【Objective】As a typical climacteric fruit,the preharvest physiological maturity of kiwifruit critically determines its postharvest storage performance,sensory characteristics and nutritional quality. Assessing maturity based solely on fruit size,shape,or skin color at harvest is often unreliable,and the optimal harvest timing varies considerably among kiwifruit cultivars.Both premature and delayed harvesting negatively affect fruit quality and storage performance.Accordingly,precise harvest scheduling is essential for guaranteeing high fruit quality.This study aimed to identify the optimal harvest windows and assess the variations in fruit quality among five major kiwifruit cultivars cultivated in the Xiangxi region of Hunan Province,China,so as to provide a scientific foundation for developing region-specific standardized harvest protocols.【Methods】Fruits were harvested at six developmental stages, which corresponded to 108,118,128,138,148,and 158 days after full bloom(DAFB).A comprehensive range of physicochemical and storage-related attributes was analyzed,including fruit weight,longitudinal diameter,transverse diameter,exocarp firmness,and pulp firmness(measured at harvest and after softening),soluble solids content(SSC),dry matter content(DMC),titratable acidity(TA),soluble sugar content,ascorbic acid(AsA)content,and sugar-acid ratio.Additionally,postharvest performance was evaluated during 35 days of storage at room temperature by tracking weight loss,softening rate,and decay incidence.Two-way ANOVA and principal component analysis(PCA)were used to analyze and integrate these multi-dimensional data,and comprehensive scores were calculated to determine the optimal harvest window for each cultivar.【Results】Two-way ANOVA showed that both cultivar and harvest date, as well as their interaction,had highly significant effects(P＜0.01)on soluble solids content(SSC),titratable acidity(TA),and fruit firmness.Principal component analysis(PCA)extracted three principal components, which together accounted for 85.83% of the total cumulative variance. Comprehensive evaluation identified distinct optimal harvest windows: 148 days after full bloom (DAFB) was determined to be the ideal harvest period for Jinhong 1, Hongyang, and Huangxin B (A. chinensis), while Huangxin A(A.chinensis)and Miliang 1 reached peak quality at 158 DAFB.We observed significant differences in storability across these cultivars.Jinhong 1 and Hongyang are classified as rapid-ripening,highly perishable cultivars.When harvested at or after stageⅣ,their fruit decay rate exceeded 70% after only 14 days of storage.In contrast,Huangxin A and Huangxin B showed low,stable weight loss rates.After 35 days of storage,their decay rates ranged between 80% and 90%,so they are classified as slow-ripening,storable cultivars.For Miliang 1,although harvesting at early stages resulted in relatively high weight loss,its storability was significantly improved when harvested in the mid-to-late season.【Conclusion】Optimal harvest windows vary considerably among these five kiwifruit cultivars.Jinhong 1 and Hongyang are rapid-ripening cultivars that require prompt marketing after harvest.In contrast,the Huangxin series and Miliang 1 feature slower ripening and superior storability,providing greater commercial adaptability for the kiwifruit industry.
【Objective】Soil salinization is a major environmental constraint affecting apple cultivation in coastal regions of northern China,including the Bohai Rim area,where the high soil salt content limits tree growth and reduces fruit quality.Although moderate salt stress has been reported to enhance fruit flavor quality in certain horticultural crops such as cherry tomato and cucumber,the metabolic responses of apple fruits to salt stress and their associations with flavor changes remain largely unclear. Using the salt-tolerant rootstock Yanxing crabapple grafted with Jiping 5 apple,this study systematically investigates the changes in fruit metabolite profiles under five different concentrations of salt stress (0,0.2%,0.4%,0.6%,and 0.8% soil salt contents).The objective is to clarify the activation or suppression effects of salt stress on specific metabolic pathways,to identify key differential metabolites associated with flavor quality,and to characterize how salt stress concentration affects the metabolic features of fruit flavor quality,thereby providing a theoretical basis for high-quality apple cultivation in saline-alkali soils.