Screening of core microorganisms in healthy and diseased peaches and effect evaluation of biocontrol bacteria (Burkholderia sp.)

Biological antagonists serve as the most important green alternatives to chemical fungicides, a class of microorganism that inhibits the growth of pathogenic fungi to reduce fruit incidence. In this paper, healthy and diseased peach fruit was selected for amplicon sequencing of the epiphytic microbiota on their surface to obtain a comprehensive understanding. Community structure, diversity and LefSe analysis were performed to screen Acetobacter, Muribaculaceae and Burkholderia as the core bacteria, Mycosphaerella, Penicillium and Alternaria as the core fungi, they showed significant differences and were highly enriched. Two strains fungi (Penicillium K3 and N1) and one strain antagonistic bacteria (Burkholderia J2) were isolated. The in intro test results indicated the bacterial suspension, fermentation broth and volatile organic compounds of antagonistic bacteria J2 were able to significantly inhibit pathogen growth. In vivo experiments, peach was stored at 28 °C for 6 days after different treatments, and samples were taken every day. It was found that Burkholderia J2 enhanced peach resistance by increasing the activities of antioxidant-related enzymes such as SOD, POD, PAL, PPO, GR, MDHAR, and DHAR. The results improved that Burkholderia J2 has great biocontrol potential and could be used as a candidate strain for green control of blue mold.

Tandem transcription factors PpNAC1 and PpNAC5 synergistically activate the transcription of the PpPGF to regulate peach softening during fruit ripening

Peach fruit rapidly soften after harvest, a significant challenge for producers and marketers as it results in rotting fruit and significantly reduces shelf life. In this study, we identified two tandem genes, PpNAC1 and PpNAC5, within the sr (slow ripening) locus. Phylogenetic analysis showed that NAC1 and NAC5 are highly conserved in dicots and that PpNAC1 is the orthologous gene of Non-ripening (NOR) in tomato. PpNAC1 and PpNAC5 were highly expressed in peach fruit, with their transcript levels up-regulated at the onset of ripening. Yeast two-hybrid and bimolecular fluorescence complementation assays showed PpNAC1 interacting with PpNAC5 and this interaction occurs with the tomato and apple orthologues. Transient gene silencing experiments showed that PpNAC1 and PpNAC5 positively regulate peach fruit softening. Yeast one-hybrid and dual luciferase assays and LUC bioluminescence imaging proved that PpNAC1 and PpNAC5 directly bind to the PpPGF promoter and activate its transcription. Co-expression of PpNAC1 and PpNAC5 showed higher levels of PpPGF activation than expression of PpNAC1 or PpNAC5 alone. In summary, our findings demonstrate that the tandem transcription factors PpNAC1 and PpNAC5 synergistically activate the transcription of PpPGF to regulate fruit softening during peach fruit ripening.

Study on the control effect and physiological mechanism of Wickerhamomyces anomalus on primary postharvest diseases of peach fruit

Brown rot, aspergillosis and soft rot are the primary diseases of postharvest peach fruit. Our study aimed to investigate the biocontrol effect of Wickerhamomyces anomalus on the primary postharvest diseases of peach fruit and to explore its underlying physiological mechanism. The findings demonstrated that W. anomalus had an obvious inhibitory effect on Monilinia fructicola, Aspergillus niger and Rhizopus stolonifer. At the same time, W. anomalus can grow stably on the wound and surface of peach fruit at 25 °C and 4 °C and can form biofilm. W. anomalus increased the activity of resistance-related enzymes such as PPO, POD, GLU and the content of secondary metabolites such as total phenols, flavonoids and lignin in peach. Furthermore, the application of W. anomalus led to a reduced MDA level in peach fruit and increased activity of the active oxygen-scavenging enzyme system. This increase involved various antioxidant defense enzymes such as SOD and CAT, as well as ascorbic acid-glutathione (AsA-GSH) enzymes, including APX, GPX, GR, DHAR, and MDHAR. Our findings demonstrate that W. anomalus exerts its biocontrol effect by growing rapidly, competing with pathogens for nutrition and space, and enhancing the disease resistance and antioxidative capabilities of the peach fruit.

Redetection and description of the European dagger nematode Xiphinema diversicaudatum on peach (Prunus persica L.) in Canada

The study reports the detection of Xiphinema diversicaudatum in a peach field in Ontario, Canada. Comprehensive population characterization involved morphological and molecular analyses using 18S and 28S rDNA sequences. Morphological and molecular analysis demonstrated a close relationship between the Ontario population and those from Central Europe. This is the first report of X. diversicaudatum from peaches (Prunus persica) in Canada and in North America.

Combined analysis of mRNA and miRNA transcriptomes reveals the regulatory mechanism of Xanthomonas arboricola pv pruni resistance in Prunus persica

BACKGROUND

Peach bacterial shot hole, caused by Xanthomonas arboricola pv pruni (Xap), is a global bacterial disease that poses a threat to the yield and quality of cultivated peach trees (Prunus persica).

RESULTS

This study compared the mRNA and miRNA profiles of two peach varieties, 'Yanbao' (resistant) and 'Yingzui' (susceptible), after inoculation with Xap to identify miRNAs and target genes associated with peach tree resistance. mRNA sequencing results revealed that in the S0-vs-S3 comparison group, 1574 genes were upregulated and 3975 genes were downregulated. In the R0-vs-R3 comparison group, 1575 genes were upregulated and 3726 genes were downregulated. Through miRNA sequencing, a total of 112 known miRNAs belonging to 70 miRNA families and 111 new miRNAs were identified. Notably, some miRNAs were exclusively expressed in either resistant or susceptible varieties. Additionally, 59 miRNAs were downregulated and 69 miRNAs were upregulated in the R0-vs-R3 comparison group, while 46 miRNAs were downregulated and 52 miRNAs were upregulated in the S0-vs-S3 comparison group. Joint analysis of mRNA and miRNA identified 79 relationship pairs in the S0-vs-S3 comparison group, consisting of 48 miRNAs and 51 target genes. In the R0-vs-R3 comparison group, there were 58 relationship pairs, comprising 28 miRNAs and 20 target genes. Several target genes related to resistance, such as SPL6, TIFY6B, and Prupe.4G041800_v2.0.a1 (PPO), were identified through literature reports and GO/KEGG enrichment analysis.

CONCLUSION

In conclusion, this study discovered several candidate genes involved in peach tree resistance by analyzing differential expression of mRNA and miRNA. These findings provide valuable insights into the mechanisms underlying resistance to Xap in peach trees.

Mining plant phenology records from Kanazawa, Japan in the 1807-1838 Kakuson Diary

Mining the various records of plant phenology before the era of modern weather observations is an important but challenging task. We mined descriptions of plant phenology in Kanazawa, Japan, during the first half of the nineteenth century in the Kakuson Diary. We retrieved records of full bloom of 28 plant species, appearance of 31 seasonal foods, and peak leaf colouring. In particular, we found more than 10 years of records of plum, peach, cherry blossoms, udo, and bamboo shoots in spring; watermelon in summer; and persimmon, chestnut, and peak leaf colouring in autumn. The records suggest that spring phenology during 1807 to 1838 was later and autumn phenology was earlier than now. Despite spatio-temporal uncertainty in records in old diaries, we need to mine records of plant phenology in more old diaries and publish them in English.

Integrated analysis of HSP20 genes in the developing flesh of peach: identification, expression profiling, and subcellular localization

BACKGROUND

Plant HSP20s are not only synthesized in response to heat stress but are also involved in plant biotic and abiotic stress resistance, normal metabolism, development, differentiation, survival, ripening, and death. Thus, HSP20 family genes play very important and diverse roles in plants. To our knowledge, HSP20 family genes in peach have not yet been characterized in detail, and little is known about their possible function in the development of red flesh in peach.

RESULTS

In total, 44 PpHSP20 members were identified in the peach genome in this study. Forty-four PpHSP20s were classified into 10 subfamilies, CI, CII, CIII, CV, CVI, CVII, MII, CP, ER, and Po, containing 18, 2, 2, 10, 5, 1, 1, 2, 1, and 2 proteins, respectively. Among the 44 PpHSP20 genes, 6, 4, 4, 3, 7, 11, 5, and 4 PpHSP20 genes were located on chromosomes 1 to 8, respectively. In particular, approximately 15 PpHSP20 genes were located at both termini or one terminus of each chromosome. A total of 15 tandem PpHSP20 genes were found in the peach genome, which belonged to five tandemly duplicated groups. Overall, among the three cultivars, the number of PpHSP20 genes with higher expression levels in red flesh was greater than that in yellow or white flesh. The expression profiling for most of the PpHSP20 genes in the red-fleshed 'BJ' was higher overall at the S3 stage than at the S2, S4-1, and S4-2 stages, with the S3 stage being a very important period of transformation from a white color to the gradual anthocyanin accumulation in the flesh of this cultivar. The subcellular localizations of 16 out of 19 selected PpHSP20 proteins were in accordance with the corresponding subfamily classification and naming. Additionally, to our knowledge, Prupe.3G034800.1 is the first HSP20 found in plants that has the dual targets of both the endoplasmic reticulum and nucleus.

CONCLUSIONS

This study provides a comprehensive understanding of PpHSP20s, lays a foundation for future analyses of the unknown function of PpHSP20 family genes in red-fleshed peach fruit and advances our understanding of plant HSP20 genes.

