Cloning and Expression of a cDNA Encoding Endopolygalacturonase from Feicheng Peach (Prunus persica)

Polygalacturonase (PG,EC3.2.1.15) is the key cell wall hydrolase in fruit ripening. The identification and characterization of a full length cDNA (pMT18) encoding for PG from Feicheng peach (Prunus persica (L.) Batsch cv. Feicheng) is described. The pMT18 clone is 1188 bp in length, with an open reading frame of 393 amino acids. The homology and phylogenetic analyses indicate a remarkable similarity between peach PG and other ripening related PG. And seven consensus sequences have revealed in peach PG compared to the PG from other plants. However, the profound divergence with other PG and the unique structure features suggest that peach PG probably belongs to a new evolutionary class. In RT PCR analysis, pMT18 related RNA was undetectable in leaves, and was much abundant in ripe fruits. The ripening specific expression pattern of this cDNA will be useful in investigating the roles of PG in fruit ripening and developing a transgenic peach with the improved post harvesting quality in the future.

Effects of Weak Light on the Ultrastructural Variations of Phloem Tissues in Source Leaves of Three-Year-Old Nectarine Trees(Prunus persica L.var. nectarina Ait.)

Leaves from three_year_old solar greenhouse nectarine trees ( Prunus persica L. var. nectarina Ait. “Zao Hong Yan”) were used as materials in this study. It was the first time that the ultrastructural characteristics of phloem tissues of source leaves were observed and compared in normal and weak light intensities using the transmission electron microscopy. Results showed that the average diameters of companion cells (CC) and sieve elements (SE) of all kinds of veins were bigger in normal than that in weak light intensity, indicating that light could influence the cell development and growth. Dense cytoplasm with abundant mitochondria, endoplasmic reticulums, multivesicular bodies, vesicles and plastids were observed in normal light intensity. On the contrary, CC with small vacuolar structures and few mitochondrias, endoplasmic reticulums were shown in weak light. Misalignment of grana thylakoid margins of nectarine leaves also was seen in weak light. The sieve pores of SEs were obstructed in weak light. Chloroplasts with numerous starch grains and few mitochondrias were noticed in the mesophyll cell (MES) surrounding the bundle sheath in weak light. The storage of starch grains appeared to result from an unbalance between photosynthate production and export of photosynthates. This observation provided a strong support to the point that most leaves export the most of assimilates in the light time. Plasmodesmal densities between SE/CC, CC/PP (phloem parenchyma cell), PP/PP and PP/BSC (bundle_sheath cell) decreased in weak light. Plasmodesmata were observed between CC/SE (NS) (nacreous_walled sieve element), PP/BSC in branch veins in normal light intensity, but not in weak light. Thus apoplasmic pathway may be the main mode of transport of assimilates in weak light, however symplasmic pathway may be the main mode of transport of assimilates in normal light intensity. These results demonstrated that the solar greenhouse nectarine trees could be adapted to the weak light via the ultrastructure variation of phloem tissues of the source leaves.

Study on SSR Markers Linked to Flesh Color around the Stone of Prunus persica(L.) Batsch

[Objective] This study aimed to select SSR molecular markers linked to flesh color around the stone of Prunus persica （L.） Batsch. [Method] P. persica （L.） Batsch varieties Chongyanghong and Yanhong were used as parents to construct F1 orthogonal group. A total of 138 FI individuals were selected as experimental materi- als for construction of color around the stone gene pool （B1） and non-color around the stone gene pool （B2） by using bulked segregant analysis （BSA） method, molec- ular markers linked to the flesh color around the stone of P. persica （L.） Batsch were selected with SSR molecular marker technology. [Result] After selection with 256 pairs of SSR primers, three pairs of molecular markers linked to the gene con- trolling flesh color around the stone of P. persica （L.） Batsch were selected （UDP96- 003, ch04g09 and UDP97-402）. In addition, genetic distances between the three molecular markers and the gene controlling flesh color around the stone of P. persi- ca （L.） Batsch were calculated, which were 16.7, 10.1 and 17.0 cM, respectively. [Conclusion] This study laid the foundation for further selection of co-dominant molecular markers with closer genetic distance.

