Chemical characterization and sensory properties of apple brandies aged with different toasted oak chips and ultra-high-pressure treatments

Aging is an important processing step of producing high quality apple brandy. In this study, apple brandies aged by traditional method and using three different toasted oak chips combined with or without ultra-high-pressure (UHP) treatment were prepared to compare their differences in chemical characterization and sensory properties. The results indicated that the brandies aged with toasted oak chip increased the levels of total acidity, volatile acidity and phenolic compounds. It also had the desirable color and taste. The brandy aged with toasted oak chip combined with UHP reached the highest levels of total acidity (1.06 g/L), total phenolic content (284.92 mg/L) and aromatic esters (49.37 %). Therefore, the aging with high toasted oak chip combined with UHP treatment could cut the traditional aging time to meet the same quality as traditional aging method. The results are very useful to develop a fast and efficient aging technique for brandy production.

The microRNA miR482 regulates NBS-LRR genes in response to ALT1 infection in apple

Plants are frequently attacked by a variety of pathogens and thus have evolved a series of defense mechanisms, one important mechanism is resistance gene (R gene)-mediated disease resistance, but its expression is tightly regulated. NBS-LRR genes are the largest gene family of R genes. microRNAs (miRNAs) target to a number of NBS-LRR genes and trigger the production of phased small interfering RNAs (phasiRNAs) from these transcripts. phasiRNAs cis or trans regulate NBS-LRR genes, which can result in the repression of R gene expression. In this study, we screened for upregulated miR482 in the susceptible apple cultivar 'Golden Delicious' (GD) after inoculation with the fungal pathogen Alternaria alternata f. sp. mali (ALT1). Additionally, through combined degradome sequencing, we identified a gene targeted by miR482, named MdTNL1, a gene encoding a TIR-NBS-LRR (Toll/interleukin1 receptor-nucleotide binding site-leucine-rich repeat) protein. This gene exhibited a significant down-regulation post ALT1 inoculation, suggesting an impact on gene expression mediated by miRNA regulation. miR482 could cleave MdTNL1 and generate phasiRNAs at the cleavage site. We found that overexpression of miR482 inhibited the expression of MdTNL1 and thus reduced the disease resistance of GD, while silencing of miR482 increased the expression of MdTNL1 and thus improved the disease resistance of GD. This work elucidates key mechanisms underlying the immune response to Alternaria infection in apple. Identification of the resistance genes involved will enable molecular breeding for prevention and control of Alternaria leaf spot disease in this important fruit crop.

Genome-wide analysis of C2H2 zinc finger family and their response to abiotic stresses in apple

C2H2-type zinc finger proteins are one of the most widely studied families in plants and play important roles in abiotic stress responses. In the present study, the physicochemical properties, chromosomal locations, evolutionary relationships, and gene structures of 54 C2H2 zinc finger protein (ZFP) family members were analyzed in apple. The MdC2H2-ZFP genes were phylogenetically clustered into seven subfamilies distributed in different densities on 16 chromosomes. The RNA-seq data from various tissues revealed that MdC2H2-ZFPs differentially expressed among root, stem, leaf, flower, and fruits. Quantitative analysis of its expression characteristics showed that the MdC2H2-ZFP genes were rapidly induced as exposure to abiotic stresses such as drought, salt and low temperature etc. Under drought stress, the expression of eight members was significantly up-regulated, and the highest was obtained from MdC2H2-17; as exposure to salt stress, nine MdC2H2-ZFPs was obviously up-regulated, with the highest expression of MdC2H2-13; and under low temperature stress, the expression of seven members was highly up-regulated, and MdC2H2-13 also demonstrated the highest expression which is same as the case under salt stress. Therefore, some members of MdC2H2-ZFP gene family considerably involve in the multiple abiotic stress responses, which may better understand the function of this family and facilitate the breeding of apple for stress tolerance.

The proteome of Penicillium expansum during infection of postharvest apple is revealed using Label-Free and Parallel Reaction Monitoring(PRM)Techniques

Penicillium expansum is the main pathogen in the postharvest storage of apples. Penicilliosis caused by P. expansum infection not only seriously affects the appearance and quality of fruits, but also the secondary metabolite Patulin (PAT) can cause harm to human health. Until now, little attention has been paid to the molecular mechanism of P. expansum infecting apples. Studying its molecular mechanism can help us better prevent and control apple postharvest blue mold. In this present investigation, we will use Label-Free technology to perform proteomic sequencing on apple samples at key time points of P. expansum infection, explore and screen key proteins and metabolic pathways during infection, and use Parallel Reaction Monitoring (PRM) technology to thoroughly validate proteomic data. The infection of P. expansum activates the MAPK signaling pathway, plant-pathogen interaction metabolic pathway and phenylpropanoid biosynthesis pathway of apple, participates in the regulation of ROS generation and oxidative stress process, promotes the synthesis of lignin and flavonoids, and the synthesis of Pathogenesis-Related Protein helps apple directly defend against P. expansum infection. This study provides the foundation for relevant postharvest control strategies, paving the way for further exploration of the proteome of pathogens infecting fruit and vegetables. SIGNIFICANCE: Proteins are macromolecules essential to the life of organisms, as they participate in the function and structure of cells. Proteomics technology is currently one of the important means to study the the response mechanism of pathogenic bacteria to plant infection, which can reveal the essence of physiological and pathological processes and help to clarify the possible relationship between protein abundance and plant stress. The present study essentially uses recent proteome analysis technology, namely label-free and PRM techniques, and lays the foundations for studying the of the infection response between P. expansum and apples. In particular, it provides a broad perspective on the molecular mechanism of P. expansum in the early stage of apple infection through detailed functional exploration and verification of associated proteins. Thus, it provides a theoretical basis for preventing and treating apple postharvest blue mold.

MdTPR16, an apple tetratricopeptide repeat (TPR)-like superfamily gene, positively regulates drought stress in apple

The Tetratricopeptide repeat (TPR)-like superfamily with TPR conserved domains is widely involved in the growth and abiotic stress in many plants. In this report, the gene MdTPR16 belongs to the TPR family in apple (Malus domestica). Promoter analysis reveal that MdTPR16 incorporated various stress response elements, including the drought stress response elements. And different abiotic stress treatments, drought especially, significantly induce the response of MdTPR16. Overexpression of MdTPR16 result in better drought tolerance in apple and Arabidopsis by up-regulating the expression levels of drought stress-related genes, achieving a higher chlorophyll content level, more material accumulation, and overall better growth compared to WT in the drought. Under drought stress, the overexpressed MdTPR16 also mitigate the oxidative damage in cells by reducing the electrolyte leakage, malondialdehyde content, and the H2O2 and O2- accumulation in apples and Arabidopsis. In conclusion, MdTPR16 act as a beneficial regulator of drought stress response by regulating the expression of related genes and the cumulation of reactive oxygen species (ROS).

Designing a size exclusion-based hapten and the development of a quantitative and visual time-resolved fluorescence immunochromatography assay strip for detecting dimethomorph and flumorph in a group-specific manner

Based on the size and surface properties of dimethomorph and flumorph, we used a computer simulation-assisted size exclusion hapten design strategy to develop group-specific monoclonal antibodies that can simultaneously recognize dimethomorph and flumorph. For this, we performed quantitative and visual semi-quantitative time-resolved fluorescence immunochromatography (TRFICA) to simultaneously detect dimethomorph and flumorph in potatoes and apples. In potato samples, the visual limit of detection (vLOD) for dimethomorph and flumorph was 4 ng/mL and 8 ng/mL, respectively, whereas the quantitative limit of detection (qLOD) for dimethomorph and flumorph was 0.26 and 0.33 ng/mL, respectively. The vLOD of dimethomorph and flumorph in apple samples was 8 ng/mL, whereas the qLOD of dimethomorph and flumorph was 0.17 and 0.38 ng/mL, respectively. The average recovery of potato and apple samples ranged from 77.5% to 121.7%, which indicated that the method can be used to rapidly detect dimethomorph and flumorph in food samples.

The Mh-miR393a-TIR1 module regulates Alternaria alternata resistance of Malus hupehensis mainly by modulating the auxin signaling

miRNAs govern gene expression and regulate plant defense. Alternaria alternata is a destructive fungal pathogen that damages apple. The wild apple germplasm Malus hupehensis is highly resistant to leaf spot disease caused by this fungus. Herein, we elucidated the regulatory and functional role of miR393a in apple resistance against A. alternata by targeting Transport Inhibitor Response 1. Mature miR393 accumulation in infected M. hupehensis increased owing to the transcriptional activation of MIR393a, determined to be a positive regulator of A. alternata resistance to either 'Orin' calli or 'Gala' leaves. 5' RLM-RACE and co-transformation assays showed that the target of miR393a was MhTIR1, a gene encoding a putative F-box auxin receptor that compromised apple immunity. RNA-seq analysis of transgenic calli revealed that MhTIR1 upregulated auxin signaling gene transcript levels and influenced phytohormone pathways and plant-pathogen interactions. miR393a compromised the sensitivity of several auxin-signaling genes to A. alternata infection, whereas MhTIR1 had the opposite effect. Using exogenous indole-3-acetic acid or the auxin synthesis inhibitor L-AOPP, we clarified that auxin enhances apple susceptibility to this pathogen. miR393a promotes SA biosynthesis and impedes pathogen-triggered ROS bursts by repressing TIR1-mediated auxin signaling. We uncovered the mechanism underlying the miR393a-TIR1 module, which interferes with apple defense against A. alternata by modulating the auxin signaling pathway.

