Stored Apples Research Articles

Integral evaluation for intermittent cold storage of apples by using mathematical modeling

AbstractThis study proposes an integrated approach to evaluate the efficiency of intermittent warming (IW) on cooling rate, uniformity, energy efficiency, mass loss, and the development of CIs by combining experiment and computational fluid dynamics (CFD) modeling. The results show that the cooling homogeneity and mass loss increases with increasing the warming duration and frequency, although the incidence of chilling injuries (CIs) and energy consumption decrease under these conditions. Near the bottom of the pallet, CIs increased and mass loss decreased because of the higher cooling rate of fruit in this zone. The accuracy of the CFD simulations was confirmed by a good agreement with experiments. The root‐mean‐square error and mean absolute percentage error for fruit temperature were 0.879°C and 21.42%, respectively.Practical applicationsReducing energy consumption and chilling injuries (CIs) is vital for improving the overall economic benefits of the cold chain and maintaining poststorage quality in fresh fruit. This research provides a reliable theoretical and experimental basis for improving the efficacy of IW and for ensuring optimum IW treatment and thereby minimizing energy consumption and CIs during fruit storage.

Biological method based on track membranes to form controlled gaseous media for fruit cold storage

The article proposes a biological method based on the use of gas-selective track membranes to form a modified gas atmosphere, considering the respiration rate of fruit. The work aims to study the change in the respiration rate of apples depending on the variety and storage time to substantiate the formation of the gas medium composition depending on the respiration rate of the fruit and the area of track membranes, and to study the kinetics of oxidation reactions of biologically active substances during cold storage of apples. The research is based on autumn apple varieties: Grushovka Yudicheva, Kordonovka and Pepin Shafranny. We have obtained the kinetic curves of changes in the content of mono- and disaccharides, ascorbic and organic acids in autumn apple varieties depending on the gas composition in terms of oxygen and carbon dioxide content, as well as the duration of fruit storage using track membranes. For maximum quality preservation, nutritional and biological value of the studied apple varieties at t = (3 ± 1) °C, we have determined a recommended composition of the controlled gas atmosphere: oxygen concentration - (5.2 ± 0.1%), carbon dioxide - (3.6 ± 0.1%). Controlled atmosphere is created using a gas-selective composite membrane with an area of 14-22 cm2/kg, depending on the variety and respiration rate.

An assessment of the air quality in apple warehouses: new records of Aspergillus europaeus, Aspergillus pulverulentus, Penicillium allii and Penicillium sumatraense as decay agents.

Airborne fungi are one of the major components of aeromycobiota known to produce several fungal diseases in fruits. Their presence in indoor environment of warehouses may limit the storage period of apples. Qualitative and quantitative analyses of airborne fungal spores were conducted using gravity settling techniques to detect fungal airspora present in the atmosphere of two apple warehouses in Tunisia. In this study, 375 fungal isolates were obtained and purified. Phylogenetic analysis of calmodulin, beta-tubulin and ITS regions coupled with phenotypic characterization helped to identify 15 fungal species. Penicillium exhibited the highest diversity with ten species detected (Penicillium allii, P. chrysogenum, P. citrinum, P. expansum, P. italicum, P. polonicum, P. solitum, P. steckii, P. sumatraense and P. viridicatum), followed by four species of Aspergillus genus (Aspergillus europaeus, A. flavus, A. niger and A. pulverulentus) and Alternaria alternata. In vivo experiments confirmed the pathogenicity of 13 species at room temperature and under cold-storage conditions. Among them, A. europaeus, A. pulverulentus, P. allii and P. sumatraense were described for the first time as pathogens on apples. The present study identified the major airborne fungi associated with postharvest rot in apple storage facilities in Tunisia and may help in efficient control of postharvest and storage fruit diseases.

