Search Results (17)

The efficacy of natamycin (Fruitgard Nat 20) and Proallium (an extract of allium including propyl thiosulfinate oxide (PTSO)) against sour rot and green mold in mandarins was evaluated under controlled and commercial conditions. The study involved artificial inoculation of Nova, Tango, Orri, Afourer, Murcott, and Nules Clementine mandarins with isolates of Penicillium digitatum resistant to imazalil and pyrimethanil and an isolate of Geotrichum citri-aurantii susceptible to propiconazole fungicides. Under laboratory conditions, natamycin applied at 1500 µg mL⁻¹ significantly reduced green mold by 61.2% in Orri and sour rot by 62.8% in Nova and 80% in Tango. Increasing the concentration to 2000 µg mL⁻¹ further improved control of sour rot in Nova to 92.8%. In commercial trials, natamycin at 1500 µg mL⁻¹ was ineffective on Afourer; however, 2000 µg mL⁻¹ reduced sour rot by 39% on Nules Clementine. Proallium (12–16 µg mL⁻¹ PTSO) applied under controlled conditions effectively reduced green mold by 33% in Nova and 31% in Nules Clementine, and sour rot by 19%, 41%, and 36% in Nules Clementine, Nova, and Afourer, respectively. Under commercial conditions, using the same dose of Proallium, there was a 51.5% reduction in the incidence of imazalil and pyrimethanil-resistant P. digitatum strains and a 36.5% reduction in sour rot. Both natamycin and PTSO showed promising results for managing green mold caused by fungicide-resistant strains, but further research is needed to optimize control of sour rot in mandarins. Full article

Postharvest fungal diseases are the main cause of economic losses in lemon production. The continued use of synthetic fungicides to control the diseases favors the emergence of resistant strains, which encourages the search for alternatives. The aim of this study was to assess the efficacy of metallic nanoparticles (NPs) as antifungal agents against local isolates of Penicillium digitatum and Penicillium italicum, each of them in a fungicide-sensitive and -resistant version, and a Geotrichum citri-aurantii isolate. NPs of ZnO, CuO, and Ag were synthesized and characterized by spectroscopy and microscopy, presenting average sizes < 25 nm and spherical shapes. ZnO-NPs did not present antifungal activity at the assayed conditions, while the minimum fungicidal concentrations (MFCs) were 1000 and 10 µg mL⁻¹ for CuO-NPs and Ag-NPs, respectively. The NPs’ antimicrobial action included conidial membrane permeability and strong intracellular disorganization. Moreover, the Ag-NPs reduced green mold incidence on inoculated lemons when applied to the fruit. Taken together, Ag-NPs were effective in inhibiting both fungicide-sensitive and -resistant isolates of the main lemon postharvest pathogens, suggesting their potential use as an alternative approach. Full article

Sour rot, caused by Geotrichum citri-aurantii, is a significant post-harvest disease in citrus, resulting in economic losses due to the lack of effective fungicides. This study investigates the antifungal activity of citrus essential oils in controlling sour rot in Tahiti acid lime fruits. Essential oils were extracted via hydrodistillation with chemical composition analyzed by CG-MS and tested in vitro and in vivo. In vitro assays evaluated mycelial growth inhibition at 2 to 32 µL mL⁻¹ concentrations. In vivo trials involved preventive and curative treatments on artificially inoculated fruits stored at 25 °C ± 2, and the results showed that Pera IAC sweet orange oil, at 32 µL mL⁻¹, reduced disease severity by 96% in curative treatments. In contrast, Late IAC 585 willowleaf mandarin oil demonstrated moderate inhibition (44%) at the highest concentration in vitro. The oils did not affect key fruit quality parameters such as juice yield and total soluble solids. These findings suggest that citrus essential oils could be natural alternatives to synthetic fungicides for post-harvest sour rot management, combining effectiveness with maintaining fruit quality. Full article

