Decay Of Apples Research Articles

Prevalence and Management of Post-harvest Rots of Apple in Himachal Pradesh

During a survey of post-harvest diseases of apple in Himachal Pradesh conducted during July to September 2021, fourteen different types of rots were observed. Among these, Penicillium expansum (blue mould) was most destructive with exclusive incidence of 43.8%. Surveys of different markets/stores of Himachal Pradesh revealed that the total losses due to apple decay at various locations varied from 7.80 to 21.93%. Ten important commercial varieties of apple were screened for their comparative susceptibility against fruit decay.Tydeman’s Early Worcester was found to be most tolerant to all the rot causing fungi with mean per cent rotting of 23.26%.Cow urine was found most effective in providing 79.21% growth inhibition of test fungi under study. The next best bio-products were Emblica officinalis (amla), Melia azadirach (darek) and Dodonaea viscose (mehandu) with per cent growth inhibition of 75.66, 73.59 and 68.48%, respectively. Under in vitro conditions, mancozeb (0.1%) was the most effective fungicide providing 84.83% growth inhibition. The efficacy of mancozeb as dip treatment at 0.1% concentration was judged to be significantly superior followed by 0.05% carbendazim with per cent control of 95.97 and 92.35%, respectively. Preharvest spray of mancozeb (0.3%) was highly effective in checking all the test fungi under different type of storage for 2 months. 1-methyl cyclopropene (MCP) fumigation of apple fruits immediately after harvesting for 12 hours was most effective in checking the test fungi under study providing 89.60% control.

Molecular characterization of apple endophytic bacteria and biological effect on Alternaria rot on apple

AbstractApple rot disease, caused by Alternaria alternata, is causing significant losses in apple production, especially in post‐harvest periods. Alternaria alternata, was isolated from rotten apple fruit of cv Amasya. Identification of the strain isolated from rotten apple fruit was made by ITS sequence and morphological analysis. In the present study, 58 different endophytic bacteria strains were isolated from apple fruit for use in apple rot disease control. Among the isolated strains, 26 endophyte strains were determined to inhibit the radial growth of mycelia of A. alternata in binary culture in PDA media. Based on 16S rRNA sequencing analysis, these antagonistic endophytic bacteria strains were identified as Bacillus ssp. Bacillus methylotrophicus (ib17) showed the highest significant inhibitory effect on the mycelial growth of A. alternata at a rate of 79.5% in PDA medium. The results of in vivo experiments showed that Bacillus licheniformis (ib20) achieved 100% biocontrol when endophyte bacterial strains were inoculated 24 h before the inoculation of A. alternata. When the three bacteria species and A. alternata were inoculated simultaneously, Bacillus myloliquefaciens (ib1), Bacillus licheniformis (ib21) and the Endophytic bacterium (ib16) showed the highest biocontrol efficacy against A. alternata at 81.8%. Furthermore, when the bacterial strains were inoculated at 24 h after inoculation of A. alternata, B. licheniformis (ib21) showed the highest biocontrol efficacy of 83.3% against the fungal pathogen compared to the controls. The endophytic bacterial strains produced fungal cell wall hydrolysing enzymes such as chitinase, cellulase, amylase and protease. According to the results of this study, apple endophytic bacteria are potential candidates to control apple decay caused by A. alternata through cell wall hydrolysing enzymes and reduce disease severity. However, the efficacy of the biological control was dependent on the applied time of epiphytic bacterial strains. Further research is needed on the biochemical mechanisms underlying the activity of these bacteria against A. alternata.

Avirulent Isolates of Penicillium chrysogenum to Control the Blue Mold of Apple Caused by P. expansum.