【Methods】Jiping 5 apple was grafted onto Yanxing crabapple rootstock.Five salt stress treatments were applied:0(CK),0.2%,0.4%,0.6%,and 0.8% soil salt contents.Fruit samples were collected at maturity.Non-targeted metabolomics analysis was performed using UPLC-MS/MS.Data processing included peak detection, alignment, normalization, and filtering (RSD ＞30% in QC samples removed). PCA and OPLS-DA were conducted using the ropls package in R. Differential metabolites were screened based on VIP＞1.0 and P＜0.05.Metabolite annotation and KEGG pathway enrichment analysis were performed using HMDB, Metlin, KEGG databases, and the scipy. stats package in Python.【Results】A total of 1854 metabolites were identified across all samples.The major categories included organooxygen compounds (17.91%), carboxylic acids and derivatives (13.05%), fatty acyls (8.68%), prenol lipids (8.63%), and flavonoids (8.20%). PCA showed gradual separation of samples along PC1(36.20% variance explained)with increasing salt concentration,indicating significant metabolic reprogramming.PLS-DA further confirmed distinct clustering among treatment groups.The number of differential metabolites increased progressively with salt concentration: 297 (0.2% vs CK), 422 (0.4% vs CK),588(0.6% vs CK),and 764(0.8% vs CK).Upregulated metabolites dominated all comparisons, accounting for 75.8%, 84.6%, 86.2%, and 91.4%, respectively. Venn diagram analysis revealed 223 common differential metabolites across all four treatment groups,representing a core salt-responsive metabolome. Unique differential metabolites increased with salt concentration, reaching 250 in the 0.8% vs CK comparison.VIP analysis identified Multinoside A,cyclomorusin,ursolic acid,and myricetin as highly responsive metabolites across multiple comparisons. Under low to moderate salt stress(0.2%-0.4%),flavonoids and terpenoids were prominent,while under high salt stress(0.8%),carbohydrate derivatives and terpenoids became more important.KEGG pathway analysis showed that the citrate cycle(TCA cycle),pentose and glucuronate interconversions,fructose and mannose metabolism, and galactose metabolism were consistently enriched across all treatment groups.Four pathways were constitutively activated under all salt concentrations:ABC transporters,biosynthesis of plant secondary metabolites,phenylpropanoid biosynthesis,and amino acid metabolism(especially arginine and proline metabolism).Quantitative analysis of representative metabolites revealed the following trends.TCA cycle intermediates(citrate,isocitrate,cis-aconitate,and 2-oxoglutarate)increased progressively with salt concentration,reaching peak levels at 0.8%.Amino acids and derivatives(L-glutamine,L-citrulline,Nacetyl-L-glutamate,and acetyl-β-alanine)generally increased under salt stress,with L-citrulline and Nacetyl-L-glutamate showing the highest levels at 0.6%-0.8%.Sugar derivatives(maltotriose,neohesperose,and phosphorylated sorbitol)decreased with increasing salt concentration,most notably at 0.8%. Terpenoid aroma compounds (β-ionone, rhododendrol, and caryophyllene oxide) showed overall decreasing trends,with the most pronounced reductions at 0.4% and 0.6%.【Conclusion】Salt stress significantly reprograms the fruit metabolome of Jiping 5 apple grafted on Yanxing crabapple.Four core pathways constitute the conserved metabolic features in response to salt stress:(1)The TCA cycle,which enhances energy metabolism and carbon skeleton supply;(2)Amino acid metabolism,leading to accumulation of compatible solutes such as glutamine and citrulline for osmotic adjustment; (3) Phenylpropanoid biosynthesis,which supports flavonoid-mediated antioxidant defense;(4)ABC transporters,involved in ion compartmentation and secondary metabolite transport.These pathways are consistently activated across all tested salt concentrations,indicating a robust and conserved metabolic response.The effect of salt stress on fruit flavor quality is concentration-dependent.Under low to moderate salt stress (0.2%-0.4%),the TCA cycle and amino acid metabolism are moderately activated.Sugar accumulation remains largely unaffected,while organic acids(citrate,and isocitrate)and certain aroma-related compounds show moderate increases.This metabolic profile suggests enhanced flavor intensity without significant loss of sweetness.Under high salt stress(0.8%),however,sugar derivatives decrease,organic acids accumulate to higher levels,and terpenoid aroma compounds decline.These changes collectively lead to a reduced sugar-to-acid ratio and diminished aroma, indicating a deterioration of fruit flavor quality.This study provides a systematic metabolomic characterization of salt stress responses in fruits of apple grafted on a salt-tolerant rootstock.The findings establish a theoretical basis for high-quality apple cultivation in saline-alkali soils of the Bohai Rim region.