This study identified and tested fruit-isolated Metschnikowia yeasts against three major postharvest citrus pathogens, namely, Penicillium digitatum, Penicillium italicum, and Geotrichum citri-aurantii, and further evaluated the impact of FeCl₃ on the biocontrol efficiency of pulcherrimin-producing M. pulcherrima strains. Based on the characterization of the pigmented halo surrounding the colonies and the analysis of the D1/D2 domain of 26S rDNA, a total of 46 Metschnikowia sp. were screened and identified. All 46 Metschnikowia strains significantly inhibited the hyphal growth of Penicillium digitatum, Penicillium italicum, and Geotrichum citri-aurantii, and effectively controlled the development of green mold, blue mold and sour rot of citrus fruit. The introduction of exogenous FeCl₃ at certain concentrations did not significantly impact the pulcherriminic acid (PA) production of pigmented M. pulcherrima strains, but notably diminished the size of pigmented zones and the biocontrol efficacy against the three pathogens. Iron deficiency sensitivity experiments revealed that P. digitatum and P. italicum exhibited higher sensitivity compared to G. citri-aurantii, indicating that iron dependence varied among the three pathogens. These results suggested that M. pulcherrima strains, capable of producing high yields of PA, possessed great potential for use as biocontrol agents against postharvest citrus diseases. The biocontrol efficacy of these yeasts is mainly attributed to their ability to competitively deplete iron ions in a shared environment, with the magnitude of their pigmented halo directly correlating to their antagonistic capability. It is worth noting that the level of sensitivity of pathogens to iron deficiency might also affect the biocontrol effect of pulcherrimin-producing M. pulcherrima. Full article

Geotrichum citri-aurantii (G. citri-aurantii) is one of the most important postharvest pathogens leading to a postharvest loss of citrus by causing sour rot. In this study, the antifungal activity of trans-2-hexenal, a natural component of essential oil, against G. citri-aurantii was evaluated. Trans-2-hexenal treatment inhibited the mycelia growth of G. citri-aurantii with a minimum inhibitory concentration and minimum fungicidal concentration of trans-2-hexenal at 0.50 and 1.00 μL/mL, respectively. Moreover, trans-2-hexenal efficiently reduced the incidence of sour rot of Satsuma fruit inoculated with G. citri-aurantii. Ultrastructural observations and Fourier transform infrared (FT−IR) results showed that trans-2-hexenal treatment affected the cell wall and cell membrane instructions of G. citri-aurantii. The content of β-1,3-glucan was significantly decreased after trans-2-hexenal treatment, but the cell wall permeability was not changed. The decrease in lipid and ergosterol contents might be responsible for this antifungal activity. Several important genes, FKS1, ERG1, ERG7, and ERG11, showed decreasing expression levels after trans-2-hexenal treatment. Molecule-docking results also indicated that trans-2-hexenal could join with the protein of FKS1, ERG1, ERG7, and ERG11 to impact enzyme activities. These results demonstrated that trans-2-hexenal is a promising fungicide for controlling sour rot of harvested citrus fruit by damaging the membrane integrity of G. citri-aurantii. Full article

Sour rot, caused by Geotrichum citri-aurantii, can produce significant postharvest losses of citrus fruits and, currently, cannot be effectively controlled by the postharvest fungicides registered in EU countries. Therefore, novel antifungal edible coatings (ECs) based on citrus pectin and beeswax and enriched with eugenol (EG), geraniol (GR), propolis extract (PR) or essential oils (EOs) from Satureja montana (SA), Cinnamomum zeylanicum (CI), or Commiphora myrrha (CM), were developed as alternatives to reduce sour rot and preserve the postharvest quality of ‘Valencia’ oranges. These natural agents were incorporated into the EC formulation and then applied to inoculated oranges. ECs enriched with EG (2–8 g/kg), GR (4 and 8 g/kg), PR (5–20 g/kg), and CM EO (15 g/kg) reduced disease incidence and severity by 75 to 100% compared to uncoated oranges after 20 days of incubation at 20 °C. ECs containing EG (8 g/kg), GR (4 g/kg), and PR (20 g/kg) reduced weight loss and retained firmness of oranges after 14 days of shelf life at 20 °C. Furthermore, all tested ECs maintained the fruit’s sensory and physicochemical quality. Overall, the EG-enriched pectin EC performed best, showing potential as a safe, bio-based alternative to conventional waxes containing synthetic fungicides for the management of citrus postharvest sour rot. Full article

