Tomato Root Rot Research Articles

Characterization of biologically synthesized copper nanoparticles by Aspergillus carbonarius and evaluation of their activity in reducing the pathogenic stress of tomatoes infected with Fusarium oxysporum

This study was conducted to evaluate the efficiency of the fungus Aspergillus carbonarius in the synthesis of copper nanoparticles (CuNPs) from copper chloride solution, with the characterization of these nanoparticles and the demonstration of their effectiveness in inhibiting the pathogenic fungus Fusarium oxysporum causing tomato root rot disease. The results indicated that the treatment of copper chloride solution at 150 mM with A. carbonarius filtrate led to the production of CuNPs which characterized by a color change from blue to green, with the highest absorbance observed at 300 nm. X-ray diffraction (XRD) results revealed the crystalline structure with peaks at angles 28.47286, 47.43258, and 56.20644 ◦ corresponding to (111), (220), and (311) planes, respectively, matching the JCPDS card number 01-081-1841. Scanning electron microscopy images showed cubic, pyramidal, and prismatic shapes with dimensions ranging from 15 - 84.291 nm. In laboratory experiment, CuNPs inhibited the growth of the pathogenic fungus, with an inhibition zone of 1.6 cm, compared to copper chloride which recorded 0.9 cm. In the field, , the treatment of CuNPs led to an increase in the stress resistance indicators, reaching the highest values for CuNPs when combined with the fungicide Medazim in the American tomato cultivar. The concentrations of total phenols and glutathione in this treatment were 2.56 mg/g and 0.322 µg/g, respectively. The lowest concentration of proline was recorded as 4.31 µg/g in the treatment involving CuNPs against the fungal infection. CuNPs with the fungicide medazim, significantly outperformed other treatments, registering lowest disease severity at 12.22% in the American cultivar, compared to the highest disease severity was recorded in the treatment with the pathogenic fungus alone, reaching 91.16% in the Dutch cultivar. CuNPs significantly increased tomato fruit weight, both in healthy and infected plants. The American, Turkish, and Dutch tomato cultivars infected with the pathogenic fungus and treated with under + medazim showed higher productivity, reaching 6432.55, 6334.34, and 6305.73 g.plant-1, compared to the lowest productivity in the treatment of these cultivars with the pathogenic fungus, reaching 1008.34, 977.45, and 833.78 g.plant-1, respectively

Role of Hydrogen Peroxide (H2O2) and Trichoderma koningii in Reducing Root Rot Disease of Tomato Causing by Fusarium solani

Two isolates of the pathogenic fungus Fusarium solani the causative of tomato root rot disease named Fs1 and Fs2 were isolated from tomato plants infected with root rot disease. Results showed that both examined isolates had significant effects on the percentage of seed germination of tomato and damping-off disease. Thus, isolate Fs1 was more effective than isolate Fs2, as it recorded a percentage of germination and damping-off 56.6 and 71.6% respectively, compared to the control treatment, which recorded 100 and 0% respectively. It was found that the use of hydrogen peroxide (H2O2) at concentrations of 50, 100 and 200 ppm had a significant effect on the fungal radial growth, dry weight (DW) and sporulation of F. solani. Antifungal activity of H2O2 appeared even at the lowest concentration (50 ppm), which inhibited radial growth to 49.33%, and decreased the dry weight to 498 mg, and the sporulation to 3.75×106 spores. Additionally, the results indicated significant inhibitory effects of hydrogen peroxide (H2O2) and the bioagent Trichoderma koningii on F. solani growth. It was noticed that H2O2 has compatible effects with T. koningii, where the antagonistic ability of T. koningii against F. solani increased when the concentration of H2O2 had increased. The results revealed that the treatment F. solani + H2O2 (200 ppm) + T. koningii significantly reduced the percentage of damping-off and plant survival to 9.40 and 5.39% respectively, in comparison with the control treatment and F. solani alone treatment, which reached 20.22, 14.48, 34.32 and 67.41% respectively.

First report of Fusarium falciforme causing root rot and wilt on strawberry in Sinaloa, Mexico.

