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Early blight is a disease that greatly affects Solanaceae, mainly damaging tomato plants, and causing significant economic losses. Although there are methods of biological control, these are very expensive and often their mode of action is slow. Due to this, there is a need to use new techniques that allow a more efficient control of pathogens. Nanotechnology is a new alternative to solve these problems, allowing the creation of new tools for the treatment of diseases in plants, as well as the control of pathogens. The aim of the present investigation was to evaluate the foliar application of selenium and copper in the form of nanoparticles in a tomato crop infested by Alternaria solani. The severity of Alternaria solani, agronomic variables of the tomato crop, and the changes in the enzymatic and non-enzymatic antioxidant compounds were evaluated. The joint application of Se and Cu nanoparticles decreases the severity of this pathogen in tomato plants. Moreover, high doses generated an induction of the activity of the enzymes superoxide dismutase, ascorbate peroxidase, glutathione peroxidase (GPX) and phenylalanine ammonia lyase in the leaves, and the enzyme GPX in the fruit. Regarding non-enzymatic compounds in the leaves, chlorophyll a, b, and totals were increased, whereas vitamin C, glutathione, phenols, and flavonoids were increased in fruits. The application of nanoparticles generated beneficial effects by increasing the enzymatic and non-enzymatic compounds and decreasing the severity of Alternaria solani in tomato plants.

In this study, two phenol compounds, magnolol and honokiol, were extracted from Magnolia officinalis and identified by LC-MS, 1H- and 13C-NMR. The magnolol and honokiol were shown to be effective against seven pathogenic fungi, including Alternaria alternata (Fr.) Keissl, Penicillium expansum (Link) Thom, Alternaria dauci f.sp. solani, Fusarium moniliforme J. Sheld, Fusarium oxysporum Schltdl., Valsa mali Miyabe & G. Yamada, and Rhizoctonia solani J.G. Kühn, with growth inhibition of more than 57%. We also investigated the mechanisms underlying the potential antifungal activity of magnolol and honokiol. The results showed that they inhibited the growth of A. alternata in a dose-dependent manner. Moreover, magnolol and honokiol treatment resulted in distorted mycelia and increased the cell membrane permeability of A. alternata, as determined by conductivity measurements. These results suggest that magnolol and honokiol are potential antifungal agents for application against plant fungal diseases.

Fungal green biosynthesis of nanoparticles (NPs) is a promising eco-friendly method for mass-scale production. In the present study Ag, CuO and ZnO nanoparticles were biogenically synthetized using a cell filtrate of a strain of Trichoderma harzianum as a reducer and stabilizer agent. The structure, morphology and physicochemical properties of the NPs were characterized through transmission electron microscopy, dynamic light scattering, wide angle X-ray scattering and thermogravimetric analysis. Since nanotechnology could offer promising applications in agricultural area, we evaluated the ability of the NPs to reduce the growth of important fungal phytopathogens as Alternaria alternata , Pyricularia oryzae and Sclerotinia sclerotiorum . Silver and CuO NPs reduced significantly the mycelial growth of A. alternata and P. oryzae in a dose dependent manner. This is the first report of a multiple extracellular biosynthesis of NPs from T. harzianum and the first time that CuO and ZnO NPs were obtained from this fungus. In addition, we highlighted the rapid production of NPs, as well as, the potential of Ag and CuO for the control of phytopathogens. On the other hand, the three types of NPs could be easily and sustainably produced on a large scale with the chance of having multiple applications in biotechnological processes.

Black spot caused by Alternaria alternata is one of the important diseases of pear fruit during storage. Isothiocyanates are known as being strong antifungal compounds in vitro against different fungi. The aim of this study was to assess the antifungal effects of the volatile compound 2-phenylethyl isothiocyanate (2-PEITC) against A. alternata in vitro and in pear fruit, and to explore the underlying inhibitory mechanisms. The in vitro results showed that 2-PEITC significantly inhibited spore germination and mycelial growth of A. alternata—the inhibitory effects showed a dose-dependent pattern and the minimum inhibitory concentration (MIC) was 1.22 mM. The development of black spot rot on the pear fruit inoculated with A. alternata was also significantly decreased by 2-PEITC fumigation. At 1.22 mM concentration, the lesion diameter was only 39% of that in the control fruit at 7 days after inoculation. Further results of the leakage of electrolyte, increase of intracellular OD260, and propidium iodide (PI) staining proved that 2-PEITC broke cell membrane permeability of A. alternata. Moreover, 2-PEITC treatment significantly decreased alternariol (AOH), alternariolmonomethyl ether (AME), altenuene (ALT), and tentoxin (TEN) contents of A. alternata. Taken together, these data suggest that the mechanisms underlying the antifungal effect of 2-PEITC against A. alternata might be via reduction in toxin content and breakdown of cell membrane integrity.