Genome-wide identification of nucleotide-binding domain leucine-rich repeat (NLR) genes and their association with green peach aphid (Myzus persicae) resistance in peach

Resistance genes (R genes) are a class of genes that are immune to a wide range of diseases and pests. In planta, NLR genes are essential components of the innate immune system. Currently, genes belonging to NLR family have been found in a number of plant species, but little is known in peach. Here, 286 NLR genes were identified on peach genome by using their homologous genes in Arabidopsis thaliana as queries. These 286 NLR genes contained at least one NBS domain and LRR domain. Phylogenetic and N-terminal domain analysis showed that these NLRs could be separated into four subfamilies (I-IV) and their promoters contained many cis-elements in response to defense and phytohormones. In addition, transcriptome analysis showed that 22 NLR genes were up-regulated after infected by Green Peach Aphid (GPA), and showed different expression patterns. This study clarified the NLR gene family and their potential functions in aphid resistance process. The candidate NLR genes might be useful in illustrating the mechanism of aphid resistance in peach.

The Dissipation Behavior and Risk Assessment of Carbendazim Under Individual and Joint Applications on Peach (Amygdalus persica L.)

Dissipation, residue levels, and ingestion risks of carbendazim in peach (Amygdalus persica L.) were investigated with individual and joint applications in the present study. The dissipation kinetics of carbendazim, chlorpyrifos, prochloraz, and imidacloprid were evaluated by the first-order kinetics. When carbendazim was individually applied, the final residual concentration was 2.97 mg kg-1 and the half-life was 17.4 d. In the joint application of carbendazim with chlorpyrifos, prochloraz, and imidacloprid, the residual concentrations at 35 d after spraying were 7.16, 7.50, and 4.26 mg kg-1 and the half-lives were 30.8, 23.7, and 23.2 d, respectively, which showed an increase of 1.3-1.8 times compared with the single application of carbendazim. In addition, the effects of household processing of rinsing and peeling were investigated, and a high removal rate of 54.6% and 76.5% were found. Furthermore, the carbendazim ingestion risk assessment was conducted, which indicated that the acute health risk (aHI) and hazard quotient (HQ) of carbendazim were all within acceptable levels ranging from 21.7% to 40.9%. However, a higher ingestion risk of carbendazim was found under the joint application. This study provides some preliminary guidance for the joint application and risk assessment of carbendazim in peach, which is worth further investigation.

Post-harvest ripening affects drying behavior, antioxidant capacity and flavor release of peach via alteration of cell wall polysaccharides content and nanostructures, water distribution and status

Effect of post-harvest ripening on cell wall polysaccharides nanostructures, water status, physiochemical properties of peaches and drying behavior under hot air-infrared drying was evaluated. Results showed that the content of water soluble pectins (WSP) increased by 94 %, while the contents of chelate-soluble pectins (CSP), Na₂CO₃-soluble pectins (NSP) and hemicelluloses (HE) decreased during post-harvest ripening by 60 %, 43 %, and 61 %, respectively. The drying time increased from 3.5 to 5.5 h when the post-harvest time increased from 0 to 6 days. Atomic force microscope analysis showed that depolymerization of hemicelluloses and pectin occurred during post-harvest ripening. Time Domain -NMR observations indicated that reorganization of cell wall polysaccharides nanostructure changed water spatial distribution and cell internal structure, facilitated moisture migration, and affected antioxidant capacity of peaches during drying. This leads to the redistribution of flavor substances (heptanal, n-nonanal dimer and n-nonanal monomer). The current work elucidates the effect of post-harvest ripening on the physiochemical properties and drying behavior of peaches.

First Report of Peach Scab Caused by Cladosporium tenuissimum in Mexico

Peach (Prunus persica) is one of the most popular stone fruits in the world. From 2019 to 2022, typical scab symptoms were observed on 70% of peach fruits in a commercial orchard in Tepeyahualco, Puebla, Mexico (19°30'38"N 97°30'57"W). Fruit symptoms are black circular lesions of 0.3 mm in diameter. The fungus was isolated from symptomatic fruit pieces that were surface sterilized with 1% sodium hypochlorite for 30 s, rinsed in autoclaved distilled water three times, placed on PDA medium, and incubated at 28°C in darkness for 9 days. Cladosporium-like colonies were isolated. Pure cultures were obtained by single spore culture. Colonies on PDA showed aerial mycelium abundant, smoke-grey, fluffy, and with margin glabrous to feathery. Conidiophores were solitary, long, intercalary conidia narrow erect, macro- and micronematous, straight or slightly flexuous, cylindrical-oblong, olivaceous-brown, and often subnodulose. Conidia (n= 50) catenate in branched chains, obovoid to limoniform, sometimes globose, aseptate, olivaceous-brown, apically rounded, 3.1 to 5.1 × 2.5 to 3.4 µm. Secondary ramoconidia (n= 50) were fusiform to cylindrical, smooth-walled, 0-1-septate, pale brown or pale olivaceous-brown, measuring 9.1 to 20.8 × 2.9 to 4.8 μm. Morphology was consistent to that described for Cladosporium tenuissimum (Bensch et al. 2012; 2018). A representative isolate was deposited in the Culture Collection of Phytopathogenic Fungi of the Department of Agricultural Parasitology at the Chapingo Autonomous University under the accession number UACH-Tepe2. To further confirm the morphological identification, total DNA was extracted using the cetyltrimethylammonium bromide method (Doyle and Doyle 1990). The internal transcribed spacer (ITS) region, partial sequences of the translation elongation factor 1-alpha (EF1-α) and actin (act) genes were amplified by PCR, and sequenced using the primer pairs ITS5/ITS4 (White et al. 1990), EF1-728F/986R, and ACT-512F/783R (Carbone and Kohn 1999), respectively. The sequences were deposited in GenBank under the accession numbers OL851529 (ITS), OM363733 (EF1-α), and OM363734 (act). BLASTn searches in GenBank showed 100% identity with available sequences of Cladosporium tenuissimum accession (ITS: MH810309; EF1-α: OL504967; act: MK314650). A phylogenetic analysis using the maximum likelihood method placed isolate UACH-Tepe2 in the same clade as C. tenuissimum. To verify the pathogenicity of the fungus, 20 healthy peach fruits were inoculated with four drops of 15 μl of a conidial suspension (1 × 106 spores /ml). Ten control fruit were treated with sterilized water. All the fruits were kept in a moist chamber at 25°C for 10 days. Circular and necrotic lesions were produced eight days after inoculation, whereas control fruits remained healthy. Pathogenicity test was conducted three times with similar results. Fungal colonies were reisolated from the artificially inoculated fruit, thus fulfilling Koch's postulates. Cladosporium tenuissimum has been previously reported to cause diseases on strawberry, cashew, papaya, and passionfruit in Brazil (Rosado et al. 2019; Santos et al. 2020), as well as diseases on pitaya, hydrangea, and carnation in China (Xu et al. 2020; Li et al. 2021; Xie et al. 2021). Cladosporium carpophilum is reported as the causal agent of peach scab. The environmental conditions for the development of C. carpophilum are 20-30 °C in warm humid areas (Lawrence and Zehr 1982), however, in this case the infection by C. tenuissinum occurred in a temperate semi-dry climate, with temperatures of 5 -15 °C and R.H. less than 50 % with an incidence of 80 %. To our knowledge, this is the first report of Cladosporium tenuissimum causing peach scab in Mexico and worldwide.

Immunotherapy with Pru p 3 for food allergy to peach and non-specific lipid transfer protein: a systematic review

BACKGROUND

Non-specific lipid-transfer protein (nsLTP) is a pan-allergen in the plant world, and a cause of significant concern as food allergen in the Mediterranean area, due to its general heat- and acid-resistance and hence the risk of severe allergic reactions. Pru p 3, the peach nsLTP, is considered the primary sensitizer to this allergen family and this allergy is usually persistent. Allergen-free diet and acute treatment of manifestations are the main recognized management goals in food allergy.

MAIN TEXT

The role of immunotherapy for treating food allergy in adult patients is controversial, but immunotherapy for Pru p 3 could potentially represent a relevant therapeutic strategy. We systematically searched databases for studies assessing the role of immunotherapy Pru p 3 in food allergy. Overall, nine studies were included. Immunotherapy with Pru p 3 appears to be effective and with a good safety profile in both peach and LTP allergy for some foods, such as peanut, in both RCT and real-life studies.

CONCLUSIONS

Immunotherapy with Pru p 3 is a possible treatment option for food allergy to the peach LTP in the Mediterranean area, although at present have not reached routinary clinical practice. Larger studies are needed to confirm these findings and identify predictive biomarkers.