Blue mold is an economically significant postharvest disease of pome fruit that is primarily caused by Penicillium expansum. To manage this disease and sustain product quality, novel decay intervention strategies are needed that also maintain long-term efficacy. Biocontrol organisms and natural products are promising tools for managing postharvest diseases. Here, two Penicillium chrysogenum isolates, 404 and 413, were investigated as potential biocontrol agents against P. expansum in apple. Notably, 404 and 413 were non-pathogenic in apple, yet they grew vigorously in vitro when compared to the highly aggressive P. expansum R19 and Pe21 isolates. Whole-genome sequencing and species-specific barcoding identified both strains as P. chrysogenum. Each P. chrysogenum strain was inoculated in apple with the subsequent co-inoculation of R19 or Pe21 simultaneously, 3, or 7 days after prior inoculation with 404 or 413. The co-inoculation of these isolates showed reduced decay incidence and severity, with the most significant reduction from the longer establishment of P. chrysogenum. In vitro growth showed no antagonism between species, further suggesting competitive niche colonization as the mode of action for decay reduction. Both P. chrysogenum isolates had incomplete patulin gene clusters but tolerated patulin treatment. Finally, hygromycin resistance was observed for both P. chrysogenum isolates, yet they are not multiresistant to apple postharvest fungicides. Overall, we demonstrate the translative potential of P. chrysogenum to serve as an effective biocontrol agent against blue mold decay in apples, pending practical optimization and formulation.

Glycine Enhances Oxidative Stress Tolerance and Biocontrol Efficacy of Sporidiobolus pararoseus against Aspergillus niger Decay of Apples.

Apples are deeply loved by people because of their rich nutritional value, but they are susceptible to rotting. The use of antagonistic yeast is a promising method for controlling postharvest fruit diseases, but biocontrol efficacy of yeast will be weakened in environmental stress. In this study, the effects of glycine (Gly) on the oxidative stress tolerance and the biocontrol efficacy of Sporidiobolus pararoseus (S. pararoseus) against Aspergillus niger (A. niger) are discussed. Under the stimulation of H2O2, the yeast cells treated with Gly (1 mM) showed lower ROS content, less mitochondrial impairment and cellular oxidative damage, and the cell survival rate was significantly higher than Gly-untreated yeast. The yeast cells exposed to Gly significantly increased the activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and the content of glutathione (GSH). Notably, Gly-treated yeast cells had better biocontrol efficacy against A. niger in postharvest apples. The lesion diameter and decay incidence were reduced by 17.67 mm and 79.63% compared to the control, respectively, when S. pararoseus was treated with 1 mM Gly. Moreover, Gly-treated yeast increased the antioxidant enzymes activities and their gene expression were up-regulated in apples. These results indicated that 1 mM Gly not only reduced the oxidative damage of yeast, but also induced resistance-related enzymes of apples under oxidative stress, which contributed to enhancing the biocontrol efficacy of S. pararoseus against A. niger in apples.

Transcriptome analysis provides insights into potential mechanisms of epsilon-poly-L-lysine inhibiting Penicillium expansum invading apples

Penicillium expansum (P. expansum) is a harmful pathogenic mold responsible for huge postharvest losses in apples. Epsilon‐poly‐L‐lysine (ε-PL) is a non-toxic antiseptic peptide derived from Streptomyces albulus. Many food preservative strategies use ε-PL to suppress foodborne pathogens in condiments, cakes, fruit and vegetable juices. In the present research, ε-PL’s inhibitory effects against P. expansum in vitro and in apples were investigated. The molecular mechanisms of ε-PL inhibiting P. expansum in apples were investigated by transcriptome analysis. Results showed that doses of 600 mg L−1 of ε-PL could prevent the development of P. expansum in vitro and control blue mold decay in apples. Plausible mechanisms of ε-PL against P. expansum in apples include: (i) reduction of antioxidant potential, including decreasing the expression of genes encoding superoxide dismutase (SOD), catalase (CAT), glutathione s-transferase (GST), xanthine dehydrogenase (XDH), D-amino-acid oxidase (DAO), weakening ROS scavenging ability of P. expansum cells and causing oxidative damage to cell, (ii) weakening its virulence towards apples, including reducing the expression of genes coding for cell wall degrading enzymes (CWDEs) such as pectinase and cellulase, (iii) disrupting mitochondrial function of P. expansum, including reducing expression of several rate-limiting enzyme coding genes of energy metabolic pathways such as EMP, TCA cycle and oxidative phosphorylation, which interfered with the cells’ energy metabolism, leading to insufficient ATP synthesis, weakening P. expansum’s resistance to external stress, and finally slowing down the invasion process into apples, (ⅳ) damaging the membrane integrity of P. expansum, including reducing the expression of genes encoding diaphragm wall degradation enzymes, cytomembrane lipid and ergosterol synthetase, multi-drug transporter, and inhibiting the differentiation of conidia.

