat2 were significantly higher than those of the tomato wild-type plant Micro-Tom (MT) according to the wilt rate and severity. The chlorophyll levels, photosynthetic rates, and callus deposition quantity in slsnat2 were notably lower while the reactive oxygen species (ROS) level was considerably higher than those in the MT after inoculation. Additionally, the SlSNAT2 deficiency depressed the expression of the mitogen-activated protein kinase (MAPK) pathway genes (SlMPK1, SlMKK2), salicylic acid pathway genes (SlGluA, SlPR-1a), jasmonic acid pathway gene SlPin2, and pathogenesis-related (PR) protein genes (SlPR-STH2a, SlPR-STH2b, SlPR-STH2c, SlPR-STH2d). These results revealed SlSNAT2 enhanced the tomato resistance against R. solanacearum by orchestrating ROS homeostasis, callose deposition, MAPK signaling, hormone pathways, and PR gene transcripts. Full article

The aim of this study was to explore the effects of different lactic acid bacteria additives (Lactiplantibacillus plantarum or Lentilactobacillus buchneri) on the fermentation quality, chemical composition, in vitro digestibility, bacterial community structure, and predictive function of S. perfoliatum silage feed. Fresh S. perfoliatum was wilted overnight, then its moisture content was adjusted between 65 and 70%. The experiment was performed in three groups as follows: (1) the control group (CK group), which lacked a Lactobacillus preparation; (2) the Lactiplantibacillus plantarum (L. plantarum) group (LP group), which was inoculated with L. plantarum at 5 × 10⁶ cfu/g FW; and (3) the Lentilactobacillus buchneri (L. buchneri) group (LB group), which was inoculated with L. buchneri at 5 × 10⁶ cfu/g FW. The results showed that L. plantarum significantly reduced pH and increased lactic acid (LA) content in S. perfoliatum silage compared with the control. L. buchneri, on the other hand, excelled in reducing ammonia nitrogen (NH₃-N) content and significantly increased acetic acid (AA) content. At 60 days of fermentation, the CP content was significantly higher (p < 0.05) in the LP and LB groups than in the CK group (19.29 vs. 15.53 and 15.87). At 60 days of fermentation, the ivCPD was significantly higher (p < 0.05) in the LB group than in the CK and LP groups (57.80 vs. 54.77 and 55.77). The 60-day silage process completely altered the bacterial community of S. perfoliatum silage. In the fresh samples, the dominant genera were Weissella_A and Pantoea_A. Weissella_A and Pantoea_A were gradually replaced by Lentilactobacillus and Lactiplantibacillus after S. perfoliatum ensiling. After 45 days of fermentation, L. buchneri became the dominant strain in CK, LP and LB groups. Inoculation with L. plantarum altered the succession of the bacterial community from 7 to 15 days of fermentation of S. perfoliatum. In contrast, inoculation with L. buchneri affected the succession of the bacterial community from 30 to 60 days of S. perfoliatum fermentation. In S. perfoliatum silage aged 7 to 60 days, the amino acid metabolic pathway in the LB group remained upregulated. The experimental results revealed that inoculation with L. buchneri had a stronger effect on S. perfoliatum silage than inoculation with L. plantarum. Thus, L. buchneri should be selected as an additive for S. perfoliatum silage fermentation in practical production. Full article

Potato early dying disease complex (PED) leads to premature senescence and rapid decline in potato plants. Unlike potato wilt caused solely by Verticillium species, PED symptoms are more severe due to the synergistic effects of multiple pathogens, including root-lesion nematodes, fungi such as Colletotrichum and Fusarium, and soft-rot bacteria. To investigate the microbiome responsible for PED, soil and stem samples from healthy-looking and symptomatic plants were analyzed using amplicon-targeted next-generation sequencing (Illumina MiSeq and PacBio technologies). Samples were collected from four locations in New Brunswick, Canada from fields previously rotated with barley or oat. Comparative analysis of the bacterial, fungal, and eukaryotic diversity in soil samples showed minimal differences, with only bacterial alpha diversity influenced by the plant health status. Verticillium dahliae was abundant in all soil samples, and its abundance was significantly higher in the stems of diseased plants. Additional fungal species implicated in PED, including Plectosphaerella cucumerina, Colletotrichum coccodes, Botrytis sp., and Alternaria alternata, were also identified in the stems. This study highlights the complex, plant-associated microbial interactions underlying PED and provides a foundation for microbiome-informed disease management strategies. Full article