First report of anthracnose caused by Colletotrichum grevilleae on apple in Korea

In October 2022, typical symptoms of anthracnose were observed on apple (Malus ⅹ domestica cv. Fuji) fruits collected from Pocheon in Gyeonggi province, South Korea (N37.98074°, E127.33995°). In the surveyed orchard, the incidence rate of apple anthracnose was less than 1%. The initial symptoms were brown-to-dark brown lesions, and with disease progression, they enlarged and the pulp became soft, forming a brown band. In total 29 apple fruits were collected, and the causal agent was isolated by removing the peel, and the diseased tissues were directly transferred onto potato dextrose agar (PDA), followed by incubation for 7 days at 25°C. As the results, two isolates (GgPc22-1-11 and GgPc22-1-13) were obtained. For describing morphological and cultural characteristics, isolate GgPc22-1-11 was cultured on PDA and synthetic nutrient-poor agar (SNA) at 25°C under near-UV light with a 12-h photoperiod for 10 days. The colonies of GgPc22-1-11 on PDA were initially white and subsequently appeared light gray to olivaceous with white margins. The reverse side of the plates were dark brown and slate blue (Supplementary Fig. S1). Colonies on SNA were flat with an entire margin and short sparse white aerial mycelium. No setae were observed. Conidia on PDA were hyaline, straight, aseptate with a rounded apex, clavate to cylindrical, and measured 16.4 ± 2.4 (10.8-23.8) × 5.5 ± 0.7 (3.6-7.7) μm (n = 200). Appressoria were medium-to-dark brown, aseptate, solitary or in groups with irregular outlines, and lobate or having undulate margins (Supplementary Fig. S1). These morphological and cultural characteristics of GgPc22-1-11 were consistent with those of Colletotrichum grevilleae F. Liu, Damm, L. Cai & Crous, pathogens of Proteaceae and Punica granatum (Liu et al. 2013; Huang et al. 2023). DNA was extracted from GgPc22-1-11, PCR was performed and Phylogenetic analysis of concatenated partial sequences of the internal transcribed spacer (ITS) of rDNA, β-tubulin (TUB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), chitin synthase 1 (CHS-1), and actin (ACT) genes was conducted (Weir et al. 2012). The resulting sequences were deposited in GenBank under the accession numbers LC773710-LC773714. A nucleotide BLAST search revealed that the ITS sequences of the isolates were 98.95% identical to those of C. grossum CAUG7 (KP890165.1). The TUB2, GAPDH, CHS-1, and ACT sequences of the isolates were 99.79%, 99.24%, 100%, and 100%, respectively, identical to those of C. grevilleae WP4. GgPc22-1-11 was clustered with C. grevilleae WP4 using neighbor joining analysis conducted with MEGA X software (Kumar et al. 2018) (Supplementary Fig. S2). Pathogenicity tests were conducted using GgPc22-1-11 and repeated three times. A total of 12 symptomless apples of each variety were selected, including Fuji, Hongro, Tsugaru, and RubyS. The apples were surface-sterilized with 70% ethanol and wounded using a sterile needle. Both wounded and unwounded apples were inoculated with mycelium plugs and paper disks containing a conidial suspension (1 × 106 conidia/ml) and placed in a plastic box with moist paper towels (>90% relative humidity) at 25°C in dark. At 5 days after inoculation, all artificially wounded fruits exhibited symptoms and 30% (4 out of 12) of unwounded inoculated fruits showed symptoms in each apple variety while control fruits were asymptomatic both the unwounded and wounded inoculations (Supplementary Fig. S1). To fulfill Koch's postulates, the fungi were reisolated from symptomatic tissues and were identical to GgPc22-1-11 confirmed by morphological and molecular analysis. To the best of our knowledge, C. grevilleae has been reported in Protea sp. and pomegranate (Liu et al. 2013; Huang et al. 2023) but not in apples to date, and this is the first report of C. grevilleae causing anthracnose in apple fruits. This research of the newly emerged unreported Colletotrichum species can offer valuable information for development of an effective fungicide spray program to control apple anthracnose.

Introduction of a diverse genetic background of Pyrus into Malus through intergeneric hybridization

Wide hybridizations across species and genera have been employed to enhance agriculturally important traits in crops. Within the tribe Maleae of the Rosaceae family, different genera and species exhibit several traits useful for increasing diversity and gene pool through hybridization. This study aimed to develop and characterize intergeneric hybrid individuals between Malus and Pyrus. Through seed germination, shoot multiplication, and rooting in vitro, acclimatized seedlings showing vegetative growth on their own roots were obtained from crosses of Malus × domestica pollinated by Pyrus communis, P. bretschneideri, and the Pyrus interspecific hybrid (P. communis × P. pyrifolia). Comparative analysis of leaf morphology, flow cytometry, and molecular genotyping confirmed the hybrid status of the individuals. Genome-wide genotyping revealed that all the hybrid individuals inherited genomic fragments symmetrically from the Malus and Pyrus parents. To the best of our knowledge, this is the first report on the development of intergeneric hybrid seedlings between Malus × domestica and P. bretschneideri. Furthermore, the Pyrus interspecific hybrid individual served as a bridge plant for introducing the genetic background of P. pyrifolia into Malus × domestica. The results of this study provided a crucial foundation for breeding through intergeneric hybridization between Malus and Pyrus, facilitating the incorporation of valuable traits from diverse gene pools.

The WRKY17-WRKY50 complex modulates anthocyanin biosynthesis to improve drought tolerance in apple

Drought stress is increasing worldwide due to global warming, which severely reduces apple (Malus domestica) yield. Clarifying the basis of drought tolerance in apple could accelerate the molecular breeding of drought-tolerant cultivars to maintain apple production. We identified a transcription factor MdWRKY50 by yeast two-hybrid (Y2H) assays as an interactor of the drought-tolerant protein MdWRKY17, and confirmed their interaction by bimolecular fluorescence complementation (BiFC) and pull-down assays. MdWRKY50 was induced by drought and when overexpressed in apple, conferred transgenic apple plants enhanced drought tolerance by directly binding to the promoter of anthocyanin synthetic gene Chalcone synthase (MdCHS) to upregulate its expression for higher anthocyanin. Increased anthocyanin relieves apple plants from oxidative damage under drought stress. MdWRKY50 RNA-interference transgenic apple plants showed opposite phenotypes. The dimerization of MdWRKY50 with mutated MdWRKY17DP mimicking drought-induced phosphorylation by the mitogen-activated protein kinase kinase 2 (MEK2)-MPK6 cascade, compared with MdWRKY17AP and MdWRKY17, further promoted anthocyanin biosynthesis, suggesting dimerization with MdWRKY17 makes MdWRKY50 more powerful in promoting anthocyanin biosynthesis under drought stress. Taken together, we isolated an entire MEK2-MAPK6-MdWRKY17-MdWRKY50-MdCHS pathway for drought tolerance and generated transgenic apple germplasm with enhanced drought tolerance and higher anthocyanin levels.

First report of Apple bitter rot caused by Colletotrichum godetiae in Ontario

Bitter rot is an emerging disease of apple (Malus domestica) fruit in Ontario in part due to changing weather conditions. The disease was mostly documented in warm and humid regions such as the southern USA, and Central and South America. Thirteen Ontario orchards in the fall of 2019 and 15 in 2020 were scouted for bitter rot based on their previous history of the disease. 100 fruit were collected from ten asymptomatic trees per cultivar and two susceptible cultivars, 'Empire' and 'Ambrosia' were scouted per orchard. If an orchard did not have either one of these cultivars, 'Honeycrisp' or 'Gala' were used. The fruit was stored at 4-5 oC for five months and then left at 22 oC for two weeks and assessed thereafter for bitter rot symptoms. Monoconidial cultures of Colletrotrichum spp. were established from the symptomatic fruit using potato dextrose agar media with antibiotics at 22 oC 14-hour light cycles. The fungal isolates were divided into two groups based on colony morphology observations seven days after culturing. The first group showed light grey, cottony, aerial mycelium on top and a pink to dark red color on the reverse of the plate. The second group showed light to dark grey, cottony mycelium on top and dark green colonies on the reverse of the plate. It is difficult to identify Colletrotricuhum species solely based on morphology, therefore the representative isolates from each group were used for multilocus gene sequencing and species identification. Genomic DNA was extracted using the Qiagen DNeasy Plant Mini Kit according to the manufacturer's protocols. The ITS region was amplified and sequenced using the primers ITS-1F (Grades & Bruns 1993) and ITS-4 (White et al. 1990). Primers T1 and T2 (O'Donnell & Cigelnik 1997) were used to amplify and sequence the 750 bp region of the TUB gene. Primers GDF1 and GDR1 (Guerber et. al. 2003) were used to amplify a 280 bp region of the GADPH gene. Following an NCBI nucleotide blast search, the isolates from group 1 were identified as C. fioriniae.The ITS sequences of group 2 isolates were matched 100% to the Colletotrichum godetiae type strain CBS133.44 and they were 99% matched to the closest species C. Johnstonii CBS128532. The TUB sequences matched 100% identity to 20 sequences belonging to C. godetiae, 99.59 % identity to C. godetiae type strain CBS133.44, and 97.75% to C. Johnstonii CBS128532. The GADPH sequences matched with 100% identity to C. godetiae ON241087.1 or MT816329.1 and 99-99.5% identity to the type strain CBS133.44 and 98.61-99% identity to CBS128532. Based on the blast results the group 2 isolates were identified as C. godetiae and their sequences were submitted to GenBank with ID OP702962 for ITS and OP972240 and OP972241 for GADPH and OP972242 for the TUB gene. Out of 50 isolates collected in this work, 94% belonged to group 1 and 6% belonged to group 2. Koch's postulates were performed on selected isolates by artificial inoculation of 5 healthy detached fruits of the cultivar, 'Empire.' Fruit surfaces were wiped with 70% ethanol, dried, wounded with a sterile needle, and then inoculated with a 10 µl of spore suspension containing 1x10^6 spores /ml. Inoculated fruits were incubated in a humid chamber at 22°C in dark. Symptoms started to appear at 5 days post-inoculation and looked like small brown circular lesions which developed orange spore masses as they grew into larger lesions. The non-inoculated control fruit did not develop lesions. Fungal colonies were established from the spores collected from the inoculated fruit and found to have identical morphological characteristics to the original isolates. C. godetiae has previously been reported to cause bitter rot in apples from various countries in Europe (Baroncelli et al. 2014; Munda, 2014; Wenneker et al. 2016). C. fioriniae has previously been reported as the dominant species causing bitter rot in apples although other species including C. chrysophilum and C. noveboracense have also been reported as causal agents from the Eastern USA (Khodadadi et al. 2020). To the best of our knowledge, this is the first report of Colletotrichum godetiae causing the bitter rot of apples in Ontario, Canada.