In Mexico strawberry production has great economic importance for the local and export markets as the country is the main strawberry supplier to the United States (SIAP, 2020). In 2022, strawberry plants with yellowing and wilting leaves, root rot and wilting, necrosis of vascular bundles and small fruits symptoms were observed in different commercial fields in the north-central Mexican state of Sinaloa, causing yield losses of about 10%. Typical Fusarium spp. colonies were recovered from all samples. They produced abundant white aerial mycelium with cream to orange pigment and branched septate hyphae (Fig. 1) (Leslie and Summerell, 2006). A total of 18 monosporic isolates were obtained by serial dilutions. The 18 isolates grown for 10 days on carnation leaf agar (CLA) produced hyaline microconidia with 0-2 septa, measuring 9.2 - 15.4 by 4.5 - 6.5 μm (n = 40) and hyaline macroconidia with three septa that measured 28.4 - 53.5 by 4.5 - 9 μm (n = 40). Chlamydospores were not observed. A fragment of the translation elongation factor 1-alpha (EF1-alpha) gene was amplified by polymerase chain reaction (PCR) using the primer pair EF-1/EF-2 (O'Donnell et al. 1998) from two monosporic isolates. The sequences were registered in the NCBI GenBank under accession numbers OR878541 and OR878543 (FRESIN178 and FRESIN194). BLASTn queries of NCBI GenBank identified the sequences as F. falciforme with 98% and 100% similarity to accession numbers OQ262968 and DQ246941 respectively. Fusarium ID database also identified the sequences as F. falciforme, is a member of the F. solani species complex (FSSC). Phylogenetic analysis revealed the partial EF1 sequences grouped with F. falciforme (Fig. 2). A pathogenicity test was performed on thirty strawberry plants (cv. Cabrillo) grown in sterile vermiculite. The plants were inoculated by immersing roots in 20 mL of a conidial suspension (1 × 105 conidia/mL) of isolate FRESIN194. Twelve uninoculated plants served as the control. All plants were grown for 60 days under greenhouse conditions (28 to 35°C). The assay was repeated twice. After 50 days, symptoms of root rot and wilting leaves like those observed in the field were observed. Uninoculated control plants did not develop symptoms. The fungus was reisolated from necrotic tissues of the inoculated plants and identified as F. falciforme by sequencing the EF1-alpha gene and morphological characteristics, completing Koch's postulates. Fusarium falciforme has been reported as the causal agent of root rot, stem rot, and wilt of tomato, papaya, chickpea, onion, common bean, and maize in Mexico (Díaz-Najera et al. 2021, Douriet-Angulo et al. 2021, Felix et al 2022, Tirado-Ramírez et al 2018, Vega-Gutiérrez et al. 2019a, Vega-Gutiérrez et al. 2019b). To our knowledge this is the first report of F. falciforme causing root rot and wilt on strawberry in Sinaloa, Mexico. This result provides useful information for the development and implementation of disease control strategies to mitigate damage caused by F. falciforme.

Effects of phosphite fertilizers and picarbutrazox on tomato root rot under pot conditions

Effects of phosphite fertilizers and picarbutrazox on tomato root rot under pot conditions

The efficacy of chemical inducers and fungicides in controlling tomato root rot disease caused by Rhizoctoniasolani

Chitosan is an environmentally friendly natural substance that is used in crop disease management as an alternative to chemical pesticides. A significant issue restricting output in Egypt is root rot, which is a disease, caused by Rhizoctonia solani. Therefore, a greenhouse experiment was conducted to assess the effects of R. solani on 60-day-old tomato plants under fungal infection and to determine the antifungal activity of chitosan and Rizolax T fungicide against the pathogenic fungus. The findings demonstrated that 4 g/L of chitosan seed application completely obstructed the radial mycelial growth of R. solani and decreased the disease severity. Pathogenic infection significantly decreased morphological characteristics and total chlorophyll but significantly increased carotenoid, total thiol, non-protein thiol, protein thiol, antioxidant enzymes, oxidative stress, total phenolic, total flavonoid, and isoflavone compared to healthy plants. Tomato plants treated with chitosan exhibited lower rates of oxidative stress, but higher levels of all previously mentioned parameters compared to untreated infected plants. The number and molecular mass of protein banding patterns varied in all treated tomato plants as compared to the healthy control. There are 42 bands in the treatments, and their polymorphism rate is 69.55%. Moreover, the number and density of α- and β-esterase, and peroxidase isozymes in treated tomato plants exhibited varied responses. Moreover, in treated and control plants, chitosan treatment raised the expression levels of phenylalanine ammonia-lyase, pathogenesis-related protein-1, β-1,3-glucanases and chitinase. In conclusions, chitosan reduces R. solani infection by controlling the biochemical and molecular mechanisms in tomato plants during infection.

