Valorization of Peach Fruit and Wine Lees through the Production of a Functional Peach and Grape Juice

The valorization of agri-food products not only represents important economic and environmental benefits but can also be a source of potentially profitable, functional, and safe ingredients. This study aimed to valorize peach fruit and wine lees (WL) by producing functional juice. WL were incorporated at different concentrations (1.5 and 2%; w:w) in unpasteurized peach and grape juice and subsequently stored under refrigeration (5 °C). The antimicrobial activity of WL in peach and grape juices was assessed against Listeria monocytogenes and Saccharomyces cerevisiae as well as physicochemical, nutritional microbiological, and sensory acceptability. The maximum addition of WL to the juice (2%) showed a significant inhibitory effect against L. monocytogenes (4-log reduction) and increased the content of total soluble solids (TSS) (10%), total polyphenol content (TPC) (75%), and total antioxidant activity (AOX) (86%). During storage, AOX, TPC, TSS, pH, and titratable acidity (TA) remained stable. A significant correlation was observed between TPC and AOX. Total mesophilic aerobic bacteria and yeast counts increased during storage. Fifty-seven percent of tasters (n = 26) rated the functional juice positively. Thus, these agri-food products could be useful for producing functional juices with a longer shelf life, contributing to their valorization.

Genetic Variation of Monilinia fructicola Population in Korea

Brown rot disease, caused by Monilinia spp., poses a significant threat to pome and stone fruit crops globally, resulting in substantial economic losses during pre- and post-harvest stages. Monilinia fructigena, M. laxa, and M. fructicola are identified as the key agents responsible for brown rot disease. In this study, we employed the amplified fragment length polymorphism (AFLP) method to assess the genetic diversity of 86 strains of Monilinia spp. isolated from major stone fruit cultivation regions in South Korea. Specifically, strains were collected from Chungcheong, Gangwon, Gyeonggi, Gyeongsang, and Jeolla provinces (-do). A comparative analysis of strain characteristics, such as isolation locations, host plants, and responses to chemical fungicides, was conducted. AFLP phylogenetic classification using 20 primer pairs revealed the presence of three distinct groups, with strains from Jeolla province consistently forming a separate group at a high frequency. Furthermore, M. fructicola was divided into three groups by the AFLP pattern. Principal coordinate analysis and PERMANOVA were applied to compare strain information, such as origin, host, and fungicide sensitivity, revealing significant partition patterns for AFLP according to geographic origin and host plants. This study represents the utilization of AFLP methodology to investigate the genetic variability among M. fructicol isolates, highlighting the importance of continuous monitoring and management of variations in the brown rot pathogen.

Insights into the Transcriptional Reprogramming of Peach Leaves Inoculated with Taphrina deformans

The dimorphic fungus Taphrina deformans is the causal agent of peach leaf curl disease, which affects leaves, flowers, and fruits. An RNA-seq approach was employed to gain insights into the transcriptional reprogramming of a peach cultivar during leaf inoculation with the yeast phase of the fungus across a compatible interaction. The results uncovered modulations of specific peach differentially expressed genes (DEGs) in peaches and pathways related to either the induction of host defense responses or pathogen colonization and disease spread. Expression profiles of DEGs were shown to be highly time-dependent and related to the presence of the two forms of the fungal growth, the inoculated yeast form and the later biotrophic phase during mycelial development. In parallel, this differential reprogramming was consistent with a diphasic detection of fungal load in the challenged leaves over the 120 h after inoculation (HAI) period. Leaf defense responses either occurred during the early yeast phase inoculation at 24 HAI, mediated primarily by cell wall modification processes, or more pronouncedly during the biotrophic phase at 72 HAI, as revealed by the activation of DEGs related to pathogen perception, signaling transduction, and secondary metabolism towards restraining further hypha proliferation. On the contrary, the expression patterns of specific DEGs at 120 HAI might further contribute to host susceptibility. These findings will further allow us to elucidate the molecular responses beyond the peach-T. deformans interaction.

The Impact of Peach Rootstocks and Winter Cover Crops on Reproduction of Ring Nematode

Two peach rootstocks ('Guardian' and 'MP-29') and ten winter cover crops (rye, wheat, barley, triticale, oat, Austrian winter pea, crimson clover, balansa clover, hairy vetch, and daikon radish) were evaluated in a greenhouse environment to determine their suitability to host ring nematode, Mesocriconema xenoplax. Each crop was inoculated with 500 ring nematodes, and the experiments were terminated 60 days after inoculation. The reproduction factor (ratio of final and initial nematode population) ranged from 0 to 13.8, indicating the crops greatly varied in their host suitability to ring nematode. 'Guardian' has been known to tolerate ring nematode; however, results from the current study suggest the tolerance statement is anecdotal. Another peach rootstock, 'MP-29', was also a good host for ring nematode, suggesting an urgency to develop ring nematode-resistant peach rootstocks. Wheat supported the least to no nematode reproduction while pea supported the greatest reproduction. The rest of the cover crops were poor to good hosts to ring nematodes. Although planting cover crops in peach orchards is not common, employing non or poor host crops can help suppress nematodes in addition to having soil health benefits. Furthermore, peach breeding programs should focus on finding and introgressing ring nematode resistance in commercial rootstocks.

Commodity risk assessment of plants of 12 selected Prunus species from Moldova

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as 'High-risk plants, plant products and other objects'. This Scientific Opinion covers plant health risks posed by defoliated 1- or 2-year old bare root plants for planting (grafted or not) of 12 Prunus species (Prunus armeniaca, P. avium, P. canescens, P. cerasifera, P. cerasus, P. davidiana, P. domestica, P. dulcis, P. fontanesiana, P. persica, P. salicina, P. tomentosa) imported from Moldova, taking into account the available scientific information, including the technical information provided by the applicant country. The evaluation identified three EU-quarantine pests, Erwinia amylovora (protected zone quarantine pest), Xiphinema rivesi non-EU populations and Xanthomonas arboricola pv. pruni (protected zone quarantine pest), which were selected for further evaluation, based on defined criteria, including their presence in the applicant country. It should be noted that there is uncertainty regarding whether all relevant pests have been identified due to a limited number of scientific publications and pest surveys in Moldova. For the three selected pests, the risk mitigation measures proposed in the technical dossier from Moldova were evaluated taking into account the possible limiting factors. For these pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on it, including uncertainties associated with the assessment. The degree of pest freedom varies among the pests evaluated, with Erwinia amylovora being the pest most frequently expected on the imported plants. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9823 and 10,000 bundles (comprising 10-20 plants per bundle) out of 10,000 bundles would be free from E. amylovora.

Host Suitability of Summer Cover Crops and Peach Rootstocks to the Peach Root-Knot Nematode, Meloidogyne floridensis

Greenhouse experiments were conducted to determine the host suitability of ten summer cover crops and two peach rootstocks to Meloidogyne floridensis by inoculating them with 10,000 M. floridensis eggs. Brown top millet and sunn hemp were nonhosts as they did not support nematode reproduction. Buckwheat, cowpea, pearl millet, Japanese millet, and sunflower supported more than 25,000 eggs/pot, which indicated that these crops are good hosts to M. floridensis. The crops that supported poor nematode reproduction were sesame, grain sorghum, and sorghum-sudangrass, with their reproduction ranging from 219 to 7,750 eggs/pot. In addition to having many galls on the roots, the peach rootstock Guardian had 10,100 eggs on the roots and 450 second-stage juveniles in the pot, which indicated that 'Guardian' is a good host to M. floridensis. Although the nematode reproduction on MP-29 rootstock was relatively lower, the presence of many large galls on the roots indicates MP-29 is susceptible to M. floridensis. Results from the current study suggest that the employment of nonhost cover crops and poor-host rootstocks could aid in effective nematode management programs for peaches.

Almond can be infected by Plum Pox Virus-D isolate Penn4 and is a transmission-competent host

While currently eradicated from the U.S., Plum pox virus (PPV) poses an ongoing threat to U.S. stone fruit production. Although almond (Prunus dulcis) is known to be largely resistant to PPV, there is conflicting evidence about its potential to serve as an asymptomatic reservoir host for the virus and thus serve as a potential route of entry. Here, we demonstrate that both Tuono and Texas Mission cultivars can be infected by the U.S. isolate PPV-D Penn4 and that Tuono is a transmission-competent host, capable of serving as a source of inoculum for aphid transmission of the virus. These findings have important implications for efforts to keep PPV out of the U.S. and highlights the need for additional research to test the susceptibility of almond to other PPV-D isolates.

