Postharvest Disease Management Research Articles

Optimization, characterization and biosafety of oregano, rosemary and mint oil mixture against Penicillium digitatum in citrus using L-optimal mixture design

The increasing demand for natural alternatives to synthetic fungicides has prompted research into natural products like essential oils for postharvest disease management. This study investigated the antifungal, antioxidant, cytotoxic, and genotoxic potential of essential oil mixtures derived from oregano, rosemary, and mint against Penicillium digitatum, the predominant fungal pathogen causing green mold in orange fruits. P. digitatum NPAGRASU 2024 was isolated and identified as the most abundant species (60.2%) from infected oranges. It was deposited in GenBank with gene accession number PP930644 and deposited in MIRCEN culture collection as EMCC 358874. The antimicrobial activity of individual essential oils was evaluated, with oregano exhibiting the highest antifungal activity (inhibition zone diameter of 4.2 cm) against P. digitatum. L-optimal mixture design of response surface methodology (RSM) optimization revealed a highly effective mixture (Run 8) comprising 46.26% oregano and 53.74% rosemary, with a 99.65% actual growth reduction. The oregano oil demonstrated potent antioxidant activity, reaching approximately 75% DPPH radical scavenging at 3.125 mg/mL. Cytotoxicity assessment using the MTT assay showed morphological changes and reduced cell viability in liver cells treated with the PEOs mixture at 300 µg/mL. However, the optimized mixture did not induce significant chromosomal aberrations compared to the control, suggesting minimal genotoxic effects. In vivo, evaluation on oranges revealed 60% inhibition of green mold by the 1% (v/v) optimized mixture for 7 days. Histological analysis indicated low toxicity to the liver at the highest tested concentration (1% mixture). GC-MS analysis identified major compounds like cavarcol, caryophyllene, eucalyptol, phenols and levomenthol in oregano oil, contributing to its bioactivities. This study demonstrates the potential of optimized essential oil mixtures as effective and eco-friendly alternatives for postharvest disease control.

Fungal Biocontrol Agents in the Management of Postharvest Losses of Fresh Produce-A Comprehensive Review.

Postharvest decay of vegetables and fruits presents a significant threat confronting sustainable food production worldwide, and in the recent times, applying synthetic fungicides has become the most popular technique of managing postharvest losses. However, there are concerns and reported proofs of hazardous impacts on consumers' health and the environment, traceable to the application of chemical treatments as preservatives on fresh produce. Physical methods, on the other hand, cause damage to fresh produce, exposing it to even more infections. Therefore, healthier and more environmentally friendly alternatives to existing methods for managing postharvest decays of fresh produce should be advocated. There is increasing consensus that utilization of biological control agents (BCAs), mainly fungi, represents a more sustainable and effective strategy for controlling postharvest losses compared to physical and chemical treatments. Secretion of antifungal compounds, parasitism, as well as competition for nutrients and space are the most common antagonistic mechanisms employed by these BCAs. This article provides an overview of (i) the methods currently used for management of postharvest diseases of fresh produce, highlighting their limitations, and (ii) the use of biocontrol agents as an alternative strategy for control of such diseases, with emphasis on fungal antagonists, their mode of action, and, more importantly, their advantages when compared to other methods commonly used. We therefore hypothesize that the use of fungal antagonists for prevention of postharvest loss of fresh produce is more effective compared to physical and chemical methods. Finally, particular attention is given to the gaps observed in establishing beneficial microbes as BCAs and factors that hamper their development, particularly in terms of shelf life, efficacy, commercialization, and legislation procedures.

Antifungal Activity of Ethanolic Extracts from Aeroponically Grown Cape Gooseberry (Physalis peruviana L.) with LED Lights and In Vitro Habituated Roots.

