Citrus Green Mold Research Articles

Isolation, identification and in vitro screening of Chongqing orangery yeasts for the biocontrol of Penicillium digitatum on citrus fruit

The aim of this study was to explore the diversity of yeasts in the orangery of Beibei Chongqing and their potential for biological control of Penicillium digitatum on oranges. Yeasts were isolated from the surface of fruit, leaves and soil in three citrus orchards in this district. The yeasts were identified by PCR amplification and partial sequencing of internally transcribed spacer (ITS) regions and 5.8S ribosomal DNA (rDNA). The 71 yeast isolates belonged to 8 genera: Metschnikowia, Pichia, Candida, Pseudozyma, Kazachstania, Issatchenkia, Hanseniaspora, and Barnettozyma. All yeast isolates were tested for the inhibition of green mold on potato dextrose agar (PDA) medium, and 45 isolates reduced the growth of fungal mycelium as shown by inhibition zone formation. Twelve isolates were tested for antagonistic activity against Penicillium digitatum on navel oranges, and the biocontrol activity of the various isolates in reducing disease incidence ranged between 26% and 93%. In particular, Metschnikowia sp. FL02 completely inhibited the occurrence of green mold rot on the seventh day after inoculation. The results of this study suggest that antagonist yeasts frequently found on leaves and fruit in Beibei Chongqing orangery have potential for inhibiting citrus green mold.

Ag-zeolites as fungicidal material: Control of citrus green mold caused by Penicillium digitatum

One of the most economically important postharvest diseases of citrus fruit is green mold caused by the fungus Penicillium digitatum. In this investigation, the antifungal properties of silver FAU and silver LTA zeolites against P. digitatum either alone or incorporated into edible coatings were evaluated in citrus fruit. The Ag-zeolites were characterized by different techniques such as ICP, TPR, XRD and electronic microscopy. These techniques demonstrated that ion exchange was a suitable method for the incorporation of silver cations into zeolites without changing the structure of the matrix. It was observed that silver was present in the zeolite mainly as well dispersed Ag+ and that different silver species with different reduction properties were formed depending on the zeolite structure. It was found that the resulting materials had potential to control citrus green mold caused by P. digitatum. The results confirmed that incorporation of these zeolites into coatings provided an affordable and safe method to control decay of fresh oranges. The antifungal activity depended on the amount of silver contained in zeolites, but a high silver content induced phytotoxicity in the fruit surface. Nevertheless, Ag-zeolites with low silver content were also active without phytotoxic effects. The best results were obtained with the FAU zeolite, which had the largest pores and the highest Si/Al, showing the influence of the topology and composition of the zeolites on their antifungal properties.

Efficacy of Some Plant Extracts and Biodegradables Wrapping Materials as an Alternative to Fungicides in Increasing Shelf Life Citrus Fruits

Increasingly global there is an interest to develop a new method by replacing fungicides in packaging fresh fruit by using environment-friendly bio-pesti-cides, such as use of botanicals or biological control. Five ethanol extracts (concentrations 500 - 5000 ppm) of Cerbera odollam L. (Pong-pong), Capsicum frutescence L. (Chili), Azadirachta indica L. (Neem), Cymbopogon nardus L. (Lemon grass), Zingiber officinale L. (Ginger), were tested for their anti-fungal activity for citrus green mold, black and brown rot, compared with the control fungicide (Guazatine). Efficacy of the selected plant extract in cooperated with biodegradable materials wrappers (Polylactic acid, Pectin and Newspaper) was determined during storage at room temperature (±25℃) to control fruit-pathogen decay under modified atmosphere packaging (MAP) to increase shelf life and improve the fruit quality. Crude extracts from pong-pong and chili showed fungal inhibition zone at 3000 ppm (c.100%), and increased shelf life and decreased weigh loss for fruits wrapped and stored at room temperature compared with untreated fruit.

Transcriptional profiling analysis of Penicillium digitatum, the causal agent of citrus green mold, unravels an inhibited ergosterol biosynthesis pathway in response to citral.

