Postharvest ASM or Harpin Treatment Induce Resistance of Muskmelons Against Trichothecium roseum

Induced resistance was studied in muskmelons （cv. Yindi） inoculated Trichothecium roseum with postharvest 1,2,3- benzothiadiazole-7-carbothioic acid S-methyl ester （ASM） （100 mg L^-1） or harpin （50 mg L^-1） treatment. Both ASM and harpin significantly reduced lesion diameter in inoculated fruit. Lesion diameter was limited in the treated and untreated halves of the same fruit, indicating that the local and systemic resistance was induced. Inhibiting efficacy of elicitors lasted 7 and 5 days in the treated and untreated halves. The resistance increased by the chemicals was associated with the activation of peroxidase （POD） and chitinase （CHT）. The elicitors induced a significantly and progressively increasing activity of POD and CHT in the treated and untreated halves, and the activation lasted at least 5 days. The activities of POD isoenzymes increased in the treated fruit. However, no new enzyme band was found in the treated and untreated halves.     

Hot air treatment activates defense responses and induces resistance against Botrytis cinerea in strawberry fruit

The effect of hot air(HA, 45°C, 3.5 h) treatment on reducing gray mold caused by Botrytis cinerea in strawberry fruit and the possible mechanisms were investigated. The results showed that HA treatment significantly reduced lesion diameter and enhanced activities of chitinase(CHI), β-1,3-glucanase and phenylalanine ammonia-lyase(PAL) in strawberry fruit. Total phenolic contents were also increased by HA treatment. The activities of antioxidant enzymes including superoxide dismutase(SOD), catalase(CAT) and ascorbate peroxidase(APX) were higher in HA treated strawberry fruit than those in control. Expression of three defense related genes such as CAT, CCR-1 allele and PLA6 was greatly induced in HA treated strawberry fruit with or without inoculation by B. cinerea. In addition, the in vitro experiment showed that HA treatment inhibited spore germination and tube growth of B. cinerea. These results suggested that HA treatment directly activated disease resistance against B. cinerea in strawberry fruit without priming response and directly inhibiting growth of B. cinerea.     

Effects of INA on postharvest blue and green molds and anthracnose decay in citrus fruit

As a synthetic functional analog of salicylic acid, 2,6-dichloroisonicotinic acid(INA) is effective in inducing the host disease resistance of a plant against a pathogen. The effects of INA on controlling postharvest blue and green molds and anthracnose decay and defense-related enzymes on citrus fruits were investigated, and the ascorbic acid of naturally infected citrus flavedo was also measured. Results showed that 1.0 mmol L~(–1) INA treatments significantly reduced blue and green molds and anthracnose decay development on both wound-inoculated fruit and naturally-infected fruit compared with the control fruit. The treatment effectively enhanced the β-1,3-glucanase(GLU), chitinase(CHI), phenylalanine ammonia-lyase(PAL) and peroxidase(POD) activities and the polyphenol oxidase(PPO) in flavedo. The results presented here suggest that INA might be used as a chemical fungicide substitution to control postharvest diseases in citrus fruits.     

Regulation of Propylene and 1-Methylcyclopropene on Expressions of ACS and ACO Genes in Persimmon Fruits

The regulation of postharvest treatment with propylene and 1-MCP on ethylene release rate and expressions of 1- aminocyclopropane-l-carboxylic acid synthase （ACS） and 1-aminocyclopropane-1-carboxylic acid oxidase （ACO） genes in Fuping Janshi persimmon （Diospyros kaki L.） fruit were investigated. Fruits were treated with propylene and 1-MCP, then stored at 20℃, ethylene release rate of the treated fruits was measured at regular intervals and RNA was extracted for Northern blotting analysis. The results suggested that treatment with propylene accelerated the expressions of ACS and ACO genes and then enhanced the ethylene biosynthesis, while treatment with 1-MCP inhibited the expressions of two genes and their ethylene biosynthesis. Furthermore, different effects on expressions caused by treatments with propylene and 1-MCP existed in various fruit tissues, the inhibitory effect on ACS and ACO genes by 1-MCP was the strongest in pericarp, followed by pulp and core tissues, in the area near fruit stalk, the inhibitory effect was the weakest. While the enhanced effect on ACS and ACO genes by propylene increased from pulp, core, and pericarp to the area near fruit stalk. Expression of each member of ACS and ACO families in various tissues was also completely different, in control and propylene treatment, DKACS3 gene just expressed in the area near fruit stalk and did not express in other tissues, but DKACS2 gene expressed in four tissues by treatment with propylene.     