Antifungal activity of copper oxide nanoparticles derived from Zizyphus spina leaf extract against Fusarium root rot disease in tomato plants

Incorporating green chemistry concepts into nanotechnology is an important focus area in nanoscience. The demand for green metal oxide nanoparticle production has grown in recent years. The beneficial effects of using nanoparticles in agriculture have already been established. Here, we highlight some potential antifungal properties of Zizyphus spina leaf extract-derived copper oxide nanoparticles (CuO-Zs-NPs), produced with a spherical shape and defined a 13–30 nm particle size. Three different dosages of CuO-Zs-NPs were utilized and showed promising antifungal efficacy in vitro and in vivo against the selected fungal strain of F. solani causes tomato root rot disease, which was molecularly identified with accession number (OP824846). In vivo results indicated that, for all CuO-Zs-NPs concentrations, a significant reduction in Fusarium root rot disease occurred between 72.0 to 88.6% compared to 80.5% disease severity in the infected control. Although treatments with either the chemical fungicide (Kocide 2000) showed a better disease reduction and incidence with (18.33% and 6.67%) values, respectively, than CuO-Zs-NPs at conc. 50 mg/l, however CuO-Zs-NPs at 250 mg/l conc. showed the highest disease reduction (9.17 ± 2.89%) and lowest disease incidence (4.17 ± 3.80%). On the other hand, CuO-Zs-NPs at varied values elevated the beneficial effects of tomato seedling vigor at the initial stages and plant growth development compared to either treatment with the commercial fungicide or Trichoderma Biocide. Additionally, CuO-Zs-NPs treatments introduced beneficial results for tomato seedling development, with a significant increase in chlorophyll pigments and enzymatic activity for CuO-Zs-NPs treatments. Additionally, treatment with low concentrations of CuO-Zs-NPs led to a rise in the number of mature pollen grains compared to the immature ones. however the data showed that CuO-Zs-NPs have a unique antifungal mechanism against F. solani, they subsequently imply that CuO-Zs-NPs might be a useful environmentally friendly controlling agent for the Fusarium root rot disease that affects tomato plants.Graphical

Determination of Phytophthora Species Causing Root and Crown Rot on Tomatoes Grown in Antalya Province and Reactions of Some Tomato Genotypes against Phytophthora nicotianae

Antalya province is the main center of vegetable production in Türkiye. Tomato comes first in terms of crops cultivated under greenhouse. Phytophthora species causing root and crown rot are among the factors negatively affecting tomato yield and quality. This research aimed to determine the prevalence of root and crown rot of tomatoes grown in Antalya province and to identify Phytophthora species causing disease. During surveys performed in 170 tomato greenhouses, plant and soil samples were taken from the areas where root and crown rot, stem blight, and drying symptoms were observed. Disease prevalence and incidence in the investigated greenhouses were 25.88% and 4.87%, respectively. Phytophthora symptoms were not observed in the greenhouses in Demre and Kepez districts, while the highest disease prevalence was found in Elmalı district with 75%. Eighty of 84 Phytophthora isolates were identified as P. nicotianae and four as P. capsici, according to their cultural, morphological and molecular characterisation. Virulence of 18 selected isolates were determined by using stem inoculation technique and all isolates caused lesions with different lengths on tomato stems. The reactions of 22 tomato genotypes in the gene pool of BATEM against P. nicotianae were also investigated and the genotype DT-15 was found as the most susceptible genotype with the largest lesions, while A-286 was the most resistant genotype. This study formed the basis for further studies on tomato breeding and integrated disease management.