Green mold caused by Penicillium digitatum is a major post-harvest disease in citrus fruits. Therefore, the search for sustainable and low-environmental-impact alternatives for the management of these fungi is of utmost importance. Physalis peruviana L. is a native fruit of the Peruvian Andes with rich bioactive components present throughout the plant. Its antifungal activity stands out, attributed to its high content of phenols, coupled with its antioxidant capacity and antimicrobial activity. Plants were cultivated aeroponically under a combination of red, mixed (50% red, 50% blue), and green LED lights. Additionally, in vitro-habituated roots free of plant growth regulators were also cultivated. An ethanol extraction assisted by ultrasound for 30 min followed by maceration for 72 h was performed, and the extract was filtrated and evaporated in an extraction hood. Antioxidant activity was assessed using the DPPH method, total polyphenols were measured using the Folin-Ciocâlteu method, and an antifungal test in vitro by the poisoned food method was conducted against P. digitatum. In vitro assays revealed that extracts from leaves, roots, and fruits exerted a significant inhibitory effect on the growth of P. digitatum, as evidenced by a reduction in colony radius when cultured employing the poisoned food method, with IC50 values of 62.17, 53.15, and 286.34 µg·mL-1, respectively, compared to 2297 µg·mL-1 for the commercial fungicide Captan 50WP. Although leaves had higher total polyphenol content, no direct correlation with antifungal activity was found. Colored LEDs enhanced phenol accumulation, antioxidant capacity, and antifungal properties in plant parts compared to white LEDs and in vitro roots. These findings suggest P. peruviana as a new alternative biological production system to provide natural compounds for post-harvest disease management.

Characterization and Management of Post-harvest Fungal Diseases in Banana (Musa paradisiaca)

Banana (Musa spp.) is a vital crop globally, contributing significantly to food security and income generation, particularly in tropical regions like India. However, post-harvest fungal diseases pose a considerable threat to banana production, affecting both fruit quality and marketability. The current study investigated the isolation, characterization, and management of post-harvest fungal diseases in banana (Musa paradisiaca). Infected banana fruits were collected from the Dharashiv fruit market (Maharashtra, India), and pathogenic fungi were isolated and identified. Fusarium napiforme, Talaromyces atroroseus, Cladosporium cladosporioides, Fusarium sp., and Fusarium equiseti were the primary pathogens identified. DNA extraction and sequencing were employed for accurate identification, and sequences were submitted to GenBank. The antifungal activity of essential oils and plant extracts was evaluated using the Poisoned Food Technique. Essential oils from Syzygium aromaticum, Mentha piperita, and Punica granatum showed significant inhibition (P<0.05) of fungal growth, with clove and peppermint oils achieving 100% inhibition at higher concentrations. Plant extracts of Ocimum sanctum, Eucalyptus globulus, Mentha piperita, Zingiber officinale, Curcuma longa, Azadirachta indica, Piper betel, and Cymbopogon citratus were also tested, revealing notable efficacy, particularly with neem and peppermint extracts. The study that the efficacy of essential oils was more compared to aqueous plant extracts. The results suggested sustainable strategies for managing post-harvest fungal diseases in bananas and explained the importance of conducting field trials to validate laboratory results.

Discovery of natural rosin-based preservative candidates to control Phytophthora capsici for postharvest disease management of solanaceae vegetables

To mitigate the postharvest harm of pathogens on solanaceous vegetables, a series of natural rosin-1,2,4-triazole derivatives (totally 24) have been designed and developed. In vivo fungicidal activity evaluation showed that Co. 5 f could inhibit the growth of Phytophthora capsici (EC50 = 0.22 mg/L). In vivo activity suggested that Co. 5 f presented certain protective effect on bell pepper (64.93 % – 32.68 %) and tomato (91.93 % – 67.85 %) fruit. Additionally, Co. 5 f prevented declines in both weight and ascorbic acid levels and reduced the malondialdehyde content of bell peppers and tomato, suggesting its efficacy in vegetable preservation during storage. The physiological research revealed that Co. 5 f disrupted the mycelial cell membrane, accelerated the accumulation of reactive oxygen species, and decreased the enzyme activity of peroxidase (POD) and catalase (CAT) protein activities. Subsequently, quantum chemical calculations and molecular docking successfully predicted the active site of Co. 5 f. Metabolomics was then employed to elucidate the mechanism of physiological disorders, suggesting that differential metabolites were primarily enriched in the biosynthesis of amino acid and secondary metabolites. Transcriptomics was also utilized to further uncover the mechanism of mycelial metabolic disorders, revealing that differential genes were primarily enriched in the biosynthesis of secondary metabolites and amino acid. Additionally, the integration of physiology, metabolomics, transcriptomics, and computer-aided drug design unveiled the action mechanism of Co. 5 f against P. capsici, indicating that the regulation of POD and CAT biosynthesis involved six core genes, while the regulation of ARG, HIS, and TRP biosynthesis involved four core genes. Finally, the expression of these ten core genes was validated using quantitative real-time polymerase chain reaction (qRT-PCR). In summary, the above research integrated physiology, metabolomics, transcriptomics and computer-aided drug design to reveal the action mechanism of Co. 5 f, providing a certain theoretical support for the postharvest disease management of bell pepper and tomato fruit.