First Report of Fusarium avenaceum Causing Postharvest Decay of European Pear in Mid-Atlantic United States.

Fruit losses due to postharvest decay caused by several fungal species is a major challenge for pear production (Sardella et al. 2016). In December 2021, a European pear (Pyrus communis L.) 'Dawn' with brown, circular, watery, and sunken lesions was observed in cold storage at the USDA Appalachian Fruit Research Station in Kearneysville, West Virginia. Only 1 of 14 'Dawn' pears examined in cold storage had the described disease symptoms. The fruit was surface sterilized, and symptomatic tissue was transferred to potato dextrose agar (PDA) and incubated at 25°C under continuous light. The isolate was hyphal tip purified and propagated on PDA plates at 25°C. The colonies grew an average of 8 mm/day and produced fluffy white aerial mycelium and pigmented rings of golden yellow which then darkened to pink with a dark pink on the reverse. The isolate was also cultured in liquid basal medium with carboxymethyl cellulose (Moura et al. 2020) for 7 days at 25°C to promote macroconidia formation. Macroconidia were slightly falcate with a tapering apical cell, usually 2 to 4 septate, and on average 16.8 µm long by 2.8 µm wide. The isolate was identified as Fusarium spp. based on morphology. Identity of the isolate was confirmed through sequencing of the ITS and TEF1 gene region (Stielow et al. 2015). The ITS and TEF1 sequences were deposited in GenBank (OP007197 and OP007198). BLAST analysis of the ITS amplicon identified multiple Fusarium spp. with 100% identity and 100% query coverage including F. avenaceum KJ562378. BLAST analysis of the TEF1 amplicon showed 99% identity and 99-100% query coverage with F. avenaceum isolates KM189442 and MK512754. Organic Bartlett pears were surface sanitized with a 1% aqueous chlorine solution, rinsed with sterile water and dried in a laminar flow hood. Fruit were then wounded with a sterile nail (4 mm diameter x 4 mm depth) and inoculated with a 4 mm mycelial plug taken from a 7- to 10-day old culture on PDA and wrapped with Parafilm. Plugs taken from sterile PDA were used as a control. Inoculated fruit were stored at 25°C in fruit trays in plastic bins for 7 days. Six fruit composed a replicate, and the experiment was repeated for a total of two replications. Lesions developed within 48 hours and expanded to an average of 28.5 mm by day 7. No lesions were observed on control fruit. Symptoms observed on inoculated pears were the same as the decay observed on the original pear obtained from cold storage. Fungal colonies isolated from the lesions and cultured on PDA morphologically resembled the original isolate from the infected pear. In 2014, F. avenaceum was first reported in the United States to cause post-harvest decay of apples in Pennsylvania (Kou et al. 2014). In the Netherlands, F. avenaceum has been reported to cause postharvest decay of 'Conference' pears but was observed at low frequencies (1-5%) in packing-house surveys (Wenneker et al. 2016). Fusarium spp. was also recently found on European pears in Southern Oregon (KC and Rasmussen 2020). F. avenaceum can produce mycotoxins which is a concern for fruit processing (Munkvold et al. 2021). Monitoring for this pathogen to prevent losses and mycotoxin contamination of processed fruit products will be import for consumer safety. To our knowledge, this is the first report of F. avenaceum causing postharvest decay of European pear in the Mid-Atlantic region of the United States.