Characterization and Potential Action Mode Divergences of Homologous ACO1 Genes during the Organ Development and Ripening Process between Non-Climacteric Grape and Climacteric Peach

Ethylene is one crucial phytohormone modulating plants' organ development and ripening process, especially in fruits, but its action modes and discrepancies in non-climacteric grape and climacteric peach in these processes remain elusive. This work is focused on the action mode divergences of ethylene during the modulation of the organ development and ripening process in climacteric/non-climacteric plants. We characterized the key enzyme genes in the ethylene synthesis pathway, VvACO1 and PpACO1, and uncovered that their sequence structures are highly conserved, although their promoters exhibit important divergences in the numbers and types of the cis-elements responsive to hormones, implying various responses to hormone signals. Subsequently, we found the two have similar expression modes in vegetative organ development but inverse patterns in reproductive ones, especially in fruits. Then, VvACO1 and PpACO1 were further validated in promoting fruit ripening functions through their transient over-expression/RNAi-expression in tomatoes, of which the former possesses a weaker role than the latter in the fruit ripening process. Our findings illuminated the divergence in the action patterns and function traits of the key VvACO1/PpACO1 genes in the tissue development of climacteric/non-climacteric plants, and they have implications for further gaining insight into the interaction mechanism of ethylene signaling during the modulation of the organ development and ripening process in climacteric/non-climacteric plants.

Colonization and population dynamics of total, viable, and culturable cells of two biological control strains applied to apricot, peach, and grapevine crops

The ecological fitness of the biological control strains Bacillus velezensis A17 and Lactiplantibacillus plantarum PM411 was evaluated in different crops, geographical zones, and growing seasons. Both strains (2 g L-1 of dried formulation) were spray-inoculated on apricot trees, peach trees, and grapevines. Depending on the crop, flowers, fruits, and leaves were picked at several sampling time points. The population dynamics of viable, viable but non-culturable, and dead cells were studied by comparing viability qPCR (v-qPCR), qPCR, and plate counting estimations. A17 showed high survival rates in apricot, peach, and grapevine organs. The A17 viability was confirmed since qPCR and v-qPCR estimations did not significantly differ and were rather constant after field applications. However, higher population levels were estimated by plate counting due to the non-selective characteristics of the medium used. The viability of PM411 was constrained by plant organ, crop, and climate conditions, being higher in apricot than in grapevine. PM411 survival declined after field application, indicating difficulties in its establishment. The PM411 population level was made up of dead, culturable, and viable but non-culturable cells since significant differences between the three methods were observed. In conclusion, A17 and PM411 differ strongly in their survival in grapevine, peach, and apricot.

Class III Peroxidases in the Peach (Prunus persica): Genome-Wide Identification and Functional Analysis

Class III peroxidases are plant-specific and play a key role in the response to biotic and abiotic stresses, as well as in plant growth and development. In this study, we investigated 60 POD genes from Prunus persica based on genomic and transcriptomic data available in NCBI and analysed the expression of individual genes with qPCR. Peroxidase genes were clustered into five subgroups using the phylogenetic analysis. Their exon-intron structure and conserved motifs were analysed. Analysis of the transcriptomic data showed that the expression of PpPOD genes varied significantly in different tissues, at different developmental stages and under different stress treatments. All genes were divided into low- and high-expressed genes, and the most highly expressed genes were identified for individual tissues (PpPOD12 and PpPOD42 in flower buds and PpPOD73, PpPOD12, PpPOD42, and PpPOD31 in fruits). The relationship between cold tolerance and the level of peroxidase expression was revealed. These studies were carried out for the first time in the peach and confirmed that chilling tolerance may be related to the specificity of antioxidant complex gene expression.

Genome-Wide Identification of Trehalose-6-phosphate Synthase (TPS) Gene Family Reveals the Potential Role in Carbohydrate Metabolism in Peach

Trehalose-6-phosphate synthase (TPS) is essential for plant growth and development, linking trehalose-6-phosphate (T6P) to carbon metabolism. However, little is known about the TPS gene family in peaches and their potential roles in regulating carbohydrates in peach fruit. In this study, nine TPS genes were identified in the peach genome and named according to the homologous genes in Arabidopsis. Phylogenetic analysis showed that three subfamilies were identified, including TPSI, TPSII-1, and TPSII-2, which were also consistent with gene structure analysis. Considerable cis-elements were enriched in the promoters, including plant hormone-related elements. Tissue-specific analysis showed that these TPS genes were mainly expressed in leaves, stems, and fruit, showing different expression patterns for each gene. In addition, during fruit development, the content of trehalose-6-phosphate (T6P) was positively correlated with the expression of PpTPS7a and negatively with sucrose non-fermenting-1-related kinase 1 (SnRK1) activity. Transient overexpression and silencing of PpTPS7a in peach fruit validated its function in regulating T6P content and SnRK1 activity.

Physiochemical Responses and Ecological Adaptations of Peach to Low-Temperature Stress: Assessing the Cold Resistance of Local Peach Varieties from Gansu, China

In recent years, extreme weather events have become increasingly frequent, and low winter temperatures have had a significant impact on peach cultivation. The selection of cold-resistant peach varieties is an effective solution to mitigate freezing damage. To comprehensively and accurately evaluate the cold resistance of peaches and screen for high cold resistance among Gansu local resources, nine different types of peach were selected as test resources to assess physiological, biochemical, and anatomical indices. Subsequently, 28 peach germplasms were evaluated using relevant indices. The semi-lethal temperature (LT50) was calculated by fitting the change curve of the electrolyte leakage index (ELI) with the Logistic equation; this can be used as an important index for identifying and evaluating the cold resistance of peach trees. The LT50 values ranged from -28.22 °C to -17.22 °C among the 28 tested resources; Dingjiaba Liguang Tao exhibited the lowest LT50 value at -28.22 °C, indicating its high level of cold resistance. The LT50 was positively correlated with the ELI and malondialdehyde (MDA) content with correlation coefficients of 0.894 and 0.863, respectively, while it was negatively correlated with the soluble sugar (SS), soluble protein (SP), and free proline (Pro) contents with correlation coefficients of -0.894, -0.721, and -0.863, respectively. The thicknesses of the xylem, cork layer, cork layer ratio (CLR) and thickness/cortex thickness (X/C) showed negative correlations (-0.694, -0.741, -0.822, -0.814, respectively). Finally, the membership function method was used to evaluate cold resistance based on the ELI, MDA, Pro, SP, SS, CLR, and xylem thickness/cortex thickness (X/C) indices. The average membership degree among all tested resources ranged from 0.17 to 0.61. Dingjiaba Liguang Tao emerged prominently in terms of high-cold-resistance (HR) membership value (0.61).

Short- and long-term effects of season-long infestation of Lycorma delicatula (Hemiptera: Fulgoridae) on young apple (Malus domestica) and peach (Prunus persica) trees

Lycorma delicatula White, commonly called spotted lanternfly, is an invasive fulgorid that was first detected in the United States in Pennsylvania in 2014 and has spread across Eastern states. Lycorma delicatula is a phloem feeder, and feeding of persistent populations can cause wilt and dieback in host plants. Vineyards in infested regions have experienced vine loss, where damage has been attributed to L. delicatula. Nymphal and adult lifestages have been observed on cultivated apple and peach trees, but the feeding effects of this pest on these crops have not been quantified. Here, we caged young potted apple and peach trees and infested them with 50 nymphal or 25 adult L. delicatula per plant for 3 months and tracked plant health. Horticultural measurements including trunk diameter, height, leaf drop, and photosynthesis rates were recorded before, during, and after the infestation. To evaluate the long-term effects of infestation, all apple and peach trees were removed from pots and planted in an orchard block where their phenology, growth, and physiology could be evaluated the following growing season. Short- and long-term measurements showed no significant differences in apple tree health between infested and noninfested trees. There was a significant reduction in the growth of trunk diameter in peach trees during exposure to early-instar nymphs; infested peach trees also had significantly increased frost damage to buds the following spring. However, there were no long-term impacts on peach growth and physiology. These results indicate that L. delicatula likely will not be a major threat to these deciduous fruit crops.

Organic orchard floor management in peach: effects on arthropods and associated fruit injury in the Intermountain West

Understanding orchard floor management is critical to organic tree-fruit production systems given its impact on weeds, soil fertility, tree health, and crop yield. Several viable options are available to producers for weed management and promotion of organic fertility, including use of turf and broadleaf alleyway covers and living and nonliving tree-row mulches. While these measures can be effective, little is known about how these strategies influence arthropod pests, which cause fruit injury. Here, we assessed 6 organic orchard floor management strategies for their impact on arthropod abundance and diversity in an organic peach production system in northern Utah from 2010 to 2014, using sweep netting and pitfall collections along with observed peach fruit damage. Generally, we found that alleyway and tree-row treatments had no impact on total arthropod diversity, species richness, or community diversity. However, earwig (Forficula auricularia) abundance was significantly impacted by alleyway and tree-row treatments that resulted in increased fruit injury. Trefoil alleyway treatments consistently increased earwig abundance across life-history stages, while mulch or Alyssum (straw) tree-row treatments harbored more earwigs and, as a result, increased earwig fruit injury. Since earwigs are especially prone to damaging young, developing fruits, it is imperative that more work is done to assess earwig abundances and life-history traits. Our results demonstrate that detrimental arthropods are sensitive to orchard floor management and can further inform integrated pest management approaches that complement sustainability goals.