Phenolic Compounds Synthesized by Trichoderma longibrachiatum Native to Semi-Arid Areas Show Antifungal Activity against Phytopathogenic Fungi of Horticultural Interest

Fungal diseases are a major threat to the horticultural industry and cause substantial postharvest losses. While secondary metabolites from Trichoderma sp. have been explored for their antifungal properties, limited information exists on the phenolic compounds produced by less studied species like Trichoderma longibrachiatum. In this study, phenolic compounds were extracted from a liquid culture of T. longibrachiatum using various solvents and methods (conventional and ultrasonic-assisted). Phenolic compounds were quantified by spectrophotometry and identified by high-performance liquid chromatography with diode array detection (HPLC-DAD). The antifungal activity against Alternaria alternata and Fusarium oxysporum was determined by mycelial growth inhibition assays, maximum growth rate (µmax) by the Gompertz equation, and spore germination tests. Although no significant differences (p ≥ 0.05) were found between the extraction methods, the type of solvent significantly influenced the phenolic content (p ≤ 0.05). Extraction with 70% ethanol showed the highest content of phenolic compounds and flavonoids. More than eight phenolic compounds were detected. Further, this is the first report of the phenolics ferulic, chlorogenic and p-coumaric acids identification in T. longibrachiatum, along with flavonoids such as epicatechin and quercetin, among others. The 70% ethanolic extracts notably inhibited the mycelial growth of A. alternata and F. oxysporum, reducing their maximum growth rate by 1.5 and 1.4 mm/h, respectively. Furthermore, p-coumaric and ferulic acids significantly inhibited spore germination of both pathogens, with a minimum inhibitory concentration (MIC) of 1.5 mg/mL and a minimum fungicidal concentration (MFC) of 2 mg/mL. These findings demonstrate the potential of T. longibrachiatum and its phenolic compounds as viable alternatives for biological control in horticulture and postharvest disease management.

Synergistic biocontrol mixture: free-cell extract with β-glucanase activity and chitosan against Thielaviopsis paradoxa, Colletotrichum gloeosporioides, and Rhizopus stolonifer

Biocontrol, which uses antagonistic microorganisms to manage plant diseases, holds promise for reducing postharvest losses but faces challenges due to varied pathogen responses. In response, biocontrol mixtures were proposed to enhance the antagonistic effect. This study evaluates the efficacy of chitosan and extracellular glucanase (EG) from Wickerhamomyces anomalus, both individually and combined, against Thielaviopsis paradoxa, Colletotrichum gloeosporioides, and Rhizopus stolonifer. The maximum inhibition of mycelial growth by chitosan for these fungi was 90.25% at 3 mg/mL, 14.2% at 5 mg/mL, and 56.28% at 3 mg/mL, respectively. Additionally, chitosan significantly inhibited spore germination across all fungi. While W. anomalus cells prevented mycelial filament association, EG alone had minimal impact on mycelial development but inhibited spore germination in a concentration-dependent manner. Combining EG with chitosan enhanced spore germination inhibition, notably achieving 98.18%. The biocontrol mixture effectively protected fruit under laboratory-controlled conditions, suggesting a robust biocontrol strategy for postharvest fungal disease management.

Inhibition of Monilinia fructicola sporulation and pathogenicity through eucalyptol-mediated targeting of MfCat2 by Streptomyces lincolnensis strain JCP1-7.