Postharvest Treatment with β-Aminobutyric Acid Induces Resistance Against Dry Rot Caused by Fusarium sulphureum in Potato Tuber

The effectiveness ofpostharvest β-aminobutyric acid （BABA） treatment was studied for inducing resistance against dry rot caused by Fusarium sulphureum in tubers and slices of two potato cultivars （resistant cultivar Shepody and susceptible cultivar Xindaping）. The results showed that BABA at 100 mmol L-1 significantly reduced lesion diameter in inoculated both tubers and slices. The chemical at 100 mmol L-1 showed an effective reduction in infection ability ofF. sulphureum inoculated 48 and 72 h after treatment in slices of resistant cultivar, and 72 and 96 h in susceptible ones. BABA increased the activitives of peroxidase （POD）, polyphenoloxidase （PPO） and phenylalanine ammonialyase （PAL）, and accumulated the contents of lignin, flavonoids and phenolics in slices. The resistant cultivar had a stronger resistant response than the susceptible one. These findings suggest that the BABA treatment can induce the resistance in potato tubers, however, the inducing degree depends on the original level of resistance present in each cultivar.     

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 Chlorine Dioxide Gas on Postharvest Physiology and Storage Quality of Green Bell Pepper （Capsicum frutescens L. var. Longrum）

The effects of treatment of chlorine dioxide (ClO2) gas on postharvest physiology and preservation quality of green bell peppers were studied. Green bell peppers were collected in bags and treated with 0, 5, 10, 20, and 50 mg L-1 ClO2 gas at 10 ± 0.5℃ for over 40 d, and the changes in postharvest physiology and preservation quality of the peppers were evaluated during the storage. The inhibition of rot of the peppers was observed for all the tested ClO2 gas treatments. The rot rates of the treated samples were 50% lesser than those of the control after day 40 of storage. The highest inhibitory effect was obtained after 50 mg L-1 ClO2 gas treatment, where the peppers did not decay until day 30 and showed only one-fourth of the rot rate of the control at day 40 of storage. The respiratory activity of the peppers was significantly (P ＜ 0.05) inhibited by 20 and 50 mg L-1 ClO2 treatments, whereas no significant effects on respiratory activity were observed with 5 and 10 mg L-1ClO2 treatments (P＞ 0.05). Except for 50 mg L-1 ClO2, malondialdenyde (MDA) contents in the peppers treated with 5,10, or 20 mg L-1 ClO2 were not significantly (P＞0.05) different from those in the control. Degradation of chlorophyll in the peppers was delayed by 5 mg L-1 ClO2, but promoted by 10, 20, or 50 mg L-1 ClO2. The vitamin C content, titratable acidity,and total soluble solids of the peppers treated by all the tested ClO2 gas did not significantly change during the storage.The results suggested that ClO2 gas treatment effectively delayed the postharvest physiological transformation of green peppers, inhibited decay and respiration, maintained some nutritional and sensory quality, and retarded MDA accumulation.     