Synergistic effects of Bacillus velezensisSDTB038 and phenamacril on Fusarium crown and root rot of tomato

AbstractFusarium crown and root rot (FCRR) is a damaging ailment that can affect tomato production. It is caused by Fusarium oxysporum f. sp. radicis‐lycopersici (FORL). The use of biological agents, in conjunction with fungicides, has become a practical strategy for combating fungal diseases in crops. Lipopeptide extracts from a potential biocontrol strain of Bacillus velezensis (SDTB038) exhibited an inhibitory effect on the mycelial growth of FORL; the EC50 value was 59.95 mg/L, and at a concentration of 256 mg/L the inhibition rate reached 97.4%. The SDTB038 strain produces metabolites such as protease and siderophores. Additionally, it is capable of forming a biofilm and swimming. Phenamacril, an antifungal agent, also displayed an inhibitory effect on FORL, demonstrating an EC50 value of 1.074 mg/L. The control effects of the combination of Bacillus velezensis SDTB038 and phenamacril against FORL on tomato plants were also studied in the greenhouse. The combination of phenamacril and 108 CFU/mL SDTB038 fermentation broth exhibited a strong synergistic control effect on FORL, of up to 84.0%. The combination also led to a 35.6% increase in tomato yield compared to the control. These results demonstrate that SDTB038 possesses antifungal activity. Moreover, when combined with phenamacril, it exhibits a strong synergistic effect against FORL. This solution proves to be an effective means of controlling FCRR in tomato plants.

Does straw returning affect the root rot disease of crops in soil? A systematic review and meta-analysis

Straw returning is a sustainable way that does not destroy soil ecology in agronomic management. Some studies have found that straw returning may aggravate or reduce soilborne diseases in the past few decades. Despite the increasing number of independent studies investigated the effect of straw returning on root rot of crops, the quantitative analysis regarding the relationship between straw returning and crop root rot is still undefined. In this study, keywords co-occurrence matrix was extracted from 2489 published studies (published from 2000 to 2022, the same below) on controlling soilborne diseases of crops. The methods used for soilborne diseases prevention have shifted from chemical to biological and agricultural control since 2010. As root rot is the soilborne disease with the largest weight in keyword co-occurrence according to statistics, we further collected 531 articles focusing on crop root rot. Notably, the 531 studies are mainly distributed in the United States, Canada, China and other countries in Europe and the south and southeast of Asia, and focus on the root rot of soybean, tomato, wheat and other important grain crops or economic crops. Based on the meta-analysis of 534 measurements in 47 previous studies, we explored how 10 management factors (soil pH/texture, type/size of straw, depth/rate/cumulative amount of application, days after application, beneficial/pathogenic microorganism inoculated before application and annual N-fertilizer input) during straw returning affect root rot onset worldwide. The results showed that straw size and microorganisms inoculated before straw returning are the key factors affecting the incidence of root rot. In combination with actual agricultural production, detailed advice applicable to traditional farming system on the optimization management of straw returning was given. This study emphasized the significance of straw pretreatment and farmland management to reduce soilborne diseases during straw returning.

Revealing the Mechanisms for Linalool Antifungal Activity against Fusarium oxysporum and Its Efficient Control of Fusarium Wilt in Tomato Plants

Fusarium oxysporum f. sp. radicis-lycopersici (Forl) is a destructive soil-borne phytopathogenic fungus that causes Fusarium crown and root rot (FCRR) of tomato, leading to considerable field yield losses. In this study, we explored the antifungal capability of linalool, a natural plant volatile organic component, against Forl and its role in controlling FCRR symptoms in tomatoes. Our results showed that Forl mycelial growth was inhibited by the linalool treatment and that the linalool treatment damaged cell membrane integrity, enhanced reactive oxygen species levels, depleted glutathione, and reduced the activities of many antioxidant enzymes in Forl. Transcriptomic and proteomic analyses demonstrated that linalool also downregulated metabolic biosynthetic pathways at the transcript and protein levels, including redox, transporter activity, and carbohydrate metabolism in Forl. Moreover, linalool significantly decreased the expression of many Forl pathogenic genes, such as cell wall degrading enzymes (CWDEs) and G proteins, which is likely how a Forl infection was prevented. Importantly, exogenously applied linalool activated the salicylic acid (SA) and jasmonic acid (JA) defensive pathways to improve disease resistance and relieved the negative effects of Forl on plant growth. Taken together, we report that linalool is an effective fungicide against Forl and will be a promising green chemical agent for controlling FCRR.

Evaluation of the Fungicidal Effect of Some Commercial Disinfectant and Sterilizer Agents Formulated as Soluble Liquid against Sclerotium rolfsii Infected Tomato Plant.