【Objective】Based on field investigations and laboratory inoculation experiments conducted by our research group,the peach cultivar 3Z-1 exhibits a resistant phenotype to powdery mildew,whereas the cultivar 9-25-23 is highly susceptible.Previous studies have shown that,during pathogen infection,changes in the expression of genes related to cuticular wax biosynthesis and metabolism,cell wall remodeling,and plant hormone signaling are closely associated with pathogen attachment,penetration, hyphal expansion,and host defense responses.Therefore,this study aimed to compare the difference in time-course transcriptional responses between 3Z-1 and 9-25-23 during powdery mildew infection.By integrating disease-resistance gene family analysis and co-expression network analysis, we intend to identify candidate resistance-related genes, thereby providing a reproducible transcriptomic evidence for molecular breeding of powdery mildew resistance in peach.【Methods】Leaves of similar size and free from other pathogen infections were collected from peach cultivars 3Z-1 and 9-25-23 and subjected to powdery mildew inoculation,with non-inoculated leaves used as controls.After inoculation,leaves were sealed with plastic film to maintain humidity and incubated at 25℃ for 7 days for phenotypic observation. Leaf samples were dynamically collected at 0, 24, 48, and 72 hours post-inoculation.Total RNA was extracted from all samples for transcriptome sequencing and differential expression analysis. In addition,the NBS-LRR gene family was identified in the peach genome,and its expression patterns under powdery mildew infection were analyzed.Weighted gene co-expression network analysis(WGC-NA) was further employed to screen candidate genes associated with infection responses, and the expression trends of selected candidate genes were validated by RT-qPCR.【Results】At 7 days post-inoculation,scattered powdery mildew lesions were observed on the leaf surface of 9-25-23,whereas no obvious disease symptoms were detected on 3Z-1. Transcriptome sequencing and quality control yielded 34.60-57.09 million clean reads per sample,and the sequencing data showed good alignment with the peach reference genome.Time-course comparisons using 0 hours post-inoculation as the baseline revealed that,in the resistant cultivar 3Z-1,2219 genes were upregulated and 1713 genes were downregulated at 24 hours post-inoculation;5525 genes were upregulated and 1899 genes were downregulated at 48 hours;and 3231 genes were upregulated and 3271 genes were downregulated at 72 hours.In the susceptible cultivar 9-25-23, 2908 genes were upregulated and 2027 genes were downregulated at 24 hours;2028 genes were upregulated and 1466 genes were downregulated at 48 hours;and 5646 genes were upregulated and 1522 genes were downregulated at 72 hours.Notably,at 48 hours post-inoculation,the resistant cultivar 3Z-1 exhibited a markedly stronger upregulated transcriptional response,with 5525 upregulated genes,which was substantially exceeding the number of upregulated genes(2028)observed in the susceptible cultivar "9-25-23" at the same time point.Moreover,cross-cultivar comparisons at identical time points indicated that transcriptional differences were particularly pronounced at 48 hours.Therefore,48 hours post-inoculation was selected as the key time point for pathway enrichment and candidate gene screening.KEGG enrichment analysis was subsequently performed on differentially expressed genes at 48 hours post-inoculation using the corresponding 0-hour samples of each cultivar as controls.The results showed that differentially expressed genes in the resistant cultivar 3Z-1 were mainly enriched in plant hormone signal transduction and plant-pathogen interaction pathways, whereas those in the susceptible cultivar 9-25-23 were predominantly enriched in phenylpropanoid biosynthesis and starch and sucrose metabolism pathways.At the resistance gene family level, a total of 367 NBS-LRR genes were identified in the peach genome,among which more than 80% met the criteria for differential expression under powdery mildew infection,indicating an extensive involvement of this gene family in transcriptional responses to infection.Three NBS-LRR genes with significant upregulation during infection were further identified, namely