Postharvest Fungal Pathogens Research Articles

Quince (Cydonia oblonga Mill.) Waste By-Product Characterization as a Potential Functional Ingredient

Currently, the production of waste in the food industry is increasing, which is a serious problem. However, most of these residues, especially those derived from fruits and vegetables, have great unknown properties that are not used. The main objective of this article is the analysis and characterization of the waste from quince after its processing to observe its properties and its potential use in different industries as a functional ingredient, thus favoring the circular economy and sustainability. Quince by-product nutritional parameters such as proteins, fibers, sugars, vitamins, and minerals were analyzed. Also, the antioxidant capacity was measured by various methods: 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity (DPPH), antioxidant capacity in Trolox equivalent antioxidant capacity (TEAC/ABTS), and total polyphenol content (TPC). Finally, the antimicrobial capacity against different postharvest-pathogenic fungi was measured in direct sample and extract. The nutritional results showed a nutritional profile rich in soluble and insoluble fiber, potassium, calcium, and magnesium, and low in fat. The antioxidant results from the extract showed significant levels of phenols and higher antioxidant capacity from the extracted sample. No positive results were found in the antimicrobial capacity study. Quince by-products could be a potential ingredient in the industry due to their nutritional composition and antioxidant content.

Mycotoxicity of leaf extract of Tabernaemontana pachysiphon Stapf against Fusarium oxysporum Schlecht, a postharvest fungal rot pathogen of taro

Mycotoxicity of leaf extract of Tabernaemontana pachysiphon Stapf against Fusarium oxysporum Schlecht, a postharvest fungal rot pathogen of taro

Mycotoxicity of leaf extract of Tabernaemontana pachysiphon Stapf against Fusarium oxysporum Schlecht, a postharvest fungal rot pathogen of taro

Taro, otherwise known as cocoyam, is one of the major sources of calories in the tropics. However, losses of its corm during storage are high, partly due to pathogenic diseases. Fusarium oxysporum is one of the principal fungal pathogens causing about 50% of postharvest losses of taro corms in the tropics. The rise in pesticide-resistant fungal pathogens, amongst other factors, has necessitated the recent search for alternatives to synthetic pesticides. This work aimed to evaluate the effects of six concentrations (0%, 10%, 20%, 30%, 40%, and 50%) of aqueous leaf extract of T. pachysiphon on spore germination, mycelial growth and reproduction of F. oxysporum both in vitro and in vivo. The in vitro experiment was conducted using the poison bait technique, while the in vivo experiment involved 21 corms (200 g) artificially infected with F. oxysporum and treated with the respective concentrations of the test extracts or griseofulvin. The control consisted of fungus-infected corms only. Generally, the experiments consisted of 7 treatments replicated 3 times and were laid out in a completely randomized design. Results of the cultures studies showed that all aqueous extract of T. pachysiphon significantly (P< 0.05) and to varying degrees impeded spore germination (56.38–70.24%) and retarded radial growth of the pathogen (68.27–82.01%). The percentage rot expression in the living tissues treated with the extracts ranged between 19.4% and 40.4%. All results were statistically (P< 0.05) superior to the control but comparable to the results (75.06%, 86.41%, and 17.2%) obtained with griseofulvin for these features, respectively. The inhibitions were linearly correlated with the dose of application of the biotoxicant both in vitro and in vivo.

Bioactive molecules isolated from Cymbopogon flexuosus and Monarda citriodora essential oils: Chemical profiling, antimycotic potential, and molecular docking studies against green and blue molds of Kinnow