Heterologous Expression of a Ferritin Homologue Gene PpFer1 from Prunus persica Enhances Plant Tolerance to Iron Toxicity and H2O2 Stress in Arabidopsis thaliana

In plants, ferritin proteins play an important role in iron (Fe) storage which contributes to plant growth and development. However, the biological functions of ferritins in fruit trees are essentially unknown. In this study, three Ferritin genes were isolated from 'Zhentong No. 3' peach, which were named PpFer1-PpFer3. The expression levels of these genes were different in distinct tissues/organs. Notably, PpFer1 was the most abundantly expressed Ferritin family gene in all tested tissues of 'Zhentong No. 3' peach; its expression levels were significantly enhanced throughout the entire peach seedling under Fe toxicity and H2O2 stress, particularly in the leaves. In addition, over-expression of PpFer1 was effective in rescuing the retarded growth of Arabidopsis fer1-2 knockout mutant, embodied in enhanced fresh weight, primary root length, lateral root numbers, total root length, total leaf chlorophyll, stomatal conductance (Gs), net photosynthetic rate (Pn), transpiration rate, and tissue Fe concentration. This study provides insights into understanding the molecular mechanisms of Fe storage and sequestration in perennial fruit trees.

Melatonin Promotes Iron Reactivation and Reutilization in Peach Plants under Iron Deficiency

The yellowing of leaves due to iron deficiency is a prevalent issue in peach production. Although the capacity of exogenous melatonin (MT) to promote iron uptake in peach plants has been demonstrated, its underlying mechanism remains ambiguous. This investigation was carried out to further study the effects of exogenous MT on the iron absorption and transport mechanisms of peach (Prunus persica) plants under iron-deficient conditions through transcriptome sequencing. Under both iron-deficient and iron-supplied conditions, MT increased the content of photosynthetic pigments in peach leaves and decreased the concentrations of pectin, hemicellulose, cell wall iron, pectin iron, and hemicellulose iron in peach plants to a certain extent. These effects stemmed from the inhibitory effect of MT on the polygalacturonase (PG), cellulase (Cx), phenylalanine ammonia-lyase (PAL), and cinnamoyl-coenzyme A reductase (CCR) activities, as well as the promotional effect of MT on the cinnamic acid-4-hydroxylase (C4H) activity, facilitating the reactivation of cell wall component iron. Additionally, MT increased the ferric-chelate reductase (FCR) activity and the contents of total and active iron in various organs of peach plants under iron-deficient and iron-supplied conditions. Transcriptome analysis revealed that the differentially expressed genes (DEGs) linked to iron metabolism in MT-treated peach plants were primarily enriched in the aminoacyl-tRNA biosynthesis pathway under iron-deficient conditions. Furthermore, MT influenced the expression levels of these DEGs, regulating cell wall metabolism, lignin metabolism, and iron translocation within peach plants. Overall, the application of exogenous MT promotes the reactivation and reutilization of iron in peach plants.

Effects of gamma irradiation on the sensory and metabolic profiles of two peach cultivars

BACKGROUND

The suitability of commercial peaches for minimal processing (MP) is limited, mainly due to shortened shelf-life. Gamma irradiation has emerged in MP fruits as a promising technology. This study aimed to investigate the effects of gamma irradiation on the sensory and metabolic profiles of MP peaches from two cultivars - 'Forastero' (FT) and 'Ruby Prince' (RP) - and evaluate the relationship between both profiles. MP peaches were packaged and divided into two groups: one without additional treatment (K) and the other subjected to gamma irradiation (1.0 kGy, I- irradiation treatment), making a total of four samples (FTK, FTI, RPK and RPI). The sensory profile was carried out by an assessor panel. Metabolite analysis was accomplished by gas chromatography-mass spectrometry.

RESULTS

Irradiation significantly affected color, homogeneity, peach aroma, total flavor intensity, peach flavor, sweetness and juiciness in FT, increasing their intensities. In the RP cultivar, irradiation increased brightness, total aroma intensity, peach aroma, and flavor and texture descriptors. Regarding metabolites, only malic acid and sucrose increased their concentrations in the irradiated samples. Partial least squares showed that sucrose was mainly correlated with sweet, total aroma intensity and peach flavors, and linked with FTI sample. Bitter along with peach aroma and total intensity flavor were associated with RPI sample.

CONCLUSION

The applied dose accelerated the ripening process of the peach. The study highlights the importance of complementing sensory analysis with metabolomics tools to optimize fruit quality in minimally processed peaches. © 2023 Society of Chemical Industry.

Don) Hara straw increases selenium accumulation in peach seedlings under selenium-contaminated soil

To promote the selenium (Se) uptakes in fruit trees under Se-contaminated soil, the effects of water extract of Fagopyrum dibotrys (D. Don) Hara straw on the Se accumulation in peach seedlings under selenium-contaminated soil were studied. The results showed that the root biomass, chlorophyll content, activities of antioxidant enzymes, and soluble protein content of peach seedlings were increased by the F. dibotrys straw extract. The different forms of Se (total Se, inorganic Se, and organic Se) were also increased in peach seedlings following treatment with the F. dibotrys straw extract. The highest total shoot Se content was treated by the 300-fold dilution of F. dibotrys straw, which was 30.87% higher than the control. The F. dibotrys straw extract also increased the activities of adenosine triphosphate sulfurase (ATPS), and adenosine 5'-phosphosulfate reductase (APR) in peach seedlings, but decreased the activity of serine acetyltransferase (SAT). Additionally, correlation and grey relational analyses revealed that chlorophyll a content, APR activity, and root biomass were closely associated with the total shoot Se content. Overall, this study shows that the water extract of F. dibotrys straw can promote Se uptake in peach seedlings, and 300-fold dilution is the most suitable concentration.

Low temperature inhibits pectin degradation by PpCBFs to prolong peach storage time

Low-temperature storage is a widely used method for peach fruit storage. However, the impact of PpCBFs on pectin degradation during low-temperature storage is unclear. As such, in this study, we stored the melting-flesh peach cultivar "Fuli" at low temperature (LT, 6°C) and room temperature (RT, 25°C) to determine the effect of different temperatures on its physiological and biochemical changes. Low-temperature storage can inhibit the softening of "Fuli" peaches by maintaining the stability of the cell wall. It was found that the contents of water-soluble pectin and ionic-soluble pectin in peach fruit stored at RT were higher than those stored at LT. The enzyme activities of polygalacturonase (PG), pectate lyase (PL), and pectin methylesterase (PME) were all inhibited by LT. The expressions of PpPME3, PpPL2, and PpPG were closely related to fruit firmness, but PpCBF2 and PpCBF3 showed higher expression levels at LT than RT. The promoters of PpPL2 and PpPG contain the DER motif, which suggested that PpCBF2 and PpCBF3 might negatively regulate their expression by directly binding to their promoters. These results indicated that LT may maintain firmness by activating PpCBFs to repress pectin-degradation-related enzyme genes during storage.

Sodium alginate coating of Ginkgo biloba leaves extract containing phenylpropanoids as an ecofriendly preserving agent to maintain the quality of peach fruit

Plant constituents are of great interest in the food processing industry as potential natural preservative agents for controlling foodborne pathogens. In this study, the 95% EtOH/H2 O extract of Ginkgo biloba leaves was separated using polarity extraction solvents with petroleum ether (PE), ethyl acetate (EA), n-butanol (nB), and water (W) by the principle of similarity and compatibility. Through TLC and NMR analysis of these extracts, it can be concluded that the main component of PE extract were organic acids, for EA extract were flavonoids, for nB extract were phenylpropanoids, and water extract were oligosaccharides. Twelve monomer compounds were separated from the extracts to verify the composition of each extraction stage. Results of morphological and molecular identification revealed that Monilinia fructicola and Rhizopus stolonifer were the main fungi causing peach rot. After evaluating the antifungal activity and peach quality of the four extract/sodium alginate coatings, it was found that the n-butanol extract/sodium alginate coating containing phenylpropanoids had the lowest decay index and the best preservation effect, providing a sustainable alternative to reduce the harm to the environment of synthetic preservatives. PRACTICAL APPLICATION: The abuse of synthetic preservatives poses a threat to the ecological environment and physical health. Therefore, this study developed sodium alginate coating of Ginkgo biloba leaves extract containing phenylpropanoids, which has good effects on the preservation of peaches. The agent is a promising environmentally friendly alternative for synthetic preservatives.

Mycotoxin Determination in Peaches and Peach Products with a Modified QuEChERS Extraction Procedure Coupled with UPLC-MS/MS Analysis

Peaches are the most significant temperate fruit crop worldwide. However, peach fruits are susceptible to fungal and mycotoxin contamination. Consequently, monitoring the residual levels of multiple mycotoxins in peaches and related products is essential. In this study, a novel method based on QuEChERS extraction, followed by ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) detection, was developed for analyzing 14 mycotoxins in peaches and peach products from China. Matrix-matched calibrations were employed to accurately quantify the mycotoxins and compensate for matrix effects. Recoveries for the target analytes ranged from 84.6% to 117.6%, with intra-day and inter-day precision below 20%. The limits of quantification were 2 or 5 μg/L for the 14 mycotoxins. This method was utilized to detect the presence of target mycotoxins in 109 fresh peaches, 100 diseased peaches, and 89 peach products from China. Six mycotoxins were identified in the rotten parts of the diseased peaches, with concentrations ranging from 5.2 to 1664.3 µg/kg. In the remaining parts of the diseased peach samples, only two toxins, alternariol (AOH) and alternariol monomethyl ether (AME), were quantified at levels of 15.3 µg/kg and 15.5 µg/kg, respectively. No mycotoxins were detected in fresh peaches. For peach products, all contamination levels were below the quantitative limits and significantly lower than the maximum legal limits established for the products.