Transcriptomic analyses reveal robust changes in the defense response of apples induced by Hannaella sinensis

Research on yeast antagonists has recently demonstrated their safety and efficacy in effectively preventing apple postharvest infections. Our previous study has revealed that the antagonistic yeast Hannaella sinensis has shown control activity against blue mold decay in apples caused by Penicillium expansum. However, the molecular networks underlying H. sinensis-treated apple's disease control mechanisms are not explored. Hence, we aimed to uncover the molecular changes of apples treated with H. sinensis based on transcriptomic analysis. Differentially expressed genes of apples treated with H. sinensis were identified through RNA-seq (152 up-regulated and 1480 down-regulated DEGs) and bioinformatic analysis. Among the DEGs, significant numbers were annotated into apple defense-related pathways, such as plant-pathogen interaction, plant hormone signal transduction, phenylpropanoid biosynthesis, tyrosine metabolism, glycerolipid metabolism, and alpha-linoleic acid pathways related to resistance regulation. Our results indicated that H. sinensis could induce disease resistance in apples, which leads to increased protection against postharvest pathogens. The current study paves the way for further understanding the biocontrol mechanism of antagonistic yeast against postharvest infections by enhancing host defense.

Dynamic Mode Decomposition and Deep Learning for Postharvest Decay Prediction in Apples

The damages and diseases that may occur in apples during the storage and cannot be seen visually at early stages is a significant problem in precision agriculture leading to the loss of the lion share of crop. The difficulty of predicting postharvest degradation of apples while in storage is addressed in this article. For the prediction of postharvest decay zones, we used the Dynamic Mode Decomposition (DMD) method in conjunction with the Mask R-CNN model based on Convolutional Neural Networks (CNNs). For validating this idea we have designed a small greenhouse equipped with necessary sensors and actuators for simulating storage conditions for apples. We collected a dataset which includes 552 images of apples stored under the extreme temperatures and humidity. For DMD reconstructed images demonstrating the growth dynamics of decay in apples, the proposed approach achieves 0.999 Structural Similarity Index Measure (SSIM) and 66.813 Peak Signal to Noise Ratio (PSNR). Mask R-CNN predicted postharvest decay zones in apples with an Average Precision (AP) of 83.809% and F1-score with 83.307%. The proposed method is promising for enhancing food storage and postharvest control in precision agriculture since it is based on contactless sensing with video cameras.

Comparative Penicillium spp. Transcriptomics: Conserved Pathways and Processes Revealed in Ungerminated Conidia and during Postharvest Apple Fruit Decay.

Blue mold, caused by Penicillium spp., is an impactful postharvest disease resulting in significant economic losses due to reduced pome fruit quality and mycotoxin contamination. Using two Penicillium species with different levels of aggressiveness, transcriptomics were implemented in order to identify genes expressed during apple fruit decay and loci expressed in ungerminated conidia. Total RNA was isolated from ungerminated conidia and decayed apple fruit infected with P. expansum R19 or P. polonicum RS1. There were 2442 differentially expressed genes (DEGs) between the R19 and RS1 in apple. Comparisons within species between apple and conidia revealed 4404 DEGs for R19 and 2935 for RS1, respectively. Gene ontology (GO) analysis revealed differential regulation in fungal transport and metabolism genes during decay, suggesting a flux in nutrient acquisition and detoxification strategies. In R19, the oxidoreductase GO category comprised 20% of all DEG groups in apple verses conidia. Ungerminated conidia from both species showed DEGs encoding the glyoxylate shunt and beta-oxidation, specifying the earliest metabolic requirements for germination. This is the first study to identify pre-loaded transcripts in conidia from blue mold fungi, reveal unique genes between species expressed during apple decay, and show the expression dynamics of known fungal virulence factors. These findings will enable development of targeted approaches for blue mold abatement strategies.

