Control Of Postharvest Diseases Research Articles

Postharvest Treatments with GRAS Salts to Control Fresh Fruit Decay

Control of postharvest diseases of fresh fruits has relied for many years on the continuous use of conventional chemical fungicides. However, nonpolluting alternatives are increasingly needed because of human health and environmental issues related to the generation of chemical residues. Low-toxicity chemicals classified as food preservatives or as generally recognized as safe (GRAS) compounds have known and very low toxicological effects on mammals and minimal impact on the environment. Among them, inorganic or organic salts such as carbonates, sorbates, benzoates, silicates, etc., show significant advantages for potential commercial use, such as their availability, low cost, and general high solubility in water. Typically, these substances are first evaluated in vitro against target pathogens that cause important postharvest diseases. Selected salts and concentrations are then assayed as aqueous solutions in in vivo tests with target fresh fruit. Laboratory and small-scale experiments are conducted with fruit artificially inoculated with pathogens, whereas naturally infected fruit are used for large-scale, semicommercial, or commercial trials. Another approach that is increasingly gaining importance is evaluating GRAS salts as antifungal ingredients of novel synthetic edible coatings. These coatings could replace the fungicide-amended commercial waxes applied to many fruit commodities and could be used for organic or “zero-residue” fresh fruit production systems.

Reduction of acrylamide formation in fried potato chips by Aureobasidum pullulans L1 strain

Acrylamide is a potential carcinogenic molecule formed during food heat processing at high temperature (Maillard reaction). In the present study, the ability of the yeast Aureobasidium pullulans to deplete the acrylamide precursor free asparagine in fresh potatoes was investigated. A. pullulans applied before final frying changes the free amino acid composition of potatoes, decreasing the content of free asparagine by 16% and reducing acrylamide by 83% in fried potatoes. Potato browning was also reduced by yeast treatment without negative drawbacks on chip taste. This yeast, commonly used in fruit postharvest disease control, can therefore also be applied in potato and bakery industries to reduce food acrylamide content.

Methyl p-coumarate inhibits black spot rot on jujube fruit through membrane damage and oxidative stress against Alternaria alternata

Black spot rot caused by Alternaria alternata is one of the main postharvest diseases on jujube fruit. The aim of this study was to investigate the antifungal activity of methyl p-coumarate (MpCA) against A. alternata, and to elucidate the underlying mechanism involved. MpCA treatments significantly inhibited the development of black spot rot on the jujube fruit inoculated with A. alternata. Moreover, MpCA exhibited pronounced antifungal activity against mycelial growth and spore germination of A. alternata, with half-inhibition concentration of 242.5 mg L−1. MpCA treatments caused a great leakage of intercellular electrolytes, soluble proteins, sugars and nucleotides of A. alternata during incubation, indicating that MpCA is targeted to plasma membranes of the pathogen. Furthermore, count of cells dyed with propidium iodide by flow cytometer suggested that MpCA treatments destroyed the plasma membrane integrity of spores of A. alternata. Ultrastructural observations evidenced MpCA damaged the plasma membranes and impeded the morphogenesis and growth of A. alternata, which resulted in distortion, shriveling and lysis of spores and mycelia of the pathogen. In addition, observations by confocal laser scanning microscopy and quantitative determinations confirmed that the MpCA treatments induced the formation of intercellular endogenous reactive oxygen species in the spores of A. alternata, which would lead to oxidative stress to cellular membranes and organelles. These results indicated that MpCA exerts antifungal activity through membrane damage and oxidative stress against A. alternata, and MpCA is a promising candidate for the control of postharvest diseases of jujube fruit.

