Inhibitory effect and possible mechanism of a Pseudomonas strain QBA5 against gray mold on tomato leaves and fruits caused by Botrytis cinerea

Biocontrol of strawberry Botrytis gray mold and prolong the fruit shelf-life by fumigant Trichoderma spp

Objectives To screen high active volatile organic compounds (VOCs)-producing Trichoderma isolates against strawberry gray mold caused by Botrytis cinerea, and to explore their antagonistic mode of action against the pathogen. VOCs produced by nine Trichoderma isolates (Trichoderma atroviride T1 and T3; Trichoderma harzianum T2, T4 and T5; T6, T7, T8 and T9 identified as Trichoderma asperellum in this work) significantly inhibited the mycelial growth (13.9-63.0% reduction) and conidial germination (17.6-96.3% reduction) of B. cinerea, the highest inhibition percentage belonged to VOCs of T7; in a closed space, VOCs of T7 shared 76.9% and 100% biocontrol efficacy against gray mold on strawberry fruits and detached leaves, respectively, prolonged the fruit shelf-life by 3 days in presence of B. cinerea, completely protected the leaves from B. cinerea infecting; volatile metabolites of T7 damaged the cell membrane permeability and integrity of B. cinerea, thereby inhibiting the mycelial growth and conidial germination. Gas chromatography-mass spectrometry (GC-MS) analysis revealed the VOCs contain 23 potential compounds, and the majority of these compounds were categorised as alkenes, alcohols, and esters, including PEA and 6PP, which have been reported as substances produced by Trichoderma spp. T. asperellum T7 showed high biofumigant activity against mycelial growth especially conidial germination of B. cinerea and thus protected strawberry fruits and leaves from gray mold, which acted by damaging the pathogen's plasma membrane and resulting in cytoplasm leakage, was a potential biofumigant for controlling pre- and post-harvest strawberry gray mold.

Improved Expression of a Thermostable GH18 Bacterial Chitinase in Two Different Escherichia coli Strains and Its Potential Use in Plant Protection and Biocontrol of Phytopathogenic Fungi

Chitinases are enzymes that can break down chitin, a major component of the exoskeleton of insects and fungi. This feature makes them potential biopesticides in agriculture since they are considered a safe and environmentally friendly alternative to synthetic pesticides. In this work, we performed a comparative study between two different bacterial expression strains to produce a recombinant chitinase with improved stability. Escherichia coli strains Origami B and BL21 (DE3) were selected for their distinct cytosolic environment to express BhChitA chitinase of Bacillus halodurans C-125 and to investigate the role of disulfide bond formation and proper folding on its stability and activity. Expression of the recombinant BhChitA in bacterial strain containing oxidative cytosol (Origami B) improved its activity and stability. Although both expression systems have comparable biochemical properties (temperature range 20-80 °C and pH spectrum 3-10), BhChitA expressed in Origami strain seems more stable than expressed in BL21. Furthermore, the optimal expression conditions of the recombinant BhChitA has been carried out at 30 °C during 6 h for the Origami strain, against 20 °C during 2 h for BL21. On the other hand, no significant differences were detected between the two enzymes when the effect of metal ions was tested. These findings correlate with the analysis of the overall structure of BhChitA. The model structure permitted to localize disulfide bond, which form a stable connection between the substrate-binding residues and the hydrophobic core. This link is required for efficient binding of the chitin insertion domain to the substrate. BhChitA exhibited in vitro antifungal effect against phytopathogenic fungi and suppressed necrosis of Botrytis cinerea on detached tomato leaves. In vitro assays showed the influence of BhChitA on growth suppression of Botrytis cinerea (53%) Aspergillus niger (65%), Fusarium graminearum (25%), and Fusarium oxysporum (34%). Our results highlight the importance of the bacterial expression system with oxidative cytosol in producing promising biopesticides that can be applied for post-harvest processing and crop protection.