A metagenomic approach to assess Neofabraea infection and dynamics on stored apples

ISHS IV International Symposium on Postharvest Pathology: Next Generation Innovation and Commercial Solutions for Postharvest Pathology to Reduce Losses, Enhance Quality, and Ensure Product Safety A metagenomic approach to assess Neofabraea infection and dynamics on stored apples

SafePod: A respiration chamber to characterise apple fruit response to storage atmospheres

During long-term storage of apples, detection of low O2 stress is used to optimise low O2 storage regimes for dynamic controlled atmosphere (DCA) storage. Monitoring respiratory characteristics, specifically the respiratory quotient (RQ), provides a tool to achieve this. The objectives of this study were to evaluate protocols to monitor response of apple consignments to low O2 using a respiration chamber, the SafePod, designed for use in commercial stores and research laboratories, and to compare the RQ response to changes in chlorophyll fluorescence (CF) yield from the fruit skin as used in DCA-CF.Protocols to identify the lowest oxygen limit (LOL), the O2 concentration below which RQ rises, were tested using ‘Braeburn’ (sensitive to low O2) and ‘Gala’ (less sensitive to low O2). A protocol that allows fruit to acclimatise at each O2 concentration takes several weeks and is therefore not practical for commercial use. A rapid profile without fruit acclimatisation can be completed in 2–3 days. Although this underestimates RQ values, and results in an increase in RQ at a higher O2 concentration than observed for acclimatised fruit, the rapid RQ protocol provides a practical method to compare response of apple consignments between cultivars, orchards and seasons. By the rapid protocol, the LOL of ‘Braeburn’ consignments was near 0.6 kPa and of ‘Gala’ consignments was near 0.2 kPa, consistent with detection of alcoholic taints below the LOL in each case. The RQ response using the SafePod was consistent with increase in CF yield using HarvestWatch™.Fruit respiration rates change through the storage season, including a substantial decrease over the first 2 months after harvest. As RQ response is affected by respiration rate, accurate comparison of consignments depends on profiles being measured at the same stage in the storage season. It is more difficult to determine the LOL by RQ profiling later in the season when respiration rates are lower.

Identification of the apple spoilage causative fungi and prediction of the spoilage degree using electronic nose

AbstractApple is resistant to storage, but it is susceptible to fungal infection during transportation and storage, resulting in serious losses after harvest. A convenient and nondestructive monitoring method for fungi‐inoculated apples was proposed in this research. Four dominant spoilage fungi, including Aspergillus niger, Penicillium expansum, Penicillium chrysogenum, and Alternaria alternata, were inoculated on apple samples. The volatile information of samples with different degrees of spoilage was obtained by gas sensors. The pattern recognition methods were compared to classify the fungi and degrees of spoilage. Back propagation‐artificial neural networks (BP‐ANN) had the best identification model result with the highest recognition rates of 95.62 and 99.58% for fungi and spoilage degrees, respectively. The variable selection methods were employed, and variables of the gas sensors data for the prediction of apple spoilage area were optimized. The best prediction models of Aspergillus niger, Penicillium expansum, Penicillium chrysogenum, and Alternaria alternata were 0.854, 0.939, 0.909, and 0.918, respectively. The results show that the gas sensors can be used as a nondestructive technique in apple fungi infection evaluation. This proposed fruit spoilage detection technology is expected to provide a reference for the early detection of apple spoilage to promote food quality and safety inspection.Practical ApplicationsThis research used gas sensors to identify the four main spoilage fungi of apples and predicted the spoilage degree of apples using established prediction models. The apple spoilage detection method adopted in this research provides a reference for the early detection of fruit spoilage, which is helpful for apple storage and reduces the economic loss caused by corruption. It is an important measure to help ensure the economic benefits of apple and provide consumers with a large number of high‐quality apple products.

Changes in the Biochemical Composition and Physicochemical Properties of Apples Stored in Controlled Atmosphere Conditions

Apples are an important component of the diet and are used in the food industry in the production of food products and beverages. The aim of the study was to determine the changes in the biochemical composition and physicochemical properties of apples stored in a controlled atmosphere. We studied the biochemical composition (sugars, ascorbic acid, soluble solids, and titratable acidity) and physicochemical properties (color coordinates, peel, and flesh firmness) in the apple samples before placing them in the controlled atmosphere chambers and at the end of the experiment 8 months later. The total content of sugars and soluble solids was found to increase in the samples of apples stored in I to VIII conditions. The study showed a decrease in titratable acidity in apple samples of all cultivars stored in I to VIII conditions. The values of C*, L*, a*, and b* co-ordinates of apple colors were evaluated. Apple samples stored in VI conditions were the lightest color, and their lightness was close to that of fresh fruit. The firmness of apple peel samples of the ‘Sampion’ cultivar stored in I and III–VI conditions increased. The study is valuable and proves that, under the studied conditions, it is possible to extend the time of the provision of apples to the consumers with minimal changes in their chemical composition and nutritional value.