Effectiveness of Gum Arabic, Potassium Salts and Their Incorporation in The Control of Postharvest Diseases and Maintaining Quality of ‘Washington’ Navel Oranges during Long Term Cold Storage

Effectiveness of Gum Arabic, Potassium Salts and Their Incorporation in The Control of Postharvest Diseases and Maintaining Quality of ‘Washington’ Navel Oranges during Long Term Cold Storage

OUTBREAK OF ANTHRACNOSE AND STEM END ROT DISEASES OF MANGO IN CHANGING CLIMTE AND THEIR MANAGEMENT THROUGH HOT WATER TREATMENT

Pakistan is the 6th largest producer of mangoes which are known world over for their superior traits but export of mangoes from Pakistan is quite limited due to post-harvest diseases like anthracnose and stem-end rot (SER) mainly caused by Colletotrichum gloeosporioides and Lasiodiplodia theobromae, respectively. These diseases are aggravating day by day due to environmental changes in mango producing region of Pakistan. Quarantine of mangoes through physical methods like Hot Water Treatment (HWT) is always preferred by the foreign markets because of its high effectiveness in reducing the post-harvest diseases. During 2012-13, keeping in view the importance of HWT, a comprehensive study was conducted to standardize the temperature and dip duration levels for HWT along with a fungicide named Nativo (Trifloxystrobin + Tebuconazole) @ 0.3g/L of water for mango Cvs. Sindhri, S.B. Chaunsa, Fajri and Sufaid Chaunsa using newly developed HWT facility at Agricultural Mechanization Research Institute, Multan for the control of post-harvest diseases with a little focus on other fruit quality parameters as well. HWT resulted in better marketability of fruits due to uniform peel color development and visual quality rating (VQR). Control of (SER) with either of both high levels of temperature (54°C) and dip duration (06minutes) simultaneously or any of one high level along was noted in all the tested varieties with 77.27 to 85.26% disease reduction in contrast to control of anthracnose which was effectively minimized with the range of 77.24 to 90.36% through low temperature (52°C) and low dip level (03minutes) in case of Sindhri and S.B. Chaunsa while 52°C for 06 minutes and 54°C for 06 minutes showed good performance in case of Cvs. Fajri and Sufaid Chaunsa, respectively. Surely, this study developed the understanding of mango industry stake holders with efficient use of safe and cheaper physical method i.e. HWT to control post-harvest diseases to enhance the mango export from Pakistan.

Antifungal activity and action mechanisms of yeasts isolates from citrus against Penicillium italicum

Penicillium italicum (Blue mold) is a major postharvest disease of citrus. An alternative to controlling the disease is through the use of yeasts. The purpose of the present study was to screen effective yeast antagonists against P. italicum, isolated from soil, leaves, flowers, and citrus fruits, to assess the action mechanisms of the yeast isolates that were demonstrated to be effective for biocontrol, and to identify the most effective yeast isolates for the biocontrol of blue mold. The in vitro assays showed that six yeast strains inhibited up to 90% of the pathogen's mycelial growth. In vivo assays, evaluating the incidence of blue mold on sweet oranges, the strains ACBL-04, ACBL-05, ACBL-10 and ACBL-11 were effective, demonstrating the potential for the blue mold control when preventively applied, whereas the ACBL-08 strain showed a high potential to preventive and curative applications. Additional studies on the modes of action of these yeast strains showed that most of the evaluated yeast strains did not produce antifungal substances, in sufficient quantities to inhibit the pathogen growth. Competition for nutrients was not a biocontrol strategy used by the yeast strains. The ‘killer’ activity might be the main action mechanism involved in P. italicum biocontrol. This study indicated that the multiple modes of action against the pathogen presented by yeasts may explain why these strains provided P. italicum control under in vitro and in vivo conditions. However, further studies in future might be able to elucidate the ‘killer’ activity and its interaction with pathogen cells and the bioproduct production using Candida stellimalicola strains for control postharvest diseases.

Biocontrol of strawberry fruit infected by Botrytis cinerea: Effects on the microbial communities on fruit assessed by next‐generation sequencing

AbstractFruit grey mould, caused by the fungus Botrytis cinerea, is known to be a harmful disease of strawberry at postharvest stage. However, effects of an application of biological control agents (BCAs) on strawberry fruit in terms of shift in the microbial community are still unknown. The present research aimed to investigate the effects of an application of BCAs on postharvest microbial populations present on strawberry fruits. Strawberry plants were sprayed with three kinds of BCA, RhizoVital 42 fl. (Bacillus amyloliquefaciens FZB42), Trianum‐P (Trichoderma harzianum T22) and Naturalis (Beauveria bassiana ATCC 74040), targeting Botrytis cinerea fungus. Control plots were composed of water and fungicide treatments. Microbial communities (bacteria and fungi) were analysed via next‐generation sequencing on an Illumina MiSeq. Analysis of 16S RNA and ITS rRNA sequences indicated that the BCAs application modified both bacterial and fungal community compositions and diversity. An application of two BCAs together had more effects on microbial community composition than a single application. These results suggest that BCAs can modify bacterial and fungal community composition and diversity on strawberry fruits, which may consequently improve the efficiency and establishment of these products on control of postharvest diseases of fruits, such as grey mould.