Peach brown rot, attributed to Monilinia fructicola, presents a significant threat to postharvest peach cultivation, causing losses of up to 80%. With an increasing number of countries, spearheaded by the European Union, imposing bans on chemical agents in fruit production, there is a growing interest in mining highly active antibacterial compounds from biological control strains for postharvest disease management. In this study, we highlight the unique ability of Streptomyces lincolnensis strain JCP1-7 to inhibit M. fructicola sporulation, despite its limited antimicrobial efficacy. Through GC-MS analysis, eucalyptol was identified as the key compound. Fumigation of diseased fruits with eucalyptol at a concentration of 0.0335 μg cm-3 demonstrated an invivo inhibition rate against M. fructicola of 93.13%, completely suppressing spore formation. Transcriptome analysis revealed the impact of eucalyptol on multiple pathogenesis-related pathways, particularly through the inhibition of catalase 2 (Cat2) expression. Experiments with a MfCat2 knockout strain (ΔMfCat2) showed reduced pathogenicity and sensitivity to JCP1-7 and eucalyptol, suggesting MfCat2 as a potential target of JCP1-7 and eucalyptol against M. fructicola. Our findings elucidate that eucalyptol produced by S. lincolnensis JCP1-7 inhibits M. fructicola sporulation by regulating MfCat2, thereby effectively reducing postharvest peach brown rot occurrence. The use of fumigation of eucalyptol offers insights into peach brown rot management on a large scale, thus making a significant contribution to agricultural research.

Incidence of fungal infections in melon fruits treated with alternative products

There is an increased demand for alternative products instead of synthetic fungicides for the management of postharvest diseases in melon crops to prevent the development of quiescent infections that cause great economic losses. In the present study, we evaluated the cantaloupe and orange flesh melon cultivars after treatment with acibenzolar-S-methyl, methyl jasmonate, Agro-Mos®, calcium phosphite and potassium phosphite. Treatments with methyl jasmonate, potassium phosphite and Agro-Mos® reduced the incidence of fungal infections in the treated fruits. The use of alternative products should extend the management strategies to the pre-harvest period, with regard to enhancing the beneficial effects of these products and ensuring that they effectively target postharvest infections.

Current insights into the biocontrol and biotechnological approaches for postharvest disease management of Botrytis cinerea

Postharvest decay in fruits and vegetables caused by fungal pathogens such as Botrytis cinerea leads to substantial economic losses. The decay caused by B. cinerea can be mitigated through the application of synthetic chemicals. However, due to its toxic residual effects on human health and environment stimulated the researchers to explore alternate effective and safe methods for the postharvest B. cinerea disease management. This article explains the current understanding of B. cinerea pathogenesis and the identification of antagonists used in the management of postharvest B. cinerea decay. This article also explains the mechanism of postharvest biocontrol agents (BCAs) and bioactive compounds derived from microorganisms and other plant resources with a particular focus on current advancements in molecular genomics such as (genetic engineering, transgenes and RNAi technology), omics and nanotechnology. Moreover, encapsulation of BCAs with nanoparticles increases their efficiency by delivering the BCAs to a specific host in a controlled and effective manner, with the aim of combating B. cinerea. Advanced molecular genetics allows for the identification and characterization of genes responsible for producing antifungal compounds produced by BCAs, which can be used to engineer strains with increased production of these compounds, making them more effective in controlling fungal diseases. Similarly, crops can be modified genetically which can show more resistance against the B. cinerea. However, more research will be needed to find the novel antimicrobial compounds derived from BCAs and estimation of developing beneficial microbial consortia for postharvest disease management, as well as genetic approaches, such as the use of CRISPR/Cas9 technology.