Biocontrol potential of Pseudomonas protegens ML15 against Botrytis cinerea causing gray mold on postharvest tomato (Solanum lycopersicum var. cerasiforme)

Gray mold, caused by Botrytis cinerea is a major cause of post-harvest rot of fresh fruits and vegetables. The utilization of selected microorganisms as biocontrol agents is a promising alternative to effectively control gray mold on tomatoes. The current study was conducted to explore potential biocontrol mechanisms of the Pseudomonas strain to control infections on post-harvest tomatoes. Among the 8 tested bacterial isolates, Pseudomonas protegens ML15 demonstrated antagonistic activity to Botrytis cinerea. Moreover, P. protegens ML15 exhibited the production of siderophores, hydrogen cyanide, ammonia, exopolysaccharides, lipase, biosurfactant, 2,4-diacetylphloroglucinol, and several other antifungal compounds, such as 1-tetradecanol, cyclododecane, 2,4-di-tert-butylphenol, and 2-methyl-1-hexadecanol. A comprehensive genomic analysis of P. protegens ML15 unravels 18 distinct genetic regions with the potential for biosynthesizing secondary metabolites, known for their pivotal role in biocontrol responses against plant pathogens. In vivo, experiments showed that both culture suspension and cell-free supernatant of P. protegens ML15 significantly reduced fungal growth (53.0 ± 0.63%) and mitigated disease development (52.8 ± 1.5%) in cherry tomatoes at four days post-B. cinerea inoculation. During the infection, the application of P. protegens ML15 resulted in the augmentation of total antioxidant, phenolic content, and ascorbic acids content. Thus, our results suggested that P. protegens ML15's role as a biocontrol agent against B. cinerea-induced postharvest tomato decay achieved through the secretion of antifungal substances, induction of tomato defense responses, and inhibition of mycelial growth of B. cinerea. These findings provide a significant contribution to the ongoing search for alternative, eco-friendly methods of controlling gray mold in fresh products. The utilization of P. protegens ML15 as a biocontrol agent could help to reduce the reliance on chemical fungicides and promote sustainable agriculture practices.

Harnessing the action mechanisms of microbial endophytes for enhancing plant performance and stress tolerance: current understanding and future perspectives

Microbial endophytes are microorganisms that reside within plant tissues without causing any harm to their hosts. These microorganisms have been found to confer a range of benefits to plants, including increased growth and stress tolerance. In this review, we summarize the recent advances in our understanding of the mechanisms by which microbial endophytes confer abiotic and biotic stress tolerance to their host plants. Specifically, we focus on the roles of endophytes in enhancing nutrient uptake, modulating plant hormones, producing secondary metabolites, and activating plant defence responses. We also discuss the challenges associated with developing microbial endophyte-based products for commercial use, including product refinement, toxicology analysis, and prototype formulation. Despite these challenges, there is growing interest in the potential applications of microbial endophytes in agriculture and environmental remediation. With further research and development, microbial endophyte-based products have the potential to play a significant role in sustainable agriculture and environmental management.

Unlocking antagonistic potential of Bacillus amyloliquefaciens KRS005 to control gray mold

To establish a safe, efficient, and simple biocontrol measure for gray mold disease caused by Botrytis cinerea, the basic characteristics and antifungal activity of KRS005 were studied from multiple aspects including morphological observation, multilocus sequence analysis and typing (MLSA-MLST), physical-biochemical assays, broad-spectrum inhibitory activities, control efficiency of gray mold, and determination of plant immunity. The strain KRS005, identified as Bacillus amyloliquefaciens, demonstrated broad-spectrum inhibitory activities against various pathogenic fungi by dual confrontation culture assays, of which the inhibition rate of B. cinerea was up to 90.3%. Notably, through the evaluation of control efficiency, it was found that KRS005 fermentation broth could effectively control the occurrence of tobacco leaves gray mold by determining the lesion diameter and biomass of B. cinerea on tobacco leaves still had a high control effect after dilution of 100 folds. Meanwhile, KRS005 fermentation broth had no impact on the mesophyll tissue of tobacco leaves. Further studies showed that plant defense-related genes involved in reactive oxygen species (ROS), salicylic acid (SA), and jasmonic acid (JA)-related signal pathways were significantly upregulated when tobacco leaves were sprayed with KRS005 cell-free supernatant. In addition, KRS005 could inhibit cell membrane damage and increase the permeability of B. cinerea. Overall, KRS005, as a promising biocontrol agent, would likely serve as an alternative to chemical fungicides to control gray mold.