Apple (Malus × domestica Borkh.) production and quality in response to anti-hail nets

Anti-hail nets are the best way to mitigate the effects of hailstorms in the orchards. Apple trees covered with nets may exhibit a variety of vegetative and reproductive responses, inclusive of changes in tree vigour, cropping, sugar contents, and fruit colour. The present study was conducted to assess the effect of timing of installation and colour of anti-hail net on cropping and fruit quality in high-density apple orchard for two consecutive seasons (2021 and 2022). White and blue colour nets of size (9 m × 30 m) 80 GSM (square mesh with non-sliding threaded, leno weave, and < 30% shading factor) were installed at three different time intervals (15 days before estimated full bloom, at full bloom, and 15 days after full bloom) on apple cultivar 'Jeromine'. The installation at different time and colour of anti-hail nets significantly exhibit variability in cropping, fruit quality, and bio-chemical metrics. The significant highest cropping (fruit yield, productivity, and yield efficiency) and fruit biochemical parameters (total soluble solids) were recorded in T3C2 (15 days after full bloom + white colour anti-hail net) followed by T2C2 (installed at full bloom + white colour anti-hail net). Hence, white colour anti-hail nets installed 15 days after full bloom increased fruit production and improved quality in comparison to blue colour anti-hail net in apple under high-density plantations.

FLOWERING LOCUS T1 and TERMINAL FLOWER1 regulatory networks mediate flowering initiation in apple

Flower bud formation is a critical process that directly determines yield and fruit quality in fruit crops. Floral induction is modulated by the balance between two flowering-related proteins, FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1); however, the mechanisms underlying the establishment and maintenance of this dynamic balance remain largely elusive. Here we showed that in apple (Malus × domestica Borkh.), MdFT1 is predominantly expressed in spur buds and exhibits an increase in expression coinciding with flower induction; in contrast, MdTFL1 exhibited downregulation in apices during flower induction, suggesting that MdTFL1 has a role in floral repression. Interestingly, both the MdFT1 and MdTFL1 transcripts are directly regulated by transcription factor basic HELIX-LOOP-HELIX48 (MdbHLH48), and overexpression of MdbHLH48 in Arabidopsis (Arabidopsis thaliana) and tomato (Solanum lycopersicum) results in accelerated flowering. Binding and activation analyses revealed that MdbHLH48 functions as a positive regulator of MdFT1 and a negative regulator of MdTFL1. Further studies established that both MdFT1 and MdTFL1 interact competitively with MdWRKY6 protein to facilitate and inhibit, respectively, MdWRKY6-mediated transcriptional activation of target gene AFL1 (APPLE FLORICAULA/LFY, an apple LEAFY-like gene), ultimately regulating apple flower bud formation. These findings illustrate the fine-tuned regulation of flowering by the MdbHLH48-MdFT1/MdTFL1-MdWRKY6 module and provide insights into flower bud formation in apple.

Application of combined treatment of peracetic acid and ultraviolet-C for inactivating pathogens in water and on surface of apples

In this study, a combined treatment of peracetic acid (PAA) and 280 nm Ultraviolet-C (UVC) - Light emitting diode (LED) was applied for inactivating foodborne pathogens in water and apples. The combined treatment of PAA (50 ppm) and UVC-LED showed synergistic inactivation effects against Escherichia coli O157:H7 and Listeria monocytogenes in water. In mechanism analysis, PAA/UVC-LED treatment induced more lipid peroxidation, intracellular ROS, membrane, and DNA damage than a single treatment. Among them, membrane damage was the main synergistic inactivation mechanism of combination treatment. Cell rupture and shrink of both pathogens after PAA/UVC-LED treatment were also identified through scanning electron microscope (SEM) analysis. To examine inactivation of pathogens on the surface of apples by PAA, UVC-LED, and their combined treatment, a washing system (WS) was developed and used. Through applying the WS, PAA/UVC-LED treatment effectively inactivated two pathogens in washing solution and on the surface of apples below the detection limit (3.30 log CFU/2000 mL and 2.0 log CFU/apple) within 5 min. In addition, there was no significant difference in color or firmness of apples after PAA/UVC-LED treatment (p > 0.05).

Valorization of fruit and vegetable byproducts for the beta-glucan production from Euglena gracilis

Five fruit and vegetable byproducts were evaluated as carbon sources and media for beta-glucan production from Euglena gracilis. Orange peel showed the highest beta-glucan concentration (6.5 g/L) and productivity (1.9 g/L/day) when used as a medium. However, when employed as carbon sources, apple pomace showed the highest beta-glucan concentration (10.6 g/L) and productivity (3.5 g/L/day). The appropriate chemical oxygen demand/nitrogen ratio (71.1) and favorable carbon sources of apple contributed to beta-glucan production. Increasing sugar concentrations in apple pomace and orange peel from 10 to 30 g/L raised the beta-glucan concentration to 11.6 g/L. Using apple pomace and orange peel individually proved more effective than mixing them for beta-glucan production. Therefore, apple as a carbon source is the most effective fruit and vegetables byproduct for beta-glucan production. This is expected to reduce the cost of E. gracilis cultivation on a large-scale and contribute to the circular economy.

SpectroFood dataset: A comprehensive fruit and vegetable hyperspectral meta-dataset for dry matter estimation

In the dataset presented in this article, samples belonging to one of the following crops, apple, broccoli, leek, and mushroom, were measured by hyperspectral cameras in the visible/near-infrared spectral domain (430-900 nm). The dataset was compiled by putting together measurements from different calibrated hyperspectral imaging cameras and crops to facilitate the training of artificial intelligence models, helping to overcome the generalization problem of hyperspectral models. In particular, this dataset focuses on estimating dry matter content across various crops by a single model in a non-destructive way using hyperspectral measurements. This dataset contains extracted mean reflectance spectra for each sample (n=1028) and their respective dry matter content (%).

Transcription factor MdNAC33 is involved in ALA-induced anthocyanin accumulation in apples

5-Aminolevulinic acid (ALA), as a new natural plant growth regulator, has a significant function in promoting anthocyanin accumulation in many species of fruits. However, the mechanisms underlying remain obscure. In a transcriptome study of our group, it was found that many transcription factors (TFs) including NACs responsive to ALA treatment during anthocyanin accumulation. In the present study, we found a NAC of apple, MdNAC33 was coordinatively expressed with anthocyanin accumulation after ALA treatment in the apple fruits and leaves, suggesting that this TF may be involved in anthocyanin accumulation induced by ALA. We found that the MdNAC33 protein was localized in the nucleus and exhibited strong transcriptional activity in both yeast cells and plants, where its C-terminal contributed to the transcriptional activity. Functional analysis showed that overexpression of MdNAC33 promoted the accumulation of anthocyanin, while the silencing vector of MdNAC33 (RNAi) significantly impaired the anthocyanin accumulation induced by ALA. Yeast one-hybrid (Y1H), luciferase assay and electrophoretic mobility shift assay (EMSA) indicated that MdNAC33 could bind to promoters of MdbHLH3, MdDFR and MdANS to activate the gene expressions. In addition, MdNAC33 specifically interacts with MdMYB1, a positive regulator of anthocyanin biosynthesis, which was then in turn binding to its target genes MdUFGT and MdGSTF12, to promote anthocyanin accumulation in apples. Taken together, our data indicate that MdNAC33 plays multiple roles in ALA-induced anthocyanin biosynthesis. It provides new insights into the mechanisms of anthocyanin accumulation induced by ALA.