Cold plasma: a potential new method to manage postharvest diseases caused by fungal plant pathogens

Development of alternative, chemical‐free approaches for control of postharvest fungi on a commercial scale has become a challenge for plant pathologists in recent years. Although there are several established techniques such as heat that are used as postharvest treatments, they often have disadvantages, including alteration of food quality due to physiological responses to the treatment, or environmental pollution. A promising new postharvest treatment is cold plasma, which is a gas‐derived mix of atoms, excited molecules and charged particles. Cold plasma has no known adverse effects on fresh produce or the environment. It is an established technology in the medical field and has been demonstrated to successfully control bacterial pathogens that cause food safety issues. This review focuses on the potential of cold plasma technology for postharvest disease control, especially those caused by fungi. An overview of plasma generation systems is provided, and in vivo and in vitro research is reviewed to consider benefits, limitations and research gaps in the context of cold plasma as a potential method for controlling postharvest fungal pathogens. Finally, recommendations are provided for the application of this technology in commercial facilities.

Use of inductors in the control of Colletotrichum gloeosporioides and Rhizopus stolonifer isolated from soursop fruits: in vitro tests.

Soursop (Annona muricata) is a tropical fruit that can be infected by Colletotrichum gloeosporioides and Rhizopus stolonifer. Traditional methods used for postharvest disease control include the application of fungicides, however due to their excessive use, as well as their persistence in the environment, the development of new strategies that control pathogens are required. The application of chitosan (Chi), salicylic acid (SA) and methyl jasmonate (MJ) is an environmentally-friendly alternative with antimicrobial properties and also induces defense mechanisms in plant tissues. In this study, Colletotrichum was reactivated and Rhizopus was identified using morphological features and molecular tools. In vitro, the application of 0.5 and 1.0% of Chi alone or in combination with SA and MJ decreased mycelial growth and sporulation, a complete inhibition of spore germination was obtained. Thus, the application of Chi in combination with SA and MJ could be a smart strategy to inhibit the development of pathogens that attack soursop fruit.

Thyme and Savory Essential Oil Vapor Treatments Control Brown Rot and Improve the Storage Quality of Peaches and Nectarines, but Could Favor Gray Mold.

The effect of biofumigation, through slow-release diffusors, of thyme and savory essential oils (EO), was evaluated on the control of postharvest diseases and quality of peaches and nectarines. EO fumigation was effective in controlling postharvest rots. Naturally contaminated peaches and nectarines were exposed to EO vapors for 28 days at 0 °C in sealed storage cabinets and then exposed at 20 °C for five days during shelf-life in normal atmosphere, simulating retail conditions. Under low disease pressure, most treatments significantly reduced fruit rot incidence during shelf-life, while, under high disease pressure, only vapors of thyme essential oil at the highest concentration tested (10% v/v in the diffusor) significantly reduced the rots. The application of thyme or savory EO favored a reduction of brown rot incidence, caused by Monilinia fructicola, but increased gray mold, caused by Botrytis cinerea. In vitro tests confirmed that M. fructicola was more sensitive to EO vapors than B. cinerea. Essential oil volatile components were characterized in storage cabinets during postharvest. The antifungal components of the essential oils increased during storage, but they were a low fraction of the volatile organic compounds in storage chambers. EO vapors did not influence the overall quality of the fruit, but showed a positive effect in reducing weight loss and in maintaining ascorbic acid and carotenoid content. The application of thyme and savory essential oil vapors represents a promising tool for reducing postharvest losses and preserving the quality of peaches and nectarines.