Limiting the production of virulence factors as a mechanism of action for the control of Penicillium expansum by the Antarctic antagonistic yeast Debaryomyces hansenii F9D

Fungal decay, predominantly caused by Penicillium expansum, is the main cause of apple postharvest losses. To overcome this problem, synthetic fungicides are applied to fruit before storage. Public concern about this practice has raised interest in developing alternative biocontrol strategies for postharvest diseases. Debaryomyces hansenii F9D, a psychrotrophic Antarctic yeast, has been previously selected as a promising biocontrol agent due to its ability to reduce blue mold incidence in apples and pears. Previous in vitro studies indicated that the biocontrol mechanism of this yeast does not involve the production of antifungal metabolites or other inhibitory or competitive interactions with the pathogen. In this work, we conducted further studies in order to understand the interaction between Penicillium expansum and D. hansenii F9D within apple wounds. The growth of both microorganisms in apple wounds during cold storage was followed over time by q-PCR and viable cell counts. Scanning electron microscopy observations of co-inoculated and control wounds (inoculated only with the yeast or with the pathogen) were conducted to evaluate if the pathogen conidia could germinate in presence of the yeast and to determine the colonization patterns of P. expansum and the biocontrol yeast. Our results indicate that Debaryomyces hansenii F9D is able to prevent cold stored apples' wounds rot by inhibiting the virulence factors produced by the pathogen without impeding its growth. These findings provide circumstantial evidence for a new biocontrol mechanism associated with the prevention of fungal decay in apples by biocontrol yeasts during cold storage of fruit.

Study on the effect of Debaryomyces hansenii enhanced by alginate oligosaccharide against postharvest blue mold decay of apples and the physiological mechanisms involved

Blue mold decay is the most common disease during postharvest storage of apples caused by Penicillium expansum, leading to huge economic losses to the apple industry. Antagonistic yeasts are widely used in biological control, and organic compounds can be used as elicitors to induce antagonistic yeasts to further improve their biocontrol effect. In this study, we assessed the biocontrol efficacy of the antagonistic yeast, Debaryomyces hansenii, enhanced by alginate oligosaccharide (AOS) in controlling the postharvest decay of apples and studied the possible physiological mechanisms involved in this process. The results of this study were as follows: (1) AOS enhanced the biocontrol ability of D. hansenii against P. expansum infestation of apples. In the in vivo experiments, D. hansenii induced by 0.5% AOS significantly reduced the disease incidence and lesion diameter in apples, demonstrating good control of blue mold. When treated with D. hansenii-induced with AOS, the disease incidence rate of apples was only 21.6%, while that of yeast alone was 37.5%. (2) In the in vitro experiments, AOS significantly improved the inhibitory effect of D. hansenii on the germination rate, germ tube length, and colony diameter of P. expansum. The results suggested that AOS-induced yeast exhibited a certain inhibitory effect on the growth of P. expansum. (3) The activities of diseases resistance-related enzymes of apples treated with AOS-induced D. hansenii such as polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia-lyase (PAL) were increased compared to the yeast alone and the control group. Apart from that, the content of substances such as total phenols and flavonoids maintained the original level. These results suggest that the resistance of apples against pathogenic fungi may be improved by increasing the activities of disease resistance related enzymes activities of the fruit. In summary, the method of enhancing antagonistic yeast by AOS is very promising and efficient for improving biological control to reduce economic losses in the apple industry.