Polyphenolic profile, processing impact, and bioaccessibility of apple fermented products

Health-promoting foods have become increasingly popular due to intensified consumer interest and awareness of illnesses. There is a global market for apple fruits, which are affordable, nutritious, tasty, and produced in large quantities for direct consumption as well as food processing to make derived products. The food matrix of apples is suitable for fermentation, besides containing a high amount of phenolics and polyphenols. Fermentation of apples is one of the most common methods of preserving apple fruit and its byproducts. With different fermentation techniques, apple fruit can be used to make a wide range of products, such as fermented apple juice, cider, liqueurs, apple cider, apple vinegar and fermented apple solids, because it is not only a low-cost and simple method of processing the fruit, but it can also sometimes increase the bioavailability of nutrients and the levels of components that can improve health and sensory quality. To understand the health benefits of food products and how the fermentation process impacts polyphenols, it is also crucial to observe the effects of digestion on polyphenol bioaccessibility. Polyphenolic profile changes can be observed via both in vitro and in vivo digestion methods; however, in vitro digestion methods have the advantage of observing every step of gastrointestinal track effects and have less cost as well. In this review, the polyphenolic profile, processing impact, and bioaccessibility of apple-fermented products is assessed, with most available studies showing polyphenol profiles and bioaccessibility in apple varieties and fermented apple products.

First report of brown spot on stored apple fruits caused by Stemphylium vesicarium in Serbia

Apple is one of the most economically important fruit crops worldwide, and fungal postharvest diseases can cause significant losses during storage (Petreš et al. 2020). Apple fruits (cultivar Fuji) with necrosis symptoms were collected during the fall of 2022 from the cold storage facility (ULO - Ultra Low Oxygen) in Titel, Serbia. The fruits originated from the apple orchard in Titel, Serbia (45°12'47.1"N, 20°15'23.6"E). The pathogens were isolated from collected fruit samples using standard phytopathological techniques. Fruits were surface-sterilized, rinsed with sterile water, aseptically cut in half, and small fragments collected from the border of healthy and diseased tissue were placed into Petri dishes on Potato Dextrose Agar medium (PDA) and incubated at 25±1 °C in dark for seven days. The obtained 11 isolates were identified to the genus level as Alternaria (incidence 46%), Penicillium (36%), Fusarium (9%) and Stemphylium (9%) based on morphological characteristics. Pathogenicity of all isolates was confirmed on apple fruits of cultivars Fuji and Golden Delicious. The fruits were surface-sterilized, sprayed with 5 ml conidial suspension (1×105 conidia/ml) and incubated at room temperature for 21 days. Symptoms developed on inoculated fruits were the same as symptoms observed on apple fruit samples collected from cold storage. Reisolation from artificially inoculated fruits resulted in colonies that morphologically corresponded with the colonies used for inoculation. Stemphylium isolate was the only one included in further research. Initial symptoms and symptoms on artificially inoculated apple fruits caused by Stemphylium sp. occurred as circular dark brown necrosis located near the calyx, without visible sporulation on the fruit surface. The isolate and reisolate formed aerial, white to light brown mycelia. The pigmentation of the culture medium was pale to dark brown. Conidia were singular, cylindrical and multicellular, brown to dark brown, 22-35.1 long and 12.6-18.9 μm wide. Based on morphological properties, isolate and reisolate were identified as Stemphylium vesicarium which is in line with the description reported by Sharifi et al. (2021) and Gilardi et al. (2022). The identification of S. vesicarium isolate was confirmed by polymerase chain reaction (PCR) by amplifying and sequencing three regions using following primer pairs: Bt2a (5'- GGT AAC CAA ATC GGT GCT GCT TTC -3') and Bt2b (5'-ACC CTC AGT GTA GTG ACC CTT GGC-3') for β-tubulin region (Nasri et al. 2015), ITS1 (5'-TCC GTA GGT GAA CCT GCG G - 3') and ITS4 (5'- TCC TCC GCT TAT TGA TAT GC-3') for ITS region (White et al. 1990), and EF1 (5' - ATG GGT AAG GAG GAC AAG AC - 3') and EF2 (5'- GGA AGT ACC AGT GAT CAT GTT - 3') for TEF-1α region (O'Donnell et al. 1998). PCR products were separated by horizontal gel electrophoresis in 1.5% agarose gel, stained with ethidium bromide, and visualization under UV light revealed amplified fragments of the expected size of 500 bp for Bt2a/ Bt2b primer pair, 600 bp for ITS1/ITS4 primer pair, and 700 bp for EF1/EF2 primer pair. The obtained amplicons were Sanger sequenced (Macrogen Europe BV) in both directions. BLASTn analysis showed the identity of amplified fragments of the isolates with sequences of S. vesicarium present in the GenBank of 100% (MT881940.1 and JQ671944.1) for the β-tubulin region, 99.40% (MT520589.1 and OR256793.1) for the ITS region, and 99.49% (DQ471090.2 and MT394642.1) for the TEF-1α region. The sequences were deposited to NCBI GenBank (Accession No. OQ653540 for the β-tubulin region, OQ678016 for the ITS region, and OR232710 for the TEF-1α region). To our knowledge, this is the first finding of S. vesicarium on apple fruits in the Republic of Serbia, and the finding of a new causal agent of postharvest apple fruit rot.

The apple lipoxygenase MdLOX3 positively regulates zinc tolerance

Various abiotic stresses, especially heavy metals near factories around the world, limit plant growth and productivity worldwide. Zinc is a light gray transition metal, and excessive zinc will inactivate enzymes in the soil, weaken the biological function of microorganisms, and enter the food chain through enrichment, thus affecting human health. Lipoxygenase (LOX) can catalyze the production of fatty acid derivatives from phenolic triglycerides in plants and is an important pathway of fatty acid oxidation in plants, which usually begins under unfavorable conditions, especially under biotic and abiotic stresses. Lipoxygenase can be divided into 9-LOX and 13-LOX. MdLOX3 is a homolog of AtLOX3 and has been identified in apples (housefly apples). MdLOX3 has a typical conserved lipoxygenase domain, and promoter analysis shows that it contains multiple stress response elements. In addition, different abiotic stresses and hormonal treatments induced the MdLOX3 response. In order to explore the inherent anti-heavy metal mechanism of MdLOX3, this study verified the properties of MdLOX3 based on genetic analysis and overexpression experiments, including plant taproots length, plant fresh weight, chlorophyll, anthocyanins, MDA, relative electrical conductivity, hydrogen peroxide and superoxide anion, NBT\DAB staining, etc. In the experiment, overexpression of MdLOX3 in apple callus and Arabidopsis effectively enhanced the tolerance to zinc stress by improving the ability to clear ROS. Meanwhile, tomato materials with overexpression of ectopia grew better under excessive zinc ion stress. These results indicated that MdLOX3 had a good tolerance to heavy metal zinc. Homologous mutants are more sensitive to zinc, which proves that MdLOX3 plays an important positive role in zinc stressed apples, which broadens the range of action of LOX3 in different plants.

Analysis and experimental assessment of an optimized SERS substrate used to detect thiabendazole in apples with high sensitivity

Pesticides that linger in the environment and ecosystems for an extended period can cause severe and dangerous health problems in humans. To detect pesticides in foods, the development of high-sensitivity and quick screening technologies was required. This research investigated the performance of Au@Ag NPs with varying thicknesses of the silver shell for detecting trace quantities of thiabendazole (TBZ) in apples using surface-enhanced Raman spectroscopy (SERS). The Au@Ag NPs were synthesized by coating 32 nm gold seeds with different thicknesses of silver shell ranging from 2.4 to 8.7 nm, achieved by adjusting the incorporation of AgNO3 and ascorbic acid. The optimized Au@Ag NPs with a 7.3 nm silver shell demonstrated outstanding SERS activity, high sensitivity, and a detection limit of 0.05 μg/mL for TBZ. The R2 values, representing the goodness of fit, were found to be 0.990 and 0.986 for standard and real TBZ samples, respectively, indicating a strong correlation between the measured signal and the TBZ concentration. The recovery analysis showed a reliable and accurate detection capability (96 to 105%), suggesting good reliability and accuracy of the SERS-based detection using the optimal Au@Ag NPs. Overall, this research highlights the potential of SERS with optimal Au@Ag NPs for rapid and effective monitoring of pesticides in the food industry.

Genetic variations in MdSAUR36 participate in the negative regulation of mesocarp cell division and fruit size in Malus species

Final fruit size of apple (Malus domestica) cultivars is related to both mesocarp cell division and cell expansion during fruit growth, but it is unclear whether the cell division and/or cell enlargement determine most of the differences in fruit size between Malus species. In this study, by using an interspecific hybrid population between Malus asiatica "Zisai Pearl" and Malus domestica cultivar "Red Fuji," we found that the mesocarp cell number was the main causal factor of diversity in fruit size between Malus species. Rapid increase in mesocarp cell number occurred prior to 28 days after anthesis (DAA), while cell size increased gradually after 28 DAA until fruit ripening. Six candidate genes related to auxin signaling or cell cycle were predicted by combining the RNA-seq data and previous QTL data for fruit weight. Two InDels and 10 SNPs in the promoter of a small auxin upregulated RNA gene MdSAUR36 in Zisai Pearl led to a lower promoter activity than that of Red Fuji. One non-synonymous SNP G/T at 379 bp downstream of the ATG codon of MdSAUR36, which was heterozygous in Zisai Pearl, exerted significant genotype effects on fruit weight, length, and width. Transgenic apple calli by over-expressing or RNAi MdSAUR36 confirmed that MdSAUR36 participated in the negative regulation of mesocarp cell division and thus apple fruit size. These results could provide new insights in the molecular mechanism of small fruit size in Malus accession and be potentially used in molecular assisted breeding via interspecific hybridization.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-024-01441-4.