Alternative control of post-harvest diseases in Tainung 1 papaya

ABSTRACT Controlling post-harvest papaya diseases without using agrochemicals is a challenge for producers. This study aimed at evaluating the effect of clove essential oil, biological fungicide (Trichodermil®), resistance inducer (Cob Sistem®) and chemical fungicide (Imazacure®) on the in vitro control of phytopathogenic fungi isolates from papaya as well as on the post-harvest quality of Tainung 1 papaya. The in vitro experiment was conducted in a complete randomized design, with five fungal species x five treatments and five replications. The in vivo experiment was conducted in a complete randomized design, with five treatments x five storage times, five replications and three fruits per replication. The fruits were stored under refrigeration at 10 ± 2 ºC and 90 ± 5 % of relative humidity and evaluated at 0, 7, 14, 21 and 28 days of storage, plus two shelf life days at 25 ± 2 ºC, to simulate marketing conditions. The inhibition of mycelial growth was evaluated in the in vitro experiment, while the diseases occurrence and post-harvest quality of the fruits were evaluated in the in vivo experiment. The clove essential oil and Trichodermil® were as efficient as Imazacure® in inhibiting the mycelial growth of Alternaria sp., Colletotrichum gloeosporioides and Rhizopus sp. The treatments with clove essential oil, Trichodermil® and Imazacure® were similar in controlling the pathogens up to 21 days of storage. The treatments had no effect on the fruits soluble solid contents.

Evaluation of sulfur dioxide-generating pads and modified atmosphere packaging for control of postharvest diseases in blueberries

Evaluation of sulfur dioxide-generating pads and modified atmosphere packaging for control of postharvest diseases in blueberries

Volatile organic compounds from Wickerhamomyces anomalus, Metschnikowia pulcherrima and Saccharomyces cerevisiae inhibit growth of decay causing fungi and control postharvest diseases of strawberries

The effectiveness of Wickerhamomyces anomalus, Metschnikowia pulcherrima and Saccharomyces cerevisiae as biocontrol agents on postharvest decay of strawberry (Fragaria x ananassa, cv. ‘Alba’) fruit, and their inhibitory activities on some decay-causing fungi were evaluated. Volatile organic compounds from these yeasts decreased mycelial growth of Botrytis cinerea by 69%, and by less for Monilinia fructicola, Alternaria alternata, Aspergillus carbonarius, Penicillium digitatum, Cladosporium spp., and Colletotrichum spp. Strawberry fruit exposed to 6-day-old liquid cultures of W. anomalus, M. pulcherrima and S. cerevisiae for 48h showed 89%, 40%, and 32% reductions, respectively, in gray mold McKinney Index. Vapours of ethyl acetate, the main volatile organic compound of these yeasts, completely inhibited B. cinerea growth at 8.97mg/cm3, and suppressed gray mold on strawberry fruit at 0.718mg/cm3. The biocontrol activities of these yeasts can be ascribed to ethyl acetate, which can be used for control of postharvest gray mold of strawberry fruit.

Protective role of epiphytic fluorescent Pseudomonas on natural postharvest decay of tomato at room temperature.

Following harvest, tomato fruits are susceptible to attack by many fungal pathogens, but healthy fruits may also harbor beneficial microflora, which can delayed the spoilage of fruit. In this study, 30 isolates of epiphytic fluorescent Pseudomonas were isolated from healthy fruits of lemon, melon, grapefruit, tomato and orange. Twelve isolates were identified on molecular basis by amplifying 16S rDNA using a genus-specific primer set PA-GS-F 5’-GACGGGTGAGTAATGCCTA-3’ and PA-GS-R F 5’-CACTGGTGTTCCTTCCTATA-3’ on a conserved sequence of the genus Pseudomonas with a product size ~618 bp. Three potential isolates were examined for their ability to delayed the postharvest natural spoilage and maintained the physiochemical properties during storage for fifteen days in season 2013 and 2014. All three isolates showed promising control of postharvest diseases of tomato in comparison with control in both seasons up to fifteen days of storage at room temperature (23±4 oC, Rh 25-70%). The epiphytic bacterial isolates has delayed the fruit weight loss and maintained fruit firmness, total solids, pH and titratable acidity. Isolates also slowed the accumulation of lycopene indicating their potential in controlling the major changes in physiochemical properties. In both season Pseudomonas treated tomatoes showed no or negligible infestation of common postharvest fungi and bacteria as compared to control and positive control (1% K-sorbate).