Among the most alarming postharvest fungal pathogens affecting the shelf life of citrus fruits are green (Penicillium digitatum) and blue (Penicillium italicum) molds. This in vitro study was aimed to evaluate the essential oils (EOs) of Cymbopogon flexuosus (CF) and Monarda citriodora (MC) and their principal components against these fungal pathogens. The composition of selected EOs was analyzed using Gas Chromatography- Mass Spectrometry (GC-MS) and Gas Chromatography-Flame Ionization Detector (GC-FID). Citral (83.81%) and thymol (62.51%) were identified as major components and were isolated by column chromatography from CF and MC EO respectively followed by characterization using spectral techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR) and Carbon Nuclear Magnetic Resonance Spectroscopy (13C-NMR). Among EOs and their major components, thymol displayed promising potential against both Penicillium species with MIC values of 50 and 80 mg L-1 respectively. Molecular docking studies also confirmed the stable binding interaction of both components, particularly thymol with the active sites of target proteins i.e. 14-α-demethylase and chitin synthase of P. digitatum and P. italicum with the docking scores of -5.07, -5.41 kcal/mol and -5.78, -5.23 kcal/mol respectively. Optical microscopy studies revealed hyphal thinning and fragmentation at frequent sites with contraction of cytoplasmic content indicating incipient plasmolysis. The tested principal components, citral and thymol were predicted to exhibit similar mechanism of action to that of synthetic recommended molecules as revealed by molecular docking. Therefore, these findings provide empirical support to explore thymol as a promising eco-friendly antifungal agent for postharvest application in Kinnow.

Effect of ethylene production by four pathogenic fungi on the postharvest diseases of green pepper (Capsicum annuum L.)

Ethylene produced by plants generally induces ripening and promotes decay, whereas the effect of ethylene produced by pathogens on plant diseases remains unclear. In this study, four ethylene-producing fungi including Alternaria alternata (A. alternata, Aa), Fusarium verticilliodes (F. verticillioides, Fv), Fusarium fujikuroi 1 (F. fujikuroi 1, Ff-1) and Fusarium fujikuroi 2 (F. fujikuroi 2, Ff-2) were severally inoculated in potato dextrose broth (PDB) media and postharvest green peppers, the ethylene production rates, disease indexes and chlorophyll fluorescence parameters were determined. The results showed that Ff-2 and Fv in the PDB media had the highest and almost the same ethylene production rates. After inoculation with green peppers, Ff-2 treated group still exhibited the highest ethylene production rate, whereas Aa treated group had a weak promotion effect on ethylene production. Moreover, the ethylene production rate of green peppers with mechanical injury was twice that without mechanical injury, and the ethylene production rates of green peppers treated with Aa, Ff-1, Ff-2 and Fv were 1.2, 2.6, 3.8 and 2.8 folds than those of green peppers without treatment, respectively. These results indicated that pathogen infection stimulated the synthesis of ethylene in green peppers. Correlation analysis indicated that the degreening of Fusarium-infected green pepper was significantly positively correlated with the ethylene production rate of green pepper, whereas the disease spot of Aa-infected green pepper had a significant positive correlations with the ethylene production rate of green peppers. Chlorophyll fluorescence results showed that the green peppers already suffered from severe disease after being infected with fungi for 4 days, and Fusarium infection caused early and serious stress, while the harm caused by A. alternata was relatively mild at the early stage. Our results clearly showed that α-keto-γ-methylthiobutyric acid (KMBA)-mediated ethylene synthesis was the major ethylene synthesis pathway in the four postharvest pathogenic fungi. All the results obtained suggested that ethylene might be the main infection factor of Fusarium spp. in green peppers. For pathogenic fungi, stimulating green peppers to produce high level of ethylene played a key role in the degreening of green peppers.

Characterization and Antioxidant and Antibacterial Activities of Carboxymethylated Tamarind Seed Polysaccharide Composite Films Incorporated with ε-Polylysine and Their Application in Fresh-Cut Green Bell Pepper Preservation.

Traditional petroleum-based food-packaging materials have poor permeability, limited active packaging properties, and difficulty in biodegradation, limiting their application. We developed a carboxymethylated tamarind seed polysaccharide composite film incorporated with ε-polylysine (CTPε) for better application in fresh-cut agricultural products. The CTPε films exhibit excellent water vapor barrier properties, but the mechanical properties are slightly reduced. Fourier transform infrared spectroscopy and X-ray diffraction spectra indicate the formation of hydrogen bonds between ε-PL and CTP, leading to their internal reorganization and dense network structure. With the increase of ε-PL concentration, composite films showed notable inhibition of postharvest pathogenic fungi and bacteria, a significant enhancement of 2,2'- azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical-scavenging activity, and gradual improvement of wettability performance. Cytotoxicity experiments confirmed the favorable biocompatibility when ε-PL was added at 0.3% (CTPε2). In fresh-cut bell pepper preservation experiments, the CTPε2 coating effectively delayed weight loss and malondialdehyde increase preserved the hardness, color, and nutrients of fresh-cut peppers and prolonged the shelf life of the fresh-cut peppers, as compared with the control group. Therefore, CTPε composite films are expected to be a valuable packaging material for extending the shelf life of freshly cut agricultural products.