Globally, root rot disease of tomato plants caused by Sclerotium rolfsii is a severe disease leading to the death of infected plants. The effect of some commercial antiseptics and disinfectant agents, such as chloroxylenol (10%), phenic (10%) and formulated phenol (7%) on the control of root rot pathogen and its impact on growth and chemical constituents of tomato seedlings cv. Castle Rock were investigated in vitro and in vivo. The antifungal activity was measured in vitro following the poisoned food technique at different concentrations of 1000, 2000, 3000 and 4000 µL/L. Disinfectant agents and atrio (80%) were tested in vivo by soaking 20-day-old tomato seedlings in four concentrations of 125, 250, 500 and 1000 µL/100 mL water for 5 min and thereafter planting in soil infested by S. rolfsii. Fresh and dry weight, shoot and root length, and chemical constituents of tomato seedlings infected by S. rolfsii were investigated at 35 days after planting (DAP). Experimental results indicated that chloroxylenol (10%) was the most effective on fungus in vitro, recorded an effective concentration (EC50 = 1347.74 µL/L) followed by phenic (10%) (EC50 = 1370.52 µL/L) and formulated phenol (7%) (EC50 = 1553.59 µL/L). In vivo, atrio (80%) and disinfectant agents at different concentrations significantly (p ≤ 0.05) reduced disease incidence, increased shoot and root lengths and increased dry and fresh weight. Additionally, it significantly increased chlorophyll a, chlorophyll b, total carotenoids, total carbohydrates, total proteins, and total phenols. The highest reduction of root rot incidence and increase tomato growth parameters, as well as chemical compositions, were recorded on tomato seedlings treated with atrio (80%) as well as formulated phenol (7%) at different concentrations, followed by chloroxylenol (10%) at 125 and 250 µL/100 mL, whereas phenic (10%) was found to be the least effective treatment. Therefore, the application of formulated phenol (7%) could be commercially used to control tomato root rot diseases and increase the quality and quantity of tomato plants since it is promising against the pathogen, safe, and less expensive than fungicides.

Green Synthesized of Thymus vulgaris Chitosan Nanoparticles Induce Relative WRKY-Genes Expression in Solanum lycopersicum against Fusarium solani, the Causal Agent of Root Rot Disease.

Fusarium solani is a plant pathogenic fungus that causes tomato root rot disease and yield losses in tomato production. The current study's main goal is testing the antibacterial efficacy of chitosan nanoparticles loaded with Thyme vulgaris essential oil (ThE-CsNPs) against F. solani in vitro and in vivo. GC-MS analysis was used to determine the chemical constituents of thyme EO. ThE-CsNPs were investigated using transmission electron microscopy before being physicochemically characterized using FT-IR. ThE-CsNPs were tested for antifungal activity against F. solani mycelial growth in vitro. A pot trial was conducted to determine the most effective dose of ThE-CsNPs on the morph/physiological characteristics of Solanum lycopersicum, as well as the severity of fusarium root rot. The relative gene expression of WRKY transcript factors and defense-associated genes were quantified in root tissues under all treatment conditions. In vitro results revealed that ThE-CsNPs (1%) had potent antifungal efficacy against F. solani radial mycelium growth. The expression of three WRKY transcription factors and three tomato defense-related genes was upregulated. Total phenolic, flavonoid content, and antioxidant enzyme activity were all increased. The outfindings of this study strongly suggested the use of ThE-CsNPs in controlling fusarium root rot on tomatoes; however, other experiments remain necessary before they are recommended.

Microbial volatile organic compounds 2-heptanol and acetoin control Fusarium crown and root rot of tomato.

Some microbial volatile organic compounds (mVOCs) can act as antagonistic weapons against plant pathogens, but little information is available on the contribution of individual mVOC to biocontrol and how they interact with plant pathogens. In this study, the Bacillus subtilis strain N-18 isolated from the rhizosphere of healthy plants grown in areas where Fusarium crown and root rot (FCRR) of tomatooccurs could reduce the 30% of the incidence of FCRR. Moreover, the volatile organic compounds (VOCs) produced by N-18 had inhibitory effects on Fusarium oxysporum f. sp. radicis-lycopersici (FORL). The identification of VOCs of N-18 was analyzed by the solid-phase microextraction coupled to gas chromatography-mass spectrometry.Meanwhile, we conducted sensitivity tests with these potential active ingredients and found that the volatile substances acetoin and 2-heptanol can reduce the 41.33% and 35% of the incidence of FCRR in tomato plants. In addition, the potential target protein of acetoin, found in the cheminformatics and bioinformatics database, was F. oxysporum of hypothetical protein AU210_012600 (FUSOX). Molecular docking results further predicted that acetoin interacts with FUSOX protein. These results reveal the VOCs of N-18 and their active ingredients in response to FORL and provide a basis for further research on regulating and controlling FCRR.