The role of stress factors in severity of Cytospora plurivora in greenhouse and field plantings of 13 peach (Prunus persica) cultivars

Understanding the host-pathogen-environmental interactions in a pathosystem is essential for management of diseases and diminished crop yields. Abiotic stressors such as cold damage, water deficit, and high pH soils can be major limiting factors to tree fruit production. Along with decreased yields, these abiotic factors can have direct implications for disease severity within orchards. Cytospora plurivora is a ubiquitous fungal canker pathogen in western Colorado, USA and is a major focus in integrated pest management strategies. This research evaluated the influence of biotic and abiotic stress factors on peach tree health. Thirteen peach cultivars were placed under abiotic stress and inoculated with C. plurivora in greenhouse and field conditions. Under deficit irrigation, C. plurivora infections were significantly larger and more severe in both the greenhouse and field trials when compared with those under the full-irrigation controls. In controlled greenhouse conditions, a positive correlation between lesion size and water potential was evident, but no trend of cultivar tolerance was observed. Furthermore, increase in irrigation water pH, through additions of sodium carbonate and bicarbonate, in the greenhouse trials resulted in decreased leaf water potentials and increased pathogen necrotic tissue volumes (mm3). In field trials, there was no positive relationship between lesion size and water potential; trees with the most negative water potentials had the smallest lesions sizes that did not correspond to cultivar, suggesting that other abiotic or biotic factors may be shielding water stressed trees from increased pathogen aggression. This research highlights the importance of proper irrigation and soil pH management as tools for the management of Cytospora canker in peach orchards.

Bees and thrips carry virus-positive pollen in peach orchards in South Carolina, United States

Prunus necrotic ringspot virus (PNRSV) and prune dwarf virus (PDV) are pollen-borne viruses of important stone fruit crops, including peaches, which can cause substantial yield loss. Although both horizontal and vertical (i.e., seed) transmission of both viruses occurs through pollen, the role of flower-visiting insects in their transmission is not well understood. Bees and thrips reportedly spread PNRSV and PDV in orchards and greenhouse studies; however, the field spread of PNRSV and PDV in peach orchards in the southeastern United States is not explored. We hypothesized that bees and thrips may facilitate virus spread by carrying virus-positive pollen. Our 2-yr survey results show that 75% of captured bees are carrying virus-positive pollen and moving across the orchard while a subsample of thrips were also found virus positive. Based on morphology, Bombus, Apis, Andrena, Eucera, and Habropoda are the predominant bee genera that were captured in peach orchards. Understanding the role of bees and thrips in the spread of PNRSV and PDV will enhance our understanding of pollen-borne virus ecology.

Exogenous BR delayed peach fruit softening by inhibiting pectin degradation enzyme genes

Peach fruit deteriorates and senesces rapidly when stored at room temperature. Brassinosteroids (BRs) play an important role in regulating plant growth and development and maintaining fruit quality. However, little information is available on the effect of BRs on the senescence of harvested peach fruit. In this study, different concentrations of BR were used to treat 'Hongniang' peach fruit, and the results showed that 10 μM BR was the most beneficial concentration to delay the senescence of peach fruits. BR treatment delayed the decrease of fruit firmness, the release of ethylene, the increase in water-soluble pectin (WSP) and ionic-soluble pectin (ISP) content and the decrease in covalently bound pectin (CBP) content, inhibited the activities of pectin degradation enzymes, and inhibited the gene expression of PpPME1/3, PpPG, PpARF2, and PpGAL2/16. In addition, BR treatment also inhibited the expression of PpBES1-5/6. Cis-acting regulatory element analysis of pectin degradation enzyme promoters showed that many of them contained BES1 binding elements. All the above results showed that BR treatment had a positive effect on delaying the senescence of peach fruit and prolonging its storage period.

Identification of the Light-Harvesting Chlorophyll a/b Binding Protein Gene Family in Peach (Prunus persica L.) and Their Expression under Drought Stress

In higher plants, light-harvesting chlorophyll a/b binding (Lhc) proteins play a vital role in photosynthetic processes and are widely involved in the regulation of plant growth, development, and response to abiotic stress. However, the Lhc gene family has not been well identified in peaches (Prunus persica L.). In this study, 19 PpLhc genes were identified in the peach genome database, which were unevenly distributed on all chromosomes. Phylogenetic analysis demonstrated that PpLhc proteins could be divided into three major subfamilies, each of whose members had different exon-intron structures but shared similar conserved motifs. A total of 17 different kinds of cis-regulatory elements were identified in the promoter regions of all PpLhc genes, which could be classified into three categories: plant growth and development, stress response, and phytohormone response. In addition, transcriptomic data analysis and RT-qPCR results revealed that the expression profiles of some PpLhc genes changed under drought treatment, suggesting the crucial roles of Lhc genes in the regulation of plant tolerance to drought stress. Taken together, these findings will provide valuable information for future functional studies of PpLhc genes, especially in response to drought stress.

Chitinase-Like Protein PpCTL1 Contributes to Maintaining Fruit Firmness by Affecting Cellulose Biosynthesis during Peach Development

The firmness of the flesh fruit is a very important feature in the eating process. Peach fruit is very hard during development, but its firmness slightly decreases in the later stages of development. While there has been extensive research on changes in cell wall polysaccharides during fruit ripening, little is known about the changes that occur during growth and development. In this study, we investigated the modifications in cell wall components throughout the development and ripening of peach fruit, as well as its impact on firmness. Our findings revealed a significant positive correlation between fruit firmness and cellulose content at development stage. However, the correlation was lost during the softening process, suggesting that cellulose might be responsible for the fruit firmness during development. Members of the chitinase-like protein (CTL) group are of interest because of their possible role in plant cell wall biosynthesis. Here, two CTL homologous genes, PpCTL1 and PpCTL2, were identified in peach. Spatial and temporal expression patterns of PpCTLs revealed that PpCTL1 exhibited high expression abundance in the fruit and followed a similar trend to cellulose during fruit growth. Furthermore, silencing PpCTL1 expression resulted in reduced cellulose content at 5 DAI (days after injection), this change that would have a negative effect on fruit firmness. Our results indicate that PpCTL1 plays an important role in cellulose biosynthesis and the maintenance of peach firmness during development.

First report of Calosphaeria pulchella causing cankers in peach (Prunus persica) in Chile

Peach (Prunus persica) is an important stone fruit crop in Chile, with 7,665 h in 2022. Trunk diseases symptoms, including shoot dieback, longitudinal cankers and internal dark-brown to purple discolorations in cross sections were observed in a commercial orchard, in March of 2021. In severe cases, mostly in old trees, periderm sections were detached from the cankers, showing circinate groups of black long necked perithecia. To isolate the causal agent, wood samples were collected from March 2021 to October 2022, from symptomatic trees (n=23) of commercial orchards (n=12) (34°12'36.47"S 70°46'3.43"O to 34°34'26.48"S 70°58'17.97"O), located in O'Higgins Region, in the center of Chile. Isolations were performed cutting wood sections (0.5 cm) from the necrosis progress area, disinfecting them in sodium hypochlorite (10%), plating on a quarter-strength potato dextrose agar amended with 1 mg/L tetracycline (aPDA-tet) and incubating at 25°C, until mycelial development. Cultures were purified on PDA and identified by morphological means. Colonies on PDA were dark-pink and purple to orange-red, with regular margins, usually white, and produced abundant hyaline ellipsoidal to allantoid conidia (3.8-5.7 × 1.3 μm). In some cases, perithecia developed on disinfected wood on culture media, showing clavate unitunicate asci with hyaline allantoid ascospores 4.5-6.2 × 0.7 μm. The morphological characteristics of anamorph and teleomorph structures of field and culture isolates accorded to those described for Calosphaeria pulchella (1,2). DNA from representative isolates was extracted and the ITS region was amplified by PCR using ITS1/ITS4 primers (3), sequenced and BLAST analyzed. BLAST results revealed that ITS sequences identity of the representative isolates HMDu263 and HMDu271, shared 99 and 100% similarity, respectively, when compared to isolate CBS115999 (EU367451) (1,2,4). Sequences were accessioned to GenBank (OP216663 and OP216664 [ITS]). To determine the pathogenicity of C. pulchella, 17 representative isolates were inoculated on peach canes (25 cm) (n=7 per isolate), that were previously rooted on tap water amended with 500 ppm of indole-butyric acid, for 30 d. Mycelial plugs (0.5 cm) from actively growing colonies on PDA were placed on circular injuries made in the upper third of the shoots using a sterile corkborer and covered with plastic film. Sterile agar was used for controls. After 60 d of incubation in aerated tap water, at 23 +/-3 °C, bark was removed, and the necrosis length was measured and compared. Mean length values of lesions went from 9.5 to 27 cm. The most virulent isolates (n=7) were inoculated on fresh cuts of main shoots of nursery plants (n=3 per isolate) cv. Royal Glory, with 200 µL conidial suspensions (1x10⁵ conidia/mL), on March 18th, 2022. Plants were incubated at shadehouse for 102 d and after the incubation period, shoots were cut (30 cm), bark was removed, and discoloration length was measured. All the isolates were pathogenic, with differences among their virulence (ANOVA, LSD, P < 0.05) from 5.2 cm (HMDu246) to 24.3 cm (HMDu266). Fungus was successfully reisolated from symptomatic canes (100%) and trees (98.7%), but not from the controls in both pathogenicity tests, fulfilling Koch's postulates. Calosphaeria pulchella was recently reported causing trunk disease in sweet cherry in Chile (4) and these results contribute to the knowledge of trunk diseases of fruit crops in Chile and to the understanding of the pathogen worldwide.

