Changes of Reactive Oxygen Species and Related Enzymes in Mitochondrial Respiration During Storage of Harvested Peach Fruits

Peach fruits [Prumus persica （L.） Batsch, cv. Yuhuasanhao] were used as materials to investigate the changes of reactive oxygen species （ROS） and related enzymes in mitochondria respiration during storage and then their influence on senescence of harvested Peach fruits was studied. The results showed that low temperature （5℃） strongly inhibited the reduction of firmness and the increase in respiration rate. During storage at ambient temperature （20℃）, ROS had a cumulative process while malondialdehye （MDA） content continued to increase in associated with enhanced membrane lipid peroxidation. Lipoxygenase （LOX） activity was strongly inhibited under the low temperature condition. The activities of succinic dehydrogenase （SDH）, cytochrome C oxidase （CCO）, and Ca^2＋-ATPase declined to a certain extent at ambient temperature, while they showed higher activities at low temperature, which may be related to lower membrane lipid peroxidation at low temperature. Higher Ca^2＋ content at ambient temperature may be responsible for impairment of mitochondrial function, thus, leading to fruit senescence. The results showed that under low temperature condition, the low accumulation of ROS and the low level of membrane lipid peroxidation could maintain the function of mitochondria that would help to delay the senescence of peach fruits. These suggested a close relationship existed between ROS metabolism and mitochondrial respiration. It can be inferred that the low temperature helps to delay senescence of peach fruits via suppression of ROS and related enzymes, maintain better homeostasis of Ca^2＋ in mitochondria and thus better mitochondrial functions.

Polyphenol Oxidase, Peroxidase and PhenylalanineAmmonium Lyase Induced in Postharvest Peach Fruitsby Inoculation with Pichia membranefaciensor Rhizopus stolonifer

Rhizopus rot of peach fruits could be significantly suppressed by Pichia membranefaciens. Polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonium-lyase (PAL) activities induced by inoculation with P. membrane faciens or R. stolonifer were studied in postharvest peach fruits. The activities of PPO and PAL in peaches increased significantly after being inoculated with P. membrane faciens + R. stolonifer by 24 h, the activities maintained at a high level throughout the experiment. Under the condition of infected with R. stolonifer alone, activity of PPO and PAL could also increased, but the levels were lower than those treated with P. membrane faciens+ R. stolonifer. However, fruits inoculaed with P. membrane-faciens + R. stolonifer or R. stolonifer alone did not stimulated POD activity. The results suggest that the activation of these defense enzymes is involved in the action of P. membrane faciens against R. stolonifer.

Changes of Reactive Oxygen Species and Related Enzymes in Mitochondria Respiratory Metabolism During the Ripening of Peach Fruit

The fruits of peach cultivar Yuhua 3 were used as materials to investigate the changes of active oxygen and related enzymes in mitochondria respiratory metabolism during ripening of peach fruit, involving their influence on the proceeding of peach fruit senescence. The results showed that the large decrease in firmness occurred between maturity II and IV. The decrease in firmness coincided with an increase in respiratory intensity. Obvious peaks of respiratory intensity lagging to the rapid change of fruit firmness could be shown during peach ripening. Reactive oxygen species （ROS） had a cumulative process and positively correlated with respiratory intensity. During peach ripening, the content of Ca^2＋ increased, the activities of succinic dehydrogenase （SDH）, cytochrome C oxidase （CCO）, H＋-ATPase, and Ca^2＋-ATPase decreased varying in different degree at the later step of ripening. These suggested a close relationship existed between ROS metabolism and mitochondrial respiration, namely, both ROS metabolism and mitochondrial respiration probably played important roles in ripening and senescing of peach fruit.