Chorisia speciosa Extract Induces Systemic Resistance against Tomato Root Rot Disease Caused by Rhizoctonia solani

Chemical pesticides and fungicides are used extensively, negatively affecting people’s health and the environment. Reducing synthetic pesticides and increasing the efficiency of sustainable food production using plant extracts as natural chemicals is a win–win. Here, we first describe and evaluate an ethanolic extract of Chorisia speciosa for its protective and curative activities against Rhizoctonia solani in greenhouse-grown tomato plants. The results showed that the mycelial growth of R. solani was completely suppressed in vitro by C. speciosa extract (10 µg/mL). Twenty days after fungal inoculation, the results demonstrated that using C. speciosa extract (10 µg/mL) in vivo significantly improved shoot and root growth parameters in protective and curative treatments. Further, the protective and curative treatments decreased the disease index by 26.67% and 53.33%, respectively. C. speciosa-treated tomato plants showed significantly increased antioxidant enzyme production (PPO, CAT, and SOD) and up-regulated PR-1, PR-2,PR-3, PAL, and CHS expression levels compared to untreated plants. According to HPLC examination, the most prevalent phenolic acids or flavonoid components quantities (µg/mL) noticed in C. speciosa extract were 7-OH-flavone (10.36), kaempferol (9.23), p-coumaric acid (8.65), ferulic acid (8.14), caffeic acid (7.59), gallic acid (6.33), and iso-ferulic (5.71). Our findings are the first to demonstrate that a C. speciosa extract can assist plants in combating fungal infestation. Therefore, the data imply that C. speciosa extract, as a natural and renewable product, could be adopted as a long-term approach for regulating plant fungus.

Biocontrol activity and action mechanism of Bacillus velezensis strain SDTB038 against Fusarium crown and root rot of tomato.

Fusarium crown and root rot of tomato is a soilborne diseases that has brought serious harm and economic losses to tomato production in facilities in recent years. The disease has been reported in more than 30 countries worldwide, but there are few reports on its biological control. A Bacillus velezensis strain SDTB038 with biocontrol effects was isolated and identified in a previous study and is considered one of the most important PGPRs. Seven secondary metabolite biosynthesis gene clusters were found in strain SDTB038 by whole genome sequencing, explaining its biocontrol effects. Results indicated that different concentrations of SDTB038 fermentation broth inhibited the mycelial growth of Fusarium crown and root rot of tomato. Strain SDTB038 could generate indole acetic acid and promote healthy growth of tomatoes, while the effect of 108 CFU/ml SDTB038 concentration on promoting tomato growth was the most obvious. B. velezensis SDTB038 significantly reduced the accumulation of ROS in tomato plants, induced the up-regulation of antifreeze genes, and promoted the rapid recovery of tomato plants at low temperatures in a pot experiment. At the same time, SDTB038 had good control effect on Fusarium crown and root rot of tomato, and 108 CFU/ml SDTB038 fermentation broth had the best control effect, which was 42.98%. In summary, the strain B. velezensis SDTB038 may be a promising bacterial agent for biological control of Fusarium crown and root rot of tomato, and an important source of potential antimicrobial compounds.

Endophytic Bacillus subtilis SR22 Triggers Defense Responses in Tomato against Rhizoctonia Root Rot.