MdDEWAX decreases plant drought resistance by regulating wax biosynthesis

Apple epidermal wax protects plants from environmental stresses, determines fruit gloss and improves postharvest storage quality. However, the molecular mechanisms underlying the biosynthesis and regulation of apple epidermal waxes are not fully understood. In this study, we isolated a MdDEWAX gene from apple, which localized in the nucleus, expressed mainly in apple fruit, and induced by drought. We transformed the MdDEWAX gene into Arabidopsis, and found that heterologous expression of MdDEWAX reduced the accumulation of cuticular waxes in leaves and stems, increased epidermal permeability, the rate of water loss, and the rate of chlorophyll extraction of leaves and stems, altered the sensitivity to ABA, and reduced drought tolerance. Meanwhile, overexpression or silencing of the gene in the epidermis of apple fruits decreased or increased wax content, respectively. This study provides candidate genes for breeding apple cultivars and rootstocks with better drought tolerance.

Exploring apple pectic polysaccharides: Extraction, characterization, and biological activities - A comprehensive review

Apple (Malus domestica) is a popular and ancient fruit of the Myrtaceae family. Apple fruit is well-known for its great nutritional and phytochemical content consisted of beneficial compounds such as polyphenols, polysaccharides, sterols, and organic acids. Polysaccharides extracted from different parts of the apple fruit, including the peel, pomace, or the whole fruit, have been extensively studied. Researchers have investigated the structural characteristics of these polysaccharides, such as molecular weight, type of monosaccharide unit, type of linkage and its position and arrangement. Besides this, functional properties and physicochemical and of apple polysaccharides have also been studied, along with the effects of extraction procedures, storage, and processing on cell wall polysaccharides. Various extraction techniques, including hot water extraction, enzymatic extraction, and solvent-assisted extraction, have been studied. From the findings, it was evident that apple polysaccharides are mainly composed of (1 → 3), (1 → 6): α-β-glycosidic linkage. Moreover, the apple polysaccharides were demonstrated to exhibit antioxidant, hepatoprotective, anti-cancer, hypoilipidemic, and enzyme inhibitory properties in vitro and in vivo. The potential applications of apple polysaccharides in the food, cosmetic, pharmaceutical, nutraceutical industries have also been explored in the present review. Overall, the research on apple polysaccharides highlights their significant potential as a source of biologically active compounds with various health benefits and practical applications.

The apple autophagy-related gene MdATG10 improves drought tolerance and water use efficiency in transgenic apple plants

The Loess Plateau is the main apple production area in China; low precipitation is one of the most important factors limiting apple production here. Autophagy is a conserved process in eukaryotes that recycles cell contents or damaged macromolecules. Previously, we identified an autophagy-related gene MdATG10 from apple plants, which was involved in the responses to stressed conditions. In this study, we found that MdATG10 improved the drought tolerance and water use efficiency (WUE) of transgenic apple plants. MdATG10-overexpressing (OE) apple plants were more tolerant of short-term drought stress, as evidenced by their fewer drought-related injuries, compared with wild-type (WT) apple plants. In addition, the WUE of OE plants was higher than that of WT plants under long-term moderate water deficit conditions. The growth rate, biomass accumulation, photosynthetic efficiency, and stomatal aperture were higher in OE plants than in WT plants under long-term moderate drought conditions. During the process of adapting to drought, the expressions of genes involved in the abscisic acid (ABA) pathway were reduced in OE plants to decrease the synthesis of ABA, which helped maintain the stomatal opening for gas exchange. Furthermore, autophagic activity was higher in OE plants than in WT plants, as evidenced by the higher expressions of ATG genes and the greater number of autophagy bodies. In sum, our results suggested that overexpression of MdATG10 improved drought tolerance and WUE in apple plants, possibly by regulating stomatal movement and enhancing autophagic activity, which then enhanced the photosynthetic efficiency and reduced damage, as well as the reactive oxygen species (ROS) accumulation in apple plants.

γ-Aminobutyric acid enhances salt tolerance by sustaining ion homeostasis in apples

Soil salinization had become a global ecological problem, which restricts the plant growth, and the quantity and quality of fruits. As a signaling molecule, γ-Aminobutyric acid (GABA) mediates a series of physiological processes and stress responses. Our previous research showed that GABA could alleviate drought, low phosphorus, cadmium stresses in apples, but the further research about its physiological mechanisms under salt stress was even more needed. The present study showed that the inhibition of salt stress on plant growth might be effectively alleviated by the treatment of 0.5 mM GABA, and the osmotic balance and photosynthetic capacity of plants could be maintained. Exogenous GABA could effectively inhibit the enrichment of reactive oxygen species and the uptake of Na+, while maintaining ion homeostasis. The experiment results indicated GABA could markedly promote the expression amount of Na+ and K+ transport-related genes (e.g., HKT1, AKT1, NHX1, SOS1, SOS2, and SOS3) in apples under salt stress. Overexpression and interference (RNAi) of MdGAD1 in apple roots, which is a crucial enzyme in the GABA biosynthesis, affected the salt tolerance of plants. Transgenic apple plants with roots of overexpression MdGAD1 showed less relative electrolyte leakage and more expression level of related ion transport genes than CK group, but RNAi MdGAD1 led to the opposite results. These results indicated that GABA accumulation could effectively strengthen the resistance of apple plants to salt stress and alleviate the injury of apple seedlings resulted from salinity.

Optimization of apple fruit flavor by MdVHP1-2 via modulation of soluble sugar and organic acid accumulation

For fleshy fruits, the content and ratio of organic acids and soluble sugars are key factors for their flavor. Therefore, a better understanding of soluble sugar and organic acid accumulation in vacuoles is essential to the improvement of fruit quality. Vacuolar-type inorganic pyrophosphatase (V-PPase) has been found in various plants with crucial functions based on the hydrolysis of PPi. However, the effects of V-PPase on the soluble sugar and organic acid accumulation in apple fruit remain unclear. In this study, MdVHP1-2, a V-PPase protein in the vacuolar membrane, was identified. The results showed a positive correlation between the expression of MdVHP1-2 and the sugar/acid ratio during ripening of apple fruits. A series of transgenic analyses showed that overexpression of MdVHP1-2 significantly elevated the contents of soluble sugars and organic acids as well as the sugar/acid ratio in apple fruits and calli. Additionally, transient interference induced by MdVHP1-2 expression inhibited the accumulation of soluble sugars and organic acids in apple fruits. In summary, this study provides insight into the mechanisms by which MdVHP1-2 modulates fruit flavor through mediation of soluble sugar and organic acid accumulation, thereby facilitating improvement of the overall quality of apple and other fruits.

Authentication of apples from the Loess Plateau in China based on interannual element fingerprints and multidimensional modelling

Apple is an important fruit, and fruit authentication is significant for quality and safety control. The Loess Plateau (LP) in China is an important apple-producing region. However, the geographic authentication of LP apples has not been well studied. In this study, we discriminated LP apples based on multielement analysis. We analysed the differences in 29 elements of 522 samples collected from LP and others in 2018-2020 and constructed discriminant models for LP apple authentication. Linear discriminant analysis, partial least square-discriminant analysis, back-propagation artificial neural networks, and random forest (RF) showed different rates in training and validation accuracy. RF showed better tolerance to the removal of the less-important elements in model optimization. The final RF was optimized on 11 elements, which obtained 95.30% training accuracy for the 2018-2019 samples and 97.29% validation accuracy for the 2020 samples. The multielement-based authentication of LP apples could aid further studies of geographical origins.

Cold atmospheric plasma fumigation suppresses postharvest apple Botrytis cinerea by triggering intracellular reactive oxygen species and mitochondrial calcium

Infection by Botrytis cinerea poses a great threat to the postharvest life of apple fruit. In this study, the effects of cold atmospheric plasma (CAP) fumigation on apple B. cinerea under different exposure times and intensities were investigated. The growth of B. cinerea in vitro and in vivo was significantly suppressed by the CAP fumigation at least 700 μL/L for 5 min. To reveal the possible mechanism of antifungal activity of CAP fumigation, the pathogen was exposed to 700 μL/L and 1000 μL/L for 5 min, respectively. The results indicated that the CAP-treated spores of the pathogen underwent shrinkage, cell membrane collapse and cytoplasmic vacuolation. The results obtained from the fluorescent probe assay and flow cytometry indicated that CAP caused the accumulation of reactive oxygen species (ROS), the elevation of mitochondrial and intracellular Ca2+ levels, and the decrease in mitochondrial membrane potential of the pathogen. Investigation on statues of cell life showed that typical hallmarks of apoptosis in the CAP-treated B. cinerea spores occurred, as indicted by a large degree of increased phosphatidylserine externalization, dysfunction of membrane permeability, DNA fragmentation, distortion of morphology, chromatin condensation, and metacaspase activation observed in B. cinerea spores after CAP fumigation. Overall, CAP fumigation triggered a metacaspase-dependent apoptosis of B. cinerea spores mediated by intracellular ROS burst and Ca2+ elevation via mitochondrial dysfunction and disruption, and therefore reduced the pathogenicity of B. cinerea and suppressed postharvest Botrytis rot of apple fruit. These results would provide an insight into the underlying mechanism of CAP fumigation acting on the pathogen. The CAP fumigation makes much convenient application of CAP in storage environment to deactivate microorganism.