Effects of 1-MCP on proline,polyamine,and nitric oxide metabolism in postharvest peach fruit under chilling stress

Peach(Prunus persica Batsch‘Yuhualu’)fruit are sensitive to chilling injury(CI).Proline,polyamine(PA),and nitric oxide(NO)are important small regulators of various metabolic pathways under chilling stress that mitigate CI.Ethylene is known to promote senescence and CI,while 1-methylcyclopropene(1-MCP)is an antagonist that inhibits the effects of ethylene.However,how1-MCP and ethylene affect proline,PA,and NO levels under chilling stress remains unclear.To address these questions,1-MCP(1μL·L^(−1))and ethylene(1μL·L^(−1))treatments were applied to peach fruit.Fruit were stored at 4°C for 28 d,then moved to 25°C for 3 d immediately after cold storage.Peach fruit exhibited CI symptoms after 7 d of cold storage with enhanced electrolyte leakage and malondialdehyde contents.The 1-MCP treatment significantly(P<0.05)restrained peach CI,and fruit did not exhibit CI symptoms until 14 d of cold storage.Proline and PAs in peach under chilling stress weremostly synthesized from glutamate and arginine,which were catalyzed by1-pyrroline-5-carboxylate synthetase and arginine decarboxylase,respectively.1-MCPtreated fruit exhibited higher proline and PA contents and enhanced chilling tolerance compared to the control,while ethylene-treated fruit had lower proline and PA contents and reduced chilling tolerance.Ethylene-treated fruit,which exhibited more severe CI symptoms compared to the control,had significantly(P<0.05)lower NO contents and NO synthase activities.However,NOmay not be a direct acting factor in 1-MCPinduced chilling tolerance,as 1-MCP-treated fruit had lower NO contents and NO synthase activities compared to the control.In conclusion,proline and PA clearly played direct and important roles in 1-MCP-induced peach chilling tolerance,while NO may not be actively involved.

The Relationship Between Senescence and Ca^(2+)-ATPase Activity of Microsomal Membrane and Lipid Peroxidation in Harvested Peach Fruit

Peach fruit easily soften and have a short storage time at normal temperature. In this study, peach fruit （Prunus persica sieb et Zucc cv. Yingqing） were picked and stored at 25 and 4℃ to investigate the senescence in correlation with Ca^2＋- ATPase activity of microsomal membrane and lipid peroxidation during ripening and senescence. In comparison with that stored at 25~C, the fruit stored at 4℃ exhibited a higher flesh firmness, lower respiration rate, and generated the late bigger peak value of Ca^2＋-ATPase activity as well as maintained the higher activity of the enzyme. Meanwhile, the lower levels of super oxygen radical （O2^-.） production and content of malondialdehyde （MDA）, a product of membrane lipid peroxidation were observed. Sodium orthovanadate （SO） and erythrosin B （EB）, as Ca^2＋-ATPase inhibitors, could stimulate the respiration rate. The results suggested that the slower senescence rate of peach fruit was closely related to the higher peak value and longer duration of Ca^2＋-ATPase activity in microsomal membrane, with the slighter membrane lipid peroxidation and lower O2^-. production rate.

Biocontrol Efficacy of Two Antagonistic Yeasts Against Postharvest Diseases in Peach Fruits During Storage Periods

Two antagonistic yeasts, Thichosporon pullulans and Cryptococcus laurentii, were investigated for their biocontrol potential to blue mold rot and rhizopus rot on harvested peach fruits(Prunus persica L. Batsch, cv. Okubao), alone or in combination with a low dose of iprodione(50 μg ml-1). The results indicated that T. pullulans and C. laurentii were effective at reducing disease incidence and severity of blue mold rot and rhizopus rot in peach fruits. Biocontrol efficacy of C. laurentii and T. pullulans were significantly enhanced by combination with a low dose of iprodione(50 μg ml-1)against blue mold and rhizopus rot in peach fruits. T. pullulans and C. laurentii combined with a low dose of iprodione(50 μg ml-1)resulted in better disease control than either iprodione or the yeasts used alone. Dipping fruits in suspensions of antagonist cells showed the similar control effect as the treatment with iprodione(500μg ml-1).

Review on Effects of Nitrogen on the Internal Quality of Peach Fruit

On the basis of referring plenty of literatures, we summarized the research advance in effects of nitrogen on the internal quality of peach fruit. Most studies have shown that proper nitrogen application can improve internal quality of fruit, and excessive nitrogen application can reduce soluble solid and sugar contents of fruit, increase organic acid content, reduce fruit aroma, increase protein and amino acid contents, and increase or reduce vitamin C content. Relevant issues were discussed.