Study on the biocontrol effect and physiological mechanism of Hannaella sinensis on the blue mold decay of apples

Blue mold decay is a major postharvest disease of apples, causing considerable losses to the apple industry. In the early stage of this research, an antagonistic yeast, Hannaella sinensis, with a good control effect on the blue mold of apples, was selected. On this basis, the main purpose of this work was to study the biocontrol effect of H. sinensis on the blue mold of apples and the mechanisms involved. The results showed that H. sinensis could effectively control the blue mold decay of apples, reduce the rot rate and diameter, and the antagonistic effect strengthened with the increase of H. sinensis concentration (1 × 108 cells/mL). Further in vitro experiments proved that H. sinensis could significantly inhibit the spore germination and germ tube length of P. expansum. In addition, stable colonization of H. sinensis on apple wounds and surfaces confirmed the environmental adaptability and the ability to compete with other microbiota for nutrition and space. Moreover, H. sinensis induced the activities of resistance-related enzymes such as polyphenol oxidase (PPO), peroxidase (POD), ascorbate peroxidase (APX), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) in apples and the content of the coding genes corresponding to these enzymes was also higher than that of the control group. Our results indicate that H. sinensis treatment could induce the disease resistance of apples. In summary, H. sinensis served as a promising antagonistic yeast for the prevention and treatment of postharvest blue mold decay of apples.

Impact of vanillin on postharvest disease control of apple.

Apple fruits are susceptible to infection by postharvest fungal pathogens, which may cause fruit decay and severe economic losses. This study investigated the antifungal spectrum of vanillin against common decay pathogens of apple and explored the antifungal mechanisms of vanillin in vitro. In vivo experiments were carried out to evaluate the effects of vanillin on apple postharvest disease control and fruit quality. Moreover, the induced resistance mechanism of vanillin on apple fruit was preliminarily explored. The results showed that vanillin has broad-spectrum antifungal effects, especially on Alternaria alternata. Vanillin could significantly inhibit the growth rate, mycelium biomass, and spore germination of pathogenic fungi by increasing the cell membrane permeability and lipid peroxidation. Importantly, vanillin treatment reduced the incidence of apple decay caused by A. alternata and Penicillium expansum, and contributed to improve fruit quality. Further studies indicated that vanillin could induce elevation in the activities of defense-related enzymes in apple fruit, such as phenylalanine ammonia-lyase (PAL), chitinase (CHI) and β-1,3-glucanase (β-1,3-GA), and increase total phenols and flavonoids contents. Generally, these results suggest that vanillin may contribute to the induced resistance of apple fruits to pathogenic fungi. To conclude, the results of this research provide theoretical foundations for the application of vanillin in the control of apple postharvest decay caused by fungal pathogens.

Integrated transcriptomic and metabonomic analysis reveal mechanisms of disease resistance in apples induced by Wickerhamomyces anomalus

The antagonistic yeast Wickerhamomyces anomalus was reported to have a biocontrol efficacy against blue mold decay of apples, and possible physiological biocontrol mechanisms were investigated in our previous research. However, the molecular mechanisms related to the resistance response were unclear. In this study, the related molecular mechanisms of disease-resistance in apples induced by W. anomalus based on transcriptomic and metabonomic analysis were investigated. The results of the transcriptome data showed that W. anomalus induced the up-regulation of genes related to resistance, plant signal transduction, genes involved in regulating the synthesis of resistance related substances, and genes related to antioxidant and stress resistance. Integrated transcriptomic and metabonomic analysis indicated that multiple genes involved in the phenylpropane biosynthesis pathway, ubiquinone and other terpenoid-quinone biosynthesis pathway and phenylalanine metabolism pathway were up-regulated, and the contents of corresponding metabolites were also increased, so as to improve the disease resistance of apple fruit.

Application of Bioactive Coatings with Killer Yeasts to Control Post-Harvest Apple Decay Caused by Botrytis cinerea and Penicillium italicum.