Molecular cloning,identification,and chromosomal localization of two MADS box genes in peach(Prunus persica)

MADS box proteins play an important role in floral development. To find genes involved in the floral transition of Prunus species, cDNAs for two MADS box genes, PpMADS1 and PpMADSIO, were cloned using degenerate primers and 5＇- and T-RACE based on the sequence database of P. persiea and P. duleis. The full length of PpMADS1 cDNA is 1,071 bp containing an open reading frame （ORF） of 717 bp and coding for a polypeptide of 238 amino acid residues. The full length of PpMADSIO cDNA is 937 bp containing an ORF of 633 bp and coding for a polypeptide of 210 amino acid residues. Sequence comparison revealed that PpMADS1 and PpMADSIO were highly homologous to genes API and PI in Arabidopsis, respectively. Phylogenetic analysis indicated that PpMADS1 belongs to the euAP1 clade of class A, and PpMADSIO is a member of GLO/PI clade of class B. RT-PCR analysis showed that PpMADS1 was expressed in sepal, petal, carpel, and fruit, which was slightly different from the expression pattern ofAPl; PpMADS10 was expressed in petal and stamen, which shared the same expression pattern as PI. Using selective mapping strategy, PpMADSI was assigned onto the Binl：50 on the G1 linkage group between the markers MCO44 and TSA2, and PpMADSIO onto the Bin1：73 on the same linkage group between the markers Lap- 1 and FGA8. Our results provided the basis for further dissection of the two MADS box gene function.

Accumulated chilling hours during endodormancy impact blooming and fruit shape development in peach(Prunus persica L.)

Winter chill is essential for the growth and development of deciduous species. To understand the relationship between accumulated chilling hours during endodormancy and blooming and fruit shape development, we controlled chilling hours and investigated their effects on blooming date and fruit shape of peaches. The results showed that the number of days to full bloom date and the heat requirement for blooming were negatively correlated with accumulated chilling hours. Accumulated chilling hours were significantly negatively correlated with fruit shape index and fruit tip lengths, suggesting that the number of chilling hours affect the fruit shape development. Fewer accumulated chilling hours may be the major reason for longer fruit shape and protruding fruit tips. In conclusion, our results indicate specifically that decreased winter chilling hours can delay the bloom date and may lead to aberrant fruit shape development in peaches. Our study provides preliminary insights into the response of temperate fruit species to global climate change.

Characterization and Expression of Ammonium Transporter in Peach (Prunus persica) and Regulation Analysis in Response to External Ammonium Supply

As the preferred nitrogen(N)source,ammonium(NH_(4)^(+))contributes to plant growth and development and fruit quality.In plants,NH 4+uptake is facilitated by a family of NH_(4)^(+) transporters(AMT).However,the molecular mechanisms and functional characteristics of the AMT genes in peach have not been mentioned yet.In this present study,excess NH_(4)^(+) stress severely hindered shoot growth and root elongation,accompanied with reduced mineral accumulation,decreased leaf chlorophyll concentration,and stunned photosynthetic performance.In addition,we identified 14 putative AMT genes in peach(PpeAMT).Expression analysis showed that PpeAMT genes were differently expressed in peach leaves,stems and roots,and were distinctly regulated by external NH_(4)^(+) supplies.Putative cis-elements involved in abiotic stress adaption,Ca^(2+) response,light and circadian rhythms regulation,and seed development were observed in the promoters of the PpeAMT family genes.Phosphorylation analysis of residues within the C-terminal of PpeAMT proteins revealed many conserved phosphorylation residues in both the AMT1 and AMT2 subfamily members,which could potentially play roles in controlling the NH 4+transport activities.This study provides gene resources to study the biological function of AMT proteins in peach,and reveals molecular basis for NH_(4)^(+) uptake and N nutrition mechanisms of fruit trees.