Alleviation of Postharvest Skin Dimpling of MN55 Apple Fruit and a Possible Association with Apple stem pitting virus

MN55 is an apple (Malus ×domestica Borkh.) cultivar recently released by the University of Minnesota apple breeding program, with fruit marketed in the U.S. as Rave®. When stored for 4 months at 0 to 4 °C, MN55 fruit can develop several storage disorders, including skin dimpling. Skin dimpling incidence was greater for fruit harvested 1 week later than those harvested earlier. Dimpling was not alleviated by prestorage treatments of 1-methylcyclopropene or diphenylamine or by holding fruit at room temperature for 1 day before long-term cold storage. However, dimpling incidence was very low when fruit were stored at 6 to 7 °C. Because viruses have been implicated in other fruit dimpling disorders, the presence of viruses in MN55 leaves and fruit was studied. Apple stem pitting virus (ASPV) was detected by microscopy, reverse transcriptase polymerase chain reaction (RT-PCR) methodology, and high throughput sequencing (HTS) in peel of fruit from MN55 trees that exhibited skin dimpling after 4 months of storage at 0 to 1 °C. ASPV was also detected in supermarket-purchased fruit of other cultivars with noticeable skin dimpling. Although ASPV was not conclusively demonstrated to cause skin dimpling in our work, its prevalence indicates that further investigations are warranted to determine the relationship between viruses and skin deformities in stored apples.

Dynamic changes of antioxidants and fermentative metabolites in apple peel in relation to storage, controlled atmosphere, and initial low oxygen stress

Storage of apples (Malus × domestica, Borkh.) in controlled atmosphere (CA) and/or the application of initial low oxygen stress (ILOS) are very effective in controlling postharvest disorders as bitter pit and superficial scald. This work aims to evaluate the effect of CA-storage and ILOS on the stress-related compounds of apple peel and to deepen the knowledge about the possible role of the antioxidant defense system against postharvest disorders. Fermentative metabolites, ascorbate (ASA), glutathione (GSH), total ascorbate (T-ASA) and total glutathione (T-GSH), ethylene, α-farnesene, conjugated trienols (CTols), as well as standard maturity indices, were monitored on the peel of apples (cv Red Chief) subjected or not to ILOS and stored 120 days in air or CA. CA-storage caused a reduction of conjugated trienols and ethylene production in Red Chief fruit compared to storage in air. ILOS induced an increase in the production of fermentative metabolites, especially when coupled with CA-storage, but the observed increase in ethanol concentration did not affect ethylene production. ILOS pretreatment and CA-storage induced higher T-GSH and GSH content in the peel of Red Chief fruit. In particular, ILOS caused a temporary shift of GSH towards its oxidated form, which finally resulted in an induction of GSH biosynthesis. Given the positive effect of ILOS on the GSH and T-GSH content, we hypothesize that the peel antioxidant compounds might play some role in the protection against postharvest disorders.

Variation of Triterpenes in Apples Stored in a Controlled Atmosphere.

Apples are seasonal fruits, and thus after harvesting apples of optimal picking maturity, it is important to prepare them properly for storage and to ensure proper storage conditions in order to minimize changes in the chemical composition and commercial quality of the apples. We studied the quantitative composition of triterpenic compounds in the whole apple, apple peel and apple flesh samples before placing them in the controlled atmosphere (CA) chambers, and at the end of the experiment, 8 months later. HPLC analysis showed that highest total amount of triterpenic compounds (1.99 ± 0.01 mg g−1) was found in the whole apple samples of the ‘Spartan’ cultivar stored under variant VIII (O2—20%, CO2—3%, N2—77%) conditions. Meanwhile, the highest amount of triterpenic compounds (11.66 ± 0.72 mg g−1) was determined in the apple peel samples of the ‘Auksis’ cultivar stored under variant II (O2—5%, CO2—1%, N2—94%) conditions. In the apple peel samples of the ‘Auksis’ cultivar stored under variant I (O2—21%, CO2—0.03%, N2—78.97%) conditions, the amount of individual triterpenic compounds (ursolic, oleanolic, corosolic, and betulinic acids) significantly decreased compared with amount determined before the storage. Therefore, in the apple flesh samples determined triterpenic compounds are less stable during the storage under controlled atmosphere conditions compared with triterpenic compounds determined in the whole apple and apple peel samples.