Chitosan-Decorated Copper Oxide Nanocomposite: Investigation of Its Antifungal Activity against Tomato Gray Mold Caused by Botrytis cinerea

Owing to the remarkable antimicrobial potential of these materials, research into the possible use of nanomaterials as alternatives to fungicides in sustainable agriculture is increasingly progressing. Here, we investigated the potential antifungal properties of chitosan-decorated copper oxide nanocomposite (CH@CuO NPs) to control gray mold diseases of tomato caused by Botrytis cinerea throughout in vitro and in vivo trials. The nanocomposite CH@CuO NPs were chemically prepared, and size and shape were determined using Transmission Electron Microscope (TEM). The chemical functional groups responsible for the interaction of the CH NPs with the CuO NPs were detected using the Fourier Transform Infrared (FTIR) spectrophotometry. The TEM images confirmed that CH NPs have a thin and semitransparent network shape, while CuO NPs were spherically shaped. Furthermore, the nanocomposite CH@CuO NPs ex-habited an irregular shape. The size of CH NPs, CuO NPs and CH@CuO NPs as measured through TEM, were approximately 18.28 ± 2.4 nm, 19.34 ± 2.1 nm, and 32.74 ± 2.3 nm, respectively. The antifungal activity of CH@CuO NPs was tested at three concentrations of 50, 100 and 250 mg/L and the fungicide Teldor 50% SC was applied at recommended dose 1.5 mL/L. In vitro experiments revealed that CH@CuO NPs at different concentrations significantly inhibited the reproductive growth process of B. cinerea by suppressing the development of hyphae, spore germination and formation of sclerotia. Interestingly, a significant control efficacy of CH@CuO NPs against tomato gray mold was observed particularly at concentrations 100 and 250 mg/L on both detached leaves (100%) as well as the whole tomato plants (100%) when compared to the conventional chemical fungicide Teldor 50% SC (97%). In addition, the tested concentration 100 mg/L improved to be sufficient to guarantee a complete reduction in the disease's severity (100%) to tomato fruits from gray mold without any morphological toxicity. In comparison, tomato plants treated with the recommended dose 1.5 mL/L of Teldor 50% SC ensured disease reduction up to 80%. Conclusively, this research enhances the concept of agro-nanotechnology by presenting how a nano materials-based fungicide could be used to protect tomato plants from gray mold under greenhouse conditions and during the postharvest stage.

Agroecological Management of the Grey Mould Fungus Botrytis cinerea by Plant Growth-Promoting Bacteria

Botrytis cinerea is the causal agent of grey mould and one of the most important plant pathogens in the world because of the damage it causes to fruits and vegetables. Although the application of botrycides is one of the most common plant protection strategies used in the world, the application of plant-beneficial bacteria might replace botrycides facilitating agroecological production practices. Based on this, we reviewed the different stages of B. cinerea infection in plants and the biocontrol mechanisms exerted by plant-beneficial bacteria, including the well-known plant growth-promoting bacteria (PGPB). Some PGPB mechanisms to control grey mould disease include antibiosis, space occupation, nutrient uptake, ethylene modulation, and the induction of plant defence mechanisms. In addition, recent studies on the action of anti-Botrytis compounds produced by PGPB and how they damage the conidial and mycelial structures of the pathogen are reviewed. Likewise, the advantages of individual inoculations of PGPB versus those that require the joint action of antagonist agents (microbial consortia) are discussed. Finally, it should be emphasised that PGPB are an excellent option to prevent grey mould in different crops and their use should be expanded for environmentally friendly agricultural practices.