Molecular Identification and Cultivar Fingerprints of Prunus persica (L.) Batsch Germplasms

[Objective] The aim was to study the molecular identification and cultivar fingerprints of Prunus persica (L.) Batsch germplasms.[Method] Sixty peach genotypes,representing China common local cultivars and European samples were screened by microsatellites (simple sequence repeats,SSRs) and Inter-Simple Sequence Repeat (ISSR) markers.[Result] 26 reproducible bands were amplified by Nine SSR primers,and 24 of which were polymorphic; 236 bands were amplified by 30 ISSR primers,and 113 of which were polymorphic.31 genotypes were discriminated with 1-3 distinct polymorphic bands generated from the primers ISSR and SSR.Seven cultivar-specific ISSR fragments and two SSR unique alleles obtained from this study were available to be converted into Sequence Characterized Amplified Region (SCAR) markers.The genetic similarity coefficient (GS) estimated from these molecular data averaged were 0.939 (ranged from 0.856 to 0.983) for ISSR and 0.646 (ranged from 0.240 to 1.000) for SSR,respectively.The combined grouping association indicated that most local Chinese peach cultivars and exotic accessions were clustered together.This could be related to the mode of introduction and maintenance of the peach cultivars involving limited foundation germplasm,exchange of cultivars between plantations,and periodic development of new recombinant cultivars following sexual reproduction.[Conclusion] The results obtained in this work would help to improve the conservation,molecular identification and management of peach germplasm in breeding.

Novel in silico EST-SSR markers and bioinformatic approaches to detect genetic variation among peach(Prunus persica L.)germplasm

Because there are thousands of peach cultivars,cultivar classification is a critical step before starting a breeding project.Various molecular markers such as simple sequence repeats(SSRs)can be used.In this study,67 polymorphic primers produced 302 bands.Higher values for SI index(1.903)suggested higher genetic variability in the genotype under investigation.Mean values for observed alleles(Na),expected heterozygosity(He),effective alleles(Ne),Nei’s information index(h),and polymorphic information content(PIC)were 4.5,0.83,5.45,0.83,and 0.81,respectively.The dendrogram constructed based on Jaccard’s similarity coefficients outlined four distinct clusters in the entire germplasm.In addition,an analysis of molecular variance(AMOVA)showed that70.68%of the total variation was due to within-population variation,while 29.32%was due to variation among populations.According to this research,all primers were successfully used for the peach accessions.The EST-SSR markers should be useful in peach breeding programs and other research.

Effects of nitrogen content on growth and hydraulic characteristics of peach(Prunus persica L.) seedlings under different soil moisture conditions

A pot experiment was conducted to investigate the effects of nitrogen content [Nl （no fertilizer）, N2 （0.15 g.kg-l）, and N3 （0.3 g.kg 1）] on the growth and the hydraulic characteristics of peach seedlings under different soil moisture conditions （Wl, W2 and W3, in which the soil water content was 45% to 55%, 60% to 70%, and 75% to 80% of the field water capacity, respectively） by using a specialized high pressure flow meter with a root chamber and a coupling, which was connected to plant organs. Leaf area and leaf hydraulic conductivity （KL） increased significantly in the seedlings because of increased soil moisture and N content. KL increased with leaf area. A linear correlation was documented between KL and leaf area. KL was higher in the morning and began to decline sharply after 16：00, at which KL declined after an initial increase. Soil moisture and N content enhanced shoot （Ks） and root （Kr） hydraulic conductivities, thereby improving the low soil moisture condition to a large extent. Ks and Kr of the seedlings were reduced by 32% and 27% respectively in N~, and by 14.7% and 9.4%, respectively in N2, and both in Wb compared with the control treatment. N3 had no significant effect on Ks and Kr under similar conditions. Linear negative correlations were observed between Kr and the excised root diameter as well as between Ks and the shoot stem diameter. The shoot-to-root ratio increased with in- crease in N content. The shoot-to-root ratio in N3 was increased by 14.37%, compared with N1 in W1 as well as by 12% and 4.39% in Wz and W3, respectively. Knowledge of the effects of soil moisture and N fertilizer on hydraulic characteristics and growth is important. Our results provide basic guidelines for the implementation of water-saving irrigation and fertilization management of nursery stock.