The Efficacy of Green Synthesized Nanosilver in Reducing the Incidence of Post-Harvest Apple Fruit Brown Rot.

This study aimed to green synthesize nanosilver (AgNPs) using black tea extract and use it as a nanopreservative to increase the shelf life of stored apple fruits. Ultraviolet visible absorption (UV–vis) analysis of AgNPs recorded two λ max values at 260 and 452 nm. Transmission electron microscope and dynamic light scattering analyses showed that AgNPs are spherical in shape and have an average size of 20 and 170.6 nm, respectively, with a zeta potential of −20.06 mV. An in vitro assay confirmed the antifungal potential of AgNPs against M. fructigena when applied at 200 mg/L and preincubated for 4 days, reducing the radial growth by 96.1%. At the same dose and preincubation period, AgNPs caused a significant reduction in the diameter and fresh weight of brown rotted lesions in apple fruits artificially coinoculated with the pathogen by 77.4% and 84.4%, respectively. AgNPs caused the leakage of proteins and DNA from M. fructigena conidia and did not express cytotoxicity against the human HaCaT cell lines. Accordingly, green synthesized AgNPs are eco-friendly and economical and do not pose harm to human health; thus, they could be used as an effective nanopreservative in apple fruit stores to reduce the incidence of brown rot disease.

Prevalence of Listeria Species on Food Contact Surfaces in Washington State Apple Packinghouses.

The 2014 caramel apple listeriosis outbreak was traced back to cross-contamination between food contact surfaces (FCS) of equipment used for packing and fresh apples. For Washington state, the leading apple producer in the United States with 79% of its total production directed to the fresh market, managing the risk of apple contamination with Listeria monocytogenes within the packing environment is crucial. The objectives of this study were to determine the prevalence of Listeria spp. on FCS in Washington state apple packinghouses over two packing seasons and to identify those FCS types with the greatest likelihood to harbor Listeria spp. Five commercial apple packinghouses were visited quarterly over two consecutive year-long packing seasons. A range of 27 to 50 FCS were swabbed at each facility to detect Listeria spp. at two sample times, (i) postsanitation and (ii) in-process (3 h of packinghouse operation), following a modified protocol of the FDA's Bacteriological Analytical Manual method. Among 2,988 samples tested, 4.6% (n = 136) were positive for Listeria spp. Wax coating was the unit operation from which Listeria spp. were most frequently isolated. The FCS that showed the greatest prevalence of Listeria spp. were polishing brushes, stainless steel dividers and brushes under fans/blowers, and dryer rollers. The prevalence of Listeria spp. on FCS increased throughout apple storage time. The results of this study will aid apple packers in controlling for contamination and harborage of L. monocytogenes and improving cleaning and practices for sanitation of the FCS on which Listeria spp. are the most prevalent.IMPORTANCE Since 2014, fresh apples have been linked to outbreaks and recalls associated with postharvest cross-contamination with the foodborne pathogen L. monocytogenes These situations drive both public health burden and economic loss and underscore the need for continued scrutiny of packinghouse management to eliminate potential Listeria niches. This research assesses the prevalence of Listeria spp. on FCS in apple packinghouses and identifies those FCS most likely to harbor Listeria spp. Such findings are essential for the apple-packing industry striving to further understand and exhaustively mitigate the risk of contamination with L. monocytogenes to prevent future listeriosis outbreaks and recalls.