First Report of Cytospora azerbaijanica Causing Cytospora Canker and Shoot Dieback on Peach (Prunus persica) in California, U.S.A

Peaches (Prunus persica L.) are an important crop in the United States with California leading the nation in peach production, with approximately 505,000 tons valued at $378.3 million (USDA National Agricultural Statistics Service, 2021, https://www.nass.usda.gov/). From April to July 2022, symptoms of branch and scaffold canker as well as shoot dieback were observed in three peach (cvs. Loadel, Late Ross and Starn) orchards located in San Joaquin County, California. Samples were collected from about 12 trees for each cultivar. Fast-growing, white, flat colonies were consistently isolated from active cankers on acidified potato dextrose agar (APDA) following the method described by (Lawrence et al. 2017). Pure fungal cultures were obtained by transferring single hyphal tips onto new APDA Petri plates. A total of 22 isolates were obtained. Each fungal isolate was recovered from a single diseased branch (40 to 55% recovery). All isolates in this study shared similar morphological characteristics. Fungal colonies were fast-growing with relatively even but slightly dentate margin, flat with white to off-white mycelium that turned vinaceous buff to pale greyish sepia (Rayner 1970) with age. Black, globose, ostiolated pycnidia, 0.8-(1.3)-2.2 mm diameter, with brownish surface hyphae formed on peach wood embedded in PDA after approximately three weeks and exudated buff-colored mucilage. Pycnidia were both solitary and aggregated and had multiple internal locules sharing invaginated walls. Conidiogenous cells were hyaline, smooth-walled, septate, tapering towards the apex, 13-(18.2)-25.1 × 0.8-(1.3)-1.9 µm (n = 40). Conidia were hyaline, allantoid, smooth, aseptate, 5.5-(6.3)-7.1 × 1.4-(1.9)-2.3 µm (n = 40). Genomic DNA was extracted and sequences of the internal transcribed spacer region (ITS) using ITS5/ITS4 universal primers, translation elongation factor 1α gene (TEF) using primers EF1-728F/EF1-986R, second largest subunit of RNA polymerase II (RPB2) using primers RPB2-5F2/fRPB2-7cR, and actin gene region (ACT) using primers ACT-512F/ACT-783R were obtained and compared with sequences available in GenBank (Lawrence et al. 2018; Hanifeh et al. 2022). Isolates were identified as Cytospora azerbaijanica following DNA sequencing and morphological identification. Consensus sequences of the four genes of two representative isolates (SJC-66 and SJC-69) were deposited into GenBank database (ITS: OQ060581 and OQ060582; ACT: OQ082292, OQ082295; TEF: OQ082290 and OQ082293; RPB2: OQ082291 and OQ082294). The Basic Local Alignment Search Tool (BLAST) indicated that the sequenced RPB2 genes of isolates (SJC-66 and SJC-69) were at least 99% identical to that of Cytospora sp. strain shd47 (Accession: MW824360) covering at least 85% of the sequences. The actin genes from our isolates were at least 97.85% identical to that of Cytospora sp. strain shd47 (Accession: MZ014513), covering 100% of the sequences. The translation elongation factor gene from isolates (SJC-66 and SJC-69) was at least 96.4% identical to that of Cytospora sp. strain shd166 (Accession: OM372512), covering 100% of the query. Those top hit strains belong to C. azerbaijanica, recently reported by Hanifeh et al. (2022). Pathogenicity tests were performed by inoculating eight wounded, 2- to 3-year-old healthy branches on each of eight 7-year-old peach trees, cvs. Loadel, Late Ross and Starn, using 5-mm-diameter mycelium plugs collected from the margin of an actively growing fungal colony on APDA. Controls were mock-inoculated with sterile agar plugs. Inoculation sites were covered with petroleum jelly and wrapped with Parafilm to keep moisture. The experiment was performed twice. After four months, inoculation tests resulted in vascular discoloration (canker) above and below the inoculation sites (average necrosis length of 114.1 mm). Cytospora azerbaijanica was re-isolated from all infected branches (70 to 100% recovery) completing Koch's postulates. Controls remained symptomless and no fungi were isolated from the slightly discolored tissue. Cytospora species are destructive canker and dieback pathogens of numerous woody hosts worldwide. Recently, C. azerbaijanica was reported in causing canker disease of apple trees in Iran (Hanifeh et al. 2022). To our knowledge, this is the first report of C. azerbaijanica causing canker and shoot dieback of peach trees in the United States and worldwide. These findings will aid towards a better understanding of genetic diversity and host range of C. azerbaijanica.

Discovery of a key gene associated with fruit maturity date and analysis of its regulatory pathway in peach

Fruit maturity is an important agronomic trait of fruit crops. Although in previous studies, several molecular markers are developed for the trait, the knowledge about its candidate genes is particularly limited. In this study, a total of 357 peach accessions were re-sequenced to obtain 949,638 SNPs. Combing with 3-year fruit maturity dates, a genome-wide association analysis was performed, and 5, 8, and 9 association loci were identified. To screen the candidate genes for those year-stable loci on chromosomes 4 and 5, two maturity date mutants were used for transcriptome sequencing. Gene expression analysis indicated that Prupe.4G186800 and Prupe.4G187100 on chromosome 4 were essential to fruit ripening in peaches. However, the expression analysis of different tissues showed that the first gene has no tissue-specific character, but transgenic studies showed that the latter is more likely to be a key candidate gene than the first for the maturity date in peach. The yeast two-hybrid assay showed that the proteins encoded by the two genes interacted and then regulated fruit ripening. Moreover, the previously identified 9bp insertion in Prupe.4G186800 may affect their interaction ability. This research is of great significance for understanding the molecular mechanism of peach fruit ripening and developing practical molecular markers in a breeding program.

Genome-wide identification, bioinformatics and expression analysis of HD-Zip gene family in peach

BACKGROUND

HD-Zips (Homeodomain-Leucine Zippers) are a class of plant-specific transcription factors that play multiple roles in plant growth and development. Although some functions of HD-Zip transcription factor have been reported in several plants, it has not been comprehensively studied in peach, especially during adventitious root formation of peach cuttings.

RESULTS

In this study, 23 HD-Zip genes distributed on 6 chromosomes were identified from the peach (Prunus persica) genome, and named PpHDZ01-23 according to their positions on the chromosomes. These 23 PpHDZ transcription factors all contained a homeomorphism box domain and a leucine zipper domain, were divided into 4 subfamilies(I-IV) according to the evolutionary analysis, and their promoters contained many different cis-acting elements. Spatio-temporal expression pattern showed that these genes were expressed in many tissues with different levels, and they had distinct expression pattern during adventitious root formation and development.

CONCLUSION

Our results showed the roles of PpHDZs on root formation, which is helpful to better understand the classification and function of peach HD-Zip genes.

Batsch)

BACKGROUND

Organic acids are important components that determine the fruit flavor of peach (Prunus persica L. Batsch). However, the dynamics of organic acid diversity during fruit ripening and the key genes that modulate the organic acids metabolism remain largely unknown in this kind of fruit tree which yield ranks sixth in the world.

RESULTS

In this study, we used 3D transcriptome data containing three dimensions of information, namely time, phenotype and gene expression, from 5 different varieties of peach to construct gene co-expression networks throughout fruit ripening of peach. With the network inferred, the time-ordered network comparative analysis was performed to select high-acid specific gene co-expression network and then clarify the regulatory factors controlling organic acid accumulation. As a result, network modules related to organic acid synthesis and metabolism under high-acid and low-acid comparison conditions were identified for our following research. In addition, we obtained 20 candidate genes as regulatory factors related to organic acid metabolism in peach.

CONCLUSIONS

The study provides new insights into the dynamics of organic acid accumulation during fruit ripening, complements the results of classical co-expression network analysis and establishes a foundation for key genes discovery from time-series multiple species transcriptome data.

Commodity risk assessment of Prunus persica and P. dulcis plants from Türkiye

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 plants of Prunus persica and P. dulcis, as budwood/graftwood, rooted or grafted on rootstocks of either P. persica, P. dulcis, P. armeniaca, P. davidiana or their hybrids, imported from Türkiye, taking into account the available scientific information, including the technical information provided by Türkiye. All pests associated with the commodity were evaluated against specific criteria for their relevance for this opinion. Four quarantine pests (peach rosette mosaic virus, tomato ringspot virus, Anoplophora chinensis, Scirtothrips dorsalis) and 14 non-regulated pests (Hoplolaimus galeatus, Lasiodiplodia pseudotheobromae, Neoscytalidium dimidiatum, Neoscytalidium novaehollandiae, Didesmococcus unifasciatus, Euzophera semifuneralis, Lepidosaphes malicola, Lepidosaphes pistaciae, Maconellicoccus hirsutus, Malacosoma parallela, Nipaecoccus viridis, Phenacoccus solenopsis, Pochazia shantungensis, Russellaspis pustulans) that fulfilled all relevant criteria were selected for further evaluation. For these 18 pests, the risk mitigation measures proposed in the technical Dossier from Türkiye were evaluated taking into account the possible limiting factors. For the selected pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The degree of pest freedom varies among the pests evaluated, with fungi from Botryosphaeriaceae family (L. pseudotheobromae, N. dimidiatum and N. novaehollandiae) being the pests most frequently expected on the imported plants. The Expert Knowledge Elicitation indicated with 95% certainty that between 9,813 and 10,000 bundles (consisting of 10 or 25 plants each) per 10,000 would be free from the above-mentioned fungi in the Botryosphaeriaceae family.

Genome-wide identification and expression analysis of peach multiple organellar RNA editing factors reveals the roles of RNA editing in plant immunity

BACKGROUND

Multiple organellar RNA editing factor (MORF) genes play key roles in chloroplast developmental processes by mediating RNA editing of Cytosine-to-Uracil conversion. However, the function of MORF genes in peach (Prunus persica), a perennial horticultural crop species of Rosaceae, is still not well known, particularly the resistance to biotic and abiotic stresses that threaten peach yield seriously.