Transcriptome and genome analysis to identify C2H2 genes participating in low-temperature conditioning-alleviated postharvest chilling injury of peach fruit

Objectives:This work intended to identify candidate C2H2 genes participating in low-temperature conditioning(LTC)-alleviated postharvest chilling injury of peach fruit.Materials and Methods:For LTC treatment,fruit were pre-stored at 10℃for 5 d and then transferred to 0℃storage.Fruit firmness was measured by a hardness tester.H_(2)O_(2)content was determined by luminosity measurement model using a multifunctional enzyme labeler.Identification of C2H2 family members was performed by HMMSCAN according to peach genome.The cis-acting element of gene promoters was analyzed using the Plant CARE website.Weighted gene coexpression network analysis(WGCNA)was performed by the WGCNA package in the BMK Cloud platform.Results:LTC treatment decreased flesh browning rate and H_(2)O_(2)production of‘Beijing No.9’peach.Transcription factor identification of differentially expressed genes in 0℃and the LTC treatment indicated that peach C2H2 participated in the regulation of chilling injury.A total of 47 C2H2 genes were identified based on peach genome.Real-time quantitative polymerase chain reaction(qRT-PCR),phylogenetic analysis and promoter cis-acting element analysis revealed that ZFP21 was involved in the regulation of LTC-alleviated chilling injury in peach.WGCNA and dual luciferase assay suggested that ZFP21 participated in LTC-alleviated chilling injury by downregulating the expression of reactive oxygen species-related genes Rboh.Conclusions:Our investigation,based on genome and RNA-seq,revealed that ZFP21 was involved in LTC treatment-alleviated chilling injury of peach fruit.This work is useful for the identification of peach cold tolerance-related genes and the study of C2H2 family in peach.

Effects of IAA and ABA on the Immature Peach Fruit Development Process

Peach(Prunus persica cv. Dajiubao) was chosen as a model to clarify the roles of IAA and ABA during the fruit ripening process. Seventy days after flowering(DAF), the fruits were treated with IAA and ABA(0.1 mmol·L-1 and 1 mmol·L-1, respectively) and with the IAA transporter inhibitor(NPA) and the ABA biosynthesis inhibitor(NDGA). IAA decreased the fruit ABA concentration, and increased ethylene concentration, leading to fruit(70 DAF) softening and coloration. NPA had the opposite effect. ABA decreased IAA and ethylene concentrations, leading to fruit hardness and lack of color. NDGA had similar effects as with IAA application. A q PCR analysis indicated that in immature fruits, the expression levels of ethylene biosynthesis and signaling genes(PpACS, PpACO, PpETR, PpERF2), anthocyanin biosynthesis genes(PpCHS, PpDFR, PpF3 H, PpUFGT), cell wall softening genes(PpEXP1, PpEXP2, PpPG2, PpPME), and auxin biosynthesis genes(PpPIN, PpTIR1) were upregulated by IAA application but were inhibited by NPA. In contrast, these ripening-related genes were downregulated by ABA application, but upregulated by NDGA. Generally, the immature fruit ripening process requires a high IAA concentration to generate a large amount of ethylene. ABA appeared to modulate ripening through interference not only with ethylene and cell wall related genes but also with auxin-related genes.

Peach yield and fruit quality is maintained under mild deficit irrigation in semi-arid China

We conducted a two-year study of deficit irrigation impact on peach yield and quality in semi-arid northwest China. Over two years, four-year-old peach trees were irrigated at 100, 75, 50 and 25% of peach evapotranspiration （ETc）, here, ETc= Coefficient （Kc）×Local reference evapotranspiration （ET0）. During the April-July fruit production season we measured root zone soil water depletion, sap flow velocity, net photosynthetic rate （Pn）, transpiration rate （Tr）, stomatal conductance （Gs）, water use efficiency （WUE=Pn/Tr）, fruit quality, and yield under a mobile rain-out shelter. Increased soil water depletion reasonably mirrored decreasing irrigation rates both years, causing progressively greater water stress. Progressive water stress lowered Gs, which in turn translated into lower T as measured by sap flow. However, mild deficit irrigation （75% ETc） constricted T more than Pn. Pn was not different between 100 and 75% ETc treatments in both years, and it decreased only 5-8% in June with higher temperature than that in May with cooler temperature. Concurrently under 75% ETc treatment, was reduced, and WUE was up to 13% higher than that under 100% ETc treatment. While total fruit yield was not different under the two treatments, because 75% ETc treatment had fewer but larger fruit than 100% ETc trees, suggesting mild water stress thinned fruit load. By contrast, sharply decreased T and Pn of the driest treatments （50 and 25% ETo） increased WUE, but less carbon uptake impacted total fruit yield, resulting 13 and 33% lower yield compared to that of 100% ETc treatment. Irrigation rates affected fruit quality, particularly between the 100 and 75% ETc trees. Fewer but larger fruit in the mildly water stressed trees （75% ETc） resulted in more soluble solids and vitamin C, firmer fruit, and improved sugar：acid ratio and fruit color compared to the 100% ETo treatment. Overall, trees deficit irrigated at 75% ETc maintained yield while improving fruit quality and using less water.