Improvement of the prediction of a visual apple ripeness index under seasonal variation by NIR spectral model correction

Apple ripeness assessment is essential to ensure its post-harvest commercial value, and the visible/near-infrared(NIR) spectral models that are effective in achieving this goal are prone to failure due to seasonal or instrumental factors. This study has proposed a visual ripeness index (VRPI) determined by parameters such as soluble solids, titratable acids, etc., which vary during the ripening period of the apple. The R and RMSE of the index prediction model based on the 2019 sample were 0.871 to 0.913 and 0.184 to 0.213 respectively. The model failed to predict the next two years of the sample, which was effectively addressed by model fusion and correction. For the 2020 and 2021 samples, the revised model improves R by 6.8% and 10.6% and reduces RMSE by 52.2% and 32.2% respectively. The results showed that the global model is adapted to the correction of the VRPI spectral prediction model under seasonal variation.

Drying, Physical, Nutritional and Bioactive Characteristics of Apple Peel Flour Subjected to Blanching and Ultrasound Pretreatments

The aim of this work was to study the effect of blanching and ultrasound pretreatments on drying and quality characteristics of apple peel. Blanching was conducted in boiling water, ultrasound in a water bath, and drying in a batch tray dryer. The product obtained was ground into a flour, and assessed for color, water activity, proximate composition, sugars, and bioactive compounds. Results showed that effective moisture diffusivity increases with a decrease in product moisture content, being such dependence well described by a second order polynomial model. Average drying rate was higher and product moisture content was lower for blanched and sonicated flour, especially for the former. Such result suggests that blanching and ultrasound enhance water removal during drying of apple peel. Physical properties were significantly affected by pretreatments, being more intense red color and lower water activity obtained for sonicated flour. Nutritional and bioactive properties were also significantly affected by pretreatments, being lower sugar, higher protein, fiber, catechin and epicatechin content observed for blanched flour. Summarizing, blanching and ultrasound pretreatments improve drying of apple peel, both regarding process efficiency and product quality.

Regulation of a vacuolar proton-pumping P-ATPase MdPH5 by MdMYB73 and its role in malate accumulation and vacuolar acidification

As the main organic acid in fruits, malate is produced in the cytoplasm and is then transported into the vacuole. It accumulates by vacuolar proton pumps, transporters, and channels, affecting the taste and flavor of fruits. Among the three types of proton pumps (V-ATPases, V-PPases, and P-ATPases), the P-ATPases play an important role in the transport of malate into vacuoles. In this study, the transcriptome data, collected at different stages after blooming and during storage, were analyzed and the results demonstrated that the expression of MdPH5, a vacuolar proton-pumping P-ATPase, was associated with both pre- and post-harvest malate contents. Moreover, MdPH5 is localized at the tonoplast and regulates malate accumulation and vacuolar pH. In addition, MdMYB73, an upstream MYB transcription factor of MdPH5, directly binds to its promoter, thereby transcriptionally activating its expression and enhancing its activity. In this way, MdMYB73 can also affect malate accumulation and vacuolar pH. Overall, this study clarifies how MdMYB73 and MdPH5 act to regulate vacuolar malate transport systems, thereby affecting malate accumulation and vacuolar pH.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42994-023-00115-7.

The apple transcription factor MdbHLH4 regulates plant morphology and fruit development by promoting cell enlargement

The bHLH family, the second largest transcription factor (TF) family in plants, plays a crucial role in regulating plant growth and development processes. However, the biological functions and mechanisms of most bHLH proteins remain unknown, particularly in apples. In this study, we found that MdbHLH4 positively modulates plant growth and development by enhancing cell expansion. Overexpression (OE) of MdbHLH4 resulted in increased biomass, stem and root length, leaf area, and larger areas of pith, xylem, and cortex with greater cell size compared with wild-type apple plants. Conversely, RNA interference (RNAi)-mediated silencing of MdbHLH4 led to reduced xylem and phloem as well as smaller cell size compared to wild-type apple plants. Ectopic expression of MdbHLH4 in tomatoes resulted in enlarged fruits with impaired color appearance, decreased accumulation of soluble solids, and decreased flesh firmness along with larger seeds. Subsequent investigations have shown that MdbHLH4 directly binds to the promoters of MdARF6b and MdPIF4b, enhancing their expression levels. These findings suggest that MdbHLH4 potentially regulates plant cell expansion through auxin and light signaling pathways. These study results not only provide new insights into the roles of bHLH transcription factors in regulating plant growth and development but also contribute to a deeper understanding of their underlying mechanisms.

Red delicious)

BACKGROUND

Bud sport is a kind of somatic mutation that usually occurred in apple. 'Red Delicious' is considered to be a special plant material of bud sport, whereas the genetic basis of plant mutants is still unknown. In this study, we used whole-genome resequencing and transcriptome sequencing to identify genes related to spur-type and skin-color in the 'Red Delicious' (G0) and its four generation mutants including 'Starking Red' (G1), 'Starkrimson' (G2), 'Campbell Redchief' (G3) and 'Vallee Spur' (G4).

RESULTS

The number of single nucleotide polymorphisms (SNPs), insertions and deletions (InDels) and structural variations (SVs) were decreased in four generation mutants compared to G0, and the number of unique SNPs and InDels were over 9-fold and 4-fold higher in G1 versus (vs.) G2 and G2 vs. G3, respectively. Chromosomes 2, 5, 11 and 15 carried the most SNPs, InDels and SVs, while chromosomes 1 and 6 carried the least. Meanwhile, we identified 4,356 variation genes by whole-genome resequencing and transcriptome, and obtained 13 and 16 differentially expressed genes (DEGs) related to spur-type and skin-color by gene expression levels. Among them, DELLA and 4CL7 were the potential genes that regulate the difference of spur-type and skin-color characters, respectively.

CONCLUSIONS

Our study identified potential genes associated with spur-type and skin-color differences in 'Red Delicious' and its four generation mutants, which provides a theoretical foundation for the mechanism of the apple bud sport.

Genome-wide identification and expression analysis of the BURP domain-containing genes in Malus domestica

The conserved BURP-containing proteins are specific to plants and play a crucial role in plant growth, development, and response to abiotic stresses. However, less is known about the systematic characterization of BURP-containing proteins in apple. This study aimed to identify and analyze all BURP-containing genes in the apple genome, as well as to examine their expression patterns through various bioinformatics methods. Eighteen members of BURP-containing genes were identified in apple, six members lacked signal peptides, and the secondary structure was mainly a Random coil of BURP-containing genes. Gene structure and Motif analysis showed that proteins have similar structures and are conserved at the C-terminal. Cis-acting element analysis revealed that the proteins contain phytohormone and stress response elements, and chromosomal localization revealed that the family is unevenly distributed across eight chromosomes, with duplication of fragments leading to the expansion of family proteins. Tissue expression showed that MdPG3 and MdPG4 were expressed in different tissues and different varieties, MdRD2 and MdRD7 were highly expressed in 'M74' fruits and MdRD7 in 'M49' leaves, while MdUSP1 was highly expressed in 'GD' roots. The quantitative real-time PCR analysis showed that the expressions of six and seven genes were significantly up-regulated under NaCl and PEG treatments, respectively, whereas MdRD7 was significantly up-regulated under NaCl and PEG treatment over time. This study offers a comprehensive identification and expression analysis of BURP-containing proteins in apple. The findings provide a theoretical foundation for further exploration of the functions of this protein family.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01393-7.

Exploring genetic diversity and ascertaining genetic loci associated with important fruit quality traits in apple (Malus × domestica Borkh.)

Genetic diversity is the primary source of variability in any crop improvement program, and the diverse germplasm of any crop species represents an important genetic resource for gene or allele mining to meet future needs. Huge genetic and phenotypic diversity is present in the apple gene pool, even though, breeding programs have been mainly focused on a few traits of interests, which have resulted in the reduction of the diversity in the cultivated lines of apple. Therefore, the present study was carried out on 70 diverse apple genotypes with the objective of analyzing the genetic diversity and to identify the genetic loci associated with important fruit quality traits. A total of 140 SSR primers were used to characterize the 70 genotypes of apples, out of which only 88 SSRs were found to be polymorphic. The PIC values varied from 0.03 to 0.75. The value of MI, EMR, and RP varied from 0.03 to 3.5, 0.5 to 5.0, and 1.89 to 6.74, respectively. The dendrogram and structure analysis divided all the genotypes into two main groups. In addition to this, large phenotypic variability was observed for the fruit quality traits under study indicated the suitability of the genotypes for association studies. Altogether 71 novel MTAs were identified for 10 fruit quality traits, of which 15 for fruit length, 15 for fruit diameter, 12 for fruit weight, 2 for total sugar, 2 for TSS, 4 for reducing sugar, 5 for non-reducing sugar, 5 for fruit firmness, 5 for fruit acidity and 6 for anthocyanin, respectively. Consistent with the physicochemical evaluation of traits, there was a significant correlation coefficient among different fruit quality characters, and many common markers were found to be associated with these traits (fruit diameter, length, TSS, total sugar, acidity and anthocyanin, respectively) by using the different modeling techniques (GLM, MLM). The inferred genetic structure, diversity pattern and the identified MTAs will be serving as resourceful grounds for better predictions and understanding of apple genome towards efficient conservation and utilization of apple germplasm for facilitating genetic improvement of fruit quality traits. Furthermore, these findings also suggested that association mapping could be a viable alternative to the conventional QTL mapping approach in apple.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01382-w.