Sodium silicate (Na₂SiO₃) and ethylenediaminetetraacetic acid disodium salt (EDTA-Na₂) are inorganic salts classified as ‘Generally Recognized as Safe’ (GRAS) compounds with great advantages in controlling various pathogens of postharvest fruits and vegetables. Here, we determined the median effective concentration (EC₅₀) of Na₂SiO₃ (0.06%, 0.05%, 0.07% and 0.08%) and EDTA-Na₂ (0.11%, 0.08%, 0.5%, and 0.07%) against common pathogens affecting postharvest citrus fruit, including Penicillium digitatum, Penicillium italicum, Geotrichum citri-aurantii, and Colletotrichum gloeosporioides. Na₂SiO₃ and EDTA-Na₂ treatments at the EC₅₀ decreased the spore germination rate, visibly disrupted the spore cell membrane integrity, and significantly increased the lipid droplets (LDs) of the four postharvest pathogens. Moreover, both treatments at EC₅₀ significantly reduced the disease incidence of P. italicum (by 60% and 93.335, respectively) and G. citri-aurantii (by 50% and 76.67%, respectively) relative to the control. Furthermore, Na₂SiO₃ and EDTA-Na₂ treatment resulted in dramatically lower disease severity of the four pathogens, while also demonstrating no significant change in citrus fruit quality compared with the control. Therefore, Na₂SiO₃ and EDTA-Na₂ present a promising approach to control the postharvest diseases of citrus fruit. Full article

Natural products obtained from plants constitute an alternative to chemically synthesized fungicides, whose improper use might have caused the development of resistant fungal strains. In the present work, 40 products obtained from 20 native Argentinean plant species were tested against three citrus postharvest pathogens: Penicillium digitatum, Penicillium italicum, and Geotrichum citri-aurantii. Natural products were obtained by classical solvent extraction methods and the fungicidal evaluation was carried out by agar diffusion tests using commercial fungicides as negative controls and dimethyl sulfoxide as a positive one. The inhibition percentages were determined 7 and 14 days post inoculation of each fungus. Most of the products tested showed inhibition percentages higher than 50% for G. citri-aurantii, but only 20% of them were active against P. digitatum and P. italicum. The most promising products which inhibited (100%) the growth of at least one of the three phytopathogens were extracted from the following plants: Orthosia virgata, Petiveria alliacea, Funastrum clausum, Solanum caavurana, and Solanum pilcomayense. These products were tested over inoculated oranges and there were no statistically significant differences between the treatments with a commercial fungicide and the methanolic extract in the control of fruit rot. The products extracted from native plants have fungicide potential, but further studies are required. Full article

Starch is a biodegradable polymeric carbohydrate that can easily form films and coatings and can readily be obtained from some food industry by-products and wastes, which may contribute to the circular bioeconomy. In this work, we studied the potential of two edible coating emulsions based on pregelatinized potato starch (PPS) and glyceryl monostearate (GMS) alone (F6 and F10) or formulated with the food additive sodium benzoate (SB, 2%) (F6/SB and F10/SB) to control sour rot, an important citrus postharvest disease caused by the fungus Geotrichum citri-aurantii, and maintain postharvest quality of cold-stored ‘Orri’ mandarins. The PPS-GMS coating application was compared to dipping in water (uncoated controls) and dipping in a 2% SB (w/v) aqueous solution. The results showed that the coating F10/SB was the most promising treatment to control sour rot on mandarins, with reductions in disease incidence with respect to the uncoated control samples of 94, 69, and 55% after 2, 4, and 6 weeks of storage at 5 °C, respectively. Coatings formulated without SB were ineffective. Regarding fruit quality, the coating F10 was the most effective to reduce weight loss, maintain firmness, and provide gloss on mandarins stored at 5 °C for up to 6 weeks followed by a shelf-life period of 1 week at 20 °C. The addition of SB to the PPS-GMS coatings adversely affected these coating properties, but the coating F10/SB still reduced weight loss compared to uncoated controls without negatively affecting the fruit physicochemical (juice titratable acidity, soluble solids content, and volatiles content) and sensory quality (overall flavor, off-flavors, external aspect). Overall, the coating F10/SB showed the greatest potential for commercial use as an efficient and environmentally friendly alternative to conventional fungicides and waxes for sour rot control and quality preservation of cold-stored mandarins. Full article