Effect of Foliar Application of Micronutrients on Fruit Quality of Peach

This experiment was conducted to study the effect of foliar spray of micronutrients on quality of peach fruits at Horticulture Farm, University of Agriculture Peshawar during 2010. The experiment was conducted in randomized complete design with six treatments and four replications on peach orchards (early grand). Our pre-treatment soil analysis showed silt loam soil class, alkaline and calcareous in nature and adequate in organic matter. The soil was deficient in P, Zn, Fe and B, whereas adequate in Mn and Cu. The fruit quality was evaluated and maximum fruit length, diameter and yield were noted in T6 (Zn + Cu + Fe + Mn + B). The juice pH decreased and the juice acidity increased in a linear fashion after foliar spray of micronutrients. The total soluble solids of fresh fruit juice ranged 7.01%-8.88% and vitamin C ranged from 4.80%-7.90% after foliar spray. So the foliar spray of micronutrients significantly (P ≤ 0.05) affected the quality of peach fruit.

不同类型果袋对蟠桃果实品质的影响

为了明确蟠桃果实优质生产的果袋类型,以金霞油蟠和瑞油蟠2号2个蟠桃品种为试验材料,6月上旬分别选用外黄内黑双层袋、白色单层袋进行果实套袋处理,以不套袋处理为对照,研究了不同类型果袋对蟠桃果实外观品质和内在品质的影响。结果表明:与未套袋的对照相比,2个蟠桃品种果实套袋后单果重和可食率明显增大,成熟期果面黄色度增加、红色度降低,果面亮度和光洁度有效提高,果皮擦伤度和果实裂果率明显降低,带皮硬度、去皮硬度和可溶性固形物含量降低不显著,其中套外黄内黑双层袋的效果优于套白色单层袋。外黄内黑双层袋对提高蟠桃果实外观品质和内在品质的效果优于白色单层袋,研究结果可为今后生产实践中提高蟠桃果实品质,尤其是解决蟠桃裂果问题提供理论参考。

设施桃果实品质的影响因素与改善措施

设施桃果实风味偏淡、品质下降的问题比较突出,已经成为设施桃产业发展的制约因素。该文从提高设施桃品质的必要性、影响果实品质的重要因素及提高设施桃品质的技术措施等方面进行分析,期望对设施桃产业的健康发展提供参考。

桃小食心虫性信息素的合成

桃小食心虫是我国最严重的蛀果害虫之一,利用其性信息素进行防控,具有高效、环保及不易产生抗性等优点。天然桃小食心虫性信息素(Z)-12-十九碳烯-9-酮与(Z)-13-二十碳烯-10-酮在昆虫体内含量极低,通过人工提取无法满足大规模防治需求。本研究以3-溴-1-丙醇为原料,经四氢吡喃基(THP)保护、亲核取代、Brown P2-Ni还原(Ni(OAc)_(2)与NaBH4催化氢化)、格氏试剂加成与重铬酸吡啶鎓(PDC)氧化等7步反应,构建了一种高效合成桃小食心虫性信息素的方法;并首次将Brown P2-Ni还原用于桃小食心虫性信息素顺式碳碳双键的构建,总收率为5%。所构建的桃小食心虫性信息素合成方法操作简便,产品具有高度的区域选择性(Z:E>99:1),适用于桃小食心虫的绿色防控。