Lipid Metabolomic and Transcriptomic Analyses Reveal That Phosphatidylcholine Enhanced the Resistance of Peach Seedlings to Salt Stress through Phosphatidic Acid

Soil salinity is a major conlinet limiting sustainable agricultural development in peach tree industry. In this study, lipid metabolomic pathway analysis indicated that phosphatidic acid is essential for root resistance to salt stress in peach seedlings. Through functional annotation analysis of differentially expressed genes in transcriptomics, we found that MAPK signaling pathway is closely related to peach tree resistance to salt stress, wherein PpMPK6 expression is significantly upregulated. Under salt conditions, the OE-PpMPK6 Arabidopsis thaliana (L.) Heynh. line showed higher resistance to salt stress than WT and KO-AtMPK6 lines. Furthermore, we found that the Na⁺ content in OE-PpMPK6 roots was significantly lower than that in WT and KO-AtMPK6 roots, indicating that phosphatidic acid combined with PpMPK6 activated the SOS1 (salt-overly-sensitive 1) protein to enhance Na⁺ efflux, thus alleviating the damage caused by NaCl in roots; these findings provide insight into the salt stress-associated transcriptional regulation.

Nitric oxide modulates folate-mediated one-carbon metabolism and mitochondrial energy levels of peaches during cold storage

Folate-mediated one-carbon metabolism (FOCM) is closely associated with postharvest preservation. This study investigated the effects of exogenous nitric oxide (NO) on FOCM, storage quality, energy metabolism, and mitochondrial membrane integrity in cold-storage peach fruit. In this experiment, peaches were soaked with 1.5 mmol L^-1S-nitrosoglutathione (GSNO) as NO donor, and the negative treatment (NT) solution containing 5 μmol L^-1 carboxy-PTIO (c-PTIO, NO scavenger), 200 μmol L^-1 N^G-Nitro-_L-arginine methyl ester (_L-NAME, NO synthase-like enzyme inhibitor), and 200 μmol L^-1 sodium tungstate dihydrate (nitrate reductase inhibitor) and stored at 0°C. The results showed that NO decreased the activity of S-adenosylmethionine synthase and S-adenosylhomocysteine hydrolase and increased the activity of methionine sulfoxide reductase A, as well as the content of N5-methyl-THF, the ratio of tetrahydrofolate (THF), homocysteine, methionine, S-adenosylmethionine (SAM), and SAM to S-adenosylhomocysteine compared with the control, indicating that NO effectively increased FOCM flux by affecting the activity of FOCM enzymes. Meanwhile, NO increased the activities of H⁺-ATPase, Ca²⁺-ATPase, cytochrome c oxidase, succinate dehydrogenase, and the contents of adenosine triphosphate and adenosine diphosphate, and maintained high energy charge in peaches during storage. NO retarded the increase in mitochondrial permeability transition, reactive oxygen species content, and the decrease in mitochondrial membrane fluidity, membrane potential, and swelling. NT treatment exhibited the opposite results. In conclusion, these results suggested that NO could induce the accumulation of folate and FOCM flux and maintain mitochondrial energy levels, which might be responsible for maintaining the quality of peaches during cold storage.

Transcriptomic Analysis Reveals Genes Associated with the Regulation of Peach Fruit Softening and Senescence during Storage

Peach (Prunus persica (L.) Batsch) is a highly desirable fruit that is consumed around the world. However, the peach fruit is highly perishable after harvest, a characteristic that limits the distribution and supply to the market and causes heavy economic losses. Thus, peach fruit softening and senescence after harvest urgently need to be addressed. In the current study, transcriptomic analysis was performed to identify candidate genes associated with peach fruit softening and senescence, comparing peach fruit from cultivars with different flesh textures, namely melting and stony hard (SH) flesh textures during storage at room temperature. The mitogen-activated protein kinase signaling pathway-plant and plant hormone signal transduction pathways were associated with peach fruit softening and senescence according to the Venn diagram analysis and weighted gene co-expression network analysis. The expression levels of seven genes, including Prupe.1G034300, Prupe.2G176900, Prupe.3G024700, Prupe.3G098100, Prupe.6G226100, Prupe.7G234800, and Prupe.7G247500, were higher in melting peach fruit than in SH peach fruit during storage. Furthermore, the SH peach fruit softened rapidly after 1-naphthylacetic acid treatment, during which the levels of expression of these seven genes, determined by a quantitative reverse transcription polymerase chain reaction, were strongly induced and upregulated. Thus, these seven genes may play essential roles in regulating peach fruit softening and senescence.

Integrated analysis of transcriptomics and metabolomics of peach under cold stress

Low temperature is one of the environmental factors that restrict the growth and geographical distribution of peach (Prunus persica L. Batsch). To explore the molecular mechanisms of peach brunches in response to cold, we analyzed the metabolomics and transcriptomics of 'Donghe No.1' (cold-tolerant, CT) and '21^st Century' (cold-sensitive, CS) treated by different temperatures (-5 to -30°C) for 12 h. Some cold-responsive metabolites (e.g., saccharides, phenolic acids and flavones) were identified with upregulation only in CT. Further, we identified 1991 cold tolerance associated genes in these samples and they were significantly enriched in the pathways of 'galactose metabolism', 'phenylpropanoid biosynthesis' and 'flavonoids biosynthesis'. Weighted gene correlation network analysis showed that soluble sugar, flavone, and lignin biosynthetic associated genes might play a key role in the cold tolerance of peach. In addition, several key genes (e.g., COMT, CCR, CAD, PER and F3'H) were substantially expressed more in CT than CS under cold stress, indicating that they might be major factors during the adaptation of peach to low temperature. This study will not only improve our understanding towards the molecular mechanisms of peach trees under cold stress but also contribute to the screening and breeding program of peach in the future.

Yogurt Products Fortified with Microwave-Extracted Peach Polyphenols

Pectin and polyphenols have been obtained from choice peach flesh using microwave extraction, with the resulting extracts used in functionalizing strained yogurt gels. A Box-Behnken design was utilized in order to co-optimize the extraction process. Soluble solid content, total phenolic content, and particle size distributions were measured in the extracts. Extraction at pH 1 yielded the highest phenolic content, while increases in the liquid-to-solid ratio resulted in a decrease in soluble solids and an increase in particle diameter. Selected extracts were then incorporated into strained yogurt, and the resulting gel products were assessed for color and texture over a two-week period. All samples were darker and had more red tones than the control set yogurt, while exhibiting less yellow tones. The cohesiveness of all samples remained stable over the gels' aging of two weeks (break-up times always remaining within 6 s and 9 s), which is close to the expected shelf-life of such products. The work required for the deformation of most samples increases with time, indicating that the products became firmer due to the macromolecular rearrangements in the gel matrix. The extracts obtained with the highest microwave power (700 W) give less firm samples. This was due to the microwave-induced loss of conformation and self-assembly of the extracted pectins. The hardness of all samples increased over time, gaining from 20 to 50% of the initial hardness due to the rearrangement of the pectin and yogurt proteins over time. The products with pectin extracted at 700 W were again exceptions, losing hardness or remaining stable after some time. Overall, this work combines the sourcing of polyphenols and pectin from choice fruit; it uses MAE for isolating the materials of interest; it mechanically examines the resulting gels; and it performs all the above under a specifically-set experimental design aiming towards optimizing the overall process.

Somatic Mutations in Fruit Trees: Causes, Detection Methods, and Molecular Mechanisms

Somatic mutations are genetic changes that occur in non-reproductive cells. In fruit trees, such as apple, grape, orange, and peach, somatic mutations are typically observed as "bud sports" that remain stable during vegetative propagation. Bud sports exhibit various horticulturally important traits that differ from those of their parent plants. Somatic mutations are caused by internal factors, such as DNA replication error, DNA repair error, transposable elements, and deletion, and external factors, such as strong ultraviolet radiation, high temperature, and water availability. There are several methods for detecting somatic mutations, including cytogenetic analysis, and molecular techniques, such as PCR-based methods, DNA sequencing, and epigenomic profiling. Each method has its advantages and limitations, and the choice of method depends on the research question and the available resources. The purpose of this review is to provide a comprehensive understanding of the factors that cause somatic mutations, techniques used to identify them, and underlying molecular mechanisms. Furthermore, we present several case studies that demonstrate how somatic mutation research can be leveraged to discover novel genetic variations. Overall, considering the diverse academic and practical value of somatic mutations in fruit crops, especially those that require lengthy breeding efforts, related research is expected to become more active.