Molecular regulation of apple and grape ripening: exploring common and distinct transcriptional aspects of representative climacteric and non-climacteric fruits

Fleshy fruits of angiosperms are organs specialized for promoting seed dispersal by attracting herbivores and enticing them to consume the organ and the seeds it contains. Ripening can be broadly defined as the processes serving as a plant strategy to make the fleshy fruit appealing to animals, consisting of a coordinated series of changes in color, texture, aroma, and flavor that result from an intricate interplay of genetically and epigenetically programmed events. The ripening of fruits can be categorized into two types: climacteric, which is characterized by a rapid increase in respiration rate typically accompanied by a burst of ethylene production, and non-climacteric, in which this pronounced peak in respiration is absent. Here we review current knowledge of transcriptomic changes taking place in apple (Malus × domestica, climacteric) and grapevine (Vitis vinifera, non-climacteric) fruit during ripening, with the aim of highlighting specific and common hormonal and molecular events governing the process in the two species. With this perspective, we found that specific NAC transcription factor members participate in ripening initiation in grape and are involved in restoring normal physiological ripening progression in impaired fruit ripening in apple. These elements suggest the existence of a common regulatory mechanism operated by NAC transcription factors and auxin in the two species.

Ask Doctor Smartphone! An App to Help Physicians Manage Foreign Body Ingestions in Children

BACKGROUND

Foreign body ingestion (FBI) represents the most common cause of emergent gastrointestinal endoscopy in children. FBI's management can be quite challenging for physicians because of the variability of the clinical presentation, and the decision tree becomes even more intricate because of patient-specific variables that must be considered in the pediatric age range (e.g., age of patients and neuropsychiatric disorders) in addition to the mere characteristics of the foreign body. We present an application for smartphones designed for pediatricians and pediatric surgeons based on the latest guidelines from the official pediatric societies. The app aims to help physicians manage FBI quickly and properly in children.

MATERIALS AND METHODS

The latest pediatric FBI management guidelines were reviewed and summarized. The flow chart we obtained guided the development of a smartphone application. A questionnaire was administered to all pediatric surgeon trainees at our institute to test the feasibility and helpfulness of the application.

RESULTS

An app for smartphones was obtained and shared for free on the Google Play Store and Apple Store. The app guides the physician step by step in the diagnostic process, analyzing all patient- and foreign body-specific characteristics. The app consultation ends with a suggestion of the most proper decision to make in terms of further radiological investigations and the indication and timing of endoscopy. A questionnaire administered to trainees proved the app to be useful and easy to use.

CONCLUSION

We developed an app able to help pediatricians and pediatric surgeons manage FBI in children, providing standardized and updated recommendations in a smart and easily available way.

Apple-derived extracellular vesicles modulate the expression of human intestinal bile acid transporter ASBT/SLC10A2 via downregulation of transcription factor RARα

PURPOSE

Plant-derived extracellular vesicles (EVs) have been reported to exert biological activity on intestinal tissues by delivering their contents into intestinal cells. We previously reported that ASBT/SLC10A2 mRNA was downregulated by apple-derived extracellular vesicles (APEVs). ASBT downregulation is effective in the treatment of cholestasis and chronic constipation, similar to the beneficial effects of apples. Therefore, this study aimed to establish the mechanism of ASBT downregulation by APEVs, focusing on microRNAs present in APEVs.

RESULTS

APEVs downregulated the expression of ASBT, but no significant effect on SLC10A2-3'UTR was observed. Proteomics revealed that APEVs decreased the expression of RARα/NR1B1. The binding of RARα to SLC10A2 promoter was also decreased by APEVs. The stability of NR1B1 mRNA was attenuated by APEVs and its 3'UTR was found to be a target for APEVs. Apple microRNAs that were predicted to interact with NR1B1-3'UTR were present in APEVs, and their mimics suppressed NR1B1 mRNA expression.

CONCLUSIONS

Suppression of ASBT by APEVs was indirectly mediated by the downregulation of RARα, and its stability was lowered by microRNAs present in APEVs. This study suggested that macromolecules in food directly affect intestinal function by means of EVs that stabilize them and facilitate their cellular uptake.

MdGRF11-MdARF19-2 module acts as a positive regulator of drought resistance in apple rootstock

14-3-3 proteins play an important role in the response of plants to drought resistance. In this study, 14-3-3 protein MdGRF11 was cloned from Malus xiaojinensis, and its positive regulation of drought resistance was verified using Orin calli and M. xiaojinensis plants. The transcription factor MdARF19-2 was further screened for interaction with this protein in vitro and in vivo. We also conducted experiments using Orin calli and found that the overexpression of MdARF19-2 decreased the level of reactive oxygen species (ROS) and increased the activity of enzymes that scavenge ROS in plant materials. This indicates that MdARF19-2 is a positive regulator in the drought resistance of plants. The drought tolerance was further improved by the overexpression of both MdGRF11 and MdARF19-2 in the calli. In addition, we examined several genes related to ROS scavenging with auxin response factor binding elements in their promoters and found that their level of expression was regulated by the MdGRF11-MdARF19-2 module. In conclusion, the enhancement of plant drought resistance by MdGRF11 could be owing to its accumulation at the protein level in response to drought, which then combined with MdARF19-2, affecting the expression of MdARF19-2 downstream genes. Thus, it scavenges ROS, which ultimately improves the resistance of plant to drought stress.

The cytochrome P450 gene, MdCYP716B1, is involved in regulating plant growth and anthracnose resistance in apple

Apple is one of the main cultivated fruit trees worldwide. Both biotic and abiotic stresses, especially fungal diseases, have serious effects on the growth and fruit quality of apples. Cytochrome P450, the largest protein family in plants, is critical for plant growth and stress responses. However, the function of apple P450 remains poorly understood. In our previous study, 'Hanfu' autotetraploid showed dwarfism and fungal resistance phenotypes compared to 'Hanfu' diploid. Digital gene expression sequencing analysis revealed that the transcript level of MdCYP716B1 was significantly downregulated in the autotetraploid apple cultivar 'Hanfu'. In this study, we identified and cloned the MdCYP716B1 gene from 'Hanfu' apples. The MdCYP716B1 protein fused to a green fluorescent protein was localized in the cytoplasm. We constructed the plant overexpression vector and RNAi vector of MdCYP716B1, and the apple 'GL-3' was transformed by Agrobacterium-mediated transformation to obtain transgenic plants. Overexpressing and RNAi silencing transgenic plants exhibited an increase and decrease in plant height to 'GL-3', respectively. RNAi silencing transgenic plants displayed increased resistance to Colletotrichum gloeosporioides, whereas overexpression transgenic plants were more sensitive to C. gloeosporioides. According to transcriptome analysis, the transcript levels of gibberellin biosynthesis genes were upregulated in MdCYP716B1-overexpression plants. In contrast with 'GL-3', GA3 accumulation was rose in MdCYP716B1-OE lines and impaired in MdCYP716B1-RNAi lines. Collectively, our data indicate that MdCYP716B1 regulates plant growth and resistance to fungal stress.

Overview on century progress in research on mosaic disease of apple (Malus domestica Borkh) incited by apple mosaic virus/apple necrotic mosaic virus

Apple mosaic is widely distributed disease throughout the apple growing regions leading to the major adverse effects both qualitatively and quantitatively. Earlier the apple mosaic virus-ApMV was regarded as the only causal agent of the disease, but recently a novel virus apple necrotic mosaic virus-ApNMV have been reported as the causal pathogen from various apple growing countries. Accurate diagnosis of disease and detection of ApMV and ApNMV are of utmost importance, because without this ability we can neither understand nor control this disease. Both the viruses are mostly controlled through quarantine, isolation, sanitation and certification programs depending on sensitive and specific detection methods available. Here we review the 100-year progress in research on apple mosaic disease, which includes history, yield losses, causal agents, their genome organization, replication, traditional to recent detection methods, transmission, distribution and host range of associated viruses and management of the disease.

Hyperspectral dataset of pure and pesticide-coated apples for measuring the level of fertilizers used

This dataset provides three classes of hyperspectral images: pure, insecticide-immersed, and fungicide-immersed apples with different concentrations of fertilizers. The hyperspectral images were calibrated under white and dark correction and enhanced using contrast enhancement. In order to know the variations in the level of fertilizers used, we soaked the apples in 2 different concentrations of chemicals i.e., 1ml or 1g of fertilizer in 1 liter of water as low concentration, and 3ml or 3g of fertilizer in 1 liter of water as high concentration. The proposed dataset will help in finding the consumption level of fertilizers (pesticides) in apples.

Genetic footprint of population diversity and genetic structure of Venturia inaequalis infecting apple (Malus × domestica Borkh.)

