Search Results (102)

This research analyzes the innovative development of carnauba wax coatings enriched with essential oils (EOs: lemon, orange, grapefruit, clove, oregano, and cinnamon) or fruit by-products (FBPs: avocado, tomato, carrot, orange, lemon, and grapefruit) to improve postharvest preservation of organic oranges and lemons. Six EOs and six FBPs were evaluated for total phenolic content (TPC) and in vitro antifungal activity against Penicillium digitatum. Based on results, grapefruit, oregano, and clove EOs were selected for lemons, while avocado, orange, and grapefruit FBPs were selected for oranges. An in vivo test at 20 °C for 15 days with carnauba wax coatings assessed antifungal performance. Clove EO and avocado FBP showed strong in vitro inhibition and consistent hyphal suppression (~100 and ~82%, respectively). In vivo, coatings with grapefruit EO and avocado FBP significantly reduced fungal decay and sporulation (~75%) in lemons and oranges, respectively. Coated fruits also retained weight losses by ~25% compared to uncoated ones. These findings suggest that phenolic-rich natural extracts, especially from agro-industrial residues like avocado peels, offer a promising and sustainable strategy for postharvest citrus disease control. Further studies should test coating effectiveness in large-scale trials under refrigeration combined with other preservation strategies. Full article

A novel Penicillium digitatum MFS transporter, PdMFS6 (PDIP_42530), was recognized, and its function was studied to explain its relevance in the simultaneous development of resistance to different fungicide spectrums. No changes were detected after application of chemical fungicides in mutants with the deleted gene, but chemical susceptibility was severely impaired in overexpressing strains, that became persistent to different chemicals. Furthermore, P. digitatum deleted transformants showed less fungal virulence appraise upon citrus infection stored at 20 °C. In strains derived from Pd149-P. digitatum with low virulence and overexpressing PdMFS6, the signs of the disease were more evident. In addition, evaluation of gene transcription showed an increase in PdMFS6 gene expression over time in all P. digitatum strains tested. It is noteworthy that during citrus fruit infection, the wild-type Pd1 strain displayed an augmented level of transcription, indicating that this transporter plays a role in infectivity. The fungal transporter PdMFS6 could contribute to the susceptibility to chemicals commonly used in postharvest treatments, as well as to rise the virulence of P. digitatum during fruit infection. Full article

In this study, chitosan (CH) was loaded with spearmint (S) essential oil nanoemulsion (EO) to provide antifungal properties during the postharvest storage of soft citrus fruits. (S)-EO (2%) nanoemulsion–CH (0.8%) coatings inhibited 100% of Penicillium italicum and Penicillium digitatum radial mycelial growth and spore germination in vitro. The (S)-EO (2%) nanoemulsion–CH coating (0.8%) enhanced the antifungal activity by achieving 100% inhibition of P. digitatum in soft citrus cultivars ‘Nova’ and ‘Tango’ compared to the control in vivo. However, P. italicum decay was reduced to 33% and 18% in ‘Nova’ and ‘Tango’ soft citrus compared to the control. The (S)-EO (2%)-CH nanoemulsion coating system prepared by high shear homogenization showed a particle size of 252.3 nm and zeta potential of +21.6 mV, indicating changes in molecular interactions and structural reorganization between EO and CH. The polydispersity index values indicated a stable system. pH remained acidic, antifungal activity was favored, and the incorporation of the EO nanoemulsion improved the thermal stability of the CH coating. The optical properties showed less transparency and more opacity. Despite cultivar differences affecting host specificity, the study recommends using a 2% (S)EO nanoemulsion–CH (0.8%) coating instead of synthetic chemicals to extend citrus fruit storage life. Full article

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. Full article

Excimer fluorescent ultraviolet (UV) lamps (UV–228) function as mercury–free sources that use excimer emissions as excitation light sources. First, we evaluated the effects of UV–228–based irradiation (λ_max = 228 nm) on the viability of fungi, using Penicillium digitatum, and compared these effects with those of other light sources, such as OEL–222 (λ_max = 222 nm) and GL–6 (λ_max = 254 nm), to evaluate the effectiveness of the excimer fluorescent lamp. Next, we investigated the effects of UV–228–based irradiation on strawberry storage. Although UV–228 affected weight loss, Brix, ascorbic acid, polyphenol, and DPPH, the effects of UV irradiation for 5 min on strawberry fruit quality were minimal; i.e., only weight loss and ascorbic acid content were higher than those in the non–irradiated treatment. We found that 5 min of UV–C irradiation using UV–228 prevented mold emergence for up to 11 days of storage in strawberries These results indicate that UV–228 contributes to long–term strawberry storage. Full article