BackgroundGreen mold caused by Penicillium digitatum is the most damaging postharvest diseases of citrus fruit. Previously, we have observed that citral dose-dependently inhibited the mycelial growth of P. digitatum, with the minimum inhibitory concentration (MIC) of 1.78 mg/mL, but the underlying molecular mechanism is barely understood.ResultsIn this study, the transcriptional profiling of the control and 1/2MIC-citral treated P. digitatum mycelia after 30 min of exposure were analyzed by RNA-Seq. A total of 6355 genes, including 2322 up-regulated and 4033 down-regulated genes, were found to be responsive to citral. These genes were mapped to 155 KEGG pathways, mainly concerning mRNA surveillance, RNA polymerase, RNA transport, aminoacyl-tRNA biosynthesis, ABC transporter, glycolysis/gluconeogenesis, citrate cycle, oxidative phosphorylation, sulfur metabolism, nitrogen metabolism, inositol phosphate metabolism, fatty acid biosynthesis, unsaturated fatty acids biosynthesis, fatty acid metabolism, and steroid biosynthesis. Particularly, citral exposure affected the expression levels of five ergosterol biosynthetic genes (e.g. ERG7, ERG11, ERG6, ERG3 and ERG5), which corresponds well with the GC-MS results, the reduction in ergosterol content, and accumulation of massive lanosterol. In addition, ERG11, the gene responsible for lanosterol 14α-demethylase, was observed to be the key down-regulated gene in response to citral.ConclusionOur present finding suggests that citral could exhibit its antifungal activity against P. digitatum by the down-regulation of ergosterol biosynthesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2943-4) contains supplementary material, which is available to authorized users.

The effect of temperature, exposure time and pH on imazalil residue loading and green mould control on citrus through dip application

Imazalil (IMZ) is the most relied upon fungicide for use against citrus green mould, caused by Penicillium digitatum. In South Africa, the IMZ sulphate formulation is used as dip application in packhouses. Previous studies showed that IMZ efficacy and residue loading of this formulation is highly affected by pH in the application solution. This study investigated the effect of pH, exposure time and temperature on residue loading, green mould control and sporulation inhibition when citrus fruit were dipped in IMZ sulphate. Clementine mandarins, lemons and navel oranges were dipped in a 500mgL−1 solution of IMZ sulphate for 15, 45 or 90s, at a temperature of 23, 35 or 45°C, and at pH levels of 3 or 6. At pH 3, similar residues were loaded on fruit regardless of fruit type, temperature or exposure time (1.18–1.51mgkg−1). At pH 6, both temperature and exposure time influenced residue loading: at 23°C, higher residue levels were observed than at pH 3 (2.03–2.73mgkg−1, increasing with longer exposure time); at 35°C and 45°C, residue levels increased significantly with 15s, 30s and 45s exposure time (3.34, 5.11, 7.24mgkg−1 and 5.31, 9.65 and 13.10mgkg−1, respectively). Clementine mandarin fruit loaded higher residues at pH 6 (6.96mgkg−1) than lemons and navels (5.20 and 4.82mgkg−1, respectively). The MRL was frequently exceeded at longer exposure times. Green mould control was lower at pH 3 and was influenced by temperature and exposure time (92.9–97.4% and 42.8–45.1% for lemons and Clementine mandarins, respectively). Better control was observed at pH 6 regardless of temperature and exposure time (96.9–98.7% and 39.3–57.9% for lemons and Clementine mandarins, respectively). On navel oranges, increased exposure time led to increased green mould control (84.7–92.5%). Sporulation incidence was lower at pH 6 (12.5–28.8%, 19.1–39.2% and 4.6% for lemons, Clementine mandarins and navel oranges, respectively) than at pH 3 treatments (72.7–89.9%, 35.8–91.4% and 77.2% for lemons, Clementine mandarins and navel oranges, respectively). The results show that temperature, pH and exposure time are important parameters in dip application using IMZ sulphate formulation with significant effects on green mould control, more so than residue loading alone.