Prupe.8G032400, Prupe.8G109500, and Prupe.8G005200. Among them, Prupe.8G032400 was homologous to the resistance protein RUN1, Prupe.8G109500 was homologous to RPP2B,and Prupe.8G005200 was homologous to RPV1.At the coexpression network level,WGCNA identified 15 candidate genes associated with infection responses.Of these,10 genes lacked clear functional annotations,while the remaining five genes(Prupe.3G185100.1, Prupe.7G242200.1, Prupe.4G104300.1, Prupe.4G162000.1, and Prupe.1G038900.1) were functionally annotated as being related to cell wall modification, signal transduction, and light-responsive regulation.RT-qPCR validation showed that the expression trends of all 15 candidate genes were consistent with the transcriptome sequencing results,with 11 genes showing an overall upregulated trend and four genes showing an overall downregulated trend.【Conclusion】This study demonstrates that the resistant cultivar 3Z-1 and the susceptible cultivar 9-25-23 exhibit markedly different transcriptional responses during powdery mildew infection.The resistant cultivar displays a stronger upregulated transcriptional response at 48 hours post-inoculation,with differentially expressed genes significantly enriched in pathways related to phytohormone signal transduction and plant-pathogen interactions;in contrast,the susceptible cultivar showed enrichment in pathways associated with phenylpropanoid biosynthesis and starch and sucrose metabolism.Genes belonging to the NBS-LRR family showed a high rate of responsiveness to infection,indicating their extensive involvement in the transcriptional response of peach to powdery mildew;three NBS-LRR genes potentially linked to powdery mildew resistance were identified. By integrating WGCNA-based co-expression analysis, 15 candidate genes potentially associated with powdery mildew resistance were further selected,and their expression patterns were validated via RT-qPCR, providing candidate molecular targets for subsequent functional characterization and resistance breeding.
【Objective】Apolygus lucorum is a major polyphagous pest in pear orchards,causing severe damage to young fruits and reducing their commercial value.Since the 2000s,its occurrence and damage have progressively intensified,as the last-generation adults in late October lay eggs for overwintering, directly influencing the population density of the subsequent year. Critically, September-October coincides with the ripening period of pear in northern pear areas,and chemical control is constrained by pesticide residue concerns—creating an urgent demand for green physical control measures.Traditional sticky traps suffer from poor selectivity and high non-target mortality of natural enemies, which disrupts the orchard ecological balance.Based on the aposematism principle,a novel bionic striped sticky trap was developed to warn natural enemies and minimize non-target trapping.This study aimed to clarify the population dynamics of A.lucorum,evaluate the trapping efficacy and ecological safety of striped traps,optimize their deployment parameters,and assess the trapping effect on female adults when combined with sex pheromone lures, thereby providing a scientific and practical green control strategy.【Methods】The experiments were conducted in Yuluxiang(Pyrus bretschneideri)pear orchard(37° 20′N,112°29′E)in Taigu District,Jinzhong City,with an altitude of 866 m and an area of 2 hm2. Pear trees were planted with a spacing of 4 m × 3 m,a height of 2.5-3 m,and subjected to conventional management,including chemical control applications in early April,early May,early June,mid-July,and midAugust.From April to November in 2023 and 2024,sex pheromone triangular traps were employed to monitor the population dynamics of A.lucorum(15 traps/hm2, spaced 30 m apart,20 m away from the field edge,and 1.5 m above the ground).Backing plates were updated every 15 days,and lures were replaced every 30 days.Trapping effects of 11 types of sticky traps(white,red,pink,yellow,green,blue, light blue,purple,gray,black,and bionic striped trap)were compared,with 6 replicates for each type;traps were randomly hung on September 22,2024(spaced 8-12 m apart)and retrieved after 30 days. Trapped insects were classified into natural enemies,neutral insects,and pests to calculate the natural enemy-to-pest ratio.With yellow sticky traps as the control,the effects of hanging height(1.5 m,3.0 m) and density (1-8 traps per tree, based on a 12 m2 projected canopy area) on striped traps were optimized—with 12 replicates for the height