A new method was proposed to produce alginate bio-films containing Pichia membranifaciens and Wickerhamomyces anomalus killer yeast to control the post-harvest fungal decay in organic apples caused by Botrytis cinerea and Penicillium italicum. Coatings with W. anomalus killer yeast effectively controlled the growth of P. italicum during storage at 22 °C. W. anomalus killer yeast incorporated in alginate reduced the P. italicum incidence from 90% (control) to 35% after 14 days of storage at 22 °C. Alginate biofilms with W. anomalus or P. membranifaciens also limited the incidence of the fungal decay of apples inoculated with B. cinerea compared with the control fruits, although the antagonistic capability against B. cinerea was lower than against P. italicum. The survival of W. anomalus cells in alginate coating was higher than P. membranifaciens. The incorporation of killer yeasts into alginate had no significant effect on the mechanical properties (tensile strength, percent elongation at break) of alginate coating, however, they increased the thickness of the biofilm. The bioactive coating reduced the fruit weight loss and had no significant effects on the fruit firmness during storage at 2 °C. As organic apples, produced without any synthetic fungicides, are especially prone to fungal decay during storage, the proposed alginate biofilms containing killer yeast seem to be a very promising solution by offering non-chemical, biological control of post-harvest pathogens.

Pre-harvest silicon spraying: Impact on decay, metabolism, and overall quality of ‘Galaxy’ apples after harvest and cold storage

New strategies to reduce apple decay and maintain fruit quality during postharvest with low environmental impact are crucial. Thus, we aimed to assess the effects of pre-harvest foliar silicon (Si) application on decay incidence, metabolism, and overall fruit quality of ‘Galaxy’ apples at harvest and after cold storage. The experiments were performed during four seasons in commercial orchards and stored in cold rooms, and the following treatments were evaluated: 0, 1.12, 2.24, and 3.36 g L−1 of foliar sodium silicate (SS) (2015-16 and 2017-18 seasons), 0, 1.68, and 3.36 g L−1 of foliar SS (2018-19 and 2019-20 seasons), and 0, 1.68, and 3.36 g L−1 of sodium metasilicate (2019-20 season). Upon being harvested, the fruit were kept in cold storage. Foliar Si treatment of ‘Galaxy’ apples did not reduce decay incidence and severity after cold storage, and in some cases, it increased decay incidence. Moreover, Si treatment did not increase physiological disorders such as russeting, bitter pit, flesh breakdown, and mealiness. In some periods, Si treatment enhanced ripening metabolism as supported by higher ethylene biosynthesis, ACC oxidase activity, and reduced flesh firmness. Therefore, foliar Si application does not provide benefits to ‘Galaxy’ apple decay control.

Extraction and classification of apple defects under uneven illumination based on machine vision

AbstractThe extraction and classification of different kinds of defects can achieve a more sophisticated classification of apples. In this study, a region of interest (ROI) extraction algorithm based on background separation, brightness correction, and the global threshold was designed for the extraction of apple decay and bruise under uneven light conditions. After brightness correction, we calculate the average gray value of the apple region and multiply the value by 0.8 as the threshold. In this way, the threshold of different apple images can be determined automatically without a manual setting. After extracting ROI, we realized the classification of the two kinds of defects by extracting texture features. Based on the selected texture features, the support vector machine discriminant models were established. The accuracy of the model based on angular second moment was 94.8% and the model based on entropy was 94.7%. The total time from ROI extraction to classification was approximately 1.2 s. The results showed that this extraction and classification process had application prospects in practical detection classification.Practical ApplicationsUngraded fruits were not easy to store, transport, or sell at a price based on quality. The classification was directly related to fruit packaging, transportation, storage and sales of the results, and benefits, so it was very important to carry out fruit classification. Machine vision technology can achieve objective and nondestructive rapid detection. Many studies had achieved extraction of defective parts. However, they directly classified apples with defects into one category without further classification of types of the defects. In many classification standards, such as GBT10651‐2008, they need to classify apples more finely according to the defect types. This study achieved extraction and classification of different kinds of apple defects by machine vision technology and achieved a satisfactory accuracy and detection speed, which provided theoretical support for the realization of strict and fine classification of apple in industrial applications in the future.