Adenylyl cyclase is required for cAMP production, growth, conidial germination, and virulence in the citrus green mold pathogen Penicillium digitatum

Penicillium digitatum is the causative agent of green mold decay on citrus fruit. The cAMP-mediated signaling pathway plays an important role in the transduction of extracellular signals and has been shown to regulate a wide range of developmental processes and pathogenicity in fungal pathogens. We cloned and characterized a Pdac1 gene of P. digitatum, which encodes a polypeptide similar to fungal adenylyl cyclases. Using a loss-of-function mutation in the Pdac1 gene we demonstrated a critical requirement for hyphal growth and conidial germination. Deletion of Pdac1 resulted in decreased accumulation of cAMP and down-regulation of genes encoding a G protein α subunit, both catalytic and regulatory subunits of PKA, and two transcriptional regulators StuA and Som1. Fungal mutants lacking Pdac1 produced abundant conidia, which failed to germinate effectively and displayed an elevated sensitivity to heat treatment. Pdac1 mutant failed to utilize carbohydrates effectively and thus displayed severe growth retardation on rich and synthetic media. Slow growth seen in the Pdac1 mutants could be due to a defect in nutrient sensing and acquisition. Quantitative RT-PCR analysis revealed that Pdac1 was primarily expressed at the early stage of infection. Fungal pathogenicity assayed on citrus fruit revealed that P. digitatum strains impaired for Pdac1 delayed lesion formation. Our results highlight important regulatory roles of adenylyl cyclase-mediated cAMP production in P. digitatum and provide insights into the critical role of cAMP in fungal growth, development and virulence.

Effectiveness of Postharvest Treatment with Chitosan to Control Citrus Green Mold

Control of green mold, caused by Penicillium digitatum, by fungicides raises several problems, such as emergence of resistant pathogens, as well as concerns about the environment and consumers’ health. As potential alternatives, the effects of chitosan on green mold disease and the quality attributes of citrus fruits were investigated. Fruits were wounded then treated with different concentrations of chitosan 24 h before their inoculation with P. digitatum. The results of in vitro experiment demonstrated that the antifungal activity against P. digitatum was improved in concert to the increase of chitosan concentration. In an in vivo study, green mold was significantly reduced by chitosan treatments. In parallel, chitinase and glucanase activities were enhanced in coated fruits. Evidence suggested that effects of chitosan coating on green mold of mandarin fruits might be related to its fungitoxic properties against the pathogen and/or the elicitation of biochemical defense responses in coated fruits. Further, quality attributes including fruit firmness, surface color, juice content, and total soluble solids, were not affected by chitosan during storage. Moreover, the loss of weight was even less pronounced in chitosan-coated fruit.

Inhibition of Penicillium digitatum and Citrus Green Mold by Volatile Compounds Produced by Enterobacter cloacae

Penicillium digitatum causes green mold decay on citrus fruit, resulting in severe economic losses to citrus growers and packers worldwide. The present study is to evaluate the control of citrus green mold by volatiles produced by Enterobacter cloacae. An E. cloacae strain isolated from plant rhizospheres was able to produce three volatile organic compounds, which were identified as butyl acetate, phenylethyl alcohol, and 4,5-dimethyl-1-hexene by GC/MS chromatography. The volatile compounds produced by E. cloacae inhibited conidial germination and hyphal elongation of P. digitatum and reduced green mold severity. E. cloacae cultured at temperatures ranging from 16°C to 28°C, at pH values ≤6, or in a substrate carrier (sphagnum moss, vermiculite, or perlite) provided superior control against P. digitatum. A laboratory formulation using E. cloacae and perlite protected citrus fruit from green mold up to 22 days and its effectiveness outperformed fungicide application at room temperature (~25°C). The results implicate practical application of E. cloacae as a biofumigant for controlling citrus postharvest decay caused by P. digitatum. Significantly, the study provides a model for future research on how to formulate an effective biocontrol agent for disease management.