Transcriptomic investigation of the interaction between a biocontrol yeast, Papiliotrema terrestris strain PT22AV, and the postharvest fungal pathogen Penicillium expansum on apple

Biocontrol strategies offer a promising alternative to control plant pathogens achieving food safety and security. In this study we apply a RNAseq analysis during interaction between the biocontrol agent (BCA) Papiliotrema terrestris, the pathogen Penicillium expansum, and the host Malus domestica. Analysis of the BCA finds overall 802 upregulated DEGs (differentially expressed genes) when grown in apple tissue, with the majority being involved in nutrients uptake and oxidative stress response. This suggests that these processes are crucial for the BCA to colonize the fruit wounds and outcompete the pathogen. As to P. expansum analysis, 1017 DEGs are upregulated when grown in apple tissue, with the most represented GO categories being transcription, oxidation reduction process, and transmembrane transport. Analysis of the host M. domestica finds a higher number of DEGs in response to the pathogen compared to the BCA, with overexpression of genes involved in host defense signaling pathways in the presence of both of them, and a prevalence of pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) only during interaction with P. expansum. This analysis contributes to advance the knowledge on the molecular mechanisms that underlie biocontrol activity and the tritrophic interaction of the BCA with the pathogen and the host.

Plumbagin controls fungal postharvest pathogens by affecting metabolism and inducing autophagy

Botrytis cinerea is a devastating postharvest pathogenic fungus causing severe postharvest decay in a wide range of fruit and vegetables. Controlling postharvest pathogens is essential to the postharvest industry. Plumbagin is a plant-derived naphthoquinone compound with various pharmacological activities, such as antioxidant, anti-inflammatory, and antimicrobial effects. However, its antifungal effects on B. cinerea have not been fully elucidated. In this study, we investigated the antifungal activity of plumbagin against postharvest fungal pathogens and elucidated its potential mechanism on B. cinerea through transcriptomics. Plumbagin exhibited broad-spectrum antifungal activity and completely inhibited the growth of various postharvest pathogens at a concentration of 20 mg L−1in vitro. Moreover, plumbagin effectively inhibited the incidence of gray mold in grape, sweet cherry, and strawberry fruit. The spore germination and viability of B. cinerea were also suppressed by plumbagin. Transcriptomic analysis indicated that plumbagin significantly affected the metabolic processes and induced autophagy in B. cinerea. Our results suggest that plumbagin is a promising broad-spectrum plant-derived fungicide that suppresses postharvest gray mold by affecting the metabolism of B. cinerea and inducing autophagy. These findings provide a theoretical basis for applying plumbagin to control postharvest pathogens.

Exploring sustainable management by using green nano-silver to combat three post-harvest pathogenic fungi in crops

Global crop protection and food security have become critical issues to achieve the ‘Zero Hunger’ goal in recent years, as significant crop damage is primarily caused by biotic factors. Applying nanoparticles in agriculture could enhance crop yield. Nano-silver, or AgNPs, have colossal importance in many fields like biomedical, agriculture, and the environment due to their antimicrobial potential. In this context, nano-silver was fabricated by Citrus medica L. (Cm) fruit juice, detected visually and by UV–Vis spectrophotometric analysis. Further, AgNPs were characterized by advanced techniques. UV–Vis spectroscopic analysis revealed absorbance spectra at around 487 nm. The zeta potential measurement value was noted as -23.7 mV. Spectral analysis by FT-IR proved the capping of the acidic groups. In contrast, the XRD analysis showed the Miller indices like the face-centered cubic (fcc) crystalline structure. NTA revealed a mean size of 35 nm for nano-silver with a 2.4 × 108 particles mL−1 concentration. TEM analysis demonstrated spherical Cm-AgNPs with 20–30 nm sizes. The focus of this research was to evaluate the antifungal activity of biogenic AgNPs against post-harvest pathogenic fungi, including Aspergillus niger, A. flavus, and Alternaria alternata. The Cm-AgNPs showed significant antifungal activity in the order of A. niger > A. flavus > A. alternata. The biogenic Cm-AgNPs can be used for the inhibition of toxigenic fungi.