Antagonistic Activity and Mechanism of Bacillus subtilis XZ16-1 Suppression of Wheat Powdery Mildew and Growth Promotion of Wheat

Wheat powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is one of the most serious wheat diseases in the world. Biological control is considered an environmentally safe approach to control plant diseases. Here, to develop effective biocontrol agents for controlling wheat powdery mildew, antagonistic strain XZ16-1 was isolated and identified as Bacillus subtilis based on the morphological, biochemical, and physiological characteristics and 16S rDNA sequence. The culture filtrate of B. subtilis XZ16-1 and its extracts had a significant inhibitory effect on the spore germination of Bgt. Moreover, the therapeutic and prevention efficacy of the 100% culture filtrate on wheat powdery mildew reached 81.18 and 83.72%, respectively, which was better than that of chemical fungicide triadimefon. Further antimicrobial mechanism analysis showed that the XZ16-1 culture filtrate could inhibit the development of powdery mildew spores by disrupting the cell membrane integrity, causing reductions in the mitochondrial membrane potential, and inducing the accumulation of reactive oxygen species in the spores. Biochemical detection indicated that XZ16-1 could solubilize phosphate, fix nitrogen, and produce hydrolases, lipopeptides, siderophores, and indole-3-acetic acid. Defense-related enzymes activated in wheat seedlings treated with the culture filtrate indicated that disease resistance was induced in wheat to resist pathogens. Furthermore, a 10⁶ CFU/ml suspension of XZ16-1 increased the height, root length, fresh weight, and dry weight of wheat seedlings by 77.13, 63.46, 76.73, and 19.16%, respectively, and showed good growth-promotion properties. This study investigates the antagonistic activity and reveals the action mechanism of XZ16-1, which can provide an effective microbial agent for controlling wheat powdery mildew.

Determination of Reactive Oxygen or Nitrogen Species and Novel Volatile Organic Compounds in the Defense Responses of Tomato Plants against Botrytis cinerea Induced by Trichoderma virens TRS 106

In the present study, Trichoderma virens TRS 106 decreased grey mould disease caused by Botrytis cinerea in tomato plants (S. lycopersicum L.) by enhancing their defense responses. Generally, plants belonging to the ‘Remiz’ variety, which were infected more effectively by B. cinerea than ‘Perkoz’ plants, generated more reactive molecules such as superoxide (O₂⁻) and peroxynitrite (ONOO⁻), and less hydrogen peroxide (H₂O₂), S-nitrosothiols (SNO), and green leaf volatiles (GLV). Among the new findings, histochemical analyses revealed that B. cinerea infection caused nitric oxide (NO) accumulation in chloroplasts, which was not detected in plants treated with TRS 106, while treatment of plants with TRS 106 caused systemic spreading of H₂O₂ and NO accumulation in apoplast and nuclei. SPME-GCxGC TOF-MS analysis revealed 24 volatile organic compounds (VOC) released by tomato plants treated with TRS 106. Some of the hexanol derivatives, e.g., 4-ethyl-2-hexynal and 1,5-hexadien-3-ol, and salicylic acid derivatives, e.g., 4-hepten-2-yl and isoamyl salicylates, are considered in the protection of tomato plants against B. cinerea for the first time. The results are valuable for further studies aiming to further determine the location and function of NO in plants treated with Trichoderma and check the contribution of detected VOC in plant protection against B. cinerea.