Yeasts from native Brazilian Cerrado plants: Occurrence, diversity and use in the biocontrol of citrus green mould

Yeasts are some of the most important postharvest biocontrol agents. Postharvest oranges frequently deteriorate due to green mould (Penicillium digitatum), which causes significant losses. The aims of this study were to determine the composition and diversity of yeasts on plants of the Brazilian Cerrado and to explore their potential for inhibiting citrus green mould. Leaves and fruit of Byrsonima crassifolia and Eugenia dysenterica were collected from Cerrado conservation areas, and thirty-five yeasts were isolated and identified by sequencing the D1-D2 domain of the rDNA large subunit (26S). The isolates represented the Aureobasidium, Meyerozyma, Candida, and Pichia genera. Three isolates identified as Aureobasidium pullulans exhibited potential for the control of P. digitatum in both in vitro and in vivo tests; these isolates reduced the incidence of disease and increased the storage time of fruit. Aureobasidium. pullulans has immense potential for the biological control of filamentous fungi.

Biofumigation on Post-Harvest Diseases of Fruits Using a New Volatile-Producing Fungus of Ceratocystis fimbriata.

A variety of volatile organic compounds (VOCs) produced by Ceratocystis fimbriata have strong bioactivity against a wide range of fungi, bacteria and oomycetes. Mycelial growth, conidial production, and spore germination of fungi and oomycetes were significantly inhibited after exposure to cultures of C. fimbriata, and colony formation of bacteria was also inhibited. Two post-harvest diseases, peach brown rot caused by Monilinia fructicola and citrus green mold caused by Penicillium digitatum, were controlled during a 4-day storage by enclosing wound-inoculated fruits with 10 standard diameter Petri plate cultures of C. fimbriata in a 15 L box. The fruits were freshly inoculated at onset of storage and the cultures of C. fimbriata were 6 days old. Percentage of control was 92 and 97%, respectively. After exposure to C. fimbriata VOCs, severely misshapen hyphae and conidia of these two post-harvest pathogens were observed by scanning electron microscopy, and their pathogenicity was lost or greatly reduced.

Imazalil resistance in Penicillium digitatum and P. italicum causing citrus postharvest green and blue mould: Impact and options

Citrus green and blue mould, caused by Penicillium digitatum (PD) and Penicillium italicum (PI), respectively, are mostly controlled by means of postharvest fungicide applications. Currently, IMZ is regarded as the most effective fungicide in use. Effective IMZ concentrations that inhibit 50% (EC50) growth of nine PD and five PI isolates were assessed in vitro and the various isolates categorized according to their resistance (R) factors. Effective residue levels that provided 50% curative (ER50C) and protective (ER50P) control of these isolates were determined in vivo. All the PI isolates were sensitive, having EC50 values of 0.005–0.050μgmL−1. Three PD isolates were sensitive (0.027–0.038μgmL−1), while one resistant isolate was categorized as low resistant (R-factor of 19), one as moderately resistant (R-factor of 33.2), three as resistant (R-factor of 50–57.6) and one as highly resistant (R-factor of 70.7). Sensitive PD isolates had mean ER50C and ER50P values on Valencia orange fruit of 0.29 and 0.20μgg−1, and 0.33 and 0.32μgg−1 on navel fruit, respectively. ER50 values for resistant isolates did not always correlate with EC50 values and ranged from 1.22 to 4.56μgg−1 for ER50C and 1.00–6.62μgg−1 for ER50P values. ER50P values for resistant isolates could not be obtained on navel orange fruit, but ER50C values (1.42–1.65μgg−1) were similar to those obtained on Valencia fruit. The PI isolates all behaved similar to the sensitive PD isolates with ER50C and ER50P values on navel and Valencia fruit <0.38μgg−1. Alternative fungicides were assessed for the control of an IMZ sensitive, resistant and highly resistant PD isolate; these included sodium ortho-phenylpenate (SOPP), thiabendazole (TBZ), guazatine (GZT), imazalil (IMZ), pyrimethanil (PYR) and Philabuster® (PLB; a combination of IMZ and PYR), fludioxonil (FLU), azoxystrobin (AZO), Graduate®A+ (GRA; a combination of FLU and AZO) and propiconazole (PPZ). Multiple fungicide resistance was shown to IMZ, GZT, TBZ and PPZ in both resistant isolates. For the sensitive isolates, IMZ, SOPP, TBZ, GZT and PLB provided best curative control, while IMZ, GZT and PLB provided best protective control. For the IMZ-resistant isolates, SOPP, PYR and PLB gave the best curative control, while none of the fungicides provided adequate protective control.