Categorization of mycotoxin producing fungi in leguminous crops and its eco-friendly management under in vitro condition

Four legume crops, viz., groundnut (Arachis hypogea L.), soybean (Glycine max (L.) Merr.) of Kharif season, chickpea (Cicer arietinum L.), and lentil (Lens esculentum L.) of Rabi season belonging to family Fabaceae were taken for investigation of seed-borne mycoflora. Since these are severely affected by many plant-pathogenic fungi at various stages of the whole life cycle, they were chosen for the study. Many post-harvest fungal pathogens cause severe loss by contaminating the grains with various mycotoxins and also deteriorate the nutritional quality of grains. The goal of any agricultural system is to increase the yield of crops as per the population demand. Various eco-friendly management practices were performed on highly mycotoxin-producing isolates of Aspergillus flavus and A. niger isolated from these grains. Four Trichoderma isolates (T2, T3, T4 and T5) were used as a biocontrol agent in the dual culture method to check antagonism between various Aspergillus isolates and Trichoderma isolates. It gave a satisfactory result in controlling mycelial growth. Achyranthes aspera leaf and stem phytoextract (10%, 20%, 30%, and 40%) was used as a botanical treatment in the well diffusion method, which successfully restricts the Aspergillus spp. mycelial growth.

Cannabinoids: A new natural agent to control postharvest decay development

Pathogenic fungi are a major cause of postharvest loss of fresh produce. While chemical fungicides effectively control postharvest diseases their use raises concerns and alternatives are required. Natural compounds with antifungal properties and natural defense response elicitors are explored. Among those compounds, phytocannabinoids are secondary metabolites generated from Cannabis sativa that are of particular interest. Among the non-psychotropic cannabinoids are cannabidiol (CBD) and cannabigerol (CBG). The current study investigates the effect of CBD and CBG’s effect on postharvest fungal pathogens and the fruit defense response. CBD and CBG inhibit the growth of major postharvest pathogens such as Botrytis cinerea, Penicillium expansum, and Colletotrichum gloeosporioides. Moreover, CBD and CBG significantly decreased gray mold development caused by B. cinerea on grapes. Studying their mode of action indicated that both CBD and CBG affected B. cinerea fungal cell wall composition and cell-wall-related remodeling genes, as well as cell membrane fluidity and permeability. CBD treatment causes hyperpolarization of the fungal mitochondria membrane, which results in increased intracellular ROS levels. Evaluation of the effect of CBD and CBG on the fruit defense response displayed a priming effect by up-regulating pathogenic related proteins and induced salicylic acid and flavonols production resulting in inhibition of decay development. Overall, the results of the current study reveal the direct and indirect ability of natural phytocannabinoids to control fungal decay development and reduce food loss. This novel eco-friendly postharvest treatment has the potential to replace chemically hazardous fungicides.

Endophytic Stenotrophomonas geniculata KJ-6 via producing antifungal volatile organic compounds effectively control Lanzhou lily postharvest diseases

The endophytic bacterial Stenotrophomonas geniculata KJ-6, was isolated from Arisaematis rhizoma. This strain has the ability to control three postharvest pathogenic fungi of Lanzhou lily (Trichoderma lixii F-2, Talaromyces tumuli F-3, and Fusarium annulatum F-6) by releasing volatile organic compounds (VOCs). The experiment utilized the double-layer sealed bottom plate method. The results demonstrate that KJ-6 effectively inhibits the mycelial growth of F-2, F-3, and F-6, with inhibition rates of 81.59%, 79.87%, and 84.7%, respectively. Moreover, scanning electron microscopy (SEM) revealed abnormal mycelium morphology in the test pathogenic fungi treated with KJ-6 VOCs, characterized by multiple wrinkles, cracks, and distortions. Using five common phytopathogenic fungi as controls, our results demonstrated that the VOCs from KJ-6 exhibited broad-spectrum antifungal effects. Analysis using headspace gas chromatography-ion mobility spectrometry identified three components of the VOCs produced by KJ-6, including 1-propanethiol, isoamyl acetate, and 2-methyl-1-butanol. Antifungal tests revealed that 1-propanethiol plays a crucial role in the inhibitory activity of VOCs. It exhibited inhibitory rates of 64.17%, 72.73%, and 26.71% on the mycelium growth of F-2, F-3, and F-6, respectively. In vivo experiments further confirmed that VOCs can significantly reduce the disease index and decay rate of Lanzhou lily bulbs during storage. Moreover, KJ-6 treatment led to a significant reduction in the degree of browning of lily bulbs. Additionally, it enhanced the activity of defense-related enzymes, improved disease resistance, and extended the shelf life of lily bulbs. As a result, this study offers a theoretical foundation for the biological control of postharvest diseases in Lanzhou lily.