Simple Sequence Repeat Analysis of Genetic Diversity in Primary Core Collection of Peach(Prunus persica)

In this study, the genetic diversity of 51 cultivars in the primary core collection of peach （Prunus persica （L.） Batsch） was evaluated by using simple sequence repeats （SSRs）. The phylogenetic relationships and the evolutionary history among different cultivars were determined on the basis of SSR data. Twenty-two polymorphic SSR primer pairs were selected, and a total of 111 alleles were identified in the 51 cultivars, with an average of 5 alleles per locus. According to traditional Chinese classification of peach cultivars, the 51 cultivars in the peach primary core collection belong to six variety groups. The SSR analysis revealed that the levels of the genetic diversity within each variety group were ranked as Sweet peach 〉 Crisp peach 〉 Flat peach 〉 Nectarine 〉 Honey Peach 〉 Yellow fleshed peach. The genetic diversity among the Chinese cultivars was higher than that among the introduced cultivars. Cluster analysis by the unweighted pair group method with arithmetic averaging （UPGMA） placed the 51 cultivars into five linkage clusters. Cultivar members from the same variety group were distributed in different UPGMA clusters and some members from different variety groups were placed under the same cluster. Different variety groups could not be differentiated in accordance with SSR markers. The SSR analysis revealed rich genetic diversity in the peach primary core collection, representative of genetic resources of peach.

氨基酸水溶肥促进桃苗生长

氨基酸水溶肥是具有营养效果好、无污染等优点的新型绿色肥料。以桃(Prunus persica L.)苗为材料,通过盆栽试验探究施用不同稀释倍数(600、900、1200、1500倍)的氨基酸水溶肥对桃苗生长的影响,以期筛选出效果最佳的喷施浓度。结果表明,施用氨基酸水溶肥增加了桃苗各部位的生物量,其根、茎、叶及地上部分生物量在稀释倍数为1500倍时最高,较对照分别增加了54.83%、51.28%、35.73%和42.12%;施用氨基酸水溶肥提高了桃苗光合色素含量,当稀释倍数为1500倍时,桃苗的光合色素含量最大;施用氨基酸水溶肥提高了桃苗的抗氧化酶活性,但降低了桃苗的可溶性蛋白质含量。因此,稀释1500倍的氨基酸水溶肥为促进桃苗生长的最佳喷施浓度。

丛枝菌根真菌对桃幼苗生长及硒富集的影响

采用盆栽试验,研究了摩西球囊霉(Glomus mosseae)、脆无梗囊霉(Acaulospora delicata)、隐类球囊霉(Paraglomus occultum)和幼套球囊霉(Glomus etunicatum)4种丛枝菌根真菌对桃[Prunus persica(L.)Batsch]幼苗生长及硒富集特性的影响。结果表明,施用脆无梗囊霉增加了桃幼苗的生物量,促进了桃幼苗的生长,使桃幼苗的根系和地上部分生物量分别比未施用增加了11.28%和9.18%,也在一定程度上提高了光合色素含量、过氧化酶活性及过氧化氢酶活性。施用摩西球囊霉、隐类球囊霉和幼套球囊霉3种丛枝菌根真菌降低了桃幼苗的生物量、光合色素含量及抗氧化酶活性或对其没有显著影响。施用脆无梗囊霉也在一定程度上增加了桃幼苗的总硒含量及有机硒含量,其中地上部分的总硒含量和有机硒含量分别较未施用增加了8.01%和9.34%。施用摩西球嚢霉、隐类球囊霉和幼套球囊霉降低了桃幼苗的总硒含量及有机硒含量或对其没有显著影响。

Identification and expression analysis of chlorogenic acid biosynthesis key gene PpHCT in peach