Tomato bacterial wilt, caused by Ralstonia solanacearum (G⁻), is one of the most devastating plant diseases. Developing effective resistance against this pathogen remains a major challenge in plant disease management. In this study, we constructed a fusion gene BPI-LY by combining the gene encoding the lipophilic functional domains of human bactericidal/permeability-increasing protein (BPI) with the gene of human lysozyme (LY). The recombinant gene BPI-LY was heterologously expressed in yeast and tomato. Preliminary in vitro assays in yeast demonstrated that BPI enhances LY’s antibacterial activity against G⁻ bacteria. Furthermore, overexpression of BPI-LY in tomato delayed onset of the disease in the transgenic lines and lowered the degree of tissue damage and the number of bacteria present in the stems relative to those in the wild-type plant. Additionally, the expression levels of the SlSOD, SlPOD, SlPAL, SlPR5, SlPR10, and SlPR-NP24 genes were indirectly upregulated in the transgenic plants following R. solanacearum inoculation. Collectively, these findings demonstrate that BPI-LY enhances the resistance of transgenic tomato against bacterial wilt caused by R. solanacearum. Full article

With continuous improvements in people’s environmental awareness, biological control agents have garnered considerable attention owing to their advantageous impacts on improving soil fertility and alleviating plant diseases. Bacillus subtilis (B. subtilis) B579, isolated from the rhizosphere soil of cucumber, has effectively suppressed the growth of pathogenic Fusarium oxysporum. Our study investigates the effects of B. subtilis B579 on the properties of the rhizosphere soil (its physicochemical properties and enzymatic activities) and microbial community of cucumber under Fusarium oxysporum infection. An amplicon sequencing analysis of the microorganisms in the rhizosphere soil was conducted, and the soil’s properties were measured. The findings demonstrated that B. subtilis B579 exhibited 73.68% efficacy in controlling cucumber Fusarium wilt disease. B579 pretreatment substantially increased the bacterial and fungi diversity and improved the soil’s physicochemical properties (pH level and OC, TN, TP, AK, and AP contents) and enzyme activities, especially those of urease and alkaline phosphatase, which exhibited significant increases of 77.22% and 64.77%, respectively, in comparison to those under the pathogen treatment. Furthermore, the utilization of B579 reduced the abundance of Fusarium while simultaneously increasing the abundance of beneficial groups, including the Bacillus, Paenibacillus, Sphingomonas, Pseudomonas, Microbacterium, Mortierella, and Trichoderma genera. The RDA showed that the abundance of Bacillus, Paenibacillus, Sphingomonas, and Mortierella in the rhizosphere showed positive correlations with most of the soil properties, whereas Fusarium abundance was negatively correlated with most of the soil’s properties. This study provides novel insights into the disease suppression mechanisms of Bacillus subtilis B579, laying the theoretical foundation for its development as a biocontrol agent. Full article

Pantoea stewartii subsp. stewartii (Pss) is a Gram-negative bacterium causing Stewart wilt, a severe disease in maize. Native to North America, it has spread globally through the maize seed trade. Resistant maize varieties and insecticides are crucial to mitigate the disease’s economic impact. Pss is a quarantine pest, requiring phytosanitary certification for the seed trade in European countries. Accurate diagnostic tests, including real-time PCR, are fundamental to detect Pss and distinguish it from other bacteria, like Pantoea stewartii subsp. indologenes (Psi), a non-quarantine bacteria associated with maize seeds. Population genetics is a valuable tool for studying adaptation, speciation, population structure, diversity, and evolution in plant bacterial pathogens. In this study, the key activities of interlaboratory comparisons are reported to assess diagnostic sensitivity (DSE), diagnostic specificity (DSP) and accuracy (ACC) for different real-time PCR able to detect Pss in seeds. The results of complete sequencing of Italian bacterial isolates are presented. This study enhances our understanding of molecular methods for diagnosing and identifying pathogens in maize seeds, improving knowledge of Pss genomes to prevent their spread and trace possible entry routes from endemic to non-endemic areas. Full article