Hydrogen Sulfide Enhances Browning Repression and Quality Maintenance in Fresh-Cut Peaches via Modulating Phenolic and Amino Acids Metabolisms

Effects of hydrogen sulfide (H₂S) on the browning and quality maintenance of fresh-cut peach fruit were studied. The results showed that H₂S treatment repressed the development of surface browning, suppressed the increase in respiration rate and weight loss, and delayed the decline of firmness while soluble solids content (SSC) and microbial growth were unaffected during storage. H₂S treatment maintained higher contents of phenolic compounds, especially neo-chlorogenic acid, catechin, and quercetin, and delayed the degradation of phenolic compounds by enhancing the activities of phenolic biosynthesis-related enzymes and inhibiting the oxidative activities of polyphenol oxidase (PPO) in comparison with control. Moreover, H₂S stimulated the accumulation of amino acids and their derivatives including proline, γ-aminobutyric acid (GABA), and polyamines (PAs) via enhancing biosynthesis and repressing degradation compared to control. These results suggested that H₂S treatment enhanced the accumulation of phenolic, amino acids, and their derivatives by modulating phenolic and amino acids metabolisms, which contributed to the higher antioxidant activity and membrane integrity maintenance, ultimately repressing browning development and maintaining the quality. Therefore, the current study speculated that H₂S might be a promising approach for browning inhibition and quality maintenance in fresh-cut peach fruit.

Quantitative N-Glycomic and N-Glycoproteomic Profiling of Peach [Prunus persica (L.) Batsch] during Fruit Ripening

Being part of the human diet, peach is an important fruit consumed worldwide. In the present study, a systematic first insight into the N-glycosylation of peach fruit during ripening was provided. First, N-glycome by reactive matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry indicated that 6 of 24 N-glycans of peach were differentially expressed. Second, a comparative N-glycoproteome was characterized via ¹⁸O-tagged N-glycosylation site labeling followed by nano-liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MS/MS). Totally 1464 N-glycosites on 881 N-glycoproteins were identified, among which 291 N-glycosites on 237 N-glycoproteins were expressed differentially with a fold change value of 1.5 or 0.67. The enrichment analysis of GO and KEGG revealed that four pathways including other glycan degradation, phenylpropanoid biosynthesis, amino sugar and nucleotide sugar metabolism, and protein processing in endoplasmic reticulum were mainly enriched, in which several important N-glycoproteins with dynamic change during fruit ripening were further screened out. Our findings on a large scale for N-glycosylation analysis of peach fruit during ripening may provide new molecular insights for comprehending N-glycoprotein functions, which should be of great interest to both glycobiologists and analytical chemists.

Flavoromics Approach in Critical Aroma Compounds Exploration of Peach: Correlation to Origin Based on OAV Combined with Chemometrics

It is essential to seek the critical aroma compounds to identify the origins of peach as well as provide a guidance for quality evaluation. In this study, the peach was characterized by HS-SPME/GC-MS. Subsequently, the odor activity value (OAV) was calculated to specify the primary aroma-active compounds. Afterwards, the chemometrics methods were employed to explore the potentially critical aroma on the basis of p value, fold change (FC), S-plot, jack-knifing confidence interval, variable importance for projection (VIP), and the Shared and Unique Structures (SUS) plots. As a result, five compounds (methyl acetate, (E)-hex-2-enal, benzaldehyde, [(Z)-hex-3-enyl] acetate, and 5-ethyloxolan-2-one) were considered as critical aromas. Moreover, the multi-classification model was developed with an outstanding performance (accuracy of 100%) using the five critical aroma. Moreover, the potential chemical basis of odors was sought through sensory evaluation. In addition, this study provides the theoretical and practical foundation for geographical origin traceability and quality evaluation.

First report flat peach fruit rot caused by Fusarium fujikuroi in China

Flat peach (Prunus persica L. Batsch. var. compressa Bean) is a distinctive peach variety with flat shape. It is well known for its high nutritional value and pleasant flavor, and has become the primary cultivar in Shengzhou city, Zhejiang province, China. In July 2021, we discovered that 8%-10% of flat peach (data gained from a survey of fifteen trees in each orchard) fruits in three orchards (about 2.6 ha) had a fungal disease in Jinting Town, Shengzhou. The infected fruit by this pathogen showed soft, brown, and sunken lesions, accompanied by a sour odor and white mycelia. For pathogen isolation, ten infected fruits were surface sterilized (75% ethanol for 30 s and 2.0% NaClO for 3 min), then rinsed with sterile distilled water three times. The tissues from the margin of lesions were cut into 0.6×0.6 cm pieces and transferred to potato dextrose agar (PDA) medium containing 30.0 μg/mL chloramphenicol. The plates were incubated at 25 °C for 5 days in the dark. Mycelia growing from tissues were subcultured onto fresh PDA medium to get a pure isolate, which formed dense white hyphae after 4 days. The average growth rate of mycelium on PDA medium was 3.4 ± 0.2 mm/d, and the colonies were pale purple after 5 days. Macroconidia was slender, slightly curved, almost 2 to 3 septa, with a bend and tapering apical cell and poorly developed foot cell, and the size was 4.5 to 16.9 × 1.8 to 4.0 μm (n= 50) μm. No microconidia and chlamydospores were observed. This isolate's morphological and cultural characteristics were close to Fusarium fujikuroi (Leslie and Summerell. 2006). To further get the phylogenetic evidence, the nuclear ribosomal internal transcribed spacer region (ITS) and translation elongation factor-1 (TEF-1α) genes of three representative isolations were amplified by primers ITS1 (F:5'-GGAAGTAAAAGTCGTAACAAGG-3') /ITS4 (R5'-TCCTCCGCTTATTGATATGC-3') (Groenewald et al. 2013), and EF1-728F (5'-TACAARTGYGGTGGTATYGACA-3')/ EF1-986R (5'-ACNGACTTGACYTCAGTRGT-3') (Carbone and Kohn. 1999), respectively. The amplified sequences were submitted to Genbank with accession numbers OP223318 for the IST and OP394152 for the ETF-1α region. Blastn results indicated that the ITS and TEF-1α sequences from the isolated strain shared 96.25% and 98.32% similarity with two strains of F. fujikuroi (GenBank Accession No. MF281286.2, and MK311296.1). The isolates were clustered with F. fujikuroi clade (Supplementary Fig.1 and Supplementary Fig.2), consistent with the morphological identification. To evaluate Koch's postulates, 20μL of spore suspension (1×106 spores/mL) were inoculated into ten healthy flat peach fruits with sterile syringes, while another ten healthy fruits were injected with sterilized water as controls. All fruits were kept in sealed plastic boxes at 25 °C with 90% relative humidity. All inoculated fruits showed symptoms similar to those of naturally infected fruits, while uninoculated fruits remained healthy after 4 days. In addition, F. fujikuroi was an important pathogen causing bakanae disease in rice (Hou et al. 2017). This pathogen was also reported to cause Lilium lacifolium Thunb bulb rot (Fang et al. 2022) and cause root rot in peanuts in China (Sun et al. 2022). However, to the best of our knowledge, this is the first record of F. fujikuroi causing fruit rot in flat peach in China. The discovery will provide helpful information about flat peach rot disease management.

Temperature controlled microcapsule loaded with Perilla essential oil and its application in preservation of peaches

In this study, Perilla frutescens essential oil (PEO) loaded microcapsules (PEOM) were successfully prepared and their thermal stability, temperature-responsive releasing effect, antioxidant activity, antibacterial activity, and preservation of peach were systematically investigated. PEOM showed excellent encapsulation efficiency (91.5%) with a core-shell ratio of 1.4:1 and exhibited high thermal stability, indicating that PEOM could effectively maintain PEO release rate. In vitro assays indicated that the optimal kinetic model for PEO release fitted well with first order with a diffusion mechanism. A high level of antioxidant and antibacterial activity of PEOM was maintained. In addition, owing to its sustained release, PEOM could prolong the shelf life of peaches significantly. Therefore, PEOM has potential application and development prospects in the field of food preservation.