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

This study examined the efficacy and mechanisms of action of the antimicrobial peptide BP15 and its lipopeptides, HBP15 and LBP15, against Penicillium digitatum, the primary causative agent of green mold in citrus fruits. The findings revealed that all three antimicrobial peptides markedly inhibited the spore germination and mycelial growth of P. digitatum, with minimum inhibitory concentrations (MICs) of 3.12 μM for BP15, HBP15, and LBP15. The peptides induced morphological alterations in hyphae and elevated intracellular Sytox Green (SG) fluorescence signals, which is indicative of increased cell membrane permeability and disruption. This membrane damage was further supported by the heightened extracellular conductivity and the release of intracellular nucleic acid and protein. A gel retardation assay demonstrated that the peptides showed significant DNA binding and retardation effects. Furthermore, the peptides exhibited significantly lower hemolytic activity (p < 0.05) compared to commercial prochloraz in normal mammalian erythrocytes (sheep erythrocytes) at the tested concentrations. Therefore, BP15 and its lipopeptides, HBP15 and LBP15, show potential as effective agents for preventing green mold in citrus fruits. 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

Essential oils (EOs) are natural products widely used in sustainable agrochemistry, not only because they are biodegradable and safe but also because they are regarded as alternatives to chemical fungicides against fungal species that attack crops. Allelopathy, another field of study, falls within the most recent and sustainable strategies applied to weed suppression to replace synthetic herbicides. Therefore, this study reports the chemical composition and allelopathic and antifungal effects of the EOs extracted from Calyptranthes concinna dried leaves (Cc-EO) and its pure major constituent elemicin. Their antifungal activities were evaluated by the disk diffusion method (DDM) at doses between 0.05 mg/mL and 0.4 mg/mL of Cc-EO and elemicin. The allelopathic effect was evaluated by studying the inhibition of germination and the growth of Lactuca sativa seeds. The chemical composition of Cc-EO was determined by GC-MS and GC-FID analyses. The major constituents of Cc-EO were elemicin (60.5%), α-cadinol (9.0%) and caryophyllene oxide (8.3%). Cc-EO and elemicin were assayed in vitro against 17 fungi of agronomic interest (Aspergillus niger, A. flavus, A. nomius, Penicillium digitatum, P. expansum, Sclerotinia sclerotiorum, S. rolfsii, S. minor, Fusarium graminearum, Myrothecium verrucaria, Corynespora cassiicola, Erwinia psidii, Colletotrichum musae, Alternaria carthami, Rhizoctonia solani, Rhizopus stolonifer and Macrophomina phaseolina). The concentration of Cc-EO (0.4 mg/mL) inhibited 100% of the mycelium growth of seven strains, equal to the fungicide fluazinam, which was used as a positive control. Elemicin showed antifungal activity against all fungi at all concentrations under investigation (above 50%). A strong allelopathic effect was recorded for Cc-EO and elemicin at the dose of 0.28 mg/mL, with the almost total inhibition of germination. This study revealed, for the first time, the strong and remarkable fungicidal and allelopathic effects of Cc-EO and elemicin, an important finding for the agrochemical field. Full article

In this study, yeasts isolated from citrus groves, trees and leaves were identified, phylogenetic analyzes were performed and their antifungal effects were determined. Wickerhamomyces anamolus (M72), Meyerozyma guilliermondii (M77), and Pichia kudriavzevii (M74) species were identified and were found to have antifungal effects against P. digitatum and P. italicum. Pichia kudriavzevii (M74), which has the highest antifungal effect, showed 67% and 62% inhibition rates against P. digitatum and P. italicum, respectively. An encapsulation study was carried out using a microencapsulation process to ensure that the M74 strain, which has the most antifungal effect, is long-lived enough to be a biopesticide. The optimum spray drying process parameters as well as the optimum concentration values of wall materials were investigated in the spray drying process for the microencapsulation of Pichia kudriavzevii (M74) through the Taguchi methodology. The formulation containing 0.1% sodium alginate (SA) and 10% corn starch (CS) showed a good performance in the inhibition of P. digitatum, a mold that causes losses in orange, thanks to its high percentage of viability (73%). The inhibition percentages may indicate that this formulation may be a candidate to be considered as a potential alternative application to synthetic fungicides on orange fruits for the effective control of P. digitatum mold. Full article