Dimethyl dicarbonate (DMDC), a food additive, can be added to a variety of foods as a preservative. This study aimed to evaluate the inhibitory effects of DMDC on Geotrichum citri-aurantii in vitro and in vivo, as well as the potential antifungal mechanism. In vitro experiments showed that 250 mg/L DMDC completely inhibited the growth of G. citri-aurantii and significantly inhibited spore germination by 96.33%. The relative conductivity and propidium iodide (PI) staining results showed that DMDC at 250 mg/L increased membrane permeability and damaged membrane integrity. Malondialdehyde (MDA) content and 2, 7-Dichlorodihydrofluorescein diacetate (DCHF-DA) staining determination indicated that DMDC resulted in intracellular reactive oxygen species (ROS) accumulation and lipid peroxidation. Scanning electron microscopy (SEM) analysis found that the mycelia were distorted and the surface collapsed after DMDC treatment. Morphological changes in mitochondria and the appearance of cavities were observed by transmission electron microscopy (TEM). In vivo, 500 mg/L DMDC and G. citri-aurantii were inoculated into the wounds of citrus. After 7 days of inoculation, DMDC significantly reduced the disease incidence and disease diameter of sour rot. The storage experiment showed that DMDC treatment did not affect the appearance and quality of fruits. In addition, we found that DMDC at 500 mg/L significantly increased the activity of citrus defense-related enzymes, including peroxidase (POD) and phenylalanine ammonia-lyase (PAL). Therefore, DMDC could be used as an effective method to control citrus sour rot. Full article

The peptide PAF56 (GHRKKWFW) was reported to be an effective control for the main diseases of citrus fruit during postharvest storage. However, the mechanism of action of PAF56 is still unknown. In this paper, PAF56 might not induce defense resistance of citrus fruit. The SEM results visually indicated that the fungi mycelia became shrunken and distorted after being treated with PAF56. The destructive effects of PAF56 on the mycelial cell membrane of three kinds of pathogenic fungi (Penicillium digitatum, Penicillium italicum, and Geotrichum citri-aurantii) were verified by the K⁺ leakage and the release of nucleic acid. Furthermore, the interaction between peptide PAF56 and the pathogen spores was investigated, including the changes in cell membrane permeability and dynamic observation of the interaction of fluorescein labeled TMR-PAF56 and Geotrichum candidum spores. The results indicated that the antifungal activity of PAF56 on spores was time-dependent and directly related to the membrane damage. This research provided useful references for further research and practical application of peptides. Full article

Antimicrobial peptides of mastatopara-S (M-S), thanatin, and ponericin W1(P W1) were able to disrupt the membrane integrity and alter the morphology of the hyphae of Geotrichum citri-aurantii and then reduced the sour rot of citrus fruit. In order to understand the mechanisms of thanatin, P W1 and M-S other than membrane disruption, the interaction betwixt the peptides and G. citri-aurantii DNA were investigated in this research. The laser confocal microscopy found that P W1, thanatin, and M-S could penetrate the cell membrane. Gel retardation assay demonstrated that P W1, thanatin, and M-S could bind to the G. citri-aurantii genomic DNA in vitro. UV-visible spectra and fluorescence spectra analysis further confirmed that the peptides can bind to the DNA, and then insert into the base pairs in the DNA helix, followed by wrecking the double-helix structure. In addition, M-S, thanatin, and P W1 can suppress the synthesis of DNA and RNA of G. citri-aurantii. Full article