Pine wilt disease (PWD) poses a significant threat to pine forest health, making sanitation thinning of infected trees and cultivation of disease-resistant pine stands crucial measures for forest ecosystem restoration. To date, limited studies have systematically investigated how post-sanitation planting of pine-wilt-disease-resistant Pinus species affects soil microbiome, especially regarding bacterial and fungal diversity characteristics, functional succession patterns, and community assembly processes. In this study, we performed a comparative analysis of soil microbial community characteristics and biochemical properties between experimental plots subjected to sanitation thinning and those replanted with disease-resistant pine species. The results indicated that compared to the sanitation-thinned experimental plot, the disease-resistant experimental plots (Pinus taeda experimental plot and Pinus thunbergii experimental plot) exhibited significantly higher activities of β-glucosidase (S-β-GC), N-acetyl-β-D-glucosidase (S-NAG), and soil arylsulfatase (S-ASF). Compared with the sanitation logging stands, our analysis revealed that the Pinus taeda experimental plot and Pinus thunbergii experimental plot exhibited significantly higher fungal community evenness (OTUs), greater species abundance (OTUs), and more unique fungal taxa. Furthermore, the edaphic properties—specifically soil moisture content (SMC), pH levels, and total potassium (TK)—significantly influenced the structures of soil bacterial and fungal communities. Compared to the sanitation-thinned experimental plot, wood saprotrophic fungi and ectomycorrhizal fungi exhibited increased abundance in both the P. taeda experimental plot and Pinus thunbergii experimental plot. Furthermore, the null models indicated that both the P. taeda experimental plot and P. thunbergii experimental plot enhanced the undominated processes of bacteria and fungi. In summary, our data elucidate the differences in bacterial and fungal responses between pine forests undergoing thinning due to infected trees and those cultivated for disease resistance. This deepens our understanding of microbial functions and community assembly processes within these ecosystems. Full article

Verticillium spp. are soil-borne fungal pathogens capable of infecting over 400 plant species via their root systems, with each species demonstrating a distinct host range. The primary host of Verticillium nonalfalfae is the hop plant (Humulus lupulus), which becomes affected by Verticillium wilt and, in severe cases, dieback. A dual screening approach was employed to isolate Streptomycetes as potential biocontrol agents from the hop root systems alongside other bacterial species from hop xylem. Three Pseudomonas strains from the xylem and three Streptomyces strains from the roots were selected based on their in vitro antifungal activity against Verticillium dahliae and/or V. nonalfalfae. Their potential for controlling Verticillium wilt was further assessed through in planta assays conducted under greenhouse conditions. The results demonstrated that Pseudomonas sp. HX1, Streptomyces luteogriseus HR40, and Streptomyces flavofungini HR77 significantly reduced the disease severity index by 32.56% compared to artificially infected control plants. In contrast, the commercial biocontrol product Serenade^® ASO, containing Bacillus amyloliquefaciens QST 713, achieved a reduction of 13.96%. These findings underscore the potential of the selected bacterial strains as promising candidates for the biological control of Verticillium wilt in hops affected by V. nonalfalfae. Full article

Ralstonia solanacearum is a highly destructive soil-borne bacterium that causes bacterial wilt disease in more than 310 plant species worldwide. The pathogenicity of the bacteria is closely associated with type III effectors (T3Es), a class of virulence factors that are delivered to host plant cells by the type III secretion system. In spite of the complex evolutionary history and genetic diversity of the R. solanacearum species complex (RSSC), more than 100 different T3Es have been identified from the genomes of various strains. Based on the available functional studies, certain T3Es interact with host plant proteins and suppress host cell immunity, whereas other T3Es are recognized by the host plant to trigger specific resistance mechanisms. This review summarizes the mechanisms by which T3Es interfere with plant immune responses and the activation of the plant defense system upon T3E recognition. This in-depth review of the molecular interactions between R. solanacearum and its host plants offers insights into the complexity of plant–pathogen interactions and provides a scientific rationale and theoretical support for the future breeding of resistant crops. Full article