Cell-free supernatant of Bacillus velezensis suppresses mycelial growth and reduces virulence of Botrytis cinerea by inducing oxidative stress

As a notorious pathogenic fungus, Botrytis cinerea has been reported to infect more than 1400 species of plants and cause postharvest gray mold of numerous economic fruits, leading to substantial economic losses. Traditional chemical fungicides in pathogen control have potential issues regarding environmental pollution, disease resistance and human health. More safety and efficacious prevention technique of postharvest gray mold are in urgent demand. This study aims to investigate the potential function and mechanism of Bacillus velezensis to control gray mold for harvested fruits. The results showed that the cell-free supernatant (CFS) generated from B. velezensis strain A4 was able to inhibit spore germination, germ tube elongation and hyphal growth of B. cinerea in vitro, and impair the pathogenicity of B. cinerea on the four tested fruits. Further analysis demonstrated that CFS significantly reduced the expression of genes associated with growth and pathogenicity and weakened the ability of B. cinerea spores to penetrate plant cell walls in a dose-dependent manner. Moreover, the CFS destroyed the membrane of hyphae, resulting in exosmosis of cell contents and caused hyphal cells to accumulate excessive reactive oxygen species (ROS), leading to hyphal oxidative damage. Our findings indicate that B. velezensis CFS can damage B. cinerea mycelial cells by promoting excessive accumulation of ROS to realize its biological control function.

Biocontrol Activity of Bacillus spp. and Pseudomonas spp. Against Botrytis cinerea and Other Cannabis Fungal Pathogens

Gray mold caused by Botrytis cinerea is one of the most widespread and damaging diseases in cannabis crops worldwide. With challenging restrictions on pesticide use and few effective control measures, biocontrol agents are needed to manage this disease. The aim of this study was to identify bacterial biocontrol agents with wide-spectrum activity against B. cinerea and other cannabis fungal pathogens. Twelve Bacillus and Pseudomonas strains were first screened with in vitro confrontational assays against 10 culturable cannabis pathogens, namely B. cinerea, Sclerotinia sclerotiorum, Fusarium culmorum, F. sporotrichoides, F. oxysporum, Nigrospora sphaerica, N. oryzae, Alternaria alternata, Phoma sp., and Cercospora sp. Six strains displaying the highest inhibitory activity, namely Bacillus velezensis LBUM279, FZB42, LBUM1082, Bacillus subtilis LBUM979, P. synxantha LBUM223, and P. protegens Pf-5, were further assessed in planta where all, except LBUM223, significantly controlled gray mold development on cannabis leaves. Notably, LBUM279 and FZB42 reduced disease severity by at least half compared with water-treated plants and prevented lesion development and/or sporulation up to 9 days after pathogen inoculation. Genomes of LBUM279, LBUM1082, and LBUM979 were sequenced de novo and taxonomic affiliations were determined to ensure nonrelatedness with pathogenic strains. Moreover, the genomes were exempt of detrimental genes encoding major toxins and virulence factors that could otherwise pose a biosafety risk when used on crops. Eighteen gene clusters of potential biocontrol interest were also identified. To our knowledge, this is the first reported attempt to control cannabis fungal diseases in planta by direct antagonism with beneficial bacteria.

Antimicrobial activity of sophorolipids produced by Starmerella bombicola against phytopathogens from cherry tomato

BACKGROUND

Phytopathogenic microorganisms are the main cause of plant diseases, generating significant economic losses for the agricultural and food supply chain. Cherry tomatoes (Solanum lycopersicum var. cerasiforme) are very perishable plants and highly demanding in the use of pesticides; therefore, alternative solutions such as biosurfactants have aroused as a potent substituent. The main objective of the present study was to investigate the antimicrobial activity of sophorolipids against the phytopathogens Botrytis cinerea, Sclerotium rolfsii, Rhizoctonia solani and Pythium ultimum.

RESULTS

The biosurfactant inhibited the mycelial growth in vitro with a minimum concentration of 2 mg mL^-1 . The application of sophorolipids at 1, 2 and 4 mg mL^-1 in detached leaves of tomato before the inoculation of the fungus B. cinerea was the best treatment, reducing leaf necrosis by up to 76.90%. The use of sophorolipids for washing tomato fruits before the inoculation of B. cinerea was able to inhibit the development of gray mold by up to 96.27%.