挥发性有机化合物对桃果实采后褐腐病控制及感官品质的影响

桃果实在采后贮藏物流过程中易受到果生链核盘菌(Monilinia fructicola)的侵染,导致褐腐病发生和果实品质劣变,有关的挥发性有机化合物(volatile organic compounds,VOCs)对褐腐病的调控效果尚不清楚。本研究分析了成熟桃果实中主要VOCs对果生链核盘菌的抑菌效果,结果表明,香芹酚、反-2-己烯醛等12种VOCs可以显著抑制病原菌在培养基上的生长。进一步开展上述12种VOCs对桃果实采后褐腐病的调控效应研究,结果表明,采用VOCs熏蒸处理可以有效抑制果生链核盘菌的生长,延缓褐腐病发生,其中挥发性醛类物质对果实品质的保持效果较好。采用25μL/L反-2-己烯醛熏蒸处理可以显著抑制果生链核盘菌生长,减轻褐腐病症状,同时不影响果实外观、乙烯释放速率、硬度、总可溶性固形物含量和感官品质指标,有效维持桃果实在采后贮藏过程中的商品性。综上所述,反-2-己烯醛具有开发为植物源抑菌剂的潜力,可为桃果实供应链提供品质保障。

褪黑素处理对桃果实采后软腐病的影响及其机理

为了研究褪黑素(melatonin,MT)处理对‘霞晖8号’桃果实采后软腐病的影响及其抗病机理,用0、0.05、0.10、0.50mmol/L和1.00mmol/L的MT溶液处理桃果实并接种匍枝根霉(Rhizopusstolonifer)病原菌,置于20℃贮藏60 h,观察其发病情况以确定最适MT处理浓度;以此研究最适浓度的MT处理对桃果实采后贮藏期间品质参数、总酚含量、木质素含量、与抗病相关酶的活性及其基因表达水平和R. stolonifer离体生长情况的影响。结果表明,0.50 mmol/L的MT处理最能显著减少桃果实采后软腐病的发生,维持果实品质;且与单一MT处理和R. stolonifer接种组相比,0.50 mmol/L MT+R. stolonifer组可表现出更为强烈的抗病反应,其几丁质酶、β-1,3-葡聚糖酶、苯丙氨酸解氨酶、肉桂酸羟化酶、4-香豆酸辅酶A连接酶、过氧化物酶和多酚氧化酶的活性、总酚和木质素含量以及PpCHI、PpGLU、PpPAL和PpPOD等防卫基因表达水平显著高于单一接种或MT处理果实。此外,MT对R. stolonifer离体生长无明显抑制作用。以上结果表明,MT可通过间接诱导桃果实采后敏化抗性,从而使果实在病原菌侵染后启动防卫反应,从而减少采后病害的发生。

桃基因 PpNAC 的鉴定及其在不同发育时期的表达分析

【目的】鉴定影响桃果实成熟的PpNAC基因,并分析其在桃果实不同发育时期的表达量变化,为解析桃果实成熟的分子机制奠定基础。【方法】通过对桃不同组织部位的转录组分析,从115个PpNAC基因家族成员中筛选在果实中特异表达的PpNAC基因,进一步进行生物信息学分析、蛋白互作分析和表达分析,筛选可能影响桃果实成熟的PpNAC基因。【结果】筛选到16个在桃果实中高表达的PpNAC基因,其在桃的8条染色体上都有分布,蛋白相对分子质量和等电点差异较大。基因编码区均含有NAM保守结构域和motif1~6,含有3~8个外显子,2~7个内含子,启动子中脱落酸响应元件和茉莉酸响应元件相对较多。此外,通过与已报道成熟相关NAC蛋白PpNAC1的互作筛选,得到4个与PpNAC1互作的PpNAC蛋白。进一步的表达分析表明,这4个PpNAC基因在果实成熟起始期和成熟后期表达量达到最高。【结论】PpNAC基因可能参与调控桃果实成熟。