Essential oils in post-harvest disease management: Metabolic impact on Narince (Vitis vinifera L. cv) grapes against Botrytis cinerea

There is an urgent need for alternative, environmentally friendly post-harvest disease management solutions because of the growing concern over the use of chemical fungicides in agriculture and their detrimental impact on human health and the environment. This study examines the effects of thymol, eugenol, and 1,8-cineole essential oils on the sugar, organic acid, and amino acid profiles of 'Narince' grape berries as well as their effectiveness against gray mold (Botrytis cinerea). Our study has noted that the application of EOs, particularly eugenol, significantly alters the metabolic profile of 'Narince' grapes, enhancing sugar content and modifying the levels of organic acids and amino acids, which suggests a potential for improving grape quality and resistance to Botrytis cinerea. The combined use of eugenol with other EOs and fungicides, as indicated by the treatments OF and OSF, not only displayed a synergistic effect in elevating the concentration of key metabolites but also appeared to be more effective in combating fungal infection compared to individual EO applications. The PCA analysis and subsequent heatmap visualization revealed distinct metabolic clustering among the treatments, with combined EO treatments, especially those including eugenol, markedly influencing the amino acid profile of the berries. Our investigation's results suggest that EOs may offer a viable, eco-friendly alternative to traditional fungicides. Our study also adds to the body of knowledge supporting the advancement of integrated pest management strategies that are efficacious yet environmentally considerate, aligning with the global shift towards more sustainable practices in agriculture and food security.

Bioprotective effects of different Plant Extracts and Essential Oils against Rhizopus stolonifer and Aspergillus niger causing Post Harvest decay in Grapes

The grapes (Vitis vinifera) are one of the largely consumed fruits in the world. Grape production in Pakistan has increased in the recent years. These are mainly consumed fresh or as dried raisins. Grapes are highly perishable, which makes them liable to rot during transport, storage, and marketing. The perishable nature of grapes leads to a considerable amount of post-harvest loss. The production and quality of grapes are adversely affected by several abiotic and biotic factors. Two different cities Pishin (Balochistan) and Faisalabad (Punjab) fruit market and stores were selected to collect rotten grapes. The fungal pathogens isolated were identified as A. niger and R. stolonifers. The pathogenicity of isolated pathogens was assessed at different temperatures (5, 20, and 30 °C) on the Thompson seedless grape variety. Infection and proliferation of fungi were found conducive at 30°C. As antifungal agents, three organic origin oils, neem, cinnamon, and clove oils with levels i.e., 500, 1000, 2000 ppm as well as marigold and neem extracts with diverse concentrations of like 12.5, 25, and 50% were employed. Among these organic compounds, cinnamon and clove oils at 2000 ppm exhibited 6.54% and 15.3% decay against A. niger, respectively. Meanwhile, against R. stolonifer, cinnamon and clove oils at 2000 ppm exhibited 12.22% and 6.74% decay, respectively. This study's findings focus on the effectiveness of both essential oils and plant extract in significantly delaying the decay process caused by fungal pathogens. The present study underscores the protective ability of the plant extracts and natural oils which could be a way forward for eco-safe management of post-harvest diseases of grapes before they reach the market.

EVALUATION OF FLAXSEED OIL AND TRICHODERMA SPECIES AGAINST GREY MOLD DISEASE OF GRAPES

Grapes (Vitis vinifera L.) are included in vital crops in the world with respect to its nutritious and economic value. Botrytis grey mold, also called noble rot, harms grapes and wine quality caused by Botrytis cinerea. Other than chemicals Trichoderma species considered as important bio control agents for management of post-harvest diseases. The current study was designed to evaluate Trichoderma species for their Micoparasitic ability using a modification of a pre-colonized plate method. In-vitro efficacy of flaxseed oil against the Botrytis cinerea of grapes were determined using disc diffusion technique with different oil concentrations 0.2%, 0.6%, and 0.8%. In-vivo efficacy of most effective formulated and non-formulated Trichoderma concentrations was determined by applying on grape bunches against Botrytis cinerea. Trichoderma Harzianum is more effective and showed 67.5% growth inhibition than Trichoderma Viridae having 64% growth inhibition while flaxseed oil with 0.2%, o.6% and 0.8% concentrations showed 30.19%, 33.32% and 34.89% growth inhibition against botrytis cinerea respectively. In water-based Trichoderma concentrations (1×10⁸) showed maximum growth inhibition after 6 days that was 76.46%. However, it was observed that the percent disease severity index of the grape fruits in oil-based formulation showed 16 %, 20 %, and 18% after the 9 days of incubation whereas the water-based Trichoderma formulations showed 20%, 22%, 24% respectively as compared with control. Trichoderma species can be considered as bio-control agent while emulsion oil can be used for better shelf life.