Apple-based coatings incorporated with wild apple isolated yeast to reduce Penicillium expansum postharvest decay of apples

The aim of this work has been to prevent the growth of Penicillium expansum on the surface of apples by means of the use of biocontrol agents in combination with edible coatings. For that, Metschnikowia pulcherrima yeast isolated from wild apples was incorporated in edible film matrices based on pectins, cellulose ethers with and without the addition of liquid culture medium (yeast extract and glucose) and apple pomace residues.The viability and biocontrol activity of the yeast incorporated in the films were evaluated after film drying process and after being stored for 21 days at 10 °C. Furthermore, the matrix that exhibited the best results was applied as a coating on apples artificially inoculated with P. expansum in order to evaluate its antifungal activity against P. expansum during storage and to prevent the production of its mycotoxin, the patulin. M. pulcherrima remained viable in films after drying step and after 21 days storage, but viability depended on the matrix composition, being lower in pectin films and higher in apple pomace films. The highest antimicrobial activity in vitro was observed in methylcellulose films supplemented with yeast extract and glucose (YEG), and in apple pomace residues films, matrix which was therefore selected to be applied as coatings on apples inoculated with P. expansum. The results proved that bioactive coatings significantly reduce P. expansum growth and patulin production during storage. The results obtained in this work give added value to the apple industry residues which, in combination with apple isolated M. pulcherrima can be applied as coatings on apples to provide protection against blue mold and its mycotoxin as an alternative of postharvest disease management.

Occurrence and Characterization of Penicillium Species Isolated from Post-Harvest Apples in Lebanon.

The apple is one of the most important fruit tree crops in the Mediterranean region. Lebanon, in particular, is among the top apple producer countries in the Middle East; however, recently, several types of damage, particularly rot symptoms, have been detected on fruits in cold storage. This study aims to identify the causal agents of apple decay in Lebanese post-harvest facilities and characterize a set of 39 representative strains of the toxigenic fungus Penicillium. The results demonstrated that blue mould was the most frequent fungal disease associated with apples showing symptoms of decay after 3–4 months of storage at 0 °C, with an average frequency of 76.5% and 80.6% on cv. Red and cv. Golden Delicious apples, respectively. The morphological identification and phylogenetic analysis of benA gene showed that most Penicillium strains (87.2%) belong to P. expansum species whereas the remaining strains (12.8%) belong to P. solitum. Furthermore, 67.7% of P. expansum strains produced patulin when grown on apple puree for 14 days at 25 °C with values ranging from 10.7 mg kg−1 to 125.9 mg kg−1, whereas all P. solitum did not produce the mycotoxin. This study highlights the presence of Penicillium spp. and their related mycotoxin risk during apple storage and calls for the implementation of proper measures to decrease the risk of mycotoxin contamination of apple fruit products.

Effect of Rhodotorula mucilaginosa on patulin degradation and toxicity of degradation products

ABSTRACT Rhodotorula mucilaginosa is an antagonistic yeast for which our research team has recently reported interesting biocontrol activities against blue mould decay of apples and a strong ability to decrease the patulin concentration in vivo. However, the possible mechanisms of patulin degradation by R. mucilaginosa and the toxicity of patulin degradation products remain unclear. In this study, the effect of R. mucilaginosa on patulin degradation and toxicity of degradation products were investigated, the results showed that viable cells of R. mucilaginosa are essential to patulin degradation. Also, R. mucilaginosa eliminated patulin without adsorbing it through its cell wall. The extracellular metabolites of R. mucilaginosa stimulated by patulin showed little degradation activity for patulin. Cycloheximide addition into the medium significantly decreased the patulin degradation capacity of R. mucilaginosa cells. The main patulin degradation product by R. mucilaginosa was ascladiol, which was proved non-toxic to human hepatoma (HepG2) cells at 0.625–10 g/mL. Furthermore, toxicological analysis using a confocal laser scanning microscope revealed that the degradation product induced cellular apoptosis to a lesser extent than patulin itself. This result offers an innovative method to detoxify patulin and limit the risks of patulin in fruits and vegetables using R. mucilaginosa.