Rhizoctonia root rot is one of the most destructive diseases of tomato and other crops. The biocontrol of plant diseases using endophytic bacteria has gained significant attention due to their distinct advantages compared with the free-living ones, as well as their new unexplored and unique properties. Endophytic Bacillus subtilis SR22 represents a promising and more effective biocontrol and growth-promoting agent for tomato plants than the free-living agents, being an ecofriendly and sustainable tool in modern agriculture. In this study, the direct antagonistic activity of B. subtilis SR22 was investigated against Rhizoctonia solani in vitro. The biocontrol activity of B. subtilis SR22 against Rhizoctonia root rot of tomato was also investigated. Effects on the level of the transcriptional expression of defense-related genes, biochemical responses, and the vegetative growth of tomato plants were also studied. The dual culture test showed 51% inhibition in the mycelial growth of R. solani due to B. subtilis SR22, indicating its potent antagonistic behavior. Using a GC-MS analysis, twenty bioactive compounds were detected to be produced by B. subtilis SR22, including chlorogenic acid, pyrrolo [1,2-a]pyrazine-1,4-dione, hexahydro, propyl thioglycolic acid, phthalic acid, and 2,3-butanediol. Under greenhouse conditions, the application of B. subtilis SR22 led to a reduction (up to 51%) in Rhizoctonia root rot of tomato. Furthermore, an upregulation in the expression of the responsive factor JERF3 (10.9-fold) and the defense-related genes POD (9.1-fold) and PR1 (4.5-fold) in tomato plants was recorded due to the application of B. subtilis SR22. In addition, this treatment enhanced the total phenolic content (76.8%) and activity of the antioxidant enzymes POD (56%) and PPO (29.2%) in tomato roots, indicating its resistance-inducing effect on tomato plants. Moreover, this treatment enhanced most of the evaluated growth parameters in tomato plants (up to 35%). We can conclude that B. subtilis SR22 is a promising biocontrol agent and growth promoter in tomato plants against Rhizoctonia root rot. An evaluation of the formulation and field application of this bio-agent is necessary in future studies.

Genetic Characteristics and Enzymatic Activities of Bacillus velezensis KS04AU as a Stable Biocontrol Agent against Phytopathogens

Bacillus velezensis has a broad application in the agricultural and industrial sectors for its biocontrol properties and its potential active secondary metabolites. The defined phenotypic characteristics of a strain vary according to its ecosystem. We report the complete genomic analysis of B. velezensis KS04AU compared to four strains of B. velezensis (SRCM102752, ONU-553, FZB42, and JS25R) and two closely related Bacillus amyloliquefaciens (LL3 and IT-45). A total of 4771 protein coding genes comprises the KS04AU genome, in comparison with 3334 genes core genes found in the six other strains and the remaining 1437 shell genes. Average nucleotide identity of the target strain to the six other strains showed 99.65% to B. velezensis ONU-553, sharing 60 orthologous genes. Secondary metabolite gene cluster analysis of all strains showed that KS04AU has a mersacidin cluster gene, which is absent in the genome of the other strains. PHASTER analysis also showed KS04AU harboring two phages (Aeribacllus AP45 NC_048651 and Paenibacillus_Tripp NC_028930), which were also unique in comparison with the other strains. Analysis on anti-microbial resistance genes showed no difference in the genome of KS04AU to any of the other genomes, with the exception of B. amyloliquefaciens IT-45 which had one unique small multidrug-resistance antibiotic efflux-pump gene (qacJ). The CRISPR-Cas systems in the strains were also compared showing one CRISPR gene found only in KS04AU. Hydrolytic activity, antagonistic activity against phytopathogens (Fusarium oxysporum, Fusarium graminearum, Alternaria alternata and Pseudomonas syringae) and biocontrol against tomato foot and root rot experiments were carried out. B. velezensis KS04AU inhibits the growth of all phytopathogens tested, produces hydrolytic activity, and reduces Fusarium oxysporum f.sp. radicis-lycopersici (Forl) ZUM2407 lesions up to 46.02 ± 0.12%. The obtained results confirm B. velezensis KS04AU as a potential biocontrol strain for plant protection.

Transcriptome Analysis Reveals the Response Mechanism of Frl-Mediated Resistance to Fusarium oxysporum f. sp. radicis-lycopersici (FORL) Infection in Tomato.