Effect of plant extracts on activity of some defense enzymes of apple fruit in interaction with Botrytis cinerea

The efficacy of seven plant extracts(neem,fennel,lavender,thyme,pennyroyal,salvia and asafetida) in controlling postharvest of apple(caused by Botrytis cinerea) was evaluated in vitro and in vivo.In vitro,all plant extracts treatments inhibited spore germination.Inhibitory rates of pore germination was 17.41 and 20.83% for neem extract treatment(methanolic and aqueous extracts,respectively) with significant difference compared to control(73.6 and 85.33%) for aqueous and methanol extracts.In the storage conditions,the application of aqueous extract of neem(at concentration of 25%) resulted in 89.11% reduction of disease severity compared with the untreated control.Results of enzymes activity showed the plant extracts can increase the activity of peroxidase,phenylalanine ammonia-lyase,β-1,3-glucanase and polyphenol oxidase in the presence of pathogens,in apple fruits.However,the results of this research revealed that application of neem extracts was more effective than the application of other plant extracts.According to this study,it could be concluded that plant extracts may be useful to control postharvest disease as a safe alternative option to chemical fungicides.     

Reduction in Activity/Gene Expression of Anthocyanin Degradation Enzymes in Lychee Pericarp is Responsible for the Color Protection of the Fruit by Heat and Acid Treatment

Heat and acid treatments were reported to be a promising substitute for SO₂ fumigation in color protection of postharvest lychee （Litchi chinensis Sonn.） fruits, but the mechanism was not clear. In the present study, hot water （70°C） dipping followed by immersion in 2% HCl （heat-acid） substantially protected the red color of the fruit during storage at 25°C and inhibited anthocyanin degradation while hot water dipping alone （heat） led to rapidly browning and about 90% loss in anthocyanin content. The pH values in the pericarp of the heat-acid treated fruit dropped to 3.2, while the values maintained around 5.0 in the heat-treated and control fruit. No significantly different pH values were detected among the arils of heat-acid, heat treated and control fruit. Heat-acid treatment dramatically reduced the activities of anthocyanin degradation enzyme （ADE）, peroxidase （POD） and polyphenol oxidase in the pericarp. A marked reduction in LcPOD gene expression was also detected in heat-acid treated fruit, in contrast, induction was found in heat treated fruit. The pericarp of heat-acid treated fruit exhibited significantly lower respiration rate but faster water loss than that of the untreated or heat treated fruit. Taken together, heat treatment triggered quick browning and anthocyanin loss in lychee fruit, while heat-acid treatment protected the fruit color by a great reduction in the activities/gene expression of anthocyanin degradation enzymes and acidification of lychee perica.     

Relationship Between Anthocyanin Biosynthesis and Related Enzymes Activity in Pyrus pyrifolia Mantianhong and Its Bud Sports Aoguan

The aim of this article is to study the relationship between biosynthesis of anthocyanin and activities of phenylalanine ammonia lyase （PAL）, chalcone ismoerase （CHI） enzymes in Pyrus pyrifolia. Changes in the level of anthocyanin and the activities of enzymes of anthocyanin biosynthesis including PAL, CHI were studied in the pericarp of Pyrus pyrifolia Aoguan and Mantianhong during the period of pigment formation. Bagging treatment was also carried out to manipulate the synthesis of anthocyanin and the activities of related enzymes during the period of pigment formation. The results demonstrated that the level of anthocyanin of Aoguan was higher than that of Mantianhong. However, the content of anthocyanins has the similar changing trend in Aoguan and Mantianhong, highest anthocyanin concentrations of two varieties appeared in immature fruit and faded toward harvest. Meanwhile, similar changing trends of activities of PAL and CHI were also observed in both varieties. Aoguan has a lower activity of PAL than Mantianhong, whereas activity of CHI in Aoguan was higher than that in Mantianhong. Activity of PAL decreased during the period of pigment formation and was apparently not limiting to color development, whereas CHI activity increased at the same period and was closely related to the synthesis of anthocyanin. The results of bagging treatment showed that bagging treatment inhibited the activity of CHI, as well as the synthesis of anthocyanin, whereas debagging enhanced both the activity of CHI and synthesis of anthocyanin. The activity of CHI in debagging Aoguan pericarp was higher than the untreated Aoguan. However, effect of bagging treatment toward PAL activity was not obvious. Anthocyanin of bagging treated Aoguan decreased toward harvest. The content of anthocyanin of Pyruspyrifolia increased at the beginning of fruit coloration period and decreased toward fruit harvest. Activity of PAL was apparently not limiting to color development, whereas CHI activity was closely related to the synthesis of ant     