Key lime (Citrus aurantiifolia) is an emerging crop in Italy, especially in the Southern regions, where the environmental conditions are suitable for its cultivation. A field survey in Sicily in a commercial orchard of Key lime revealed the widespread presence of water-soaked spots and sunken/dry lesions at the stylar-end, mainly in pre-harvest condition. Water-soaked spots were attributed to Geotrichum citri-aurantii, an agent of sour rot on Citrus spp., whereas the sunken/dry lesion was attributed to the physiological disorder known as stylar-end breakdown. Sour rot and stylar-end breakdown are usually considered post-harvest diseases and rarely found in the field on fruit still attached to the tree. Although Geotrichum citri-aurantii is not responsible for the stylar-end breakdown, its association with this alteration reveals the importance of the environmental conditions and the agronomic practices in diseases/disorders development. In addition, to our knowledge, this is the first report of Geotrichum citri-aurantii on Key lime in Europe. Full article

Consumers demand the use of eco-friendly fungicides to treat fruit and vegetables and governmental authorities have unauthorized the application of chemical antifungals for the efficient control of sour rot. In the present research, the microwave irradiation (MW) method was used to encapsulate thymol into 2-hydroxylpropyl-beta-cyclodextrin (HP-β-CD) and the effect of these HP-β-CD on controlling sour rot in citrus fruit, caused by Geotrichum citri-aurantii, was evaluated. Amounts of 25 and 50 mM of HP-β-CD-thymol were used, and compared with propiconazole, to control the decay of inoculated lemon fruit. The treatments were performed in curative and preventive experiments. The incidence and severity of Geotrichum citri-aurantii in 25 and 50 mM HP-β-CD-thymol-treated fruit were reduced in both experiments. The preventive 50 mM HP-β-CD-thymol treatment showed the best effect, reducing the sour rot, respiration rate and fruit weight loss during storage at 20 °C. HP-β-CD-thymol increased polyphenol concentration and the activity of antioxidant enzymes, such as catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD) in lemon peel, and the highest effects were found with the 50-mM dose. In conclusion, the results show that the use of thymol encapsulated by MW into HP-β-CD could be an effective and sustainable tool, a substitute to the synthetic fungicides, for G. citri-auriantii control in citrus fruit. Full article

Litsea cubeba essential oil (LCEO), as naturally plant-derived products, possess good antimicrobial activities against many pathogens, but their high volatility and poor water solubility limit greatly the application in food industry. In this research, inclusion complex based on β-cyclodextrin (β-CD) and LCEO, was prepared by saturated aqueous solution method. An optimum condition using the response surface methodology (RSM) based on Box–Behnken design (BBD) was obtained with the inclusion time of 2 h and β-CD/LCEO ratio of 4.2 at 44 °C. Under the condition, the greatest yield of 71.71% with entrapment efficiency of 33.60% and loading capacity of 9.07% was achieved. In addition, the structure and characteristic of LCEO/β-CD inclusion complex (LCEO/βCD-IC) were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR), which indicated that LCEO/βCD-IC was successfully formed. The particle size of LCEO/βCD-IC was determined to be 17.852 μm. Thermal properties of LCEO/βCD-IC evaluated by thermogravimetric-differential scanning calorimetry (TG-DTA) illustrated better thermal stability of the aimed product compared with the physical mixture. Furthermore, the tests of antifungal activity showed that LCEO/βCD-IC was able to control the growth of Penicillium italicum, Penicillium digitatum, and Geotrichum citri-aurantii isolated from postharvest citrus. Our present study confirmed that LCEO/βCD-IC might be further applied as an alternative to chemical fungicides for protecting citrus fruit from postharvest disease. Full article