Yeast Warriors: Exploring the Potential of Yeasts for Sustainable Citrus Post-Harvest Disease Management

Citrus fruits stand as pivotal and extensively cultivated fruit crops on a global scale, boasting substantial economic and nutritional significance. Despite their paramount importance, citrus growers and the industry face a formidable obstacle in the form of post-harvest losses caused by plant pathogens. Effectively addressing this challenge has become imperative. The predominant approach to tackle these pathogens has traditionally involved the use of chemical fungicides. However, the escalating environmental concerns associated with chemical interventions, coupled with a growing consumer preference for pesticide-free produce, have catalyzed an earnest quest for alternative methods of disease control in the citrus industry. The antagonistic yeasts hold great promise as biocontrol agents for mitigating post-harvest fungal diseases in citrus. In this regard, this review summarizes the current state of knowledge regarding the study of yeast strains with biocontrol potential. Thus, the various modes of action employed by these yeasts and their effectiveness against prominent citrus pathogens such as Penicillium digitatum, Penicillium italicum and Geotrichum citri were discussed. Additionally, the review delved into the challenges associated with the practical implementation of yeast-based biocontrol strategies in citrus post-harvest management and investigated the potential of yeast-based approaches to enhance the safety and quality of citrus produce, while reducing the reliance on chemical fungicides and contributing to the sustainable and environmentally responsible future of the citrus industry.

First Report of Penicillium cellarum Causing Rot Disease on Dioscorea polystachya in China.

Dioscorea polystachya (Chinese yam) is a kind of medicine and food homologous crop, the tubers as its main production organ, with high potassium, low fiber, high protein and rich nutrition characteristics. In 2022, at the Chinese herbal medicine planting experimental site in Anguo, Baoding City, Hebei Province, China, we found the symptoms of Chinese yam decay during the storage, with an incidence of 15%~25%. The diseased part of Chinese yam tuber rots expands from the outside to the inside and sags, with a brown or dark brown discoloration, and the surface covered with a thick grayish green mold. The diseased tissue was first rinsed with clean water to remove dirts from the surface. Thereafter, 3 to 4 mm Chinese yam pieces were picked from rotting edge with a sterilized forceps, sterilized with 75% alcohol for 30 s followed by 0.1% mercuric chloride solution for 1min, and then rinsed three times with sterile water. The sterilized pieces were cultured on potato dextrose agar (PDA). One isolated fungus was obtained, and conidia were observed after incubation for 5 days at 26°C. Pure cultures were isolated by single-spore isolation. Conidia were single spore, round or oval, colorless. Conidiophores produce several rounds of symmetric or asymmetric small stems after multiple branches, which were shaped like brooms. The length and width of 100 conidia were measured, and size ranged from 3 to 4×3 to 4 μm. On the basis of morphological characteristics, the isolate was identified as Penicillium spp. (Uy et al. 2022). To further assess the identity of isolated species, the genomic DNA of the fungal isolate (SYRF1) was extracted by CTAB protocol. The ribosomal DNA internal transcribed spacer (ITS) region and the ribosomal large subunit (LSU) were amplified and sequenced with primers ITS1/4, LR5/LROR respectively (White et al. 1990, Xu et al. 2010). The obtained ITS-rDNA region and LSU sequences (GenBank accession OQ707937 and OQ704185) of the isolate were more than 99% identity to the corresponding sequences of Penicillium cellarum in GenBank (KM249068 and MG714818). Phylogenetic results based on a maximum-likelihood analysis revealed that SYRF1 was grouped with P. cellarum. To determine the pathogenicity of the isolated fungi, tests were carried out by aseptic inoculation of fresh and healthy tubers. Before the experiment, the healthy tubers were washed, surface disinfected and dried. The tubers were then wounded with sterile inoculation needles, and the conidium-bearing hyphal discs (5 mm) were inoculated on the surface of the wounded tubers and covered with wet sterile cotton. Three tubers were inoculated repeatedly each time as the experimental group.Inoculate sterile PDA with three tubers as the control group. Each tuber was inoculated with four mycelium disks, and the pathogenicity test was repeated four times. The inoculated tubers were incubated at 26°C for 14 days with sterile PDA as control. After ten days, the inoculated points showed symptoms similar to those of the initial infection, whereas controls remained symptomless. The reisolated fungus matched SYRF1 based on morphological and sequence analyses, thereby fulfilling Koch's postulates. To the best of our knowledge, this is the first report of Penicillium cellarum as causative agent of postharvest rot of Chinese yam tubers in China. This finding will help inform the prevention and management of postharvest diseases of Chinese yam tubers.