The synthesis of nanomaterials from PGPB is an exciting approach and it’s often used in agriculture as nano-fertilizers and nano-pesticides. The present study reports a new approach to biosynthesis of silver nanoparticles (AgNP), using bacterial metabolites as agents to reduce Ag + , which will remain as coating agents able to prevent microbial growth. Silver NP were biosynthesized using the bacterial metabolites produced by the beneficial strain Pseudomonas sp. N5.12. Optimization of physicochemical parameters (temperature, pH, and AgNO 3 concentration) for the synthesis of AgNP was carried out. In each condition, success on AgNP synthesis was determined by UV–Visible spectra showing peaks between 400 and 450 nm. TEM analysis showed that the AgNP are spherical in shape with an average particle size ranging from 13.75 ± 0.47 nm to 20.71 ± 0.43 nm, covered with a unique organic matter corona of bacterial metabolites. The best parameters for AgNP biosynthesis by Pseudomonas sp. N5.12 occurred with 24 h bacterial metabolites, temperature of 37 °C, pH 9 and a ratio of 2:4 (v: v; bacterial supernatant: 1 mM AgNO 3 ). The biosynthesized AgNP inhibited growth of human pathogenic bacteria better than equivalent AgNO 3 concentration. Growth of bacterial and fungal phytopathogens was also inhibited with striking effects on Alternaria sp. (74% inhibition) and Stemphylium sp. (52% inhibition), appearing as promising tools to biocontrol fungal diseases in agriculture.

Pathogenic fungi have developed complex and specific infection strategies to invade host tissues successfully. Regulator of G‐protein signalling (RGS) proteins exhibit GTPase‐accelerating protein activities and play a crucial role in the formation of infection structures in pathogenic fungi. However, specific regulatory mechanisms remain unclear. In the present study, observations of infection structure indicated that the deletion of AaRgs2 resulted in a significant increase in spore germination. Appressorium‐like formation rate was compared to that of the wild‐type strain on a Gelbond hydrophobic membrane coated with 16‐hydroxyhexadecanoic acid or 1,16‐hexadecanediol, which are cutin monomers in pear peel. Transcriptome analysis during the appressorium‐like formation stage revealed 4124 differentially expressed genes (DEGs) that were annotated in the wild‐type strain and the ΔAaRgs2 mutant. KEGG enrichment analysis showed that the cAMP‐PKA signalling pathway, MAPK signalling pathway, peroxisome and autophagy pathway were closely associated with appressorium‐like formation regulated by AaRgs2. Yeast two‐hybrid and bimolecular fluorescence complementation assays demonstrated a specific physical interaction between AaRgs2 and AaGα1, further confirming that AaGα1 interacted with the Pfam domain of adenylate cyclase AC. Our studies provide evidence suggesting that AaRgs2 negatively regulates appressorium‐like formation of A. alternata induced by pear cutin monomer via the AaRgs2‐AaGα1‐AaAC module. AaRgs2 negatively regulates appressorium‐like formation of A. alternata induced by pear cutin monomer via the AaRgs2‐AaGα1‐AaAC module.

Postharvest fungal diseases cause substantial losses in horticultural crops and are commonly managed using chemical fungicides, which raise concerns regarding resistance development and environmental impact. Plant‐derived antifungal peptides represent a promising alternative for sustainable disease control. Here, we evaluated the antifungal activity and mode of action of three nodule‐specific cysteine‐rich (NCR) peptides—NCR044, NCR192 and NCR13_(P)FV2—against major postharvest fungal pathogens. Among the peptides tested, NCR13_(P)FV2 exhibited the strongest inhibitory activity against Alternaria alternata, Colletotrichum gloeosporioides, Lasiodiplodia theobromae and Penicillium expansum, although activity against C. gloeosporioides was predominantly fungistatic rather than fungicidal. Mechanistic analyses using A. alternata as a model pathogen revealed that NCR13_(P)FV2 rapidly associates with fungal membranes, induces membrane permeabilization and exhibits selective binding to anionic phospholipids and phosphoinositides. Peptide treatment was associated with mitochondrial depolarization, elevated reactive oxygen species accumulation, reduced cellular respiration and disruption of vacuolar integrity. These intracellular effects were accompanied by loss of turgor pressure and hyphal collapse. Importantly, application of NCR13_(P)FV2 to wounded bell pepper fruit significantly reduced lesion development caused by A. alternata in a concentration‐dependent manner. Together, these findings demonstrate that NCR13_(P)FV2 suppresses postharvest fungal infection through a multi‐target mechanism that disrupts fungal cellular homeostasis, highlighting its potential as a peptide‐based alternative to synthetic fungicides. NCR13_(P)FV2 triggers fungal death via membrane disruption, mitochondrial dysfunction and oxidative stress. This multi‐target plant peptide is a potent bio‐alternative to synthetic fungicides.