Cultivar discrimination of stored apple seeds based on geometric features determined using image analysis

Digital image analysis can allow determining the features of seeds and their interpretation in a fast, inexpensive, and non-destructive way. The research aimed to develop discriminative models based on geometric features to distinguish seeds belonging to different apple cultivars. Images of seeds of apples ‘Gala’, ‘Jonagold’ and ‘Idared’ were acquired using a flatbed scanner. The linear dimensions and shape factors were calculated, and after attribute selection, they were used for the discriminant analyzes of seeds for ‘Gala’ with ‘Idared’, ‘Gala’ with ‘Jonagold’, ‘Idared’ with ‘Jonagold’ and ‘Gala’ with ‘Idared’ with ‘Jonagold’ with the use of discriminative classifiers from Bayes, Function, Meta, Rules and Decision Trees groups. In the case of models build based on selected linear dimensions, the accuracy of discrimination was equal up to 84% for distinguishing seeds of all three apple cultivars for the J48 classifier from Decision Trees and 93% for analysis of ‘Gala’ and ‘Idared’ for the J48 from Decision Trees. The slightly lower correctness of up to 82% for discrimination of ‘Gala’, ‘Idared’ and ‘Jonagold’, Multi Class Classifier) and 90% (‘Gala’ and ‘Jonagold’, J48) were obtained for models build based on selected shape factors. The analyzes performed based on sets including selected combined linear dimensions and shape factors of seeds provided the correctness of up to 86% for the discrimination of three apple seed cultivars (J48) and 91% (‘Gala’ and ‘Jonagold’, J48). The results can be used in practice for the assessment of the authentication of seeds of apple cultivars with high probability.

1H-cyclopropabenzene and 1H-cyclopropa[b]naphthalene fumigation downregulates ethylene production and maintains fruit quality of controlled atmosphere stored ‘Granny Smith’ apple

The ‘Granny Smith’ is a commercial apple cultivar in Western Australia and popular in the apple world as well, for its unique green colour and flavour. The effects of two new ethylene antagonists namely 1H-cyclopropabenzene (BC) and 1H-cyclopropa[b]naphthalene (NC), as well as 1-methylcyclopropene (1-MCP) on ethylene production, rates of respiration and fruit quality were investigated in controlled atmosphere (CA) stored ‘Granny Smith’ apple. The apple fruit were fumigated with 1 μM BC (0.09 μL.L−1) or 1 μM NC (0.14 μL.L−1) or 18 μM (1 μL.L−1) 1-MCP for 18 h at room temperature (20 ± 2 °C and 65 ± 5% RH). Following 90 d and 120 d of CA storage (2.5 ± 0.64% O2 and 1.3 ± 0.45% CO2 at 0 ± 1 °C), fumigation treatments with 1-MCP, NC and BC effectively suppressed and delayed climacteric peaks of ethylene and respiration as compared to the control fruit. The 1-MCP treatment was relatively more efficient in reducing the rates of ethylene and respiration climacteric peaks than BC and NC. But all the treatments reduced physiological loss of weight (PLW) (up to 1.38 times) and maintained higher fruit firmness (up to 1.16 times), total phenols (up to 1.53 times) and ascorbic acid (up to 1.15 times), compared to the control, following the CA storage period. Therefore, BC and NC possess the potential to act as ethylene antagonists in CA stored ‘Granny Smith’ apples to retard fruit ripening process and maintain the fruit quality. The effects of different concentrations of BC and NC in antagonising the ethylene action in different cultivars warrants further investigation in CA stored apple fruit.

Evaluation of apple varieties of the Sverdlovsk horticultural breeding station according to the ethylene biosynthesis genes using molecular markers

One of the directions of apple breeding in the Middle Urals is the development of varieties with a long-term storability. The ability of apples to maintain their consumer qualities for a long period is one of the most important indicators of the variety. A significant role in the storage of apples is played by the amount of ethylene produced in them. The paper presents the results of identification of genes involved in the control of ethylene biosynthesis in apple varieties selected by the Sverdlovsk horticultural breeding station. A total of 21 apple varieties were analyzed. The main objective of the study was to detect Md-ACO1-1 and Md-ACS1-2 alleles in the homozygous state. The combination of these alleles in one genotype reduces the production of ethylene in fruits, which contributes to their long-term storability. The analysis showed the availability of polymorphism in the two studied genes. The Md-ACO1 gene is characterized by the availability of two alleles in most varieties. The homozygous Md-ACO1-1 allele was identified in the Isetskoe pozdnee variety. Analysis of the Md-ACS1 gene revealed the predominance of the Md-ACS1-1 allele form. The Md-ACS1-2 allelic form was observed only in heterozygous samples. No combination of Md-ACO1-1 and Md-ACS1-2 alleles was found in the homozygous state. However, heterozygous forms are also of interest for breeding. They can serve as a source of a character of reduced ethylene biosynthesis when creating varieties with a long-term storability. Such varieties are Sokol yasnyy, Aksena, Rozovatoe zimnee, Sverdlovchanin, Isetskoe pozdnee, Blagaya vest'. The comparison of fruit storage periods and the genotype of the variety has been made. Allelesassociated with a reduced level of ethylene biosynthesis are typical both for the varieties with low and high storability.