Evaluating the efficiency of essential oils as fumigants in controlling Penicillium digitatum in citrus fruits

Citrus fruits are highly valued for their flavor, nutritional content, and versatility, but their perishable nature makes them susceptible to postharvest losses due to fungal infections. Conventional synthetic fungicides, while effective, raise concerns about food safety and environmental impact. Essential oils have emerged as promising alternatives due to their natural antifungal properties. This study investigates the antifungal activity of four plant essential oils as antifungal fumigants against Penicillium digitatum, the primary cause of green mould disease in citrus fruits. In vitro fumigant assays, Satureja montana essential oil exhibits the highest inhibition percentage against P. digitatum. In vivo experiments confirmed the efficacy of S. montana oil in reducing fungal growth on mandarins. Further analysis of different parameters revealed potential alterations in fruit quality attributes based on ripening, acidity, and firmness. Therefore, essential oils could be a potential alternative and eco-friendly approach for postharvest disease management in citrus fruits, contributing to efforts towards food safety, environmental sustainability, and public health.

Effectiveness of Four Synthetic Fungicides in the Control of Post-Harvest Gray Mold of Strawberry and Analyses of Residues on Fruit

Fungicides are usually applied on strawberries to manage gray mold, induced by the fungal pathogen Botrytis cinerea. In this study, four reduced-risk fungicides (formulations of pyrimethanil, PYR, 175 mL/hL; boscalid, BOS, 80 g/hL; combination fludioxonil, FLU, +cyprodinil, CYP, 110 g/hL) were applied before harvest for the management of post-harvest diseases of strawberries. The resulting fungicide residues on the strawberry fruit were also quantified. Strawberry fruits were harvested at 0, 4, 8, and 12 days following treatment (dft) and kept at 20 ± 1 °C for 4 days or cold-stored for 7 days at 0.5 ± 1 °C, followed by a 4-day shelf life at 20 ± 1 °C. All fungicides significantly reduced gray mold, according to the McKinney Index. At 0 dft and 4 days of shelf life, the FLU + CYP completely prevented post-harvest strawberry gray mold, while PYR and BOS reduced the disease by 88% and 42%, respectively, in comparison to the untreated control. For the duration of experiment, fungicide residues were always below the maximum residue levels, and FLU was the most degraded, thanks to the enzymatic pool of the strawberries. Monitoring fungicide residues in strawberries is essential to provide the consumer information on the safety of this widely consumed fruit. The present study points out the safety of strawberry fruits for consumers, even if the treatment strategy implies the use of fungicide mixtures before the consumption, with fungicide levels always being below the MRL.

In Vitro Evaluation of Chitosan Hydrochloride and COS (Chito-Oligosaccharides)-OGA (Oligo-Galacturonides) on Phytopathogenic Fungi and Escherichia coli