test and 6 replicates for the density test.Traps were hung on October 30 and retrieved after 30 days.Additionally,synergistic effects of sticky traps combined with sex pheromone lures were tested in five treatments(6 replicates each):yellow sticky trap,yellow sticky trap+lure,striped sticky trap,striped sticky trap+lure,and transparent sticky trap+lure(CK).Traps (25 cm × 30 cm,uniform viscosity)were hung 1.5 m above the ground on September 24,2025(spaced 30 m apart between treatments),with lures fixed at the center using iron wire.After 30 days,the total trapping amount,number of male and female adults,and female proportion were recorded.Data were organized using Microsoft Excel 2016 and analyzed via one-way ANOVA,independent sample t-test, and Duncan's new multiple range test with IBM SPSS 27.0(P＜0.05).【Results】Results indicated that A. lucorum exhibited three annual population peaks (mid-June, mid-September, late October) in both 2023 and 2024.Notably,the population density of the last-generation adults in late October reached the highest (83.33 adults · 666.7 m-2 in 2023 and 116.00 adults · 666.7 m-2 in 2024), with total trapping amounts of 1305 and 1642 adults,respectively,demonstrating an increasing trend.Furthermore,striped sticky traps(15.83 adults per trap)and yellow sticky traps(13.67 adults per trap)demonstrated significantly higher trapping efficacy compared to other colored traps(P＜0.05),while red traps showed the lowest efficacy(2.33 adults per trap).Among all tested traps,the blue sticky trap exhibited the highest natural enemy-to-pest ratio(0.734),with an average of 19.33 natural enemies trapped per trap(90% of which belonged to Syrphidae), whereas the striped sticky trap had the lowest ratio (0.025), with only 1.83 natural enemies trapped per trap.Notably,the non-target mortality of Propylaea japonica caused by striped sticky traps was 0.21 times that of yellow sticky traps.Regarding the factors affecting trapping efficiency,density(rather than height)had a significant impact(P＜0.05):hanging 4 striped traps per tree(48.50 adults · 12 m-2)yielded a trapping amount comparable to that of hanging 6 yellow traps per tree,and the striped sticky trap exhibited significantly higher efficacy at a density of 2-4 traps per tree (P＜0.05).A significant synergistic trapping effect was observed when used in combination with sex pheromone lures: the combination of striped sticky traps and lures captured 1.23 times as many adults and 3.5 times as many female adults,respectively,compared to using the lures alone.【Conclusion】The bionic striped sticky trap demonstrates superior comprehensive performance in terms of trapping efficacy,ecological safety,and cost-effectiveness.When combined with sex pheromone lures,it establishes a synergistic model of "long-distance chemical attraction + short-distance visual capture" , which enhances the trapping efficiency of female A.lucorum.Therefore,it is recommended to employ striped traps at a density of 1500 traps · hm-2 during the three population peaks (especially late October) at a height of 1.5-3.0 m,prioritizing the "striped trap+sex pheromone lure" combination.This study offers a practical green control strategy for A.lucorum in pear orchards and provides a reference for the management of similar pests.
【Objective】Pear(Pyrus L.)is an economically important fruit crop worldwide,with significant nutritional and health-promoting properties due to its abundant phenolic compounds. However, postharvest fruit browning,particularly in fresh-cut products,severely impairs commercial quality and shelf life,representing a major constraint for the pear industry.Enzymatic browning,which is primarily mediated by polyphenol oxidase (PPO), occurs when cellular compartmentalization is disrupted upon tissue damage,allowing PPO to oxidize endogenous phenolic substrates to highly reactive quinones that subsequently polymerize into dark pigments.Despite the pivotal role of PPO in fruit browning,the PPO gene family in pear has not been systematically characterized across multiple representative germplasms, and the evolutionary dynamics, structural diversity, and functional differentiation of its members remain poorly understood.This study aims to characterize the PPO gene family in four representative pear varieties, including Yunhong No.1 (sand pear), Dangshansu (white pear), Max Red Bartlett (European pear)and Shanxiduli(wild pear),to analyze their physicochemical properties,and to explore the expression patterns of PPO members during fruit development and in different tissues.