Ralstonia solanacearum is an important pathogen causing bacterial wilt in pepper (Capsicum annuum L.). The concurrent infection of R. solanacearum and root-knot nematodes (Meloidogyne spp.) exacerbates the severity of bacterial wilt in pepper. Utilizing plant endophytic bacteria to control these mixed diseases is a viable strategy. Waltheria indica L. (Sterculiaceae) is a traditional medicine plant. A total of 209 endophytic bacteria were isolated from W. indica, and Pseudomonas aeruginosa W-126 showed an efficient antagonistic effect against R. solanacearum. Based on active compound tracking principles, a compound was isolated through silica gel column chromatography and preparative HPLC combined with TLC analysis. It was identified as phenazine-1-carboxamide (PCN) by spectral techniques (ESI-MS, ¹H-NMR, ¹³C-NMR). PCN displayed excellent inhibitory activity against R. solanacearum, with an EC₅₀ of 64.16 μg/mL in vitro. In addition, it showed certain nematocide activity, with an LC₅₀ value of 118.63 μg/mL at 72 h. PCN also showed certain inhibitory activity against five other phytopathogenic bacteria. The structure−activity relationship indicated that the phenazine skeleton and acylamide groups were the key pharmacophores for the activity of phenazine-related compounds against R. solanacearum. PCN controlled the complex diseases of R. solanacearum and M. incognita in a pot experiment, with respective 51.41 and 39.80% inhibitory rates. The exploration of secondary metabolites of biocontrol bacteria can provide reference for the development of novel and efficient pesticides. Full article

Fusarium oxysporum is a fungal plant pathogen for over 100 agricultural crop species. There are strategies for managing Fusarium wilt, including antagonistic bacteria that offer a promising and sustainable effect. In this work, among the various endophytic bacterial strains, Paenibacillus polymyxa EB.KN35 was selected as the best antifungal strain against F. oxysporum. For eco-friendly biomass production of this bacterium, some agricultural byproducts were tested for cultivation, and a soybean processing byproduct (SPBP) was found to be a suitable C/N source for P. polymyxa EB.KN35 fermentation. The utilization of a 14 L bioreactor system for P. polymyxa EB.KN35 fermentation achieved a high biomass productivity (3.46 × 10¹¹ CFU/mL) in a short time (8 h). In bioactive compound analysis, EB.KN35 was found to be secreting several plant growth-promoting compounds such as GA3, IAA, kinetin, and zeatin (via HPLC) and eleven volatile compounds (via GC–MS). The docking study indicated that some volatile compounds (1, 2, 4, and 9) may play a significant role in inhibiting F. oxysporum. The study results highlight the potential for reusing a soybean processing byproduct as a C/N source for the bioproduction of P. polymyxa EB.KN35 with potential use as a biocontrol agent and biofertilizer. Full article

Pine wilt disease, caused by Bursaphelenchus xylophilus, poses severe ecological and economic threats to coniferous forests. This study isolated two fungal (Arthropsis hispanica, Penicillium sclerotiorum) and two bacterial (Bacillus amyloliquefaciens, Enterobacter hormaechei) strains from Pinus massoniana rhizospheres, evaluating their biocontrol potential against pine wood nematodes. Molecular characterization confirmed strain identities. In vitro assays demonstrated that combined fermentation filtrates of CSX134+CSZ71 and CSX60+CSZ71 significantly enhanced plant growth parameters (height, biomass) and root-associated soil enzyme activities (urease, acid phosphatase) in P. massoniana. Treated plants exhibited elevated defense enzyme activities and upregulated defense-related gene expression. The treatments achieved 75.07% and 69.65% nematode control efficacy, respectively, compared to controls. These findings highlight the potential of microbial consortia in activating systemic resistance and suppressing pine wilt disease through the dual mechanisms of growth promotion and defense induction. Full article