Enhanced control of postharvest citrus fruit decay by means of the combined use of compatible biocontrol agents

Fourteen Pseudomonas spp. and three Trichoderma spp. strains were tested in vitro for their antagonistic properties against Penicillium digitatum, the causal agent of citrus green mold. Bacterial and fungal strains strongly inhibited the pathogen growth in vitro on PDA and on a citrus-based medium. Inhibitory effects were increased when Pseudomonas and Trichoderma strains were applied in combination. Inhibitory effects were also increased by mixtures of Pseudomonas cells and Trichoderma atroviride P1 culture filtrates. On the opposite, bacterial and fungal filtrates in mixture never induced an improved efficacy, thus indicating that the presence of living bacterial cells was required for a synergistic effect. Accordingly, incidence and severity of disease on orange cv. Tarocco and lemon cv. Femminello were consistently reduced when Pseudomonas and Trichoderma strains were applied 72h before challenging P. digitatum. Pseudomonas syringae strains were the most effective and several combinations had a biocontrol activity higher than one of the each antagonistic microorganism applied alone. The treatments comprising six P. syringae in mixture with Trichoderma strains T22, P1 and T34 were the most effective, with 80–100% control of green mold. The development of green mold decay was also effectively inhibited in small-scale dip-treatments, either by single applications or by their mixtures. These experiments suggest that the combination of Pseudomonas spp. and Trichoderma spp. strains could be considered as a promising mean for the control of citrus green mold decay, supporting the concept that an improved disease control is given by the combined action of the two agents.

INFLUENCE OF PARABEN CONCENTRATION ON THE DEVELOPMENT OF GREEN AND BLUE MOLDS ON 'VALENCIA' ORANGE FRUIT

Three paraben sodium salts (p-hydroxy-benzoate) were evaluated as postharvest treatments to control citrus green (GM) and blue (BM) mold, caused by Penicillium digitatum and Penicillium italicum, respectively. The curative activity of sodium methyl (SMP; at 0.1, 1, 10, 40, 70, 100, 150, 200 and 250 mM), ethyl (SEP; at 0.1, 1, 10, 20, 30, 40, 70, and 100 mM) and propyl (SPP; at 0.1, 1, 4, 7, 10, and 100 mM) paraben were evaluated on ‘Valencia’ oranges by inoculating the pathogens in rind wounds and, about 24 h later, placing a drop of the solutions in the same rind wound. Disease development was assessed on fruit incubated at 20°C for 6 days. All three paraben salts reduced mold development. Concentrations of 150, 200 and 250 mM of SMP were the most effective and completely controlled both diseases. Concentrations of 20, 30, 40, 70 and 100 mM of SEP reduced the incidence of GM and BM by 100, 94, 100, 100 and 73% and 87, 62, 93, 100 and 80%, respectively. Concentrations of 7, 10 and 100 mM of SPP reduced the incidence of GM and BM by 94, 89 and 94% and 70, 88 and 100%, respectively. Most of these concentrations of SMP, SEP and SPP also significantly reduced the severity of GM and BM. SMP at 200 mM, SEP at 70 mM and SPP at 100 mM were, among the range of concentrations tested, selected as the best to be used in further research.

PdbrlA, PdabaA and PdwetA control distinct stages of conidiogenesis in Penicillium digitatum