Yeast cell wall induces disease resistance against Penicillium expansum in pear fruit and the possible mechanisms involved

The results from this study showed that cell wall prepared from Rhodosporidium paludigenum induced strong disease resistance against blue mold rot caused by Penicillium expansum in pear fruit. Yeast cell wall reduced germination of P. expansum in vitro and in fruit wounds after 24h of treatment. Moreover, the cell wall treatment significantly enhanced the activities of defense-related enzymes (β-1,3-glucanase and chitinase) and the genes expression of PR proteins (PR1-like, endoGLU9, endoCHI-like and PR4), which may be an important mechanism by which cell wall reduces the fungal disease of pear fruit caused by P. expansum. These findings suggest that the mechanism by which R. paludigenum induced fruit resistance was linked to the function of its cell wall and application of cell wall might be a useful strategy for the control of postharvest disease in pear fruit.

Biocontrol activity of Bacillus subtilis EA-CB0015 cells and lipopeptides against postharvest fungal pathogens

Post-harvest diseases are responsible for significant losses worldwide, especially the plant pathogenic fungi Botrytis cinerea and Colletotrichum sp. are particularly severe and devastating. In this study, nine fungal pathogens were screened for growth inhibition by Bacillus subtilis EA-CB0015 strain and its metabolites. In vitro inhibitory assays showed that B. subtilis EA-CB0015 cells and the cell free supernatant (CFS) inhibited the growth of the tested fungal pathogens with different susceptibilities. Therefore, the antifungal activities of lipopeptides iturin A and fengycin C contained in the CFS, were tested against C. acutatum and B. cinerea. C. acutatum was more susceptible with minimal inhibitory concentrations (MIC) of 32ppm (iturin A) and 128ppm (fengycin C). Fruit and flower trials confirmed that B. subtilis EA-CB0015 cells and its lipopeptides reduced postharvest disease development but to differing degrees. Anthracnose symptoms caused by C. acutatum in tamarillo fruits were completely abolished by CFS, iturin A and fengycin C and reduced by 76% when treated with B. subtilis cells. In contrast, grey mold disease symptoms caused by B. cinerea in chrysanthemum flowers were inhibited by 72% when treated with lipopeptides and by 39% when applied with B. subtilis EA-CB0015 cells. Our results indicate that lipopeptides and cells of B. subtilis EA-CB0015 have a broad antifungal spectrum and control postharvest diseases caused by susceptible fungal pathogens. Our findings open the possibility of incorporating this biological control agent into different disease management programs.

Physiological effects and mode of action of ZnO nanoparticles against postharvest fungal contaminants

Increasing concerns continue to be expressed about health hazards and environmental pollution resulting from the use of conventional fungicides for postharvest disease control. Nanoparticles represent an alternative solution for postharvest disease management. The objective of this work was to assess the physiological effects and the antifungal efficiency of ZnO nanoparticles (ZnO NPs) against a number of fungal contaminants. The efficacy of ZnO NPs was qualitatively and quantitatively assessed against: Penicillium expansum, Alternaria alternata, Botrytis cinerea and Rhizopus stolonifer. Mycelium growth diameters were measured onto Potato Dextrose Agar (PDA) plates loaded with different ZnO NPs concentrations (from 0mM to 15mM). Hereafter, the rate of the fungal diameter increase was quantified by linear regression modelling. Microscopic analysis was performed by scanning electron microscopy (SEM) images of agar plugs excised from plates with 0mM and 12mM ZnO. All the fungi were inhibited by ZnO NPs at concentrations higher than 6mM. SEM images showed clear morphological aberrations in the fungal structures of all the isolates grown in presence of ZnO. Additionally, knowing that the chelating agent EDTA sequesters metal ions, it was added to fungal inoculated PDA plates with ZnO to study the NPs' mode of action. Cultures where ZnO was mixed with EDTA showed a decrease in the antifungal effect of the nanoparticles. In conclusion, ZnO NPs are therefore a good candidate as an effective postharvest disease control antifungal agent.