Apple scab instigated by Venturia inaequalis impels remarkable losses to apple fruit production. In an effort to comprehend the key mechanisms of evolutionary potential defining V. inaequalis population, 132 isolates of V. inaequalis from five commercial apple orchards were collected and assayed using 14 microsatellite markers. The average diversity was observed within the individuals of populations based on the Shannon-Wieners index (I) and observed heterozygosity (Ho) was average but considerably lower than expected heterozygosity (He). The genetic differentiation based on FST values was revealed as an average measure of divergence between populations and had varying proportions of gene flow and migration among themselves. Analysis of Molecular Variance (AMOVA) revealed that variance (94%) was dispersed across individuals with a significant (6%) variation between populations from different regions. To examine host specialization within the V. inaequalis population, the assignment approach based on K-means of clustering (an unsupervised machine learning approach), revealed that the clustering method supported three clusters at (K = 3) and three major clusters were also observed in Principle Component Analysis (PCA). Additionally, Nei's genetic distance values, pairwise estimates of genetic differentiation, dendrogram using the neighbor-joining and PCoA revealed the random distribution of V. Inaequalis isolates that depicted a high proportion of genotypic diversity within populations and population genetic structure.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03672-2.

Cumulative health risk assessment of pesticide residues in apple products in the Northwest of Iran using Monte Carlo simulation

Pesticide residues in fruits and vegetables cause serious health issues, especially among children. This research was carried out to monitor and evaluate the risks of organophosphate pesticide residues in Maragheh County apple products from 2020. The Monte Carlo Simulation approach (MCS) was used to evaluate the non-cancerous effects of exposure to pesticide residues in adults and children. Apple samples were taken every two weeks at the Maragheh central market during the summer and fall months. In this study, seventeen pesticide residues in 30 apple samples were estimated using a modified QuECheRS extraction technique coupled with GC/MS. Of the seventeen organophosphate pesticides, thirteen were identified as pesticide residues (76.47%). The highest concentration found in the apple samples was associated with chlorpyrifos pesticide at 1.05 mg/kg. Pesticide residues exceeding the maximum residue limits (MRLs) were found in 100% of apple specimens, and more than 75% of the samples contained ten or more pesticide residues. Approximately 45%-80% of pesticide residues on apple samples were removed after washing and peeling. Chlorpyrifos pesticide had the highest health quotient (HQ) for men, women, and children with values of 0.046, 0.054, and 0.23, respectively. Cumulative risk assessment (CRA) of non-carcinogenic effects indicates that there is no significant health risk in the adult age group from apple consumption (HI < 1). Nevertheless, children are at high non-cancer risk from eating unwashed apples (HI = 1.3). This finding shows that high levels of pesticide residues in apple samples, especially unwashed apples, can be a serious concern for the health of children. To better protect consumer health, continuous and regular monitoring, strict regulations, training, and awareness of farmers, especially control pre-harvest interval (PHI) is recommended.

Difference in calcium accumulation in the fruit of two apple varieties and its relationship with vascular bundle development in the pedicel

Calcium (Ca) is an essential mineral element for plant growth and development that plays a key role in fruit growth and quality formation. To study the absorption and transport of Ca in 'Tonami' (susceptible to bitter pit (BP)) and 'Fuji' (resistant to BP), fruiting branches of 'Tonami' and 'Fuji' were injected with 0.05% 44Ca at the fruitlet stage (37 days after full bloom (DAFB)) and fruit expansion stage (72 DAFB). At the fruitlet and fruit expansion stages, the 44Ca content of fruiting branches increased from high to low in leaves, shoots, and fruit. In fruit, the 44Ca content was highest in the peel and lowest in the flesh. In both 'Tonami' and 'Fuji', Ca uptake was more efficient at the fruitlet stage than at the fruit expansion stage. 'Tonami' had a shorter growth and development time and earlier loss of fruit pedicel xylem structure and functionality than 'Fuji', resulting in less Ca accumulation in the fruit. The low Ca uptake efficiency of 'Tonami' fruit, the short Ca accumulation time, and the high Ca dilution resulted in low 44Ca content in the fruit, which may explain the susceptibility of 'Tonami' fruit to BP disease.

Composition and Diversity of Endophytic Rhizosphere Microbiota in Apple Tree with Different Ages

In order to determine the underlying mechanism of the senescence occurring in older apple trees, the effects of tree age on the community structure and dominant genus of endophytic rhizosphere bacteria in apple were investigated. The diversity and structure of the bacterial communities and corresponding changes in the dominant genera of endophytic rhizosphere bacteria of apple at different ages (2, 8, 16, 22 years) were compared based on 16S rRNA high-throughput sequencing technology. The results revealed that the longer the tree age, the less the number of ASV in the endophytic bacteria. Moreover, the number of ASV in the endophytic bacteria gradually decreased as the tree age increased, however no significant changes were observed in the alpha diversity. At the phyla level, the relative abundance of Actinobacteria increased, while that of Proteobateria decreased. At the genus level, the relative abundance of Mycobacterium, Chujaibacter, and other genera increased, while the relative abundance of Aquabacterium, Ralstonia, Streptomyces, Asticcacaulis, Hyphomicrobium, Pseudomonas, and Sphingomonas decreased. The reduced relative abundance of endophytic rhizosphere bacteria associated with plant growth and disease resistance may thus be the cause of tree senescence. This work acts as a reference to increases the understanding of plant-microbe interactions.

Preventive Measures and Hygiene Habits of Apple Producers in the Prespa Region

Background

Agriculture is one of the most dangerous industries, both for the employees in that sector and for their families and the environment. The use of personal protective preventive measures and the maintenance of good hygienic practices are the basis for healthy production and healthy workers. The safety and hygiene of food products should be present during all stages of production.

Objectives

The study aimed to assess the use of personal protective equipment (PPE) by apple growers during agricultural procedures as well as the hygiene habits of agricultural workers.

Subjects and Methods

A cross-sectional study was conducted including 101 farmers from the Prespa region in the Republic of North Macedonia by using a questionnaire with 34 questions. The questions were formulated in order to give us an insight into the protective preventive measures undertaken at work by apple producers and their hygiene.

Results

The study included 101 apple growers from the Prespa region. Wearing a completely tidy special PPE when using pesticides was registered in 78.2% of farmers, and when lawn mowing in 42.5%. 16% of the surveyed farmers during agricultural activities did not always wash their hands after going to the toilet, and almost 30% of them did not use soap when washing their hands.

Conclusion

There is inadequate hygiene practice/personal hygiene during agricultural activities. In addition, the proper use of PPE is not at a satisfactory level and poses a risk to the health of apple growers.

Determinants of the adoption of different good agricultural practices (GAP) in the command area of PMAMP apple zone in Nepal: The case of Mustang district

The study was carried out to determine the factors affecting the adoption of good agriculture practices (GAP) for apple production in the Prime-Minister Agriculture Modernization Project's (PMAMP) apple zone of Mustang district. Altogether, 100 households from Thasang and Gharapjhong rural Municipalities were chosen for the study by a stratified random sampling technique. Descriptive statistical tools, logistic regression and t-test were used to analyze the data which were collected from the semi-structured interview schedule. Out of the ten selected good agriculture practices standards, intercropping practices were adopted by the majority of respondents (83%) while the ring method of irrigation (19%) was found to be the least adopted. The magnitude of logistic regression coefficients of good agriculture practices revealed that occupation was a highly significant (p < 0.01) socio-economic variable influencing the adoption of good agriculture practices. Similarly, age, apple cultivated land, economically active population, institutional involvement, and loan for apple cultivation was also found significant (p < 0.05) for the adoption of different good agriculture practices. From the independent t-test, the productivity of apples was found significantly different between the farmers with and without: recommended nutrient management system, intercropping (p < 0.05), recommended pit dimension and irrigation interval (p < 0.10). The major problem in apple production were also identified. Based on the findings, increase in apple cultivated land, increase number of apples growing farmers, active role of institution and availability of credit to farmers are suggested to increase the adoption of different GAP in apple. The problems identified in apple production shall be prioritized to boost apple production and marketing. The policy makers and practitioners should prioritize the significant socio-economic characters and determinants in different stages of planning and implementation of program and policies.

Comparative transcriptomic analysis provides novel insights into the difference in textural alteration between mealy and crisp apple patterns

Mealiness is a common textural deterioration of several fruit after harvest. To unravel the underlying mechanism involved in mealiness, biochemical characterization and global transcriptomic profiling were comparatively performed between mealy 'Hongjiangjun' (HJJ) and crisp 'Fuji' apples. Sensory evaluation and SEM-based microstructure observation showed that HJJ apples appeared to be mealy in only 3 d at 23 ± 1 °C, while Fuji apples did not appear to be mealy even after 28 d of storage. Textural deterioration and ethylene burst occurred more sharply in HJJ apples than in Fuji apples during storage. The results obtained from the dimensional RNA-sequencing analysis showed that a much stronger upregulation of the transcription of genes encoding polygalacturonase (PG), pectin acetylesterase (PAE), pectinesterase (PE), β-galactosidase (GAL), α-l-arabinofuranase (AF), and expansin (EXP) was observed in the pair of mealy HJJ apples vs. harvest than in the pair of Fuji apples after 28 d vs. harvest. The gene expression of ethylene responsive factor (ERF) was found to be strongly upregulated in HJJ apples compared with Fuji apples, which may mediate the regulation of downstream genes encoding cell wall-modifying enzymes. Weighted gene co-expression network analysis showed that the transcription factors MdbHLH63 and MdERF-like, and a constructure gene of MdGAL had strong connectivity with mealiness. Validation by qRT-PCR further confirmed the main findings obtained by RNA-sequencing. The occurrence of apple mealiness involves altered expression patterns of cell wall-modifying enzymes as well as MdbHLH63 and MdERF-like, which are core genes regulating the mealiness process. The above findings provide global insight into the difference in textural alteration between mealy and crisp apple patterns.