CONCLUSION

The results for tomato leaves and fruits revealed that the biosurfactant acts more effectively when used preventively. Sophorolipids are stable molecules that show promising action for the potential replacement of pesticides in the field and the post-harvest process against the main tomato phytopathogens. © 2021 Society of Chemical Industry.

Advances in Understanding Fungicide Resistance in Botrytis cinerea in China

Gray mold, caused by Botrytis cinerea, is a devastating disease that causes significant yield losses in various economically important plants. Fungicide application is one of the main strategies for management of gray mold; however, B. cinerea has developed resistance to various groups of fungicide. In China, benzimidazole-, dicarboximide-, and quinone outside inhibitor-resistant populations of B. cinerea have become dominant. Substitute mutations in fungicide target genes are responsible for resistance in B. cinerea. Based on known resistance mechanisms, molecular methods including loop-mediated isothermal amplification have been developed for rapid detection of resistant isolates of B. cinerea. Because B. cinerea is able to quickly develop resistance to various fungicides, various integrated strategies have been implemented in the last decade, including biological and agricultural practices, to manage fungicide resistance in B. cinerea.

A Biocontrol Strain of Pseudomonas aeruginosa CQ-40 Promote Growth and Control Botrytis cinerea in Tomato

Botrytis cinerea infection can be very devastating for tomato production, as it can result in a large-scale reduction in tomato fruit production and fruit quality after harvest. Thus, it negatively affects tomato yield and quality. In this study, a biocontrol bacteria CQ-4 was isolated and screened from the rhizosphere soil of tomato plants. Morphological, physiological, and biochemical characteristics and 16S rDNA sequence analysis revealed that it belongs to the species Pseudomonas aeruginosa, which has a strong antagonistic effect against Botrytis cinerea. In addition, the bacterium's antibacterial spectrum is relatively extensive, and antagonistic tests have shown that it also has varying degrees of inhibition on other 12 plant diseases. The growth promotion test showed that the strain has a clear promotion effect on tomato seed germination and seedling growth. The growth-promoting effect on plant height, stem thickness, dry and fresh weight and main root length of tomato seedlings was significantly improved after the seeds were soaked in a bacterial solution of 2.5 × 108 cfu mL-1 concentration. This did not only maintain the nutritional quality of tomato fruits, but also prevents them from rotting. In vitro and pot experiments showed that the strain CQ-4 can effectively control tomato gray mold, and the control effects on tomato leaves and fruits reached 74.4% and 66.0%, respectively. Strain CQ-4 induce plants to up-regulate the activities of four disease-resistant defense enzymes. The peak enzymatic activities of Phenylalanine Ammonia Lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD), and Superoxide Dismutase (SOD) were increased by 35.6%, 37.6%, 46.1%, and 38.4%, respectively, as compared with the control group. This study found that the strain can solubilize phosphorus, fix nitrogen, and produce cellulase, protease, ferrophilin, and other antibacterial metabolites, but it does not produce chitinase, glucanase, and HCN (hydrocyanic acid). This research screened out an excellent Pseudomonas aeruginosa strain that can stably and effectively control tomato gray mold, and it provided theoretical basis for further development and the application of biological agents.

Endophytic Fungi Isolated from Plants Growing in Central Andean Precordillera of Chile with Antifungal Activity against Botrytis cinerea

Botrytis cinerea is an important phytopathogenic fungus affecting the fruit production around the world. This fungus is controlled mainly by using synthetic fungicides, but many resistant isolates have been selected by the indiscriminate use of fungicides. Endophytic fungi or secondary metabolites obtained from them become an alternative method of control for this fungus. The aim of this work was to identify endophytic fungi with antifungal activity against the plant pathogenic fungus B. cinerea isolated from plants from Central Andean Precordillera of Chile. Three endophytic fungi (Ac1, Lc1 and Ec1) with antifungal activity against B. cinerea were isolated from native and endemic plants growing in Central Andean Precordillera of Chile. The isolates Lc1 (isolated from Lithraea caustica) and Ac1 (isolated from Acacia caven) were identified as Alternaria spp. and the isolate Ec1 (isolated from Echinopsis chiloensis) was identified as Aureobasidium spp. The isolated endophytic fungi would inhibit B. cinerea through the secretion of diffusible and volatile compounds affecting the mycelial growth, conidia germination and interestingly, it was also shown that the volatile compounds produced by the three isolated endophytic fungi suppressed the sporulation of B. cinerea.