Flesh firmness examination of scab-resistant apple varieties in a storage experiment

Of the different physical characteristics of fruits, one of the most essential qualities is flesh firmness, as is an important parameter when selling fresh apples, processing the fruit (processing industry) and during its storage. In the scope of our research, we examined five apple varieties originating from the Derecske horticultural site of KITE cPlc. in 2016. The plantation was planted to be suitable for intensive apple production. Samples were collected at the time of maturity (August-October) of the given variety. The five examined apple varieties (Gaia, Isaaq, Modí, Smeralda and Fujion) are all resistant to apple scab (fungal disease caused by Venturia inaequalis). The two-month storage experiment was conducted at 16-17 °C, which had an aggressive effect on our stored apples. Flesh firmness, weight and diameter were measured on three dates for each of the five apple varieties. Our results were evaluated using IBM SPSS Statistics 20 software. We aimed to compare flesh firmness, weight and diameter of the five apple varieties and their changes during storage. Isaaq (86.34 N/cm2), Modí (94.06 N/cm2) and Fujion (84.90 N/cm2) had outstanding initial flesh firmness results. The Modí apple variety provided the best storage parameters.

Efficacy of Essential Oil and Hydrosol Extract of Marrubium vulgare on Fungi Responsible for Apples Rot

Background: The microorganisms such as Penicillium expansum and Botrytis cinerea are wellknown pathogens in apples during postharvest. So, to protect apples from these pathogens, chemical control methods were exercised. Introduction: The main objective of this work was to study the chemical composition and the in-vitro and in-vivo antifungal properties of essential oil and hydrosol extract of Marrubium vulgare. Methods: In this work, the air-dried aerial parts of Marrubium vulgare were hydrodistilled in a Clevengertype apparatus. The essential oil and hydrosol extract isolated were analyzed using Gas Chromatography (GC) and Mass Spectrometry (GC/MS). The in-vitro antifungal activity of the both extracts was investigated against Botrytis cinerea, Penicillium expansum and Alternaria alternata fungi using radial growth technique. The effect of the essential oil and hydrosol extract on disease development of apple caused by Penicillium expansum in the in-vivo conditions was assessed. Results: The essential oil of Marrubium vulgare was characterized principally by E-β-caryophyllene (23.5%), E-β-farnesene (21%), α-humulene (14.8%), β-bisabolene (11.1%), caryophyllene oxide (6.8%) and phytol (3.1%). While, the methyl-eugenol (65.5%), α-Bisabolol (12.5%), linalool (6.5%) and caryophyllene oxide (6.2%) were the major compounds of hydrosol extract. The result of in-vitro antifungal activity of hydrosol extract showed an interesting antifungal inhibition against Botrytis cinerea, Penicillium expansum and Alternaria alternata with percentage inhibition ranging from 77% to 89% at low concentration of 0.15 mL/L. The essential oil was found to inhibit the growth of Penicillium expansum in a dose-dependent manner, with a percentage inhibition of 100% at 30 mL/L. Furthermore, essential oil and hydrosol extract have demonstrated promising in-vivo antifungal activity to control infection of apples by Penicillium expansum up to 25th day of storage, compared with the control. Conclusion: The preventive and protective effects of essential oil and hydrosol extract could be exploited as an ideal alternative to synthetic fungicides for using the protection of stored apples from fungal phytopathogens.