Characterizations of Water-Soluble Chitosan/Curdlan Edible Coatings and the Inhibitory Effect on Postharvest Pathogenic Fungi

This study focused on developing a composite coating comprising water-soluble chitosan (CTS) and curdlan (CUR). Cherry tomatoes served as the test material for assessing the preservative efficacy of these coatings. The incorporation of CUR markedly enhanced the coating’s surface properties, refined its molecular structure, and improved its tensile strength and elongation at break. Additionally, the coating demonstrated enhanced permeability to water vapor, oxygen, and carbon dioxide and improved light transmission. The storage experiment, conducted at 25 ± 1 °C with a relative humidity of approximately 92% over 10 days, revealed that the CTS/CUR composite coating at a 1:1 ratio significantly outperformed the individual CTS or CUR coating and uncoated samples in maintaining the quality of postharvest cherry tomatoes. The 1:1 CTS/CUR composite coating demonstrated superior preservative effects. This study suggested that water-soluble chitosan/curdlan composite coatings have considerable potential for use in the preservation of postharvest fruits and vegetables.

Valorisation of raw mango pickle industry waste into antimicrobial agent against postharvest fungal pathogens

In mango pickle industry, a significant quantity of mango seed kernels is discarded as solid wastes. These seed kernels can be an ideal source for obtaining extracts rich in bioactive polyphenolic compounds with good antioxidant properties. The potential of mango kernel phenolic extract (MKPE) was investigated as a natural and effective antimicrobial agent for controlling major postharvest fungal pathogen infections, a significant threat to global food supply chains. Fungal pathogens contribute to the deterioration of fruits, vegetables, and grains during storage and transportation, leading to economic losses and compromised food safety. MKPE was obtained from pickling variety 'Ramkela' raw mango kernels, and its phenolic composition was characterized using LC–MS. The in vitro antifungal activity of MKPE against Botrytis cinerea, Colletotrichum gloeosporoides, and Rhizopus stolonifer was evaluated in vitro. A concentration-dependent inhibition of fungal radial growth against all three pathogens was observed, exhibiting the potential of MKPE as a valuable natural resource for addressing postharvest losses caused by fungal pathogens. The extraction process yielded a total phenolic content of 2128 mg GAE/100 g. Major polyphenolic bioactive compounds present were mangiferin, quercetin, and rhamnetin. The in-vitro antimicrobial assay showed reduction in the radial growth and inhibition percent of the pathogens. EC50 values of MKPE for B. cineria, C. gloeosporoides, and R. stolonifer was found to 364.17, 963.8 and 926 ppm, respectively. Our results demonstrate an economical, sustainable, and eco-friendly approach to manage post-harvest diseases rendered by fungi using mango MKPE from pickling industry waste.

Antifungal Activity of Thirty Essential Oils to Control Pathogenic Fungi of Postharvest Decay.