Menadione Sodium Bisulfite-Protected Tomato Leaves against Grey Mould via Antifungal Activity and Enhanced Plant Immunity

Tomato grey mould has been one of the destructive fungal diseases during tomato production. Ten mM of menadione sodium bisulfite (MSB) was applied to tomato plants for eco-friendly control of the grey mould. MSB-reduced tomato grey mould in the 3rd true leaves was prolonged at least 7 days prior to the fungal inoculation of two inoculum densities (2 × 10⁴ and 2 × 10⁵ conidia/ml) of Botrytis cinerea. Protection efficacy was significantly higher in the leaves inoculated with the lower disease pressure of conidial suspension compared to the higher one. MSB-pretreatment was not effective to arrest oxalic acid-triggered necrosis on tomato leaves. Plant cell death and hydrogen peroxide accumulation were restricted in necrotic lesions of the B. cinereainoculated leaves by the MSB-pretreatment. Decreased conidia number and germ-tube elongation of B. cinerea were found at 10 h, and mycelial growth was also impeded at 24 h on the MSB-pretreated leaves. MSBmediated disease suppressions were found in cotyledons and different positions (1st to 5th) of true leaves inoculated with the lower conidial suspension, but only 1st to 3rd true leaves showed decreases in lesion sizes by the higher inoculum density. Increasing MSB-pretreatment times more efficiently decreased the lesion size by the higher disease pressure. MSB led to inducible expressions of defence-related genes SlPR1a, SlPR1b, SlPIN2, SlACO1, SlChi3, and SlChi9 in tomato leaves prior to B. cinerea infection. These results suggest that MSB pretreatment can be a promising alternative to chemical fungicides for environment-friendly management of tomato grey mould.

Crop Protection against Botrytis cinerea by Rhizhosphere Biological Control Agent Bacillus velezensis XT1

This study aims to evaluate the use of Bacillus velezensis strain XT1 as a plant growth-promoting rhizobacterium (PGPR) and biocontrol agent against B. cinerea in tomato and strawberry plants. Foliar and radicular applications of strain XT1 increased plant total biomass as compared to the control and B. cinerea-infected plants, with root applications being, on the whole, the most effective mode of treatment. Applications of the bacterium were found to reduce infection parameters such as disease incidence and severity by 50% and 60%, respectively. We analyzed stress parameters and phytohormone content in order to evaluate the capacity of XT1 to activate the defense system through phytohormonal regulation. Overall, the application of XT1 reduced oxidative damage, while the H₂O₂ and malondialdehyde (MDA) content was lower in XT1-treated and B. cinerea-infected plants as compared to non-XT1-treated plants. Moreover, treatment with XT1 induced callose deposition, thus boosting the response to pathogenic infection. The results of this study suggest that the signaling and activation pathways involved in defense mechanisms are mediated by jasmonic acid (JA) and ethylene hormones, which are induced by preventive treatment with XT1. The study also highlights the potential of preventive applications of strain XT1 to activate defense mechanisms in strawberry and tomato plants through hormone regulation.