Penicillium digitatum is one of the most important citrus postharvest pathogens worldwide. Reproduction of massive asexual spores is the primary factor contributing to the epidemic of citrus green mold. To understand the molecular mechanisms underlying conidiogenesis in P. digitatum, we functionally characterized the Aspergillus nidulans orthologs of brlA, abaA and wetA. We showed that deletion of PdbrlA completely blocked formation of conidiophores, whereas deletion of PdabaA led to the formation of aberrant and non-functional phialides. The PdwetA mutant showed various defective phenotypes, such as abnormal conidia with loose cell walls, delayed germination and reduced tolerance to osmotic, detergent, heat shock and menadione stresses, but elevated resistance to H2O2. PdbrlA-influenced genes were identified by comparing global gene expression profiles between the wild-type and the PdbrlA deletion mutant during conidiation. Gene ontology analysis of these differentially expressed genes (DEGs) revealed the diverse roles of PdbrlA in metabolism, transportation and cell structure. Moreover, out of 39 genes previously reported to be involved in conidiogenesis in Aspergillus, mRNA levels of 14 genes were changed in ΔPdbrlA. Our results confirm the roles of brlA, abaA and wetA in P. digitatum conidiogenesis and provide new insights into the genetics of conidiation in filamentous fungi.

Curative control of citrus green mould by imazalil as influenced by infection age, wound size, fruit exposure time, solution pH and fruit brushing after treatment

Green mould (Penicillium digitatum) is a major cause of postharvest losses in citrus. Wounds and infection can be inflicted during the harvest process and should be controlled during postharvest stages to prevent decay. Imazalil (IMZ) in the sulphate formulation is currently applied by the majority of South African packhouses through an aqueous dip treatment. In this study the effects of incubation time (infection age), exposure time, solution pH, wounds size and fruit brushing after dip treatments on residue loading and curative green mould control were investigated. Exposure time did not have a significant effect on residue loading on fruit dipped in pH 3 solutions of IMZ (<2.00μgg−1). Increasing the pH to 6 resulted in significantly increased residue loading, which increased with longer exposure time, but mostly to levels below the maximum residue level of 5μgg−1 after 180s. Post-dip treatment brushing reduced residue levels obtained in IMZ pH 3 solutions by up to 90% to levels <0.5μgg−1; however, curative control of the IMZ sensitive (S) isolate was mostly unaffected, but with poor sporulation inhibition. At pH 6, post-dip brushing reduced residues to ≈60%; again curative control of the sensitive isolate was unaffected, but with better sporulation inhibition than the pH 3 treatments. Wounded rind sections loaded higher residue levels compared with intact rind sections, and large wounds loaded higher levels than small wounds (≈10.19, ≈9.06 and ≈7.91μgg−1 for large, small and no wound, respectively). Curative control of infections originating from large wounds was significantly better than those from small wounds. The ability of IMZ to control sensitive green mould infections declined from 6 and 12h after inoculation on Clementine mandarin fruit of infections inflicted by small and large wounds, respectively; on navel orange fruit, curative control declined 18 and 36h after inoculation for the respective wound size treatments. This work shows the importance of timely fungicide treatment after harvest especially on more susceptible citrus types. Results also indicate that excess residues can be stripped from the fruit, retaining residues necessary for curative control in the wound sites. However, reduced residue loading compromised the sporulation inhibition activity of IMZ.

Effect of postharvest application of chitosan combined with clove oil against citrus green mold

The antifungal activity of chitosan combined with clove oil against Penicillium digitatum, the causal agent of citrus green mold, was tested in vitro and in vivo. Chitosan combined with clove oil inhibited mycelial growth more than individual treatments, which was related to the greater release of cellular material and the largest alterations in hyphal morphology of P. digitatum. However, compared to chitosan alone, 1% chitosan coatings combined with various amounts of clove oil (0.5, 1 or 2mL/L) showed no greater ability in controlling decay development on artificially inoculated citrus fruit. 1% chitosan combined with 0.5mL/L clove oil appeared to slightly reduce lesion diameter and enhanced the activities of defense enzymes, including chitinase and phenylalanine ammonia-lyase at the later stages of incubation. This study indicated that the synergistic antifungal activity of chitosan-clove oil observed in in vitro studies was not found in in vivo tests. Therefore, the data suggest that a coating of 1% chitosan alone, not combined with clove oil, can effectively contribute to the control of green mold on citrus fruit.

Effectiveness of phenolic compounds against citrus green mould.