Control of Postharvest Fusarium Rot and Trichothecium Rot in Harvested Muskmelon (cv. Yindi) by Harpin

Preharvest and postharvest application of Harpin was evaluated for its ability to induce resistance in muskmelon fruit and control rots. Preharvest treatments were 30 mg L-1, 60 mg L-1 Harpin or 1 mg L-1 Imazalil either 1 week or 1 day before harvest.The CK was untreated. Fruit were then inoculated with Fusarium semitectum or Trichothecium roseum 48 h after harvest,and stored at 23 ± 1℃, RH (relative humidity) 50-60% for 4 d. All treatments were effective in reducing the lesion area with 60 mg L-1 Harpin the most effectively. No treatments inhibited infection rate. Postharvest treatment was fruit dips of 30 mg L-1, 60 mg L-1 Harpin, 0.1 mg L-1 Imazalil. Fruit were inoculated with F. semitectum or T. roseum 24, 72, 120 or 168 h after treatment, and stored at 23 ± 1 ℃, RH 50-60% for 4 days. All treatments were effective in reducing the lesion area with 60 mg L-1 Harpin the most effectively. No treatments inhibited the infection rate. Postharvest Harpin treatment induced the peroxidase activity increase, peroxidase activity reached maximum after 8 d and the activation lasted at least 10 d.     

草酸处理对厚皮甜瓜采后病害及果实品质的影响

研究了草酸处理对"银帝"甜瓜采后病害及果实品质的影响.结果表明:在25 mmol/L至200 mmol/L的处理浓度范围内,以50 mmol/L处理对损伤接种Trichothecium roseum的抑制效果最好,更高浓度(100、200mmol/L)处理并未进一步提高抑制效果,也未对果实产生药害.在1 min至15 min的浸泡时间范围内,以10 min和15 min处理对损伤接种T.roseum的效果较好.草酸处理诱导了果实损伤接种T.roseum的系统获得抗病性(SAR),并且处理后48 h至96 h损伤接种T.roseum可使果实的防卫能力达到最大.草酸处理显著降低了果实损伤接种3种主要采后病原物的病斑直径;延缓了果实贮藏期间硬度和可溶性固形物(SSC)含量的下降.     

苯丙噻重氮（ASM）对果蔬采后抗病性的诱导及机理

苯丙噻重氮（acibenzolar-S-methyl, ASM）是水杨酸的类似物,也是人工合成的植物抗病性化学诱导剂,能够诱导多种植物的抗病性。采前或采后ASM处理可有效降低梨、桃、葡萄、草莓、甜瓜、橘、芒果、香蕉、枇杷、番茄和马铃薯等多种果蔬的采后病害。ASM的诱抗机理涉及诱导活性氧的积累、活化苯丙烷代谢和促进病程相关蛋白的产生等方面。本文还对扩大ASM的使用范围,提高其使用效果,以及深入阐明ASM的作用机理进行了展望。     