‘深州蜜桃’园土壤养分与果实品质相关性

【目的】对‘深州蜜桃’园的土壤养分进行评价,探究‘深州蜜桃’园土壤养分与果实品质间的关系,提出土壤养分优化方案,为‘深州蜜桃’的生产实践提供理论依据。【方法】调查‘深州蜜桃’园的土壤养分及果实品质,根据第二次土壤普查分级标准进行评估,利用皮尔逊相关性分析及逐步回归分析筛选出影响果实品质的主要土壤养分因子,建立线性方程组,获得优质果实品质所对应的土壤养分含量方案。【结果】研究区土壤大部分呈弱碱性,大部分桃园的土壤有机质处于缺乏状态,土壤养分指标均呈现适量或丰富状态。逐步回归分析结果表明果实重量主要受土壤交换性镁的影响,且为负相关关系,可溶性固形物含量主要受土壤碱解氮与速效钾的影响,与碱解氮为负相关关系,与速效钾为正相关关系,可溶性糖含量主要受土壤速效钾的影响,可滴定酸含量主要受有机质的影响,糖酸比主要受有机质与速效钾的影响;求解线性方程组结果显示,当土壤pH值为7.99、有机质为25.3 g·kg^(-1)、碱解氮87.7 mg·kg^(-1)、有效磷93.97 mg·kg^(-1)、速效钾为213.06 mg·kg^(-1)、交换性钙为718.14 mg·kg^(-1)、有效镁为215.56 mg·kg^(-1)、有效铁为15.72 mg·kg^(-1)、有效锰为7.86 mg·kg^(-1)、有效铜为1.86 mg·kg^(-1)、有效锌为1.57 mg·kg^(-1)、有效硼为1.16 mg·kg^(-1)时果实品质达到最优。【结论】研究区的桃园应调节土壤pH值,以提高桃园有机质含量为重点,适量增施有机肥与钾肥,减少氮肥用量。

Methyl Jasmonate Reduces Chilling Injury and Maintains Postharvest Quality in Peaches

Zhaohui peaches(Prunus persica Batsch)were treated with 0(CK), 1, 10 or 100 μmol L-1 methyl jasmonate(MeJA)vapor at 20℃ for 24 h before stored at 0℃ for 35 d. The untreated fruits showed chilling injury(CD symptoms after 4 wk of storage, as indicated by increased fruit firmness and reduced ex-tractable juice, which is referred as leatheriness. Treatment with 1 and 10 μmol L-1 MeJA promoted normal ripening and softening, maintained higher levels of extractable juice, titratable acidity, pectinesterase(PE)and polygalacturonase(PC)activities, inhibited increases in fruit fresh weight loss, decay incidence, electrolyte leakage and MDA content, and improved color development, thereby preventing chilling injury symptoms development and maintaining edible quality. MeJA treatment also delayed the climacteric rise in respiratory rate, but promoted ethylene production during the later period of cold storage, suggesting that ethylene may involve in CI development of peaches. These results indicate that 1 and 10 μmol L-1 MeJA treatments could be used to reduce CI development and decay incidence in peaches.

果树木屑黑木耳袋栽基质研究

黑木耳产业对栎木资源的依赖是该产业发展和生态文明建设不相适应的突出表现,因而选取果树替代传统栎木是促进黑木耳产业绿色生态发展的潜在途径。本文选取苹果树木屑、桃树木屑、桔树木屑和核桃树木屑为黑木耳主要栽培基质,通过菌丝生长速度、菌丝密度、菌丝色泽以及锁状联合数目等指标考核最佳果木木屑袋栽基质。结果表明,黑木耳菌丝在桃树木屑袋料基质上生长最好,生长速度(5.62 mm/d)比对照组(5.24 mm/d)提高了7.25%;菌丝生长势较好,边缘整齐、浓密、色泽洁白且锁状联合数目较多;选取78%、82%、86%和90%等4个不同桃树木屑配比,通过不同袋料基质对桃树木屑黑木耳袋栽基质进行优化研究,最佳果木黑木耳袋栽基质配方为:桃树木屑78%、米糠19%、红糖1.5%、石膏粉1%、石灰粉0.5%,此时黑木耳菌丝的生长速度(10.06 mm/d)比对照组的生长速度(5.88 mm/d)提高了71.09%,且锁状联合数目最多。本研究结果表明,桃树可替代栎木进行黑木耳袋料栽培,为黑木耳产业的绿色高质量发展奠定基础。