• Although the role of auxin in biotrophic pathogenesis has been extensively studied, relatively little is known about its role in plant resistance to necrotrophs. • Arabidopsis thaliana mutants defective in different aspects of the auxin pathway are generally more susceptible than wild‐type plants to the necrotrophic pathogen Alternaria brassicicola. We show that A. brassicicola infection up‐regulates auxin biosynthesis and down‐regulates the auxin transport capacities of infected plants, these effects being partially dependent on JA signaling. We also show that these effects of A. brassicicola infection together lead to an enhanced auxin response in host plants. • Application of IAA and MeJA together synergistically induces the expression of defense marker genes PDF1.2 (PLANT DEFENSIN 1.2) and HEL (HEVEIN‐LIKE), suggesting that enhancement of JA‐dependent defense signaling may be part of the auxin‐mediated defense mechanism involved in resistance to necrotrophic pathogens. • Our results provide molecular evidence supporting the hypothesis that JA and auxin interact positively in regulating plant resistance to necrotrophic pathogens and that activation of auxin signaling by JA may contribute to plant resistance to necrotrophic pathogens.

Volatile organic compounds (VOCs) produced by Aureobasidium pullulans were investigated for antagonistic actions against Alternaria alternata and Botrytis cinerea . Conidia germination and colony growth of these two phytopathogens were suppressed by A. pullulans VOCs. A novel experimental setup was devised to directly extract VOCs using solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) from antagonist-pathogen culture headspace. The proposed system is a robust method to quantify microbial VOCs using an internal standard. Multivariate curve resolution-alternating least squares deconvolution of SPME-GC-MS spectra identified fourteen A. pullulans VOCs. 3-Methyl-1-hexanol, acetone, 2-heptanone, ethyl butyrate, 3-methylbutyl acetate and 2-methylpropyl acetate were newly identified in A. pullulans headspace. Partial least squares discriminant analysis models with variable importance in projection and selectivity ratio identified four VOCs (ethanol, 2-methyl-1-propanol, 3-methyl-1-butanol and 2-phenylethanol), with high explanatory power for discrimination between A. pullulans and pathogen. The antifungal activity and synergistic interactions of the four VOCs were evaluated using a Box-Behnken design with response surface modelling. Ethanol and 2-phenylethanol are the key inhibitory A. pullulans VOCs against both B. cinerea and A. alternata . Our findings introduce a novel, robust, quantitative approach for microbial VOCs analyses and give insights into the potential use of A. pullulans VOCs to control B. cinerea and A. alternata .

Alternaria solani causes early blight disease in eggplants, threatening production and leading to significant economic losses. Fungicides are used to control fungal diseases, but their overuse raises resistance concerns. Finding novel, eco-friendly biocontrol agents is therefore a solution for the future. The coordination between antagonistic bacterial agents and plant growth hormones in defense responses against fungal pathogens are crucial. This study assessed biocontrol potential of Acinetobacter sp. SCR-11 (Accession no. OR751536.1) and indole-3-acetic acid (IAA; 100 µM), singly and in combination, against A. solani in eggplants. Strain SCR-11 produced hydrogen cyanide (HCN; 5.7 µg mL⁻ 1 ), siderophore i.e. salicylic acid (14.7 µg mL⁻ 1 ), 2,3-dihydroxybenzoic acid (23.1 µg mL⁻ 1 ) and various extracellular lytic enzymes. Strain SCR-11 exhibited antagonistic activity by strongly inhibiting (82%) A. solani . Acinetobacter sp. inoculation and IAA treatment enhanced growth, biomass, and leaf pigments of A. solani -diseased eggplants, with effectiveness in order: SCR-11 + IAA > SCR-11 > IAA >. The combined treatments (SCR-11 + IAA) most effectively increased total soluble protein (62.5%), carbohydrate (60%), total soluble sugar (81%), and phenol (74%) in A. solani -infected eggplant. Biocontrol agent and IAA application significantly ( p  ≤ 0.05) reduced proline and malondialdehyde (MDA) levels, alleviating oxidative stress in A. solani -diseased eggplant. The SCR-11 + IAA treatment significantly reduced the percent disease index (71%) and increased protection (69%) in diseased eggplant. The Acinetobacter sp. and IAA coordination enhanced disease resistance in A. solani -infected eggplants by boosting defense enzyme activities (SOD, POD, PAL, and β-1, 3 glucanase), significantly protecting plants from pathogen attack. At harvest, soil populations of A. solani decreased, while SCR-11 populations increased significantly. Acinetobacter sp. and IAA work synergistically through pathogen suppression, plant growth promotion, and induction of plant defense responses. Thus, applying antagonistic PGPR strain with exogenous IAA enhances eggplant resistance to A. solani , providing an environmentally friendly agricultural solution.