In 2022, an outbreak of fungal rot disease affected luffa crops in Shanghai and Zhejiang Province. Infected plants exhibited symptoms including yellowing, chlorosis, wilting, and water-soaked occurred on leaves and fruits. Dark brown, concave lesions developed, often accompanied by white or pale pink mold under moist conditions. Fourteen pathogen strains, morphologically resembling Fusarium species, were isolated. Molecular analysis confirmed Fusarium incarnatum as the causative agent. Pathogenicity tests on luffa plants fulfilled Koch’s postulates, with inoculated plants displaying the same symptoms. Re-isolation of the fungus from the inoculated plants confirmed its role in the disease. To our knowledge, this is the first report of F. incarnatum causing leaf spot and fruit rot on luffa in China. Moreover, the soil bacterial strain Bacillus velezensis BV171 displayed strong inhibition of F. incarnatum mycelia growth and promoted the growth of sponge gourd plants. These findings lay the foundation for the development of diagnostic tools, disease management strategies, and the breeding of resistant luffa varieties. Full article

Bacterial wilt, caused by Ralstonia solanacearum, poses a significant threat to Solanaceae crops, including potatoes. Traditionally, chemical bactericides have been the primary method of disease management. However, the excessive and repeated use of these chemicals has led to the emergence of resistant R. solanacearum strains and raised environmental and safety concerns. Therefore, the current study aimed to explore bacteriophages as a sustainable and eco-friendly alternative to chemical control. Specifically, we evaluated the efficacy of the bacteriophage RsPod1EGY as a biocontrol agent under greenhouse conditions to reduce disease severity and maintain potato productivity. To improve phage survival and activity, we tested six carrier types; compost, peat moss, clay soil, sandy soil, talc powder, and wheat bran. Our findings indicated that compost, talc powder, and wheat bran significantly prolonged the phage’s viability and activity, reducing disease severity by 90%, compared to 65% and 85% for peat moss and phage-alone treatments respectively. In contrast, pathogen control treatments resulted in complete plant mortality. Phage survival was enhanced in pathogen-infected soils, supporting its role in reducing R. solanacearum populations. Potato yield was preserved in compost and talc powder treatments comparable to pathogen-free controls. These results underscore the potential of integrating bacteriophage RsPod1EGY with suitable carriers for sustainable bacterial wilt management, highlighting the importance of delivery methods in agricultural applications. Full article

Smallholder potato farmers in Ethiopia do not realize the theoretical yield potential of the crop because they do not benefit from the advantages of using quality seed potato of improved varieties. The high disease incidence in seed potatoes has large implications on the potato farming system since the country lacks appropriate seed quality assurance mechanisms. Seed potato quality assurance relies more on the technical support provided by the national research and extension systems than the official seed certification agency. This paper elaborates systematic challenges and opportunities within the potato seed system and poses two research questions: (1) What type of seed quality assurance mechanisms (informal, quality declared, certified) are under implementation in Ethiopia? (2) How does the current seed quality assurance system operate in terms of reliability, accessibility, and quality standards to deliver quality seed potato? The data were collected through face-to-face in-depth key informant interviews with various seed regulatory laboratory managers and technicians in the Oromia, SNNP, and SWEP regions in the main seed- and ware-producing areas of Ethiopia. This was complemented by a comprehensive analysis of relevant documents. The findings show that currently there is no established procedure in place to officially certify early-generation seed potatoes. Two out of six seed quality control laboratories assessed for this study inspected seed potato fields in 2021 but as quality declared seed (QDS), and approved the fields inspected based on visual inspection alone. Our study revealed a weak linkage between early-generation seed (EGS) potato producers, commercial, and QDS seed potato producers, and seed quality control laboratories. Seed potato quality assurance operations were carried out by only a few seed regulatory laboratories with several concerns raised over the effectiveness of quality standards since seed-borne diseases, such as bacterial wilt, have been found at high frequency in the country’s seed potato system. Hence, the current procedures and challenges call for the necessity of upgrading current quality assurance in seed potato certification. Our study underlines the need for policymakers, development partners, and researchers to collaborate and pool efforts to consider transforming the quality declared system to appropriate seed certification. We recommended that institutionalizing novel plant disease diagnostics into seed regulatory frameworks is needed for sustainable potato production and food security in Ethiopia. Full article