BACKGROUND Meloidogyne incognita is a highly damaging pathogenic nematode that causes significant annual economic losses. Therefore, the development of reliable biological control agents against M. incognita is imperative. The Bacillus velezensis RKN1111 strain, isolated from inter-root soil, demonstrates the ability to directly kill M. incognita. In this study, we investigated the effect of RKN1111 in inducing resistance to M. incognita in Cucumis sativus and examined changes in the content of immune-responsive substances in the induction-treated cucumber plants. RESULT The RKN1111 treatment reduced the number of root galls in infected cucumbers, with a maximum reduction of 78.19%. RKN1111 stably colonized cucumber roots, reaching 3.65 x 106 CFU/g in 3 days. The approach and infestation rates of M. incognita on RKN1111-induced treated cucumber root tips declined at varying time points. Furthermore, RKN1111 induced significant increases (P < 0.05) in hydrogen peroxide (H2O2) and superoxide anion (O2-) contents, as well as in the callose deposition area in cucumber, by up to 59.84, 83.28, and 61.59%, respectively. CONCLUSION RKN1111 has been demonstrated to stably colonize cucumber root systems and defend against M. incognita infestation by inducing systemic resistance in the host plant. Additionally, RKN1111 elevated the levels of immune-responsive substances in cucumber plants. RKN1111 has great potential for application in the integrated pest management of M. incognita. (c) 2025 Society of Chemical Industry.

Introduction Maize stalk rot (MSR), caused by Fusarium graminearum, is the most serious soil borne disease in maize production, seriously affecting maize yield and quality worldwide. Microbial biocontrol agents are the best means of controlling MSR and reducing the use of chemical fungicides, such as Bacillus spp.Methods and results In the study, a soil-isolated strain B105-8 was identified as B. velezensis (accession No. PP325775.1 and No. PP869695.1), demonstrated a broad spectrum against various pathogens causing maize diseases, which effectively controlled MSR, exhibited a high control efficacy of more than 60% and growth-promoting effect in the pot plant. B105-8 could effectively improve soil urease (S-UE), invertase (S-SC), and catalase (S-CAT) activities. S-NP activity showed an initial increase with a peak of 20,337 nmol/h/g, followed by a decrease, but activity remained significantly better than control treatment with chemical fungicides. The application of B105-8 repaired the damage caused by F. graminearum on soil activity. The antifungal compound B-1, extracted from B105-8, was purified using a protein purifier, revealing inhibitory effects against F. graminearum. Mass spectrometry analysis indicated the potential presence of C14 Bacillomycin, C15 Iturin, C15 Mycosubtilin, C17, and C15 fengycin in B-1. In pot experiments, a 5 mu L/mL concentration of B-1 exhibited 69% control on MSR, enhancing maize root elongation, elevation, and fresh weight. At 10 mu L/mL, B-1 showed 89.0 and 82.1% inhibition on spore production and mycelial growth, causing hyphal deformities.Discussion This study presents the innovative use of B. velezensis, isolated from maize rhizosphere in cold conditions to effectively control MSR caused by F. graminearum. The findings highlight the remarkable regional and adaptive characteristics of this strain, making it an excellent candidate to fight MSR in diverse environments. In conclusion, B. velezensis B105-8 demonstrated potential as a biocontrol agent for MSR.

Tobacco (Nicotiana tabacum L.) bacterial wilt, caused by Ralstonia solanacearum, is indeed a highly destructive plant disease, leading to substantial damage in tobacco production. While biological control is considered an effective measure for managing bacterial wilt, related research in this area has been relatively limited compared to other control methods. In order to discover new potential antagonistic bacteria with high biocontrol efficacy against tobacco bacterial wilt, we conducted an analysis of the microbial composition differences between disease-suppressive and disease-conducive soils using Illumina sequencing. As a result, we successfully isolated six strains from the disease-suppressive soil that exhibited antibacterial activity against Ralstonia solanacearum. Among these strains, B4-7 showed the strongest antibacterial activity, even at acidic conditions with a pH of 4.0. Based on genome analysis using Average Nucleotide Identity (ANI), B4-7 was identified as Bacillus velezensis. In greenhouse and field trials, strain B4-7 significantly reduced the disease index of tobacco bacterial wilt, with control efficiencies reaching 74.03% and 46.88% respectively. Additionally, B4-7 exhibited plant-promoting abilities that led to a 35.27% increase in tobacco production in field conditions. Quantitative real-time (qPCR) analysis demonstrated that strain B4-7 effectively reduced the abundance of R. solanacearum in the rhizosphere. Genome sequencing and Liquid Chromatography-Mass Spectrometry (LC-MS) analysis revealed that strain B4-7 potentially produces various lipopeptide metabolites, such as microlactin, bacillaene, difficidin, bacilysin, and surfactin. Furthermore, B4-7 influenced the structure of the rhizosphere soil microbial community, increasing bacterial abundance and fungal diversity, while also promoting the growth of different beneficial microorganisms. In addition, B4-7 enhanced tobacco's resistance to R. solanacearum by increasing the activities of defense enzymes, including superoxide dismutase (SOD), phenylalanine ammonia-lyase (PAL), peroxidase (POD), catalase (CAT), and polyphenol oxidase (PPO). Collectively, these findings suggest that B. velezensis B4-7 holds significant biocontrol potential and can be considered a promising candidate strain for eco-friendly management of tobacco bacterial wilt.