Essential oils (EOs) extracted from aromatic or medicinal plants are biodegradable, safe, and regarded as alternatives to chemical pesticides to reduce fungal species attacking different crops. In this study, thirty EOs at 0.5 mg/mL were evaluated for in vitro growth inhibition of the main postharvest fungi, which are Alternaria alternata, Botrytis cinerea, and Penicillium italicum. Cinnamomum verrum EO completely inhibited the mycelial growth of A. alternata and B. cinerea, and Syzygium aromaticum EO completely inhibited the mycelia of A. alternata. B. cinerea mycelial growth was completely inhibited by Gautheria fragrantissima, Cymbopogon nardus, Pelargonium asperum, and Cupressus sempervirens EOs. G. fragrantissima EO inhibited the mycelia growth of P. italicum by 98%. Overall, B. cinerea displayed the highest sensitivity to EOs than P. italicum and A. alternata. G. fragrantissima, C. sempervirens, C. nardus, P. asperum, Mentha piperita, Foeniculum vulgare, C. verrum, and S. aromaticum EOs showed the highest inhibition for these three pathogens. Minimum inhibitory concentrations were lower for C. verrum and S. aromaticum EOs, ranging between 0.31 and 0.45 mg/mL and 0.37 to 0.57 mg/mL, respectively, against the three pathogens. The tested EOs inhibited the in vitro growth of three of the main postharvest fungal pathogens. Further studies are needed to confirm these activities in vivo.

Symptomatology and Morpho-Cultural Characterization of Colletotrichum musae, a Causal Agent of Anthracnose Disease in Banana

The study focused on the identification and characterization of Colletotrichum musae as a significant post-harvest fungal pathogen causing anthracnose disease in bananas. Symptoms included sunken, water-soaked spots on infected tissues, leading to soft, red-brown to black-coloured spots with irregular shapes. The pathogen was isolated and cultured on Potato dextrose agar medium, and its pathogenicity was confirmed by inoculating healthy banana fruits, resulting in typical anthracnose-like spots. Cultural characteristics of C. musae on PDA revealed whitish to black colonies, and microscopic examination showed oblong to cylindrical, single-celled conidia. Acervuli, which were salmon-coloured initially and later turned dark brown to black, were observed on the lesions. The fungus exhibited maximum growth and sporulation on PDA, followed by oat meal agar and Richard’s agar. Additionally, the study highlighted the morphological features of C. musae, including septate, irregularly branched, and vacuolated mycelium. The findings contribute to understanding the pathology and characteristics of C. musae, providing valuable information for managing post-harvest anthracnose in bananas.

Morpho-pathological and genomics-based identification of the Aspergillus species infecting pomegranate with nano- driven solution

Pomegranate (Punica granatum L.) is the dominant fruit for the tropical and sub-tropical area that belongs to the family Punicsceae. It has been cultivated throughout the world and drier parts of southern Asia. Good source of carbohydrates and minerals. Among post-harvest fungal pathogens attacked on pomegranate, Aspergillus niger is common store fungus that causes black mold disease. It mainly attacks in the flowering stage and early fruit developing during rainy seasons without any external symptoms. Disease samples were collected from different local markets of Faisalabad. Infection of fungus was done from the infected part of the pomegranate using artificial media. The fungus was identified on a morphological basis then Koch postulates were followed to confirm pathogenicity. The proved pathogen was determined by molecular characterization. DNA extraction and PCR have done of fungus. Antifungal potential of silver nanoparticles against Aspergillus niger were performed in three different concentration 50ppm, 100ppm and 150 ppm and compared with control The data were collected on the 3rd, 5th and 7th day of the fungal growth in which the 150ppm concentration was very affected than other concentrations. Keywords: Pomegranate, postharvest disease Aspergillus niger, nanoparticles.

Exploring the antifungal potential of Allium sativum and Ocimum gratissimum against post-harvest fungal pathogens in mango fruits

<p>Post-harvest spoilage of fruits and vegetables caused by fungal pathogens is a serious challenge to fruit production in many parts of the world. The study was conducted to evaluate the sensitivity of fungal pathogens associated with post-harvest rot of mango fruits to crude extracts from two edible plants, <em>Allium sativum</em> and <em>Ocimum gratissimum</em>, in the study area. Five different fungal isolates were isolated from diseased mango fruits collected from fruit stores in the study area and identified as <em>Aspergillus</em> spp. (M<sub>1</sub>), <em>Rhizopus</em> spp. (M<sub>2</sub>), <em>Fusarium</em> spp. (M<sub>3</sub>), <em>Penicillium</em> spp. (M<sub>4</sub>), <em>Fusarium</em> spp. (M<sub>5</sub>), <em>Penicillium</em><em> spp.</em> (M<sub>6</sub>), <em>Aspergillus</em> spp. (M<sub>7</sub>), and Colletotrichum spp. (M<sub>8</sub>) using radial growth rate and morphological features of the mycelia. A constant concentration of each of the crude extracts was applied to the growth media containing the growing cultures of the fungal isolates. The radial extension of the colonies for each isolate was measured along pre-marked perpendicular axes on the base of the petri dish after 24 h, and this continued for 10–14 days. It was observed that <em>Rhizopus</em> spp., <em>Fusarium</em> spp., <em>Penicillium</em><em> spp</em>., and Colletotrichum spp. had the least growth rate when treated with the extracts.</p>