RESULTS

In this study, to reveal the regulatory roles of RNA editing in plant immunity, we implemented genome-wide analysis of peach MORF (PpMORF) genes in response to biotic and abiotic stresses. The chromosomal and subcellular location analysis showed that the identified seven PpMORF genes distributed on three peach chromosomes were mainly localized in the mitochondria and chloroplast. All the PpMORF genes were classified into six groups and one pair of PpMORF genes was tandemly duplicated. Based on the meta-analysis of two types of public RNA-seq data under different treatments (biotic and abiotic stresses), we observed down-regulated expression of PpMORF genes and reduced chloroplast RNA editing, especially the different response of PpMORF2 and PpMORF9 to pathogens infection between resistant and susceptible peach varieties, indicating the roles of MORF genes in stress response by modulating the RNA editing extent in plant immunity. Three upstream transcription factors (MYB3R-1, ZAT10, HSFB3) were identified under both stresses, they may regulate resistance adaption by modulating the PpMORF gene expression.

CONCLUSION

These results provided the foundation for further analyses of the functions of MORF genes, in particular the roles of RNA editing in plant immunity. In addition, our findings will be conducive to clarifying the resistance mechanisms in peaches and open up avenues for breeding new cultivars with high resistance.

Assessment of total concentration and bioaccessible fraction of minerals in peaches from different cultivars by MIP OES

This paper describes studies for the determination of total concentration and bioaccessible fraction of minerals in peaches by MIP OES. The PCA analysis identified 3 distinct groups of elements concerning the total concentration, which was attributed to the origin of each cultivar. Among the macroelements, K presented higher values for total concentration, while B and Fe predominated among the microelements. Regarding the bioaccessible fraction, Mn presented the highest percentage (46-84%), followed by Zn and B (10-63% and 33-57%, respectively). Pearson's correlation coefficient revealed that reducing sugars and titratable acidity can influence the mineral bioaccessibility, highlighting the strong positive correlations between reducing sugars with Mn and total acidity with Fe. Peach cultivars have satisfactory nutritional value, but the total and bioaccessible concentrations of minerals obtained do not meet the recommended daily needs, requiring the consumption of other fruits and vegetables to complement the diet.

Phenotypic diversity of nutritional quality attributes and chilling injury symptoms in four early peach [Prunus persica (L.) Batsch] cultivars grown in west central Tunisia

The present study aimed to characterize the phenotypic diversity of agronomical and biochemical fruit quality traits in four early peach cultivars. The sensibility to chilling injury symptoms (CI) was studied after two cold storage periods (2 and 4 weeks) at 5 ºC and 95% relative humidity (RH) followed by 2 days at room temperature. Agronomical attributes such as fruit weight, firmness, soluble solids content (SSC), pH, titratable acidity (TA) and color parameters were recorded. Antioxidant compounds such as anthocyanins, flavonoids, total phenolics, vitamin C and relative antioxidant capacity (RAC) were evaluated. Chilling injury symptoms such as mealiness, graininess, flesh browning, flesh bleeding, leatheriness and off-flavor were analyzed. Results revealed high antioxidant compounds in peel regarding to flesh fruit. The antioxidant compounds content in both peel and pulp decreased during cold storage except anthocyanins which exhibited different pattern. After 2 weeks of storage, fruits presented high SSC and low score of chilling injury symptoms. At the end of the trial, the studied cultivars were unacceptable for consumption due to the severity of CI. PCA analysis showed that the cultivars Plagold 5 and Plagold 10 had less sensibility to chilling injury.

Graphical abstract

Fine mapping of the gene controlling the weeping trait of Prunus persica and its uses for MAS in progenies

BACKGROUND

Fruit tree yield and fruit quality are affected by the tree's growth type, and branching angle is an important agronomic trait of fruit trees, which largely determines the crown structure. The weeping type of peach tree shows good ventilation and light transmission; therefore, it is commonly cultivated. However, there is no molecular marker closely linked with peach weeping traits for target gene screening and assisted breeding.

RESULTS

First, we confirmed that the peach weeping trait is a recessive trait controlled by a single gene by constructing segregating populations. Based on BSA-seq, we mapped the gene controlling this trait within 159 kb of physical distance on chromosome 3. We found a 35 bp deletion in the candidate area in standard type, which was not lacking in weeping type. For histological assessments, different types of branches were sliced and examined, showing fiber bundles in the secondary xylem of ordinary branches but not in weeping branches.

CONCLUSIONS

This study established a molecular marker that is firmly linked to weeping trait. This marker can be used for the selection of parents in the breeding process and the early screening of hybrid offspring to shorten the breeding cycle. Moreover, we preliminary explored histological differences between growth types. These results lay the groundwork for a better understanding of the weeping growth habit of peach trees.

Silicon enhances the drought resistance of peach seedlings by regulating hormone, amino acid, and sugar metabolism

BACKGROUND

Drought is one of the main concerns worldwide and restricts the development of agriculture. Silicon improves the drought resistance of plants, but the underlying mechanism remains unclear.

RESULTS

We sequenced the transcriptomes of both control and silicon-treated peach seedlings under drought stress to identify genes or gene networks that could be managed to increase the drought tolerance of peach seedlings. Peach (Prunus persica) seedlings were used to analyse the effects of silicon on plant growth and physiological indexes related to drought resistance under drought stress. The results showed that silicon addition improved the water use efficiency, antioxidant capacity, and net photosynthetic rate, inhibition of stomatal closure, promoted the development of roots, and further regulated the synthesis of hormones, amino acids and sugars in peach seedlings. A comparative transcriptome analysis identified a total of 2275 genes that respond to silicon under drought stress. These genes were mainly involved in ion transport, hormone and signal transduction, biosynthetic and metabolic processes, stress and defence responses and other processes. We analysed the effects of silicon on the modulation of stress-related hormonal crosstalk and amino acid and sugar metabolism. The results showed that silicon promotes zeatin, gibberellin, and auxin biosynthesis, inhibits the synthesis of abscisic acid, then promote lateral root development and inhibit stomatal closure, and regulates the signal transduction of auxin, cytokinin, gibberellin and salicylic acid. Silicon also regulates the metabolism of various amino acids and promotes the accumulation of sucrose and glucose to improve drought resistance of peach seedlings.

CONCLUSIONS

Silicon enhanced the drought resistance of peach seedlings by regulating stress-related hormone synthesis and signal transduction, and regulating amino acid and sugar metabolism.

Interaction between PpERF5 and PpERF7 enhances peach fruit aroma by upregulating PpLOX4 expression

Ethylene plays a critical role in peach (Prunus persica) fruit ripening; however, the molecular mechanism underlying ethylene-mediated aroma biosynthesis remains unclear. Here, we compared the difference in aroma-related volatiles and gene expression levels between melting-flesh (MF) and stony hard (SH) peach cultivars at S3, S4 I, S4 II, S4 III stages, and explored the relation between volatile biosynthesis related genes and ethylene response factor (ERF) genes. The concentration of fruity aromatic compounds such as lactones and terpenes increased significantly in MF peach during fruit ripening, while it was nearly undetectable in SH peach. LOX4 and FAD1 genes expressed concomitantly with ethylene emission and significantly downregulated by 1-MCP. Besides, 1-MCP treatment could sharply influence the fruity aromatic compounds, suggesting that these genes play key roles in volatile biosynthesis during fruit ripening. Furthermore, PpERF5 and PpERF7 could bind together to form a protein complex that enhanced the transcription of LOX4 more than each transcription factor individually. Overall, this work provides new insights into the transcriptional regulatory mechanisms associated with aroma formation during peach fruit ripening.

Combined nature and human selections reshaped peach fruit metabolome

Background

Plant metabolites reshaped by nature and human beings are crucial for both their lives and human health. However, which metabolites respond most strongly to selection pressure at different evolutionary stages and what roles they undertake on perennial fruit crops such as peach remain unclear.

Results

Here, we report 18,052 significant locus-trait associations, 12,691 expression-metabolite correlations, and 294,676 expression quantitative trait loci (eQTLs) for peach. Our results indicate that amino acids accumulated in landraces may be involved in the environmental adaptation of peaches by responding to low temperature and drought. Moreover, the contents of flavonoids, the major nutrients in fruits, have kept decreasing accompanied by the reduced bitter flavor during both domestication and improvement stages. However, citric acid, under the selection of breeders’ and consumers’ preference for flavor, shows significantly different levels between eastern and western varieties. This correlates with differences in activity against cancer cells in vitro in fruit from these two regions. Based on the identified key genes regulating flavonoid and acid contents, we propose that more precise and targeted breeding technologies should be designed to improve peach varieties with rich functional contents because of the linkage of genes related to bitterness and acid taste, antioxidant and potential anti-cancer activity that are all located at the top of chromosome 5.

Conclusions

This study provides powerful data for future improvement of peach flavor, nutrition, and resistance in future and expands our understanding of the effects of natural and artificial selection on metabolites.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13059-022-02719-6.