Shikimic acid/quinic acid hydroxy cinnamyl transferase(HCT)is one of the key enzymes in the phenylpropanoid pathway.However,the role of the HCT gene in chlorogenic acid(CGA)biosynthesis in peach fruit remains unclear.For this,we identified the accumulation pattern of CGA in four peach cultivars,cloned and characterized 11 PpHCT gene members,and further analyzed the expression patterns of these PpHCT genes during fruit development.The contents of CGAs in the four peach cultivars all exhibited a trend of increasing and then decreasing during the fruit growth and development.Moreover,the contents of CGAs in the peel and flesh were tissue-specific.Gene structure analysis indicated that the PpHCT genes were highly conserved,containing two exons and one intron.The protein structure analysis demonstrated that the PpHCT proteins contained two conserved motifs(HXXXD,DFGWG)and a transferase domain(PF02458),which belonged to the BAHD acyltransferase family.The cis-acting element analysis suggested that the promoters of PpHCT genes contained many light-related,hormone-related,stress-related,tissue-specific,and circadian-related elements,and they could participate in a variety of biological processes.Phylogenetic analysis showed that the HCT proteins of peach were closely related to the HCT proteins of plum and had a close evolutionary relationship.The qRT-PCR analysis indicated that the expression levels of PpHCT1 and PpHCT2 showed an opposite trend to the accumulation of CGA,whereas the expression levels of PpHCT4,PpHCT5,PpHCT7,PpHCT8,and PpHCT11 demonstrated the same trend as CGA accumulation.It was worth noting that only PpHCT4 and PpHCT5 were highly expressed in the two high-CGA cultivars but showed low levels of expression in the two low-CGA cultivars.Therefore,it was hypothesized that these two genes might be key genes to the synthesis of CGA in peach fruit.Those findings provide a theoretical basis for further study on the biological functions of the HCT gene and help to reveal the molecular mechanism of CGA.

The Potential Efficacy of Glycyrrhizic Acid and Its Nanostructure Against Brown Rot of Peach fruits

Production of peaches(Prunus persica(L.)Batsch)for both local market and export is increasing each year in Egypt.Brown rot disease,caused by Monilinia laxa and Monilinia fructigena,is considered one of the most important postharvest rots affecting peaches in Egypt and economic losses are increasing.Antifungal activity of glycyrrhizic acid nanoparticles(GA-NPs)and glycyrrhizic acid(GA)at 0.2 and 0.4 mmol/L was investigated as a control for both these brown rot pathogens on peach fruits in both in vitro and in vivo studies.In the in vitro studies,GA-NPs were the most effective as shown by the ability to decrease linear growth of both brown rot pathogens in potato dextrose agar(PDA)amended with 0.4 mmol/L GA-NPs.Micrographs of M.fructigena exposed to 0.4 mmol/LGA showed mycelial deformations,nodule formation,detachment of the cell wall,shrinkage and inhomogeneous cytoplasmic materials with large vacuoles.Mycelium of M.laxa exposed to 0.4 mmol/LGA-NPs resulted in thinner and distorted hyphae,nodule formation,cell wall thinning,and swellings.The GANPs and GA treatments improved fruit quality by maintaining firmness and total soluble solids(TSS).GA-NPs were more effective in decreasing decay incidence than their bulk material.The 0.4 mmol/L GA-NPs completely inhibited the disease on naturally infected peach fruits for both seasons of 2018 and 2019.Furthermore,0.4 mmol/L GA-NPs reduced the disease incidence in inoculated fruits by 95(M.laxa)and 88%(M.fructigena)in 2018 season and 96(M.laxa)and 85%(M.fructigena)in 2019 season.In conclusion,GA-NPs could enhance the resistance of peaches against brown rot caused by M.laxa and M.fructigena.

Cloning and Differential Expression of a 1-Aminocyclopropane-1-Carboxylate Synthase cDNA from Peach