ROS-mediated antifungal activity of Ocimum essential oil-loaded nanoemulsions against postharvest fungal pathogens of Kinnow

Kinnow fruit is prone to fungal and microbial attacks, leading to significant postharvest losses during marketing and storage due to two most prominent fungal pathogens, Penicillium digitatum and P. italicum. Safer alternatives of synthetic fungicides are required for management of these pathogens. Essential oils (EO) with remarkable antimicrobial activities may offer an upcoming alternative, but the high volatility, thermal sensitivity, and hydrophobicity limit their commercial applications. In the current study, coarse and nanoemulsions (CEs and NEs) of the most potent Ocimum species were evaluated as novel coatings for Kinnow. In a screening in vitro study, the efficacy of Ocimum essential oil of three species against P. digitatum and P. italicum was assessed. The CEs and NEs (0.5%–0.3% concentrations) of Ocimum viride EO (OVEO, best screened EO) with three surfactants in 1:1 oil-surfactant proportion (OSP) were prepared. The NE formulated with 1% oil having OSP (1:1) sonicated for 10 min exhibited consistent stability till 1 month with mean droplet diameter of 180.2 nm, polydispersity index 0.328, ζ-potential (−22.58 mV) and pH of 7.84) exhibited complete inhibition of hyphal growth of test fungi at 500 mg L−1. The EO-NE treatment of the fungal hyphae led to enhanced generation of reactive oxygen species (ROS) manifested as hyphal distortion and suppression of spore germination as compared to EO. OVEO NEs may offer an ecofriendly alternate to synthetic analogues for postharvest management of Kinnow.

A combinatorial approach of Monarda citriodora essential oil (MEO) and linalool vapors to control fruit rot of Citrus limon caused by a new pathogen, Aspergillus foetidus, and its underlying mode of action.

Citrus limon (lemon) is a widely cultivated citrus fruit. Significant postharvest losses due to fungi plague its production. Environmental and human health hazards have made the application of synthetic fungicides unsuitable. Despite the previous reports of antifungal activities of essential oil (EO) vapors, their synergistic combinations are understudied. Synergistic vapor combinations are advantageous due to less concentration of active components. This study aimed to isolate and identify postharvest fungal pathogens lemon and to evaluate the antifungal effects of synergistic Monarda citriodora EO (MEO)-constituent vapor combinations in vivo and in vitro. Postharvest fungal pathogens of lemon (C. limon) were isolated from various infected samples. The most pathogenic isolate was identified through morphology and its ITS-based rRNA gene sequencing as Aspergillus foetidus (O4). This is the first report of A. foetidus as a postharvest pathogen of lemon. The minimum fungicidal concentrations (MFCs) of MEO vapors treatment against O4 were 1346.15µL/L air. For carvacrol, hexanal, and linalool, MFC was same (96.16µL/L air). Checkerboard assays demonstrated that 1/4 MFC of MEO (336.54µL/L air) and 1/4 MFC of linalool (24.04µL/L air) (M+L) were synergistic against O4. M+L vapors reduced the O4 growth on lemons during storage by 64%±1.50% and preserved their quality (low weight loss %, unchanged pH, increased ascorbic acid content). Propidium iodide staining, ergosterol content analysis, calcofluor white staining and chitin content analysis revealed the integrity loss of the O4 plasma membrane and cell wall. 2',7'-Dichlorofluorescin diacetate staining revealed accumulation of intracellular reactive oxygen species (ROS), and scanning electron microscopy (SEM) analysis exposed the M+L treated mycelia with malformations. M+L vapors offer protection for lemons from A. foetidus and preserve their quality during storage.