Prunus persica transcription factor PpNAC56 enhances heat resistance in transgenic tomatoes

Members of the NAC (NAM, ATAF1,2 and CUC2) transcription factor family are involved in numerous processes of plant growth and development and play an important role in the response to abiotic stresses such as salinity, drought and heat, but little research on this topic has been done in peach. In this study, we analyzed the expression patterns of PpNAC56 under abiotic stress and found that PpNAC56 responded to high-temperature stress. To verify the function of PpNAC56, we overexpressed this gene in tomato plants and found that, compared with WT plants, the transgenic tomato plants could accumulate more osmoregulatory substances after high-temperature treatment and thus were more heat resistance. Then, using Y2H, BIFC, and pull-down assays, we found that PpNAC56 could interact with PpMIEL1. In addition, Y1H and dual-luciferase assays verified that PpNAC56 could activate the expression of PpHSP17.4 and PpSnRK2D. The above experimental results demonstrate that PpNAC56 plays an important role in the plant response to heat stress.

Chromosome-level genome assemblies of four wild peach species provide insights into genome evolution and genetic basis of stress resistance

Background

Peach (Prunus persica) is an economically important stone fruit crop in Rosaceae and widely cultivated in temperate and subtropical regions, emerging as an excellent material to study the interaction between plant and environment. During its genus, there are four wild species of peach, all living in harsh environments. For example, one of the wild species, P. mira, originates from the Qinghai-Tibet Plateau (QTP) and exhibits strong cold/ultraviolet ray environmental adaptations. Although remarkable progresses in the gene discovery of fruit quality-related traits in peach using previous assembled genome were obtained, genomic basis of the response of these wild species to different geographical environments remains unclear.

Results

To uncover key genes regulating adaptability in different species and analyze the role of genetic variations in resistance formation, we performed de novo genome assembling of four wild relatives of peach (P. persica), P. mira, P. davidiana, P. kansuensis, and P. ferganensis and resequenced 175 peach varieties. The phylogenetic tree showed that the divergence time of P. mira and other wild relatives of peach was 11.5 million years ago, which was consistent with the drastic crustal movement of QTP. Abundant genetic variations were identified in four wild species when compared to P. persica, and the results showed that plant-pathogen interaction pathways were enriched in genes containing small insertions and deletions and copy number variations in all four wild relatives of peach. Then, the data were used to identify new genes and variations regulating resistance. For example, presence/absence variations which result from a hybridization event that occurred between P. mira and P. dulcis enhanced the resistance of their putative hybrid, P. davidiana. Using bulked segregant analysis, we located the nematode resistance locus of P. kansuensis in chromosome 2. Within the mapping region, a deletion in the promoter of one NBS-LRR gene was found to involve the resistance by regulating gene expression. Furthermore, combined with RNA-seq and selective sweeps analysis, we proposed that a deletion in the promoter of one CBF gene was essential for high-altitude adaptation of P. mira through increasing its resistance to low temperature.

Conclusions

In general, the reference genomes assembled in the study facilitate our understanding of resistance mechanism of perennial fruit crops, and provide valuable resources for future breeding and improvement.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01342-y.

Generalized allergic reaction in response to exercise due to strawberry gibberellin-regulated protein: a case report

Background

The Rosaceae family includes fruits, such as peach, apple, Japanese apricot, cherry (Prunoideae subfamily), and strawberry (Rosoideae subfamily). The allergens responsible for Rosaceae fruit allergies have been reported to include Bet v 1 and profilin, which mainly cause oral symptoms, and lipid transfer protein (LTP). Recently, gibberellin-regulated protein (GRP) has been identified as an allergen that induces generalized symptoms in peach-, orange-, and plum-related allergies. Most patients with food allergies induced by GRP show allergic symptoms accompanied by cofactors, such as exercise or drugs. To date, there are very few reports of generalized symptoms induced by strawberry.

Case presentation

We evaluated the reactivity of strawberry GRP in a 15-year-old boy who was confirmed to have generalized symptoms induced by strawberry with exercise using an oral food challenge test (OFCT). The patient’s serum exhibited a strong positive reaction to strawberry GRP but not to peach GRP or peach LTP. The patient’s basophils reacted to strawberry and peach GRP but not to peach LTP.

Conclusions

Strawberry GRP may be a causative component for strawberry with exercise-induced generalized symptoms in this patient. This is the first study to investigate the role of GRP in strawberry with cofactor-induced allergic symptoms. Further epidemiological and clinical researches are necessary to improve diagnostic and therapeutic approaches for patients with strawberry allergy.

Hydrogen sulfide alleviates chilling injury in peach fruit by maintaining cell structure integrity via regulating endogenous H2S, antioxidant and cell wall metabolisms

Effects of hydrogen sulfide (H₂S) on chilling injury (CI), H₂S, antioxidant and cell-wall metabolisms of refrigerated peaches treated with H₂S and hypotaurine (HT, H₂S scavenger) were investigated in present study. Results revealed that H₂S treatment enhanced endogenous H₂S content, which was associated with increased related H₂S synthase enzymes activities, while HT showed the opposite results. Moreover, H₂S treatment induced the accumulation of ascorbic acid, glutathione and the enhancement of antioxidant enzymes activities compared to control and HT, contributing to lower hydrogen peroxide content and superoxide radical production. Furthermore, H₂S suppressed the increase of cell-wall degradation enzymes accompanied by higher levels of water-insoluble pectin, 24% KOH-soluble hemicellulose and cellulose, while HT accelerated these components degradation. Therefore, results indicated that H₂S mitigated CI of refrigerated peaches by regulating H₂S, antioxidant and cell-wall metabolisms, maintaining higher H₂S and antioxidants contents, suppressing cell-wall degradation, thereby contributing to redox homeostasis maintenance and cell structure integrity.

Genome-wide identification and characterization of the Prunus persica ferredoxin gene family and its role in improving heat tolerance

Ferredoxin is involved in many biological processes, such as carbon fixation, nitrogen assimilation, chlorophyll metabolism, and fatty acid synthesis, and it plays a role in plant resistance to stress. However, the functions of Fds in peach during stress are unclear. In this study, 11 members of the peach Fd gene family were identified and divided into six groups (I- VI). We carried out bioinformatics analysis on these sequences, analyzed the physical and chemical properties of PpFd protein and the cis-elements in its promoter region, and predicted and compared the differences in gene structure and conserved protein motifs among groups. The results showed that the PpFd protein was highly conserved in plant species. In addition, overexpression of PpFd08 significantly increased the tolerance of transgenic tomato to high-temperature stress. The transcriptome analysis and qRT-PCR results of PpFd08 transgenic apple calli showed that PpFd08 might enhance heat resistance by modulating the expression of heat tolerance related genes. The results of this study provide a new understanding for the further study of the function of PpFd protein in peach and a candidate gene for improving the heat resistance of peach.

First report of Calonectria canadiana causing peach fruit rot in China

Peach (Prunus persica (L.) Batsch) is one of the most popular fruits grown in Northern China. In July 2021, a fruit rot outbreak on the peach cultivar "Yonglian Sweet" occurred after unusual rains in Baoding, Hebei Province, China. Sixty peach trees from three orchards were assessed, and a 30% disease incidence was estimated. The disease initiated as a small concave spot on the fruit surface expanding circularly rotting the fruit (3-5 cm deep) with the appearance of grayish-white mycelia (Figure S1A). The infected fruit did not disintegrate but turned light brown. To identify the pathogen, 20 infected fruits were collected, and fruit tissues from lesion margins were inoculated on the potato dextrose agar (PDA) medium. A total of 15 fungal pure cultures with highly similar morphological characteristics were obtained by the hyphal-tipping method. The fungal culture formed smooth-edged colonies of extensive, dense, wooly aerial mycelium, with color changing from sienna to luteous, and to grayish-white along the radius of colonies (Figure S1B) Chlamydospores were extensive and developed micro-sclerotia after 20 d of growth. The conidiophore produced three branches in a "broom" shape, with the primary branch ranging 7.5-25.0 μm in length, the secondary branch 5.5-15.5 μm, and the tertiary branch 10-12.5 μm (N = 30). The top of the tertiary branch tapered and produced conidia. Conidia were colorless and culm-like, 40.0-57.5 μm long and 3.8-6.25 μm wide (N = 30). Hyphae occasionally produced spherical chlamydospores with a diameter of around 7.5 μm (N = 30). Conidia germinated after 12 h in moist conditions, and germ tubes originated from multiple points on the conidia. Based on these morphological features, the isolated fungus was identified as Calonectria spp. (Lombard et al. 2010). Six loci, including ITS, act, cmdA, his3, tef1, and tub2, were amplified and sequenced for molecular identification of an isolate F099 using primers listed in Table S1. The obtained ITS (528 bp, GenBank accession no. OL635556), act (263 bp, OL694221), cmdA (470 bp, OL694222), his3 (432 bp, OL694223), tef1 (487 bp, OL694224), and tub2 (535 bp, OL694225) sequences showed 100% similarity to the ex-type strain of Calonectria canadiana, CMW 23673 (accession nos. MT359667, MT334976, MT335206, MT335446, MT412737, and MT412958, respectively; Figure S1D) (Kang et al. 2001, Lechat et al. 2010, Liu et al. 2020). The isolate F099 of C. canadiana was further subjected to pathogenicity tests. Koch's postulates were performed by placing three mycelial disks (ten-day old, 5 mm) with conidia on the sterile needle-acupunctured surface of healthy fruits of the peach cultivar "Yonglian Sweet" (N= 10). Mock inoculations with sterile PDA disks were served as a control. All the inoculated fruits were kept in a moist chamber (25℃, 16-h light and 8-h dark period). The inoculation assay was repeated twice. Rotting symptoms developed on all the inoculated fruits about 5 days post-inoculation (dpi) and grayish-white mycelia appeared around ten days post inoculation while mock inoculated fruits did not show any rotting. The pathogen of interest was re-isolated from the inoculated fruits and validated as C. canadiana by ITS and tef1 sequences. All above evidence collectively indicates that the fungal pathogen causing the peach fruit rot is C. canadiana. The new host plant and new geographic distribution reported here will inform future management of this fungal species.