聚-γ-谷氨酸对广西龙滩珍珠李品质的影响

探讨了聚-γ-谷氨酸(poly-γ-glutamic acid,PGA)对广西地方优良品种龙滩珍珠李外观及内在品质的影响。结果表明,2015、2016年200 mg·L~(-1)PGA处理后,龙滩珍珠李单果重均极显著高于清水处理(CK);2015年100和200 mg·L~(-1)PGA处理后,Vc含量分别比CK提高了16.8%和24.6%,其中200 mg·L~(-1)PGA处理极显著高于CK,2016年200 mg·L~(-1)PGA处理后,Vc含量分别比CK和100 mg·L~(-1)处理提高了5.4%和16.2%,且差异达显著水平;2015年100和200 mg·L~(-1)PGA处理后,还原糖含量分别比CK提高了18.2%和36.1%,其中200 mg·L~(-1)PGA处理极显著高于CK,2016年还原糖含量分别比CK提高了49.3%和80.1%,差异均达极显著水平;2015、2016年200 mg·L~(-1)PGA处理后,果实蛋白质含量均高于CK和100 mg·L~(-1)处理。2015、2016年PGA对龙滩珍珠李外观及内在品质影响的变化趋势相似。     

芽孢杆菌B_1对“银帝”甜瓜主要采后病害的抑制

研究了芽孢杆菌B1原液、滤液、灭菌液和悬浮液对“银帝”甜瓜主要采后病害的抑制效果。结果表明,B1原液能显著的抑制损伤接种甜瓜果实的白霉病、粉霉病、软腐病和黑斑病,其抑制率分别为75.9 %、78.7 %、100 % 和99 %。B1滤液仅对白霉病病斑面积的扩展有所抑制,但对该病发病率及粉霉病的抑制效果不显著。B1杀菌液可有效降低黑斑病的发病率与病斑面积,减轻白霉病和粉霉病病斑面积的扩展,但对这两种病害的发病率影响不大。B1悬浮液仅能抑制粉霉病及白霉病病斑面积。     

赤霉素和戴挫霉与嘧菌酯混配对甜瓜采后病害控制的增效作用

采用体外抑菌试验和果实损伤接种试验,分别测定了赤霉素和戴挫霉与嘧菌酯混配对甜瓜采后粉霉病和白霉病控制的增效作用。结果表明,在体外抑菌试验中,赤霉素对2种病原菌没有抑制作用,对嘧菌酯的防效也没有增效作用;戴挫霉对2种病原菌具有很好的抑制效果,对嘧菌酯的防效也有增效作用。在甜瓜果实损伤接种试验中,赤霉素能有效控制病害的发生,并且与嘧菌酯配合后,对其具有一定的增效作用;戴挫霉与嘧菌酯配合应用,对甜瓜病害的防效明显高于二者单独使用。     

不同抑菌剂对荔枝采后生理变化的影响

系统评估了几种抑菌剂在低温条件下对荔枝果实的保鲜效果和采后生理进程的影响。结果表明:各种抑菌剂均可以在一定程度上减轻荔枝采后病害的发生,并延缓荔枝采后的生理衰老进程。咪鲜胺微乳剂表现出较强的优势,其次是万利得,特克多和扑海因控制荔枝采后病害的效果较差。施保克乳油虽然较好地控制了病害的发生,但由于其对荔枝果皮有一定的伤害作用,因此总体保鲜效果不理想。     

柠檬酸处理对马铃薯干腐病的抑制作用及防御酶活性的影响

研究了不同柠檬酸浓度处理对马铃薯干腐病的抑制作用及防御酶活性的影响.结果表明:浓度为45mmol.L-1的柠檬酸处理对损伤接种F.sulphureum的抑制效果最好,处理后病班直径比对照降低了74%,而60mmol.L-1的柠檬酸处理则对马铃薯产生了轻微的药害;切片在诱导处理48 h后表现最大抗病性.马铃薯块茎组织经浓度为45 mmoL.L-1的柠檬酸处理后,其过氧化物酶、多酚氧化酶、苯丙氨酸解氨酶和β-1,3-葡聚糖酶的活性均明显升高,类黄酮和总酚含量也明显高于对照.说明柠檬酸能有效抑制马铃薯干腐病与组织内这4种抗性酶的活性以及类黄酮和酚类物质的含量密切相关.