Stored citrus fruit suffer huge losses because of the development of green mould caused by Penicillium digitatum. Usually synthetic fungicides are employed to control this disease, but their use is facing some obstacles, such public concern about possible adverse effects on human and environmental health and the development of resistant pathogen populations. In the present study quercetin, scopoletin and scoparone—phenolic compounds present in several agricultural commodities and associated with response to stresses—were firstly tested in vitro against P. digitatum and then applied in vivo on oranges cv. Navelina. Fruits were wound-treated (100 µg), pathogen-inoculated, stored and surveyed for disease incidence and severity. Although only a minor (≤13%) control effect on P. digitatum growth was recorded in vitro, the in vivo trial results were encouraging. In fact, on phenolic-treated oranges, symptoms appeared at 6 days post-inoculation (DPI), i.e., with a 2 day-delay as compared to the untreated control. Moreover, at 8 DPI, quercetin, scopoletin, and scoparone significantly reduced disease incidence and severity by 69%–40% and 85%–70%, respectively, as compared to the control. At 14 DPI, scoparone was the most active molecule. Based on the results, these compounds might represent an interesting alternative to synthetic fungicides.

Effects of dog rose and watercress extracts on control of green mould decay and postharvest quality of orange fruits

Minimum inhibitory concentration (MIC) and IC50 values and total phenolics of dog rose fruits were 72.5–80 μL mL− 1, 130 μg mL− 1 and 5.7 mg GA g− 1, respectively. The Fashand watercress population and dog rose extracts exhibited mycelia growth inhibition values of 45.08% and 37.12%, respectively. The results of in vivo study indicated that the treatment of inoculated fruits with both methanol extracts especially the watercress plant extract considerably controls the citrus fruits decay (Penicillium digitatum) up to 73%. In conclusion, methanol extracts of dog rose fruits and especially watercress plant had the potential to be used against citrus green mould and even for the improvement of postharvest quality of orange fruits.

Octanal incorporated in postharvest wax of Satsuma mandarin fruit as a botanical fungicide against Penicillium digitatum

The antifungal activity of octanal against Penicillium digitatum, the causal agent of citrus green mold, was assessed by in vitro and in vivo experiments. In vitro assays results showed that the minimum inhibitory concentration and minimum fungicidal concentration (MFC) of octanal were 500 and 1000 μL/L, respectively. In vivo test results demonstrated that wax + octanal (WO; 2 × MFC) treatment but not WO (1 × MFC) treatment effectively inhibited the growth of P. digitatum after 6 d of storage at 25 ± 2 °C. The WO treatment remarkably increased the activities of antioxidant enzymes, such as catalase and superoxide dismutase, in Satsuma mandarin fruit. However, this treatment evidently decreased phenylalanine ammonia lyase activity and malondialdehyde content. The WO treatment also inhibited peroxidase activity and prevented hydrogen peroxide accumulation. Furthermore, the WO treatment did not impair the fruit quality parameters (vitamin C content, pH, coloration index, and total soluble solid content) of the tested fruit. This study provided theoretical data for the practical application of octanal to improve citrus fruit quality during postharvest storage.

Control of postharvest green mould of citrus by haliscosamine isolated from Haliclona viscosa sponge

The aim of this study was to evaluate the antifungal activity of haliscosamine isolated from Haliclona viscosa sea sponge from the Moroccan Atlantic coast against Penicillium digitatum, the causal agent of citrus green mould. The in vitro antifungal activity of haliscosamine, determined using the agar disc‐diffusion method, showed that haliscosamine and DESOGERME SP VEGETAUX® (reference product) have fungicidal activity with inhibition diameters of 19 and 18 mm, respectively. Haliscosamine and a positive control (DESOGERME SP VEGETAUX®) were tested in vivo in comparison with a negative control on orange fruits in normal storage conditions. This test showed that after four weeks of storage, the rate of decay of citrus fruits treated with haliscosamine or DESOGERME does not exceed 14%, whereas in the negative control the decay rate is 77%. The results of in vitro and in vivo tests indicate that haliscosamine and DESOGERME SP VEGETAUX® have an important antifungal potential against P. digitatum and that haliscosamine (a natural product) may represent an alternative to the use of chemical fungicides.