Multiple indeterminate domain (IDD)-DELLA1 complexes participate in gibberellin feedback regulation in peach

Peach encodes 14 INDETERMINATE DOMAIN (IDD) transcription factors. PpIDD4, -12 and -13 mediated PpDELLA1 binding to the PpGA20ox1 promoter. Each of these three PpIDD-DELLA1 complexes activated transcription of PpGA20ox1. PpTPR1 and -4 interrupted the interaction of PpIDDs with PpDELLA1. The plant growth regulator gibberellin (GA) plays an important role in the rapid growth of annual shoots in peach. Our previous study showed that the peach cultivar 'FenHuaShouXingTao' (FHSXT), a gibberellic acid receptor (gid1) mutant, accumulates active GAs in annual shoot tips. This mutant enhances GA feedback regulation in peach. The results of this study suggested that the PpIDD-DELLA1 complex is the underlying mechanism of GA feedback regulation in peach. Fourteen IDD genes were identified in peach, and three PpIDDs (PpIDD4, -12 and -13, all from group IV) interacted with PpDELLA1, an important component in GA signaling pathway. Truncation, segmentation and site mutation of the promoter of PpGA20ox1 (a GA biosynthesis gene) showed that all three PpIDD proteins recognized the core motif TTGTC. PpIDD4 and -13 mainly bind to site 3, while PpIDD12 binds to site 5 of the PpGA20ox1 promoter. All three PpIDD-DELLA1 complexes activated the PpGA20ox1 promoter-LUC fusion. These data suggested that PpIDDs bridge PpDELLA1 and the promoter of PpGA20ox1, which then activated the transcription of PpGA20ox1. In addition, PpTPR1 and -4 disrupted the interaction of PpIDDs with PpDELLA1. Our research will be helpful for understanding and possibly modifying the regulation of annual shoot growth and GA biosynthesis.

An efficient chromatin immunoprecipitation (ChIP) protocol for studying histone modifications in peach reproductive tissues

BACKGROUND

Perennial fruit trees display a growth behaviour characterized by annual cycling between growth and dormancy, with complex physiological features. Rosaceae fruit trees represent excellent models for studying not only the fruit growth/patterning but also the progression of the reproductive cycle depending upon the impact of climate conditions. Additionally, current developments in high-throughput technologies have impacted Rosaceae tree research while investigating genome structure and function as well as (epi)genetic mechanisms involved in important developmental and environmental response processes during fruit tree growth. Among epigenetic mechanisms, chromatin remodelling mediated by histone modifications and other chromatin-related processes play a crucial role in gene modulation, controlling gene expression. Chromatin immunoprecipitation is an effective technique to investigate chromatin dynamics in plants. This technique is generally applied for studies on chromatin states and enrichment of post-transcriptional modifications (PTMs) in histone proteins.

RESULTS

Peach is considered a model organism among climacteric fruits in the Rosaceae family for studies on bud formation, dormancy, and organ differentiation. In our work, we have primarily established specific protocols for chromatin extraction and immunoprecipitation in reproductive tissues of peach (Prunus persica). Subsequently, we focused our investigations on the role of two chromatin marks, namely the trimethylation of histone H3 at lysine in position 4 (H3K4me3) and trimethylation of histone H3 at lysine 27 (H3K27me3) in modulating specific gene expression. Bud dormancy and fruit growth were investigated in a nectarine genotype called Fantasia as our model system.

CONCLUSIONS

We present general strategies to optimize ChIP protocols for buds and mesocarp tissues of peach and analyze the correlation between gene expression and chromatin mark enrichment/depletion. The procedures proposed may be useful to evaluate any involvement of histone modifications in the regulation of gene expression during bud dormancy progression and core ripening in fruits.

Identification of key gene networks controlling anthocyanin biosynthesis in peach flower

Flavonoids, particularly anthocyanin is the main pigment that determined the red color of peach flowers, and help the plant to attract pollinators, protect the reproductive organs of flower from photo-oxidative effects of light and various non-communicable diseases. Through weightage gene coexpression network analysis (WGCNA) we identified a network of 15 hub genes that co-expressed throughout peach flower development including 5 genes coded for the key enzymes (CHI, F3'H, DFR, LAR and UFGT) of flavonoid biosynthetic pathway and 1 gene Prupe.1G111700 identified as R2R3 family transcription factor MYB108. Over expression of PpMYB108 significantly increased anthocyanin biosynthesis in Tobacco flowers. Moreover, the expression correlation between PpMYB108 and PpDFR, suggests that PpMYB108 play the role of transcriptional activator for PpDFR. This was further supported by a 6 bp insertion of MYB biding site in the core promoter region of PpDFR in red flower. The positive interaction of PpMYB108 with PpDFR promoter from red flower was confirmed in yeast one hybrid assay. These findings may be helpful in peach breeding programs as well as in identifying anthocyanin related genes in other species.

Genome-Wide Identification, Expression, and Interaction Analysis of BEL-Like Homeodomain Gene Family in Peach

BEL1-like homeodomain (BLH) family genes as homeodomain transcription factors are found ubiquitously in plants to play important regulatory roles in reproductive development, morphological development, and stress response. Although BLH proteins have been reported in some species, there is little information about BLH genes in peach. In this study, we identified 11 peach PpBLH genes based on the conserved domain. Phylogenetic analysis suggested that the PpBLH proteins could be divided into five groups, which might be involved in different aspects of morphogenesis. Genomics structure analysis revealed that there were four exons in the PpBLH gene, and the length of the third exon was 61 bp. Chromosomal location analysis showed that the PpBLH genes were not distributed uniformly on six chromosomes. Promoter analysis showed that the promoter sequences of six PpBLH genes contained multiple cis-acting elements for hormones and stress. Six PpBLH genes were cloned by RT-PCR, and PpBLH1, PpBLH4, and PpBLH7 showed different expression patterns in the tested fruits under common temperature and high temperature. Y2H results indicated that PpBLH7 andPpBLH10 interacted with the PpOFP6 protein, and PpBLH1 interacted with the PpOFP1, PpOFP2, PpOFP4, and PpOFP13 proteins. These results provide new insight for further study of PpBLH genes, and construction of regulatory networks of PpBLH proteins in the growth, development, and stress response of peach.

Biolistic Inoculation of Fruit Trees with Full-Length Infectious cDNA Clones of RNA Viruses

Long life cycle and lack of efficient and robust virus inoculation technique are the major technical challenges for studying virus infection in perennial woody plants such as fruit trees. Biolistic technology also called particle bombardment is a physical approach that can directly introduce virions or viral full-length cDNA infectious clones into target cells and tissues by high velocity microcarrier particles. The flexibility and high efficiency of the biolistic inoculation method facilitate research on fruit tree virology and the screening and identification of fruit tree germplasms resistant to viruses. Here, we describe a detailed protocol for the biolistic inoculation of peach with of a cDNA infectious clone of Plum pox virus (PPV) using the Helios gene gun, a biolistic particle delivery system.

Influence of Scion/Rootstock reciprocal effects on post-harvest and metabolomics regulation in stored peaches

Peach is an important stone fruit crop cultivated at commercial scale in Pakistan. While, appropriate selection of rootstock has significant impact on the quality of peach fruit. Therefore, in the current study the influence of three rootstocks viz. ‘GF-677′, ‘Peshawar Local’ and ‘Swat Local’ were evaluated on the quality of ‘Flordaking’ peaches following cold storage during two consecutive years. The fruit from these rootstocks were kept at 0 °C for five weeks were studied for various fruit physical (weight loss, colour, firmness) and biochemical (pH, soluble solids content (SSC), titratable acidity (TA), SSC:TA ratio, fruit juice pH, sugars (total, reducing and non-reducing sugars), ascorbic acid (vitamin C) and free radicals scavenging activities) were evaluated. During both years, fruit harvested form trees grafted on ‘GF-677′ exhibited reduced fruit weight loss, changes in Chroma (C*) and highest fruit firmness, Lightness (L*), ascorbic acid contents and radical scavenging activities as compared to fruit harvested from tree grafted on other rootstocks. In conclusion, the post-harvest quality of scion ‘Flordaking’ peach fruit was significantly influenced and best quality can be obtained when it is grafted on ‘GF-677′ rootstock.