Iodine deficiency is a global public health problem and dietary microgreens represent a possible cost-effective supplement. Bacillus velezensis is a commonly occurring soil bacteria that promotes plant growth. However, little attention has been paid to the effects of B. velezensis on the absorption of iodine by plants. Herein, we demonstrated that B. velezensis accelerates pepper seed germination and growth under 0.01 mmol/L KI supplement, with an 85.9% increase in fresh biomass. B. velezensis induced approximately 2.0 -fold higher iodine absorption. Likewise, colonization by B. velezensis occurred in the microgreens. Consequently, the total thiol, vitamin C, total phenolics, and the antioxidant capacity were increased. This was followed by a marked decrease in the catalase and total superoxide dismutase activities. Furthermore, the combination of B. velezensis and 0.01 mmol/L KI significantly decreased the relative water content and membrane damage (malondialdehyde and relative electrical conductivity). Intriguingly, the transcripts of ethylene biosynthesis genes CaACS10 and CaACO1 were downregulated, whereas CaACO3 expression was upregulated. Thus, the present study showed that B. velezensis accelerated iodine accumulation; improved seed germination and seedling growth; elicited antioxidant bioactivity; decreased membrane damage; and preserved vegetable microgreen quality during storage.

Introduction Southern blight, caused by Sclerotium rolfsii, poses a serious threat to the cultivation of Coptis chinensis, a plant with significant medicinal value. The overreliance on fungicides for controlling this pathogen has led to environmental concerns and resistance issues. There is an urgent need for alternative, sustainable disease management strategies. Methods In this study, Bacillus velezensis LT1 was isolated from the rhizosphere soil of diseased C. chinensis plants. Its biocontrol efficacy against S. rolfsii LC1 was evaluated through a confrontation assay. The antimicrobial lipopeptides in the fermentation liquid of B. velezensis LT1 were identified using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF-MS). The effects of B. velezensis LT1 on the mycelial morphology of S. rolfsii LC1 were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results The confrontation assay indicated that B. velezensis LT1 significantly inhibited the growth of S. rolfsii LC1, with an inhibition efficiency of 78.41%. MALDI-TOF-MS analysis detected the presence of bacillomycin, surfactin, iturin, and fengycin in the fermentation liquid, all known for their antifungal properties. SEM and TEM observations revealed that the mycelial and cellular structures of S. rolfsii LC1 were markedly distorted when exposed to B. velezensis LT1. Discussion The findings demonstrate that B. velezensis LT1 has considerable potential as a biocontrol agent against S. rolfsii LC1. The identified lipopeptides likely contribute to the antifungal activity, and the morphological damage to S. rolfsii LC1 suggests a mechanism of action. This study underscores the importance of exploring microbial biocontrol agents as a sustainable alternative to chemical fungicides in the management of plant diseases. Further research into the genetic and functional aspects of B. velezensis LT1 could provide deeper insights into its biocontrol mechanisms and facilitate its application in agriculture.

Tobacco bacterial wilt (TBW) caused by Ralstonia solanacearum is a serious soil -borne disease, which seriously damages the growth of tobacco crops. Bacillus velezensis A5 was isolated from 3000 m deep-sea sediments of the Pacific Ocean, and was found to be antagonistic to TBW. Here, we report the complete genome sequence of strain A5, which has a 4,000,699 -bp single circular chromosome with 3827 genes and a G + C content of 46.44%, 87 tRNAs, and 27 rRNAs. A total of 12 gene clusters were identified in the genome of strain A5, which were responsible for the biosynthesis of antibacterial compounds, including surfactin, bacillaene, fengycin, difficidin, bacillibactin, and bacilysin. Additionally, strain A5 was found to contain a series of genes related to the biosynthesis of carbohydrate -active enzymes and secreted proteins. Our results indicate that strain A5 can be considered a promising biocontrol agent against TBW in agricultural fields.