Sodium pheophorbide a controls cherry tomato gray mold (Botrytis cinerea) by destroying fungal cell structure and enhancing disease resistance-related enzyme activities in fruit

Sodium pheophorbide a (SPA) is a natural photosensitizer. The present study investigated the antifungal activity and mechanism of SPA against Botrytis cinerea in vitro and in vivo. Its inhibitory effect was studied on the spore germination and mycelial growth of B. cinerea. The effects of SPA on cell wall integrity, cell membrane permeability, and mycelial morphology of B. cinerea were also determined. Additionally, how SPA effected B. cinerea in vivo was evaluated using cherry tomato fruit. The results showed that SPA effectively inhibited the spore germination and mycelial growth of B. cinerea under light conditions (4000 lx). SPA significantly affected both cell wall integrity and cell membrane permeability (P < .05). In addition, SEM analysis suggested that B. cinerea treated with SPA (12.134 mg/mL) showed abnormal mycelial morphology, including atrophy, collapse, flattening, and mycelial wall dissolution. In vivo tests showed that SPA could increase the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) significantly (P < .05); however, SPA had no significant effect on phenylalanine ammonia lyase (PAL) activity. In short, SPA could destroy the fungal cell structure and enhance disease resistance-related enzyme activity in cherry tomatoes, thereby controlling cherry tomato gray mold.

Biological Control of Tomato Gray Mold Caused by Botrytis Cinerea with the Entomopathogenic Fungus Metarhizium Anisopliae

Gray mold disease caused by Botrytis cinerea is a devastating disease that leads to serious financial loss. In this study, the entomopathogenic fungus Metarhizium anisopliae that acts against the gray mold pathogen B. cinerea was evaluated. M. anisopliae produced a significant inhibition zone in front of the B. cinerea colony in the dual culture test. In addition, volatile organic compounds generated by M. anisopliae were shown to have an inhibitory effect on B. cinerea mycelia growth and reduced 41% of gray mold severity of postharvest tomatoes. The 10% concentration of the culture filtrate of M. anisopliae inhibited 88.62% of colony radial growth as well as 63.85% of sclerotia germination and all conidia germination of B. cinerea. Furthermore, the culture filtrate of M. anisopliae retained its inhibitory effect against the radial growth of B. cinerea even after heating for 15 min at 100 °C. Feasible mechanisms of M. anisopliae involved in the control of B. cinerea were explored, and it was demonstrated that the plasma membrane of B. cinerea conidia was damaged by the product of metabolism of M. anisopliae. In addition, after treating with culture filtrate of M. anisopliae, the B. cinerea phenotype was shown to be abnormal, and cell organelles of B. cinerea mycelia were damaged significantly. A significant control efficacy of M. anisopliae against tomato gray mold was detected on both the detached leaf assay (84.24%) as well as the whole plant (72.38%). In addition, a 78% reduction in tomato fruit mold was detected at a 10% treated concentration of M. anisopliae. These findings suggest that M. anisopliae possesses potential as a biocontrol agent against tomato gray mold in the greenhouse and during the postharvest stage.

Antifungal Activity of Lipopeptides From Bacillus XT1 CECT 8661 Against Botrytis cinerea

This work aims to explore the capacity of a Bacillus methylotrophicus (later heterotypic synonym of Bacillus velezensis) strain named XT1 CECT 8661 against the necrotrophic plant pathogen Botrytis cinerea and to identify the compounds responsible for its activity. Q_TOF electrospray mass spectrometry analysis allows us to detect several lipopeptides – surfactin, bacillomycin, and fengycin – in XT1 cultures. In vitro antibiosis studies demonstrated the efficiency of the lipopeptide fraction for the inhibition of fungal growth. In fact, microscopy studies (SEM/TEM) revealed, an alteration of the morphology of the phytopathogen in interaction with lipopeptides, with resistance structures appearing in the early stages of growth of the fungus. Our studies, carried out with tomatoes, grapes, and strawberries have demonstrated the efficiency of Bacillus XT1 CECT 8661 lipopeptides against B. cinerea infection and it capability to trigger the antioxidant activity in fruit. Overall, the results of this study highlight the potential of lipopeptides of this strain as an effective biological control agent against the colonisation of B. cinerea.