Spatial changes of arbuscular mycorrhizal fungi in peach and their correlation with soil properties

Arbuscular mycorrhizal (AM) fungi have beneficial effects on host plants, but their growth is influenced by various factors. This study was carried out to analyze the variation of AM fungi in soils and roots of peach (Prunus persica L. var. Golden Honey 3, a yellow-flesh variety) trees in different soil layers (0–40 cm) and their correlation with soil properties. The peach tree could be colonized by indigenous AM fungi (2.2–8.7 spores/g soil and 1.63–3.57 cm hyphal length/g soil), achieving 79.50–93.55% of root AM fungal colonization degree. The mycorrhizal growth, root sugars, soil three glomalins, NH₄⁺-N, NO₃⁻-N, available P and K, and soil organic matter (SOM) had spatial heterogeneity. Soil spores, but not soil hyphae contributed to soil glomalin, and soil glomalin also contributed to SOM. There was a significant correlation of soil hyphae with spore density, soil NO₃⁻-N, and SOM. Root mycorrhiza was positively correlated with spore density, NH₄⁺-N, NO₃⁻-N, and easily extractable glomalin-related soil protein. Notably, spore density positively correlated with NO₃⁻-N, available K, SOM, and root fructose and glucose, while negatively correlated with available P and root sucrose. These findings concluded that mycorrhiza of peach showed spatial distribution, and soil properties mainly affected/altered based on the soil spore density.

Skin Testing With Peach Peel Extract Versus Serum IgE to Pru p 3 as a Stronger Predictor of Peach-Induced Anaphylaxis

The most important peach fruit allergen is Pru p 3, followed by Pru p 1, Pru p 4, and Pru p 7. We aimed to assess their role in subjects with peach fruit-induced allergy (anaphylaxis and OAS) and compare skin prick tests (SPT) vs. specific immunoglobulin E (sIgE) for predicting anaphylaxis. We also selected a control group. SPT included prevalent inhalant and plant food allergens plus peach peel extract. The sIgE to Pru p 1, Pru p 3, Pru p 4, and Pru p 7 were quantified. Compared with controls (n = 42), cases (n = 41) were younger (P = 0.003), more frequently female (P < 0.05) and had higher SPT positivity to peach peel (44% vs. 2.4%, P < 0.0001). There were significant differences in sensitization to several pollens: Olea europaea, Artemisia vulgaris, Prunus persica, Platanus acerifolia (all P < 0.001); and fruits: apple (P < 0.04), peanut (P < 0.002), tomato (P < 0.005), and melon (P < 0.05). Pru p 3 sIgE was detected in 61% of all cases (85% anaphylaxis and 38% OAS; P < 0.01 each) and 5% of controls (P < 0.001). Pru p 4 sIgE was present in 19% of cases and 7% of controls. The sIgE to Pru p 1 and Pru p 7 were not found. The odds ratio to predict anaphylaxis for peach peel SPT was 113 (confidence interval [CI], 20–613; P < 0.0001); for sIgE to Pru p 3, 22 (CI, 5.3–93; P < 0.0001); and for SPT positivity to selected plant food allergens, 5 (CI, 1–19; P < 0.05). In our study group, SPT with peel peach extract was a better predictor of anaphylaxis than Pru p 3 sIgE or other variables considered. The role of sIgE to Pru p 1, Pru p 4, and Pru p 7 seemed negligible.

Antidiabetic potential of the isolated fractions from the plants of Rosaceae family in streptozotocin-induced diabetic rats

Background and purpose:

Diabetes is a group of multifactorial disorders characterized by chronic-elevated blood glucose levels (hyperglycemia). Natural remedies are used as alternative medications to treat diabetes. Here, we tested the protective effect of the plant extracts of the Rosaceae family on improving insulin secretion and repairing the pancreatic beta cells in diabetic rats.

Experimental approach:

The oligosaccharide fraction was isolated from the Rosaceae family of herbs. LC-MS/MS was applied to characterize the isolated fractions. The male Wistar rats were randomly divided into six groups, 10 each, including the control group with no intervention, diabetic rats without treatment, diabetic rats that received the extract of Malus domestica (apple), Cydonia oblonga (quince), Prunus persica (nectarine), and Prunus persica (peach), separately. Rats were monitored for the weight, fasting plasma glucose, and insulin levels. The effect of extracts in streptozotocin (STZ)-induced diabetic rats on the pancreatic islets was evaluated by morphometric analysis.

Findings/Results:

LC-MS/MS results indicated a similar mass spectrum of isolated fractions from nectarine and peach with Rosa canina. Oral administration of nectarine and peach extracts to STZ-induced diabetic rats showed restoration of blood glucose levels to normal levels with a concomitant increase in insulin levels. Morphometric analysis of pancreatic sections revealed the increase in number, diameter, volume, and area of the pancreatic islets in the diabetic rats treated with extracts compared to the untreated diabetic rats.

Conclusion and implications:

Nectarine and peach extracts’ anti-diabetic properties improved insulin secretion and pancreatic beta-cell function and subsequently led to restoring pancreatic islet mass in STZ-induced diabetic rats.

Physiochemical, sensorial and rheological characteristics of puree developed from Kashmiri peaches: influence of sugar, KMS and storage conditions

The present investigation was undertaken to develop puree from peaches and to study the effect of peel, sugar, KMS concentrations and storage conditions on the acidity, pH, total soluble solids, total sugar and rheological behavior of purees. Two types of Purees (Peeled and unpeeled) were prepared by adding sugar (10% and 15%) and KMS (100ppm, 200ppm, 300ppm). A decrease in viscosity with an increase in shear rate was observed. The developed purees were stored at refrigerated and ambient conditions for 45 days and were analyzed at 15 days interval. During the storage period, there was a change in G' and G"and the changes in pH and TSS were observed. The highest decrease in G' and G" was observed in P_{1 and} P₀ at ambient storage. The overall organoleptic score of all samples was acceptable, however, the organoleptic score of the P₇ at refrigerated conditions was highest.

Investigation of pesticide residues in peach and nectarine sampled from Çanakkale, Turkey, and consumer dietary risk assessment

The present study was conducted to investigate pesticide residues on peach and nectarine. For method verification, samples were spiked at 0.1, 1.0, and 10.0 times of maximum residue limit (MRL) for each pesticide. The Quick-Easy-Cheap-Efficient-Rugged-Safe (QuEChERS)-liquid chromatography/tandem mass spectrometry detection revealed that limit of quantifications (LOQs) of pesticides were below the MRL. The overall recovery was 113.51% with relative standard deviation (RSD) of 17.33% for peach and 113.61% with RSD of 11.44% for nectarine. These figures were within the Directorate-General for Health and Food Safety (SANTE) recovery limits (60-140%) and the values specified for the repeatability (RSD ≤ 20%). Samples were collected from 5 different stands at Çanakkale open markets for 12 weeks. None of the residues was not ≥ MRL in any samples. Maximum levels of 567.80 and 322.10 μg/kg boscalid were detected in peach and nectarine, respectively, corresponding approximately 1/10 and 1/15 of the MRL. Maximum levels for tebuconazole were about 1/12 and 1/10 of the MRL for peach (47.53 μg/kg) and nectarine (56.90 μg/kg), respectively. Chlorpyrifos residues of all samples were below LOQ. According to our findings and the World Health Organisation Guideline, chronic exposure levels of pesticides were low and there is no risk to human health in terms of 3 pesticides.

The downregulation of PpPG21 and PpPG22 influences peach fruit texture and softening

The downregulation of PpPG21 and PpPG22 expression in melting-flesh peach delays fruit softening and hinders texture changes by influencing pectin solubilization and depolymerization. The polygalacturonase (PG)-catalyzed solubilization and depolymerization of pectin plays a central role in the softening and texture formation processes in peach fruit. In this study, the expression characteristics of 15 PpPG members in peach fruits belonging to the melting flesh (MF) and non-melting flesh (NMF) types were analyzed, and virus-induced gene silencing (VIGS) technology was used to identify the roles of PpPG21 (ppa006839m) and PpPG22 (ppa006857m) in peach fruit softening and texture changes. In both MF and NMF peaches, the expression of PpPG1, 10, 12, 23, and 25 was upregulated, whereas that of PpPG14, 24, 35, 38, and 39 was relatively stable or downregulated during shelf life. PpPG1 was highly expressed in NMF fruit, whereas PpPG21 and 22 were highly expressed in MF peaches. Suppressing the expression of PpPG21 and 22 by VIGS in MF peaches significantly reduced PG enzyme activity, maintained the firmness of the fruit during the late shelf life stage, and suppressed the occurrence of the "melting" stage compared with the control fruits. Moreover, the downregulation of PpPG21 and 22 expression also reduced the water-soluble pectin (WSP) content, increased the contents of ionic-soluble pectin (ISP) and covalent-soluble pectin (CSP) and affected the expression levels of ethylene synthesis- and pectin depolymerization-related genes in the late shelf life stage. These results indicate that PpPG21 and 22 play a major role in the development of the melting texture trait of peaches by depolymerizing cell wall pectin. Our results provide direct evidence showing that PG regulates peach fruit softening and texture changes.