The ACC synthase is the key enzyme in ethylene biosynthesis and fruit ripening. To study the mechanism of ACC synthase in peach Prunus persica (L.) Batsch) fruit ripening, we cloned a full_length cDNA of ACC synthase pacs from peach using 5′/3′ RACE PCR. The nucleic acid sequence of pacs was 1 848 bp, containing 177 bp of 5′untranslated sequence, 1 449 bp of an open reading frame, and 219 bp of 3′untranslated sequence (excluding the stop codon TAA). The pacs open reading frame encoded a 483_amino acid polypeptide with a predicted size of 54 kD and a calculated PI of 6.43. The deduced protein from ACC synthase cDNA pacs had 65%, 70%, 75%, and 90% homology with the other deduced proteins from tomato (S19677), plum (AB031026), papaya (U68216) and apple (AB034993), which contained the active site of ACC synthase SLSKDMGFPGFR conserved among these plant ACC synthases. RNA_based PCR amplification combined with hybridization analysis with pacs and another ACC synthase cDNApacs12 (AF467782) cloned by us before as probes, indicated that expression patterns of both clones were very similar. mRNAs of both clones expressed in the alabastrum and petal, and were induced after ethylene treatment. Wounding and IAA treatments could induce ACC synthase expression of both clones in the leaves. However, the wounding treatment of leaves has induced more abundant pacs ACC synthase expression than that ofpacs12. Pacs mRNA expressed in both green mature and ripening fruit, whilepacs12mRNA was little or undetectable in green mature fruit, but apparent in ripening fruit. Both clone mRNAs accumulated more in leaves (following wounding and IAA treatments) and flowers than in fruits.

Relationships Between the Distribution of Relative Canopy Light Intensity and the Peach Yield and Quality

The aim of the present experiment was to study the relationship between the distribution of relative light intensity in canopy and yield and quality of Wanmi peach. The optimum relative canopy light intensity was judged to be 36.3% for high quality peaches, when canopy volumes of Wanmi peach trees with a relative light intensity 〈 30% accounted for 7.7 and 47.9% of the total canopy volume in June and September, respectively. The canopy volume with a relative light intensity 〉 80% was 27.7 and 3.1% of the total canopy volume in June and September, respectively. Peach canopies were divided into 0.5 m × 0.5 m × 0.5 m cubes, with the relative light intensity being measured at different positions of the canopy during the growing season. Yield and fruit quality were also measured at these positions at harvest. The results showed that the relative light intensity decreased gradually from outside to inside and from top to bottom of the tree canopy. Fruit were mainly distributed in the upper and middle portions of the canopy, 1.5-3.0 m above ground. Regression results showed that single fruit weight and soluble solid content were positively related to relative light intensity.

Effects of Temperature and Several Chemicals on Metabolic Changes During Dormancy Release in NJ72 Nectarine

Poor, delayed and ununiform budbreak is a major problem for peaches in greenhouse. To clarify the mechanism of breaking bud dormancy in nectarines, the effect of temperature and three dormancy-breaking agents on metabolic changes during dormancy release in two-year old NJ72 nectarine (Prunus persica L. Batch) was investigated. The result showed temperature and chemicals affected the budbreak and the metabolism of NJ72 nectarine during dormancy. Endogeneous peroxide content in buds increased soon after low temperature treatment. Meanwhile, catalase activity was also shown to increase significantly at low temperature treatment, coincided with increase of the activity of peroxidase and superoxide dismutase. The rate of respiration in flower buds increased at low temperature during dormancy. The rate of the pentose phosphate pathway increased, while the rate of the Embden-Meyerhof pathway decreased and the rate of tricarboxlic acid cycle changed little. Glucose 6-phosphate dehydrogenase activity increased at low temperature during dormancy. At the same time we found an accumulation of peroxide after treatment with dormancy-breaking chemicals. In flower buds treated with dormancy-breaking agents, thiourea, KNO3 and NH4NO3, catalase activity was inhibited soon after treatment, whereas peroxidase activity increased, and the changes of superoxide dismutase remained little. In this study, it was found that the rates of respiration in flower buds increased by chemicals sprays during dormancy. The activity of glucose 6-phosphate dehydrogenase, the key enzyme in the pentose phosphate pathway (PPP), increased by spraying with dormancy-breaking agents, concomitantly with the activation of the pentose phosphate pathway.