Applications of ionizing radiation for the control of postharvest diseases in fresh produce: recent advances

Postharvest diseases cause considerable losses to harvested fruits and vegetables worldwide. In addition to various treatments to control postharvest losses caused by pathogens, the global trend is shifting toward more ecofriendly alternatives safer to human health. Thus far, the main approach to postharvest disease control has mostly relied on the use of chemicals. However, the intense use of chemical fungicides has caused side effects such as environmental issues and evolution of fungicide‐resistant isolates. With increasing demand for the use of non‐chemicals, ionizing radiation has been investigated for application in many aspects of postharvest treatment, especially as an approach with significant potential for the control of postharvest disease. Recently, a number of more or less technologically advanced methodologies, e.g. irradiation combined with other types of treatments and induced disease‐resistance, have been developed to control postharvest diseases as well as to increase the quality and storage life of fresh commodities. Challenges for future application of irradiation in fresh produce are the cost, lack of irradiation facilities, lack of knowledge about optimal conditions for different commodities, and lack of acceptance of irradiated fresh produce. This review aims to document the advances in understanding of the effects of irradiation on postharvest disease, the possible modes of action, and the perspectives in commercial use.

Efficacy of cell free supernatant from Bacillus subtilis ET-1, an Iturin A producer strain, on biocontrol of green and gray mold

The present study deals with the control of two important postharvest fruit diseases by application of the supernatant obtained from Bacillus subtilis strains ET-1. The bacteria, B. subtilis was grown in a bench-scale bioreactor and a cell free supernatant (CFS) rich in Iturin A was produced. During the entire bacterial culture time, it has been observed that Iturin A production started at the end of the exponential growth phase and a maximum concentration of 422mgL−1 was observed after 57h. CFS was then used to evaluate, both in vitro and in vivo, for its antifungal activity against P. digitatum and B. cinerea the agents responsible for the green and gray mold, respectively. Concerning in vitro studies, it has been observed that the antifungal activity of CFS was correlated to Iturin A concentration. The minimum concentration of Iturin A within CFS, necessary to inhibit P. digitatum and B. cinerea, was 6.60 and 3.30mgL−1, respectively. The application of CFS on lemon and strawberry fruit artificially inoculated with P. digitatum and B. cinerea proved to be highly effective in the control of rot diseases. Compared to the positive control, in the CFS treated trials a significant decrease of disease incidence (up to 68.6% and 74.1%, in lemon and strawberry respectively) was recorded. It is also important to emphasize that the CFS treatment has drastically prevented the expansion of the fungal mycelium on the diseased fruits. The strong antifungal activity together with its already known characteristics related to high biodegradability and low toxicity, suggest that Iturin A could be a successful alternative to synthetic fungicide usage in postharvest disease control. However, it is important to do further research on large scale basis to evaluate the Iturin A production and extraction by B. subtilis ET-1 in order to study the possible formulations for its ideal application.

Biocontrol Agents Increase the Specific Rate of Patulin Production by Penicillium expansum but Decrease the Disease and Total Patulin Contamination of Apples

Synthetic fungicides are commonly employed for the control of postharvest diseases of fruits. However, due to health concerns about the use of these chemicals, alternative control methods including biocontrol based on antagonistic yeasts are gaining in popularity. In this study, we investigated the effects of two biocontrol yeasts, Rhodotorula mucilaginosa strain 3617 and Rhodotorula kratochvilovae strain LS11, on blue mold and patulin (PAT) contamination caused by Penicillium expansum strains PY and FS7 in artificially inoculated Fuji apples stored at 20°C for 9 days. To correlate the development of the P. expansum strains in yeast-treated and untreated apples with PAT production, we quantified their biomass in the infected fruits using a recently published quantitative real-time polymerase chain reaction method based on specific primers for patF, a gene from P. expansum that is involved in PAT biosynthesis. Both yeasts significantly reduced the disease incidence caused by the two strains of P. expansum up to 5–7 days of incubation, and lowered their biomass and the progression of symptoms up to 9 days. Interestingly, both yeasts strains increased the rate of PAT production (expressed as ng patulin/μg fungal DNA) by the two pathogenic strains. Nevertheless, both biocontrol agents reduced the total PAT contamination, especially in the case of P. expansum strain FS7, the higher PAT producer of the two tested P. expansum strains. Comparing between the yeast strains, R. kratochvilovae LS11 was more effective than R. mucilaginosa 3617 for the control of P. expansum.