Use of novel alternative compounds in agriculture is being promoted to reduce synthetic pesticides. An in vitro study was conducted to evaluate antimicrobial and antioxidant activities of chitosan hydrochloride (CH) and COS (chito-oligosaccharides)-OGA (oligo-galacturonides) at concentrations of 1%, 0.5%, 0.25%, 0.1%, 0.05%, and 0.025%. COS-OGA at 1% and 0.5% concentrations completely inhibited mycelial growth of Alternaria alternata, Alternaria brassicicola, Botrytis cinerea, Monilinia laxa, Monilinia fructigena, and Monilinia fructicola. Further, complete inhibition was observed with 0.25% COS-OGA for M. fructigena and M. laxa. Inhibition for B. cinerea, M. fructicola, A. alternata, and A. brassicicola at 0.25% COS-OGA was 86.75%, 76.31%, 69.73%, and 60.45%, respectively. M. laxa and M. fructigena were completely inhibited by CH concentrations of 1–0.25% and M. fructicola by concentrations of 1–0.5%. At CH 0.25%, inhibition for M. fructicola, A. brassicicola, A. alternata, and B. cinerea was 93.99%, 80.99%, 69.73%, and 57.23%, respectively. CH showed effective antibacterial activity against foodborne Escherichia coli. COS-OGA had higher antioxidant activity than CH when assessed by DPPH and hydroxyl radical scavenging assays. Our findings offer insights into the antimicrobial efficacy and mechanisms of action of these novel compounds, which have the potential to serve as alternatives to synthetic pesticides. In vivo investigations are required to validate the prospective application of these treatments for pre- and postharvest disease management.

The effect of pulcherriminic acid produced by Metschnikowia citriensis in controlling postharvest diseases of citrus fruits

The biocontrol effectiveness of Metschnikowia citriensis relies on its production of pulcherriminic acid (PA), which forms insoluble and stable pulcherrimin pigments by chelating iron ions, this inhibits pathogen growth by preventing their utilization of chelated Fe3+. In this study, ΔM. citriensis, which did not produce PA, was used as a control to examine changes in its biocontrol effectiveness by adding tryptophan to the medium. Tryptophan was shown to have no discernible impact on the growth and PA production of ΔM. citriensis; moreover, the PA synthesis-related genes PULs, Snf2, and leucyl-tRNA synthesis-related genes A3136 and A3022 were all down-regulated in ΔM. citriensis. The PA-free ΔM. citriensis eventually showed a much poorer inhibition zone against the pathogens in vitro, and a noticeably decreased control efficiency against postharvest diseases in citrus fruit. Tryptophan was added to the medium, which had no appreciable impact on inhibitory zone of ΔM. citriensis against pathogens in vitro, but enhanced its ability to control citrus postharvest diseases. Additionally, the control effects of culture broth of M. citriensis and ΔM. citriensis on postharvest diseases in citrus fruit were assessed. It was found that both culture broth of M. citriensis and ΔM. citriensis exhibited remarkable control effects against citrus postharvest diseases, with culture broth of M. citriensis which containing PA being more effective in controlling the disease. Last but not least, we extracted and dissolved pulcherrimin to obtain PA extracts, which were then injected to citrus fruits to assess the biocontrol effectiveness. The findings demonstrated that postharvest diseases of citrus fruit can be effectively controlled by PA extracts. This research suggested a new biological strategy for the management of citrus postharvest diseases.

Exploring Wild and Local Fruits as Sources of Promising Biocontrol Agents against Alternaria spp. in Apples

Biological control agents (BCAs) are a promising option for managing postharvest diseases. Their environmentally friendly nature makes them valuable for sustainable and eco-friendly postharvest disease management. This study evaluated the antagonistic potential of epiphytic yeasts isolated from a local apple genotype known as “Niğde Elması” and a range of wild fruits: rosehip, hawthorn, and wild pear. There were 375 yeast isolates obtained and screened in vitro and in vivo. Initially selected were 32 isolates able to inhibit the growth of Alternaria alternata mycelia in the in vitro experiments and identified using molecular methods as candidate BCAs. These isolates were identified as Aureobasidium pullulans using sequence analysis of the internal transcribed spacer (ITS) and the translation elongation factor EF-1α gene (EF1α). Based on two rounds of in vivo screening, four isolates were subsequently selected for their capability to control the infection of apple fruits under high inoculum pressure. Finally, their volatile and non-volatile antimicrobial activity was tested against Alternaria spp. These findings showed how wild fruits and a local apple genotype could represent a promising source for new BCA isolation. However, further studies are needed to reveal the mechanisms of action of these putative BCAs for application during the postharvest processing and storage of apples.