Prevalence and Distribution of Phony Peach Disease (Caused by Xylella fastidiosa) in the United States

Peach is an important specialty fruit crop in the United States, and phony peach disease (PPD), caused by Xylella fastidiosa subsp. multiplex, has been a major cause of yield loss since it was first observed in 1885. Under a federal eradication program, surveys of PPD were conducted from 1929 to 1972, when the program was terminated. No surveys have been conducted in approximately 50 years; therefore, the current prevalence of PPD in the United States is unknown, especially in the Southeast, where damage was previously most severe. To ascertain the status of PPD, we surveyed orchards in Alabama, Florida, Georgia, and South Carolina from June to August 2020 and, except for South Carolina and northern Georgia, PPD was prevalent. Trees in 17 orchards were subjected to confirmation of X. fastidiosa using the AmplifyRP XRT+ for X. fastidiosa to corroborate our visual assessments; based on these tests, PPD incidence in the orchards ranged from 0 to 30.5%. Ancillary written surveys of relative PPD presence and prevalence were sent to fruit pathologists from universities in 20 states where PPD was historically reported. Only 35.0% of respondents reported that PPD either currently or recently occurred in their state and, of these, three reported PPD to be of significant concern. The results of the physical and written surveys indicate that PPD remains prevalent mainly in the southeastern region of the United States but, in other states where previously reported, it is either not present or has very low prevalence when compared with historical accounts of the disease.

Valorization of Peels of Eight Peach Varieties: GC-MS Profile, Free and Bound Phenolics and Corresponding Biological Activities

Sustainability, becoming essential for food processing and technology, sets goals for the characterization of resources considered as food waste. In this work, information about the GC-MS metabolites of peach peels was provided as a tool that can shed more light on the studied biological activities. In addition, distribution patterns and contribution of the chemical profile and free and bound phenolic compounds as antioxidant, antimicrobial, and enzymatic clusters in peach peels of different varieties of Bulgarian origin were studied. The two applied techniques (alkaline and acid hydrolysis) for releasing the bound phenolics reveal that alkaline hydrolysis is a better extraction approach. Still, the results indicate the prevalence of the free phenolics in the studied peach peel varieties. Total phenolics of peach wastes were positively correlated with their antioxidant activity. The antioxidant activity results certainly defined the need of an individual interpretation for each variety, but the free phenolics fractions could be outlined with the strongest potential. The limited ability of the peels' extracts to inhibit α-amylase and acetylcholinesterase, and the moderate antimicrobial activity, on the other hand, indicate that the potential of peach peels is still sufficient to seek ways to valorize this waste. Indeed, this new information about peach peels can be used to characterize peach fruits from different countries and/or different food processes, as well as to promote the use of this fruit waste in food preparation.

Genetic diversity of Venturia carpophila populations from different hosts and geographic regions in China

Venturia carpophila, the causal agent of scab disease of peach, mume, and apricot, is widely distributed around the world. Scab of stone fruits is an important disease in China. However, little is known about the population biology and genetic diversity of the V. carpophila. To better understand the genetic diversity and population structure of V. carpophila, 186 single-spore isolates from different hosts and geographic regions were obtained and analyzed by using 31 simple sequence repeat (SSR) markers. This included 156 isolates from peach spanning 14 provinces, 15 isolates from mume and 15 isolates from apricot in Huazhong Agricultural University (HZAU). Diversity analysis with SSR markers showed a low incidence of polymorphisms within mume isolates (32.59% of markers), but a higher incidence of polymorphisms within peach isolates (42.96%) and apricot isolates (57.04%). Within peach isolates, Nei's average gene diversity ranged from 0.07 for Hebei population to 0.18 for Hubei population. AMOVA analysis revealed that 13% of the observed genetic diversity was partitioned among the geographic populations, while 40% of the observed genetic diversity was partitioned among the host populations. Other analyses (PCoA, STRUCTURE, DAPC, MSN, and UPGMA) indicated that the Chinese V. carpophila populations could be clustered into three distinct genetic groups, which correspond to the host boundaries of peach, mume and apricot. The genetic identity of V. carpophila isolates throughout the range is dependent on hosts, but not geographic regions.

Leucine Contributes to Copper Stress Tolerance in Peach (Prunus persica) Seedlings by Enhancing Photosynthesis and the Antioxidant Defense System

Heavy metal contamination has a severe impact on ecological health and plant growth and is becoming increasingly serious globally. Copper (Cu) is a heavy metal that is essential for the growth and development of plants, including peach (Prunus persica L. Batsch); however, an excess is toxic. In plants, amino acids are involved in responses to abiotic and biotic stresses, such as water deficit, extreme temperatures, high salinity, and heavy metal stress. However, the role of leucine in the regulation of heavy metal stress is currently unclear. Therefore, we investigated the effects of exogenous leucine on the growth of peach seedlings under Cu stress. Exogenous leucine improved the leaf ultrastructure and ionic balance and increased the chlorophyll content, the net photosynthetic rate, and the maximum photochemical efficiency. Furthermore, it attenuated Cu-stress-induced oxidative damage via a decrease in reactive oxygen species (ROS) and the regulation of the antioxidant and osmotic systems. These effects, in turn, ameliorated the reductions in cell viability, cellular activity, and biomass under Cu stress. Moreover, exogenous leucine increased the activities of nitrate reductase (NR), glutamine synthetase (GS), and glutamic acid synthetase (GOGAT) and thus improved the nitrogen metabolism efficiency of plants. In conclusion, leucine significantly improved the photosynthetic performance and antioxidant capacity, reduced Cu accumulation, and promoted nitrogen metabolism, which in turn improved the resistance of peach seedlings to Cu stress.

γ-Aminobutyric acid treatment induced chilling tolerance in postharvest peach fruit by upregulating ascorbic acid and glutathione contents at the molecular level

Peach fruit was treated with 5 mM γ-aminobutyric acid (GABA) to further investigate the mechanism by which GABA induced chilling tolerance. Here, we found that GABA not only inhibited the occurrence of chilling injury in peach fruit during cold storage but also maintained fruit quality. Most of the ascorbic acid (AsA) and glutathione (GSH) biosynthetic genes were up-regulated by GABA treatment, and their levels were increased accordingly, thus reducing chilling damage in treated peaches. Meanwhile, the increased transcript of genes in the AsA-GSH cycle by GABA treatment was also related to the induced tolerance against chilling. GABA treatment also increased the expression levels of several candidate ERF transcription factors involved in AsA and GSH biosynthesis. In conclusion, our study found that GABA reduced chilling injury in peach fruit during cold storage due to the higher AsA and GSH contents by positively regulating their modifying genes and candidate transcription factors.

The role of essential oils in maintaining the postharvest quality and preservation of peach and other fruits

Fruits are highly susceptible to postharvest losses induced majorly by postharvest diseases. Peach are favored by consumers because of their high nutritional value and delicious taste. However, it was easy to be affected by fungal infection. The current effective method to control postharvest diseases of fruits is to use chemical fungicides, but these chemicals may cause adverse effects on human health and the residual was potentially harmful to nature and the environment. So, it is especially important to develop safe, non-toxic, and highly effective strategies for the preservation of the fruits. Essential oil, as a class of the natural bacterial inhibitor, has been proven to exhibit strong antibacterial activity, low toxicity, environmental friendliness, and induce fruit resistance to microorganism, which could be recognized as one of the alternatives to chemical fungicides. This paper reviews the research progress of essential oils (Eos) in the storage and preservation of fruits, especially the application in peach, as well as the application in active packaging such as edible coatings, microcapsules, and electrospinning loading. Electrospinning can prepare a variety of nanofibers from different viscoelastic polymer solutions, and has broad application prospects. The paper especially summarizes the application of the new Eos technology on peach. The essential oil with thymol, eugenol, and carvacrol as the main components has a better inhibitory effect on the postharvest disease of peaches, and can be further applied. PRACTICAL APPLICATIONS: As an environmentally friendly natural antibacterial agent, essential oil can be used as a substitute for chemical preservatives to keep fruits fresh. This paper summarizes the different preservation methods of essential oils for fruits, and especially summarizes the different preservation methods of essential oils for peaches after harvesting, as well as their inhibitory effects on pathogenic fungi. It could provide ideas for preservation of fruits and vegetables by essential oils.

Silicon inhibits gummosis by promoting polyamine synthesis and repressing ethylene biosynthesis in peach

Silicon is a beneficial element for plant growth, as well as for improving plant resistance to multiple biotic and abiotic stresses. Gummosis is a common harmful disease in peach and is induced by many factors. However, the effect of silicon on gummosis of peach has not been determined yet. In this study, we reported that application of silicon significantly reduced gummosis by regulating biosynthesis of ethylene and polyamines in peach. Ethylene promoted the development of gummosis by inducing the expression of genes encoding cell wall degrading enzymes. While application of different types of polyamines, including spermidine and spermine, dramatically inhibited the occurrence of gummosis. Moreover, polyamines inhibited the ethylene biosynthesis by down-regulating expression of ethylene biosynthetic gene PpACS1 (1-aminocyclopropane -1-carboxylic acid synthase), as well as the enzymatic activity of ACS. We further found that application of silicon significantly restricted the development of gummosis in peach. Exogenous silicon dramatically inhibited expression of PpACS1 and the enzymatic activity of its product to reduce ethylene biosynthesis. Simultaneously, the activity of S-adenosylmethionine decarboxylase, a key enzyme in ployamines biosynthesis, was increased by 9.85% under silicon treatment, resulting in elevated accumulation of polyamines. Thus, our data proved that application of silicon restricted gummosis development by activating ployamines biosynthesis and inhibiting ethylene synthesis in peach.