【Methods】High-quality genome assemblies of the four pear species were obtained from the GDR database and the Pear Genome Database.PPO candidate genes were initially screened using HMMER 3.0 with the PPO characteristic domain(PF00264)from the Pfam database,followed by BLAST homology searches(Evalue＜10-5).All candidate sequences were further validated using NCBI-CDD and Pfam tools to confirm the presence of conserved PPO domains. Physicochemical properties, including polypeptide length,molecular weight,theoretical isoelectric point(pI),instability index,and grand average of hydropathicity (GRAVY), were predicted using ExPASy. Subcellular localization was determined via Plant-mPLoc,and three-dimensional protein structures were modeled using Swiss-Model.Chromosomal localization and interspecific synteny analysis were performed using TBtools, while phylogenetic trees were constructed using MEGA 11 with the maximum-likelihood(ML)method and 1000 bootstrap replicates.Gene structures were visualized using GSDS 2.0,and conserved motifs were identified using MEME.Promoter regions(2 kb upstream of the start codon)were analyzed via PlantCARE to identify cis-acting regulatory elements.Transcriptome data from fresh-cut pear fruits of the browning-resistant cultivar Hongxiangsu (HXS) and the susceptible cultivar Mantianhong (MTH) were generated by RNA-seq and analyzed to map the expression of genes involved in phenylpropanoid and tyrosine metabolic pathways.Additionally,RT-qPCR was performed to validate the expression dynamics of the core gene PpyPPO10 at different fruit developmental stages(70-120 days after full bloom)and in various tissues including pedicel, receptacle, anther, sepal, petiole, leaf, peel, and flesh.All RT-qPCR experiments included three biological replicates and three technical replicates,with PpyTubulin as the internal reference gene,and relative expression levels were calculated using the 2-ΔΔCt method.【Results】A total of 8-10 conserved PPO genes were identified,predominantly clustered at the terminal regions of Chr05 and Chr10. The encoded proteins were hydrophilic, with 586-941 amino acids, varying molecular weights,isoelectric points(5.39-8.40),and instability indices(37.85-52.21);most were predicted to localize to the cytoplasm,chloroplasts,or nucleus,except one extracellular member.Phylogenetic analysis divided all pear PPOs into nine subgroups,with the majority falling into Group I.Pear PPO genes shared high homology with those of apple and peach, but diverged greatly from non-Rosaceae crops. Strong syntenic blocks were detected between pear Chr05/Chr10 and apple Md5/Md10,whereas collinear fragments with peach and strawberry were scattered due to differing chromosome numbers.Ten conserved motifs and canonical PPO catalytic domains were identified,and gene promoters harbored abundant cis-elements responsive to light, phytohormones, and abiotic stresses. Combined with transcriptome data from the sand pear Yunhong No.1,it was confirmed that pear PPOs modulate the biosynthesis of caffeic acid,chlorogenic acid,ferulic acid,and other phenolics through the tyrosine and phenylpropane pathways.The core gene PpyPPO10 showed the closest evolutionary relationship with apple MdP-PO, and also clustered closely with PPO homologs from other woody plants, including peach, poplar, and tea.RT-qPCR results revealed that PpyPPO10 expression was significantly higher in the browningresistant cultivar Hongxiangsu than in the sensitive Mantianhong,with maximal transcript abundance in flesh and moderate levels in peel.【Conclusion】This study systematically characterizes the PPO gene family in four representative pear species, revealing that 8-10 conserved members, which share high evolutionary conservation with Rosaceae homologs, are organized as tandem arrays on Chr05 and Chr10, and encode hydrophilic proteins with typical PPO domains.The core gene PpyPPO10, identified as a key candidate regulating flesh browning,integrates signals from light,phytohormones,and abiotic stresses through its promoter, and coordinately modulates phenolic biosynthesis via the tyrosine and phenylpropanoid pathways.Its enhanced expression in browning-resistant cultivars and flesh-specific accumulation pattern underscore its pivotal role in browning regulation.These findings provide essential candidate genes and theoretical support for molecular breeding aimed at developing browning-resistant pear varieties,and lay a foundation for further functional validation of PPO genes in fruit quality regulation.