Green mold, caused by Penicillium digitatum, is the major cause of citrus postharvest decay. Currently, the application of sterol demethylation inhibitor (DMI) fungicide is one of the main control measures to prevent green mold. However, the fungicide-resistance problem in the pathogen P. digitatum is growing. The regulatory mechanism of DMI fungicide resistance in P. digitatum is poorly understood. Here, we first performed transcriptomic analysis of the P. digitatum strain Pdw03 treated with imazalil (IMZ) for 2 and 12 h. A total of 1338 genes were up-regulated and 1635 were down-regulated under IMZ treatment for 2 h compared to control while 1700 were up-regulated and 1661 down-regulated under IMZ treatment for 12 h. The expression of about half of the genes in the ergosterol biosynthesis pathway was affected during IMZ stress. Further analysis identified that 84 of 320 transcription factors (TFs) were differentially expressed at both conditions, making them potential regulators in DMI resistance. To confirm their roles, three differentially expressed TFs were selected to generate disruption mutants using the CRISPR/Cas9 technology. The results showed that two of them had no response to IMZ stress while ∆PdflbC was more sensitive compared with the wild type. However, disruption of PdflbC did not affect the ergosterol content. The defect in IMZ sensitivity of ∆PdflbC was restored by genetic complementation of the mutant with a functional copy of PdflbC. Taken together, our results offer a rich source of information to identify novel regulators in DMI resistance. Full article

This study evaluates the efficacy of the salts sodium metabisulfite (SMB), ammonium bicarbonate, sodium bicarbonate, and potassium dihydrogen orthophosphate first in vitro against the main postharvest fruit rot fungi, Alternaria alternata, Botrytis cinerea, Penicillium italicum, and Penicillium digitatum. Results showed that 0.2% SMB completely inhibited the mycelium growth of the fungal species. Ammonium bicarbonate and sodium bicarbonate were less effective at 0.2% in inhibiting mycelial growth, ranging from 57.6% to 77.6%. The least effective was potassium dihydrogen orthophosphate. Experiments were also performed in vivo on wounded apples inoculated with the most pathogenic fungus, B. cinerea, and treated with SMB at concentrations of 0.2, 0.5, 1, 2, and 3%, both preventively and curatively. Results based on the decay size showed that SMB, when used as a preventive treatment, had a reduced efficacy, even with the highest concentration. However, this salt proved to be very effective at 0.5% in curative treatment since the decay was completely blocked. Our results suggest that the appropriate concentration of SMB for post-harvest treatment is 0.5% as a curative treatment. On the other hand, the 1% dose induced the onset of phytotoxicity around the wound. To assess the extent of the phytotoxicity reaction, higher concentrations of 1–4% SMB were applied to wounded fruit. Apples and oranges were inoculated or not with B. cinerea and P. digitatum, respectively. Doses of 1–4% induced phytotoxicity in the form of a discolored ring surrounding the wound on the epidermis of the fruit; this phytotoxicity enlarged as the concentration of SMB increased. The phytotoxic features were similar on apples and oranges. The methodological procedure made it possible to carry out a quantitative assessment of SMB phytotoxicity. This method is proposed as an easy-to-use technique for quantitatively estimating the phytotoxicity of antifungal compounds on post-harvest fruit. Full article

Penicillium digitatum and Penicillium italicum are responsible for citrus green and blue moulds (GM and BM), respectively, which are major citrus postharvest diseases. The aim of this study was to develop an optimal dipping mixture of an aqueous solution of different food additives: sodium bicarbonate (SB), sodium benzoate (SBen), and potassium sorbate (PS), in combination with heat, to control GM and BM using response surface methodology. The ranges of SB (0.0%, 3.0%, 6.0%), SBen (0.0%, 0.5%, 1.0%), PS (0.0%, 0.5%, 1.0%) and temperature (20 °C, 35 °C, 50 °C) with a dipping time of 60s were tested for their impact on GM and BM on artificially inoculated oranges. Within these tested ranges, SB reduced GM severity and incidences of both GM and BM. PS affected BM severity and incidence, but not GM. SBen and temperature did not have impact on GM and BM. The most suitable food additive concentrations were identified to be 4.7% SB, 1.0% SBen and 0.7% PS, with a dipping solution temperature of 50 °C. This treatment was shown to reduce GM and BM incidence from 85 and 86% on control fruit dipped in tap water at 20 °C to 3 and 10%, respectively. Additionally, the severity of GM and BM was reduced from 64 and 26 mm on control fruit to <1 and 2.8 mm, respectively. Full article