Global transcriptomic responses orchestrate difenoconazole resistance in Penicillium spp. causing blue mold of stored apple fruit

BackgroundBlue mold is a globally important and economically impactful postharvest disease of apples caused by multiple Penicillium spp. There are currently four postharvest fungicides registered for blue mold control, and some isolates have developed resistance manifesting in decay on fungicide-treated fruit during storage. To date, mechanisms of fungicide resistance have not been explored in this fungus using a transcriptomic approach.ResultsWe have conducted a comparative transcriptomic study by exposing naturally-occurring difenoconazole (DIF) resistant (G10) and sensitive (P11) blue mold isolates to technical grade difenoconazole, an azole fungicide in the commercial postharvest product Academy (Syngenta Crop Protection, LLC). Dynamic changes in gene expression patterns were observed encompassing candidates involved in active efflux and transcriptional regulators between the resistant and sensitive isolates. Unlike other systems, 3 isoforms of cytochrome P450 monoxygenase (CYP51A-C) were discovered and expressed in both sensitive and resistant strains upon difenoconazole treatment. Active efflux pumps were coordinately regulated in the resistant isolate and were shown to mediate the global resistance response as their inhibition reversed the difenoconazole-resistant phenotype in vitro.ConclusionsOur data support the observation that global transcriptional changes modulate difenoconazole resistance in Penicillium spp. While the dogma of CYP51 overexpression is supported in the resistant isolate, our studies shed light on additional new mechanisms of difenoconazole resistance on a global scale in Penicillium spp. These new findings broaden our fundamental understanding of azole fungicide resistance in fungi, which has identified multiple genetic targets, that can be used for the detection, management, and abatement of difenoconazole-resistant blue mold isolates during long-term storage of apples.

Content of major phenolic compounds in apples: Benefits of ultra-low oxygen conditions in long-term storage

The effect of ultra-low oxygen (ULO) conditions applied during long-term storage of apples to preserve content of phenolic compounds has been studied. Contents of phenolics including gallic acid, chlorogenic acid, epicatechin, quercitrin, rutin, phloridzin, and phloretin in ten apple cultivars were determined immediately after the harvest and their changes monitored after three, five, and seven months storage in a cooled warehouse and under ULO conditions. Fast HPLC separation with UV detection using core-shell C18 column and gradient elution was applied. Different apple cultivars were tested and statistical analysis performed based on multiple hypothesis t-test with p-value cut-off adjusted by Holm-Bonferroni method. Principal component analysis was applied to further support the observations. Our results proved the benefits of ULO storage conditions for cultivars intended for longer storage. However, ULO storage conditions did not have a significant effect during short-term storage. Most of the cultivars bred for short-term storage stored in cooled or ULO conditions did not exhibit any statistical difference in the phenolics content.

The use of seed texture features for discriminating different cultivars of stored apples

The aim of this study was to identify the textural features of apple seeds with the highest discriminatory power for distinguishing the seeds of different apple cultivars with the use of discriminative classifiers. The seeds of apple cvs. Gala, Jonagold and Idared were scanned with the use of a flatbed scanner, and the acquired images were processed to calculate textural features from color channels: L, a, b, R, G, B, Y, U, V, H, S, I, X, Y and Z. The selected textures were used to develop discriminative models and distinguish the seeds of the examined apple cultivars. The analyses were performed for color spaces and color channels. The seeds of apple cvs. Gala and Idared were discriminated with 100% accuracy in models based on the textures from Lab and YUV color spaces and color channel L for the Naive Bayes, Multilayer Perceptron and Multi Class classifiers. The discriminatory accuracies of the seeds of all analyzed apple cultivars (Gala, Idared and Jonagold) ranged from 72% to 85%. The discriminatory accuracy of the textures selected from Lab color space for the Naive Bayes classifier reached 85%. The seeds of apple cvs. Gala and Jonagold were discriminated with 78–90% accuracy, and the discriminatory accuracy of the textures from Lab color space and color channel b for the Naive Bayes classifier reached 90%. The seeds of apple cvs. Idared and Jonagold were distinguished with 80–94% accuracy. The models based on textures from Lab color space and color channel b for the Naive Bayes classifier were characterized by 94% discriminatory accuracy. The study demonstrated that textural features are useful for discriminating the seeds of different apple cultivars.