Batsch) by gas chromatography-olfactometry, flame photometric detection and molecular sensory science approaches

Aroma profiles and aroma-active compounds of "Yulu" peach from Fenghua (the peach known for the best flavor and quality in China) were investigated by headspace solid-phase microextraction (HS-SPME), solvent-assisted flavor evaporation (SAFE), gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS), and flame photometric detection (FPD). The combination of these methods improved the analysis and identification of aroma substances compared to the combination of a single aroma extraction method and GC-MS. A total of 85 aroma-active compounds, including 10 sulfur compounds were detected. Methional, methyl 3-(methylthio)propionate, methionol, and benzothiazole were first detected in peaches. These aroma compounds cannot only supplement the database of aroma substances of peaches, but also provide data support for traceability of the origins of "Yulu" peaches. In addition, the odor activity value (OAV) was used to identify the contributions of the most important compounds. The results indicated that hexanal, 3-methylbutanal, (E)-2-hexen-1-ol, 3-mercaptohexyl acetate, (E,E)-2,4-decadienal, 2-methylpropanal, γ-decalactone, 2-methylbutanal, theaspirane, and δ-decalactone were the key aroma-active compounds. The key characteristic aroma components were further ascertained by aroma reconstitution and omission experiments, which showed that the fruity, floral, sulfur, and sour notes could be well simulated. Finally, the perceptual interactions between different sulfur compounds and fruity recombination (FR) were explored. 3-mercaptohexanol and 4-methyl-4-mercaptopentan-2-one could significantly decrease the threshold of FR. The possible reason was that these two sulfur compounds had synergistic effects with the aroma compounds in FR, with the U model confirming the results of these synergistic effects. The perceptual interactions provide a basis for the regulation of characteristic fruity aroma of peach products.

A Prunus necrotic ringspot virus (PNRSV)-Based Viral Vector for Characterization of Gene Functions in Prunus Fruit Trees

Virus-induced gene silencing (VIGS) is a gene silencing mechanism by which an invading virus targets and silences the endogenous genes that have significant sequence similarity with the virus. It opens the door for us to develop viruses as powerful viral vectors and modify them for molecular characterization of gene functions in plants. In the past two decades, VIGS has been studied extensively in plants, and various VIGS vectors have been developed. Despite the fact that VIGS is in particular practical for functional genomic study of perennial woody vines and trees with a long life cycle and recalcitrant to genetic transformation, not many studies have been reported in this area. Here, we describe a protocol for the use of a Prunus necrotic ringspot virus (PNRSV)-based VIGS vector we have recently developed for functional genomic studies in Prunus fruit trees.

RNA Peach and Mango: Orthogonal two-color fluorogenic aptamers distinguish nearly identical ligands

Two-channel fluorogenic RNA aptamer-based imaging is currently challenging. While we have previously characterized the Mango series of aptamers that bind tightly and specifically to the green fluorophore TO1-Biotin, the next aim was to identify an effective fluorogenic aptamer partner for two-color imaging. A competitive in vitro selection for TO3-Biotin binding aptamers was performed resulting in the Peach I and II aptamers. Remarkably, given that the TO1-Biotin and TO3-Biotin heterocycles differ by only two bridging carbons, these new aptamers exhibit a marked preference for TO3-Biotin binding relative to the iM3 and Mango III A10U aptamers, which preferentially bind TO1-Biotin. Peach I, like Mango I and II, appears to contain a quadruplex core isolated by a GAA^A type tetraloop-like adaptor from its closing stem. Thermal melts of the Peach aptamers reveal that TO3-Biotin binding is cooperative, while TO1-Biotin binding is not, suggesting a unique and currently uncharacterized mode of ligand differentiation. Using only fluorescent measurements, the concentrations of Peach and Mango aptamers could be reliably determined in vitro. The utility of this orthogonal pair provides a possible route to in vivo two-color RNA imaging.

Peach PpSnRK1α interacts with bZIP11 and maintains trehalose balance in plants

The nonreducing disaccharide trehalose is widespread in nature. It plays a very important role in plant growth and development. In plants, trehalose is present in trace amounts. High concentration of trehalose disrupts energy balance and inhibits normal growth and development. Studies have shown that high levels of trehalose and trehalose-6-phosphate (T6P), the metabolic precursor of trehalose, inhibit sucrose non-fermenting-1-related protein kinase1 (SnRK1) activity, which affect plant growth and development. However, the role of SnRK1, the energy balance center, in the regulation of trehalose metabolism in plants is unknown. In this study, exogenous trehalose at higher concentrations inhibited the expression of SnRK1 genes, especially PpSnRK1α in peach (Prunus persica) seedlings. This change in gene expression was dependent on trehalose concentration. Furthermore, overexpression of peach PpSnRK1α in Arabidopsis thaliana significantly promoted trehalase activity, reduced T6P content, and suppressed the trehalose synthesis related genes (TPSs, TPPB) expression, promoted the trehalose metabolism of gene expression (TRE1), in addition the transgenic plants alleviated photosynthetic product distribution imbalance (aboveground and underground parts), and enhanced root growth. Yeast two-hybrid and bimolecular fluorescence assays revealed the interaction between PpSnRK1α and peach basic domain leucine zipper transcription factor 11 (PpbZIP11), a key transcription factor of trehalose metabolism, in the nucleus. To summarize, PpSnRK1α overexpression improved bZIP11 transcriptional activity and regulated trehalose metabolism to protect the plants against trehalose-induced damage. This study preliminarily explained the mechanism of SnRK1 regulating trehalose metabolism balance in plants, which laid a foundation for further understanding of energy metabolism and function of SnRK1 in plants.

Botanical Control of Citrus Green Mold and Peach Brown Rot on Fruits Assays Using a Persicaria acuminata Phytochemically Characterized Extract

Persicaria acuminata (Polygonaceae) is a perennial herb that grows in the central area of Argentina and it is commonly used by native populations to heal infected wounds and other conditions related to fungal infections. In this article, we explored the in vitro antifungal activity of its ethyl acetate extract against a panel of three fruit phytopathogenic fungi including: Penicillium digitatum, P. italicum, and Monilinia fructicola. The sesquiterpenes isolated from the extract were also evaluated against these strains, demonstrating that the dialdehyde polygodial was the responsible for this activity. In order to encourage the use of the extract rather than the pure compound, we displayed ex vivo assays using fresh oranges and peaches inoculated with P. digitatum and M. fructicola, respectively, and subsequently treated by immersion with an extract solution of 250 and 62.5 µg/mL, respectively. There were no statistically significant differences between the treatments with commercial fungicides and the extract over the control of both fruit rots. The concentration of the active compound present in the extract used on fruit experiments was determined by Gas Chromatography-Mass Spectroscopy. Finally, cytotoxicity evaluation against Huh7 cells showed that P. acuminata extract was less cytotoxic than the commercial fungicides at the assayed concentrations. After these findings we could conclude that a chemically characterized extract of P. acuminata should be further developed to treat fungal diseases in fruits from an agro-ecological model.

Pru p 3 Sublingual Immunotherapy in Patients with Lipid Transfer Protein Syndrome: Is It Worth?

BACKGROUND

Lipid transfer proteins (LTPs) syndrome is an important cause of multiple plant food allergy in the Mediterranean area. The effectiveness of sublingual immunotherapy (SLIT) with the LTP Pru p 3 extract has been little investigated in the real-world setting. This study aimed to investigate the outcome of Pru p 3 SLIT in real-life patients with LTP syndrome with/without concurrent reactions to peanut and/or nuts.

METHODS

This was a prospective real-life study including all patients diagnosed with LTP allergy and treated with Pru p 3 SLIT between 2011 and 2018 in a tertiary hospital in Spain. Patients underwent open oral food challenge (OFC) tests for unpeeled peach and nuts/peanuts 1 year after the treatment started to assess food tolerance. A control group of patients diagnosed with LTP allergy who refused treatment with immunotherapy were included. Severity of symptoms and diet avoidance was recorded in both groups.

RESULTS

Twenty-nine patients with a median age of 24.7 years (range 5.5-43.1) were included: 100% were allergic to fruit; 72%, to peanut and/or nuts; 19 had a history of severe systemic reactions. Seven patients discontinued therapy; 3 (10%), due to adverse events. One year after SLIT start, 16 (73%) patients had negative OFC to peach; 95%, after 2 years; 69% had negative OFC to nuts/peanuts. The control group included 13 patients: 53.8% experienced reactions with new foods; severity of symptoms increased significantly (p < 0.001), and diet restrictions were maintained in this group.

CONCLUSIONS

SLIT with Pru p 3 shows a good safety profile, and avoid dietary restrictions in patients with LTP syndrome treated in the real-life setting.

Efficacy of commercial overhead washing and waxing systems on the microbiological quality of fresh peaches

Overhead spray washing and waxing systems (WWS) are used commercially to reduce the risk of microbial contamination and improve the quality of fresh produce during packing. This study evaluated the microbiological quality of overhead spray water and spent peach wash water, as well as fresh peaches before and after they pass the WWS. Pre- and post-washed/waxed peach samples (n = 192) and overhead spray water and spent peach wash water samples (n = 54) were collected several times over the course of a processing day in three packing facilities located in the state of Georgia. Populations of total aerobes (TA), yeasts and molds (YM), and coliforms (TC) and the presence of thermotolerant coliforms (TTC) and enterococci (EC) were measured in collected samples. The average TA and TC counts and the incidences of TTC and EC were significantly higher (P < 0.05) on peach samples collected after the WWS compared to those collected before the WWS. Counts and incidences of TA, YM, and TC in spent peach wash water were significantly higher than in the overhead spray water where neither TTC nor EC was detected. Results suggest that the commercial washing and waxing systems had little effect in improving the microbiological quality of fresh peaches.