First Report of Diaporthe fusicola Causing Postharvest Fruit Rot of Peach (Prunus persica) in China

In May 2022, rot symptoms were observed on postharvest peach (Prunus persica [L.] Batsch) fruits in a market in Nanchang, Jiangxi province (28°44' N; 115°50' E), China. A total of 80 samples were collected from three different fruit stalls through the market survey. The incidence of this disease was 10 to 15%, and severity varies from approximately 30 to 50% of fruit surface coverage. The symptom of infected fruits was circular, pale brown to brown, rotten, necrotic lesions, covered with white hyphae and small spore masses. Eight symptomatic peach fruits were surface disinfected with 75% ethanol for 30 sec and incisions were made with a sterile scalpel. Small pieces from symptomatic tissues were placed on a potato dextrose agar (PDA) medium and incubated at 25℃ for 7 days. Six isolates were obtained in total. Colonies on PDA were initially white, aerial, fluffy at first, and darkened with age. Alpha conidia were fusoid, hyaline, aseptate, guttulate, tapering towards ends, and ranged in size from 9.8 to 5.1 µm × 3.2 to 2.1 µm (x ̅=7.1 ± 1.0 × 2.6 ± 0.3 µm, n=60). Beta conidia were not seen. For further confirmation, genomic DNA was extracted from three isolates (04-10, 04-11, and 04-12), the internal transcribed spacer (ITS) region, beta-tubulin (TUB), calmodulin (CAL), partial translation elongation factor 1-alpha (TEF1-α) and histone H3 (HIS) genes were amplified by using primers ITS1/ITS4, Bt2a/Bt2b, CAL228F/CAL737R, EF1-728F/EF1-986R, CYLH3F/H3-1b (Udayanga et al. 2015), respectively. Sequences were deposited in GenBank (Accession Nos. ON994257 to ON994259 for ITS, OP076824 to OP076826 for TUB, OP076827 to OP076829 for CAL, OP076821 to OP076823 for TEF1-α, OP076830 to OP076832 for HIS). BLAST results showed that ITS and TEF1-α have 99.8% pairwise identity to Diaporthe fusicola (MN816432, KF576256), and the TUB, CAL, and HIS sequences also have 100% pairwise identity to D. fusicola (KF576287, MT978147, MT978142). Phylogenetic analyses of concatenated sequences using Bayesian inference and the maximum likelihood confirmed the identity. To verify Koch's postulates, the pathogenicity of three isolates was tested on harvested healthy peach fruits. Five surface-sterilized fruits were wounded by a sterile scalpel and inoculated with 5-mm-diameter mycelial plugs from 10-day-old PDA plates. Another set of five fruits was inoculated with sterilized PDA plugs as controls. All fruits were incubated at 26℃ with 80% relative humidity. The experiment was repeated three times. After 5 days, the fruit inoculated with mycelial plugs showed pale brown lesions with whitish mycelium mass, similar to the previous rot symptoms, whereas the control fruit remained symptomless. The same pathogen was reisolated from the inoculated fruit with symptoms and identified as D. fusicola by molecular techniques, but never from the control. Diaporthe fusicola (Diaporthe amygdali complex) was first described on leaves of Lithocarpus glabra in China (Gao et al. 2015) and reported as an agent causing leaf blotch on Osmanthus fragrans (Si et al. 2020) and pear shoot canker (Guo et al. 2020). However, this is the first report of D. fusicola causing postharvest fruit rot on peach. The managers involved must consider the impact of this disease and develop an effective fruit storage strategy.

The Peach (Prunus persica) CBL and CIPK Family Genes: Protein Interaction Profiling and Expression Analysis in Response to Various Abiotic Stresses

The plant calcineurin B-like protein-CBL interacting protein kinase (CBL-CIPK) signaling pathway is a Ca2+-related signaling pathway that responds strongly to both biological and abiotic environmental stimuli. This study identified eight CBL and eighteen CIPK genes from peach for the first time. Their basic properties and gene structure were analyzed, and the CBL and CIPK members from Arabidopsis and apple were combined to study their evolutionary relationships. Using RT-qPCR and RNA-seq data, we detected the expression patterns of PprCBLs and PprCIPKs in different tissues and fruit development stages of peach. Among them, the expression levels of PprCBL1 and PprCIPK18 were stable in various tissues and stages. The expression patterns of other members showed specificity between cultivars and developmental stages. By treating shoots with drought and salt stress simulated using PEG6000 and NaCl, it was found that PprCIPK3, PprCIPK6, PprCIPK15 and PprCIPK16 were strongly responsive to salt stress, and PprCIPK3, PprCIPK4, PprCIPK10, PprCIPK14, PprCIPK15, PprCIPK16 and PprCIPK18 were sensitive to drought stress. Three genes, PprCIPK3, PprCIPK15 and PprCIPK16, were sensitive to both salt and drought stress. We cloned four PprCBL and several PprCIPK genes and detected their interaction by yeast two-hybrid assay (Y2H). The results of Y2H show not only the evolutionary conservation of the interaction network of CBL-CIPK but also the specificity among different species. In conclusion, CBL and CIPK genes are important in peach and play an important role in the response to various abiotic stresses.

Down-regulation of NCED leads to the accumulation of carotenoids in the flesh of F1 generation of peach hybrid

Flesh color is an important target trait in peach [Prunus persica (L.) Batsch] breeding. In this study, two white-fleshed peach cultivars were crossed [Changsong Whitepeach (WP-1) × 'Xiacui'], and their hybrid F₁ generation showed color segregation of white flesh (BF1) and yellow flesh (HF1). Metabolome analysis revealed that the flesh color segregation in the hybrid F₁ generation was related to the carotenoid content. The decrease in β-carotene and β-cryptoxanthin in BF1 flesh and increase in β-cryptoxanthin oleate, rubixanthin caprate, rubixanthin laurate and zeaxanthin dipalmitate in HF1 flesh contributed to their difference in carotenoid accumulation. Transcriptome analysis demonstrated that compared with BF1, HF1 showed significant up-regulation and down-regulation of ZEP and CCD8 at the core-hardening stage, respectively, while significant down-regulation of NCED in the whole fruit development stage. The down-regulation of NCED might inhibit the breakdown of the violaxanthin and its upstream substances and further promote the accumulation of carotenoids, resulting in yellow flesh. Therefore, NCED may be a key gene controlling the fruit color traits of peach. In this study, targeted metabolomics and transcriptomics were used to jointly explore the mechanism controlling the fruit color of peach, which may help to identify the key genes for the differences in carotenoid accumulation and provide a reference for the breeding of yellow-fleshed peach.

Betulin, Synthesized by PpCYP716A1, Is a Key Endogenous Defensive Metabolite of Peach against Aphids

Wild pest-resistant germplasms employ secondary metabolites to withstand insect attacks. A close wild relative of the cultivated peach, Prunus davidiana, displays strong resistance to green peach aphids by utilizing metabolites to cope with aphid infestation; however, the underlying mechanism of aphid resistance remains mostly unknown. Here, metabolomic analysis was performed to explore the changes in metabolite levels in P. davidiana after aphid infestation. The data revealed that betulin is a key defensive metabolite in peaches that protects against aphids and possesses potent aphidicidal activity. Further toxicity tests demonstrated that betulin was toxic to pests but not to beneficial insects. Additionally, transcriptomic and phylogenetic analyses revealed that the cytochrome P450 gene PpCYP716A1 was responsible for betulin synthesis─this finding was confirmed by the heterologous expression of this gene. This study revealed a strategy whereby plants harness defense metabolites to develop resistance to pests. These findings may facilitate controlling such pests.

Nitric oxide promotes energy metabolism and protects mitochondrial DNA in peaches during cold storage

The mitochondria are important organelles related to energy metabolism and are susceptible to oxidative damage. In this experiment, peaches (Prunus persica) were treated with distilled water (as the control), 15 μmol L^-1 of nitric oxide (NO), and 20 μmol L^-1 of carboxy-PTIO (NO scavenger). The changes in mitochondrial physiological indicators, energy metabolism process, and mitochondrial DNA (mtDNA) damage and repair were quantified. Compared with the control, NO treatment reduced mitochondrial oxygen consumption and the reactive oxygen species content, increased mitochondrial respiration control rate, and promoted energy metabolism by influencing the activities of citrate synthase, aconitase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase in the tricarboxylic acid cycle and ATPase activity in peach mitochondria. NO treatment also maintained the relative copy number of mtDNA and the relative amplification of long PCR in peaches, decreased the level of 8-hydroxy-2 deoxyguanosine, and upregulated the expression of PpOGG1, PpAPE1, and PpLIG1. These results indicated that exogenous NO treatment (15 μmol L^-1) could reduce mtDNA oxidative damage, maintain mtDNA molecular integrity, and inhibit mtDNA copy number reduction by reducing the reactive oxygen species content, thereby promoting mitochondrial energy metabolism and prolonging the storage life of peaches at low temperatures.