Effects of Nitric Oxide and Exogenous Ethylene Treatments on Ethylene Biosynthesis in Feicheng Peach

The effects of nitric oxide （NO） and exogenous ethylene on ethylene biosynthesis in harvested Feicheng peaches were studied. The antagonistic actions between NO and exogenous ethylene was also investigated. The Feicheng peaches were fumigated with 10μL L^-1 NO, 1 000 μL L^-1 ethylene, or 10 μL L^-1 NO plus 1 000 μL L^-1 ethylene for 3 h. The results suggested that application of exogenous ethylene promoted the biosynthesis of endogenous ethylene in peach fruit. The treatment with NO remarkably inhibited the biosynthesis of ethylene by significantly reducing the activities of ACC synthase （ACS） and ACC oxidase （ACO）. Ethylene biosynthesis in the fruits treated with both NO and exogenous ethylene was lower than that in fruits treated with exogenous ethylene alone but higher than that in fruits treated with NO alone, suggesting that there were antagonistic actions between NO and exogenous ethylene. NO could inhibit the biosynthesis of ethylene and the catalysis of exogenous ethylene during ethylene biosynthesis in peach fruits.

Effects of Different Storage Methods on the Fruit Quality and Physiological Changes in Yihong Honey Peach

Taking Yihong,the main cultivar of mid-ripening honey peaches(Prunus persica)in Hunan,as material,this study explored the effects of different storage methods on the fruit quality and physiological changes in Yihong honey peach by the combination of polyethylene film packaging with low-temperature storage.The results showed that the weight loss rate of packaged storage at normal temperature(T1)was significantly lower than that of unpackaged storage at normal temperature(CK),but there was no significant difference in other indicators.In the middle of storage,the respiration rate and ethylene release of packaged storage at 0℃(T3)were extremely significantly lower or significantly lower than those of unpackaged storage at 0℃(T2),packaged storage at 0℃after cold adapting at 8℃for 5 d(T4),and packaged storage in a fluctuating temperature range of 0~3.5℃(T5).After storage,the structure of the middle lamella in the cell wall of T3 was compact and uniform,and the mitochondrial structure was complete,while the cell walls and mitochondria of T4 and T5 were severely deformed and disintegrated.The activities of antioxidant enzymes peroxidase(POD)and superoxide dismutase(SOD)of T3 was significantly higher than those of T4 and T5,and the content of malondialdehyde(MDA)and polyphenol oxidase(PPO)of T3 was also the lowest.Therefore,0°C packaged storage can effectively delay the senescence of Yihong honey peach and prolong its freshness period.

Effect and Functional Mechanism of the Action of Exogenous Gibberellin on Flowering of Peach

This study was conducted to assess the effect of gibberellin and its possible mechanism of action on peach flower formation. At flower induction, 100 mg L^-1 of gibberellic acid 3 （GA3） was sprayed on the leaves of peach [Prunus persica （L.） Batsch.] cv. Bayuecui. Using anatomy, immunohistochemistry, and semi-quantitation, the in situ distribution of GAs and the expression of the key genes involved in peach flower formation in the apical meristem were studied during flowering differentiation. The results showed that induction of flowering in the Bayuecui peach occurred prior to 10 July in Beijing, China. Flower induction and further differentiation of the peach flower organs were significantly inhibited by leaf-spraying of GA3 at a concentration of 100 mg L^-1 during the induction stage. The flowering rate was only 11.67% after treatment. The distribution of GA1 in the apical meristem varied during the process of flower bud differentiation. From 13 June to 25 July, the GA1 signal from control plants was detected mainly in the vascular bundles at the base of the flower buds. No GA1 signal was detected in the apical meristem. After treatment with GA3, the distribution was similar to that of the control from 13 June to 3 July. On 13 July, a GA1 signal was detected in the apical meristem accompanied by an increase in the GA1 signal in the vascular bundles at the base of the flower buds. The GA1 signal weakened significantly in both the vascular bundles and the apical meristem on 25 July. The expression of the genes PpLEAFY and MADS6 in flower buds could be detected only on 10 October in the GA3-treated plants. The critical period for flower induction of Bayuecui peach in Beijing was in early July, during which time, leaf-spraying with 100 mg L-1 GA3 could effectively inhibit flower induction and further differentiation of the flower buds. GA1 in the gibberellin family was the suppressor for flower induction in peach. Its action was affected by the stage of flower bud differentiation. Expression of the key genes PpLEAFY and MADS6 involved in flower formation was inhibited by GA3 treatment.