Tomato Fusarium crown and root rot (FCRR) is an extremely destructive soil-borne disease. To date, studies have shown that only plants with tomato mosaic virus (TMV) resistance exhibit similar resistance to tomato Fusarium oxysporum f. sp. radicis-lycopersici (FORL) and have identified a single relevant gene, Frl, in Peruvian tomato. Due to the relative lack of research on FCRR disease-resistance genes in China and elsewhere, transcriptome data for FORL-resistant (cv. ‘19912’) and FORL-susceptible (cv. ‘Moneymaker’) tomato cultivars were analysed for the first time in this study. The number of differentially expressed genes (DEGs) was higher in Moneymaker than in 19912, and 189 DEGs in the ‘plant–pathogen interaction’ pathway were subjected to GO and KEGG enrichment analyses. MAPK and WRKY genes were enriched in major metabolic pathways related to plant disease resistance; thus, we focused on these two gene families. In the early stage of tomato infection, the content of JA and SA increased, but the change in JA was more obvious. Fourteen genes were selected for confirmation of their differential expression levels by qRT-PCR. This study provides a series of novel disease resistance resources for tomato breeding and genetic resources for screening and cloning FORL resistance genes.

Rhizospheric bacteria for use in preventing Fusarium wilt and crown root rot of tomato under natural field conditions

Biocontrol, an alternative to chemical control against plant pathogens, may also improve plant health and enhance fruit yield. Tomato production in open fields or greenhouses is constrained by the pathogens Fusarium oxysporum f. sp. lycopersici race 3 (Fol R3) and F. oxysporum f. sp. radicis-lycopersici (Forl). In this work, we studied the biocontrol effect of the antagonistic bacteria Acinetobacter calcoaceticus AcDB3, Bacillus thuringiensis BtMB9, B. subtilis BsTA16, and B. amyloliquefaciens BaMA26 in field trials with four tomato hybrids over two consecutive growing seasons (2019–2020 and 2020–2021). The effect of these bacteria on plant growth was also evaluated. The presence of F. oxysporum in field soil and/or infected plants was confirmed microbiologically. All four bacterial strains significantly suppressed the severity of Fusarium crown and root rot of tomato (FCRRT) and Fusarium wilt symptoms, as well as increased tomato yield under field conditions. Among the four strains, B. subtilis BsTA16 showed the highest reduction in symptoms of Fusarium wilt (68%) and FCRRT (74%). To the best of our knowledge, this is the first report of biological control agents (BCAs) exerting antagonistic activity against both FCRRT caused by Forl and Fusarium wilt caused by Fol in tomato under field conditions.

Study on the Preparation and Effect of Tomato Seedling Disease Biocontrol Compound Seed-Coating Agent.

Tomato damping-off and root rot are the two most common diseases of tomatoes at the seedling stage. At present, biological compound seed-coating agents are gradually replacing chemical agents in preventing and controlling plant diseases and insect pests, regulating plant growth, and ensuring crop yields. In this study, five biocontrol bacteria (Bacillus amyloliquefaciens (Ba), Bacillus subtilis (Bs wy-1), Bacillus subtilis (WXCDD105), Pseudomonas fluorescens (WXCDD51), and Bacillus velezensis (WZ-37)), with broad antibacterial spectra were mixed with auxiliary factors (inactive components of seed-coating agent) after fermentation to compound a seed-coating agent. In this study, the formula for a compound seed-coating agent was selected through orthogonal experiment. Gaseous silica was used as a thickener, and gum arabic and sodium dodecylbenzene sulfonate were used as a film-forming agent and dispersant, respectively. The mass of fumed silica, gum arabic, sodium dodecylbenzene sulfonate, and pearlescent powder was 1.3 g, 1 g, 0.05 g, and 0.5 g, respectively. Adding gibberellin can improve the ability of seed-coating agents to promote seed germination and plant growth. This showed high efficiency in preventing and controlling seedling diseases and promoting seedling growth. After 6 days of inoculation with Pythium aphanidermatum, which caused tomato damping-off disease, the seedling mortality rate was 26.7% lower than that of the sterile water control, and 20% lower than that of carbendazim. After 21 days of inoculation with Fusarium sp., which caused tomato root rot disease, the seedling mortality rate was 44.31% lower than that of the control, and 22.36% lower than that of carbendazim. The plant height, stem diameter, root length, fresh weight, and dry weight of tomato seeds treated with biological compound seed-coating agent were significantly higher than that of the control. We tested the shelf life of the biological compound seed-coating agent, and found that the effect of seed germination and radicle growth did not decrease. This research provides information on the production technology and application of biological seed-coating agents in tomato production.