Demethylation inhibitors (DMIs), including prochloraz, are popular fungicides to control citrus postharvest pathogens such as Penicillium digitatum (green mold). However, many P. digitatum strains have developed prochloraz resistance, which decreases drug efficacy. Specific major facilitator superfamily (MFS) transporter gene mfs2, encoding drug-efflux pump protein MFS2, has been identified in P. digitatum strain F6 (PdF6) to confer fungal strain prochloraz resistance. However, except for the drug-efflux pump function of MFS2, other mechanisms relating to the Pdmfs2 are not fully clear. The present study reported a transcriptome investigation on the mfs2-defective P. digitatum strain. Comparing to the wild-type strain, the mfs2-defective strain showed 717 differentially expressed genes (DEGs) without prochloraz induction, and 1221 DEGs with prochloraz induction. The obtained DEGs included multiple isoforms of MFS transporter-encoding genes, ATP-binding cassette (ABC) transporter-encoding genes, and multidrug and toxic compound extrusion (MATE) family protein-encoding genes. Many of these putative drug-efflux pump protein-encoding genes had significantly lower transcript abundances in the mfs2-defective P. digitatum strain at prochloraz induction, as compared to the wild-type strain, including twenty-two MFS transporter-encoding genes (MFS1 to MFS22), two ABC transporter-encoding genes (ABC1 and ABC2), and three MATE protein-encoding genes (MATE1 to MATE3). The prochloraz induction on special drug-efflux pump protein genes in the wild-type strain was not observed in the mfs2-defective strain, including MFS21, MFS22, ABC2, MATE1, MATE2, and MATE3. On the other hand, the up-regulation of other drug-efflux pump protein genes in the mfs2-defective strain cannot recover the fungal prochloraz resistance, including MFS23, MFS26, MFS27, MFS31, MFS33, and ABC3 to ABC8. The functional enrichment of DEGs based on Kyoto Encyclopedia of Genes and Genomes (KEGG), Clusters of Orthologous Groups (COG), and euKaryotic Orthologous Groups (KOG) database resources suggested some essential contributors to the mfs2-relating prochloraz resistance, including ribosome biosynthesis-related genes, oxidative phosphorylation genes, steroid biosynthesis-related genes, fatty acid and lipid metabolism-related genes, and carbon- and nitrogen-metabolism-related genes. The results indicated that the MFS2 transporter might be involved in the regulation of multiple drug-efflux pump protein gene expressions and multiple metabolism-related gene expressions, thus playing an important role in developing P. digitatum prochloraz resistance. Full article

Penicillium digitatum is a major postharvest pathogen that threatens the global citrus fruit industry and causes great economic losses annually. In the present study, inhibitory properties of cinnamon bark oil (CBO) against P. digitatum in vitro were investigated. Results indicated that 0.03% CBO could efficiently inhibit the spore germination, germ tube elongation, mycelial growth, colonial expansion and conidial accumulation of P. digitatum. The results of fluorescein diacetate (FDA) and MitoTraker Orange (MTO) staining also proved the suppression effects of CBO against P. digitatum. Meanwhile, CBO could inhibit green mold rots induced by P. digitatum in citrus fruit when the working concentration of CBO exceeded 0.06%. In addition, the expressions of 12 genes critical for the growth and virulence of P. digitatum were also significantly regulated under CBO stress. Through a transcriptomic analysis, a total of 1802 common differentially expressed genes (DEGs) were detected in P. digitatum after 4 h and 8 h of CBO treatment. Most of the DEG products were associated with carbohydrate, amino acid and lipid metabolism. They directly or indirectly led to the disturbance of the membrane and the generation of reactive oxygen species (ROS). Our results may deepen the understanding of antifungal properties of CBO against P. digitatum and provide the theoretical foundation to uncover the antifungal mechanism of CBO at the molecular level. Full article