Control of postharvest diseases on citrus fruit by preharvest application of the biocontrol agent Pantoea agglomerans CPA-2: Part I. Study of different formulation strategies to improve survival of cells in unfavourable environmental conditions

The objective in the present study was to investigate the survival and effectiveness of different biological agent Pantoea agglomerans formulations against Penicillium spp. with different preharvest treatments. Results indicated a high sensitivity of non-adapted and osmotic-adapted P. agglomerans cells to environmental conditions in the field, resulting in preharvest treatments which were ineffective against Penicillium spp. In the second part of this study, dry conditions and solar radiation were identified as important environmental conditions that seriously affect populations of P. agglomerans cells. Different formulation strategies were tested in order to improve the resistance of cells to unfavourable environmental conditions. Osmotic-adapted P. agglomerans cells in the presence of 25 g L⁻¹ of NaCl in the production medium [osmotic-adapted treatment (P25)] or at water activities (a_w) of 0.98 [osmotic-adapted treatment (P98)] had higher survival rates than non-adapted cells, when these cells were sprayed on oranges and stored in hermetically sealed chambers at a low RH of 43%. Among seven additives tested, the presence of 5% Fungicover in the bacterial suspension improved adherence and persistence of P. agglomerans cells on oranges exposed to unfavourable conditions. Therefore, while P. agglomerans cells sprayed alone had log values of 0.5 CFU cm⁻², in combination with Fungicover the population level of P. agglomerans cells reached log values of 5 and 4.2 CFU cm⁻², at 0 and 24 h after application. Lyophilised cells showed greater resistance to unfavourable environmental conditions than fresh cells. The present study has demonstrated that the formulation improvement can provide better performance of biocontrol agents under environmental conditions non-conducive for growth and survival.     

Timing and sequence of postharvest fungicide and biocontrol agent applications for control of pear decay

Postharvest decay of pear fruit often originates at small wounds that occur during harvest and handling. Experiments were conducted to characterize the effect of timing of application of postharvest decay control materials, and to evaluate sequential postharvest applications of fungicides or fungicides and biocontrol agents. Fungicides and biocontrol agents were increasingly less effective when the period between harvest and application was prolonged. Thiabendazole (TBZ) applied to fruit without artificial wounding or inoculation effectively reduced decay when applied within 3 weeks or 6 weeks in 2 years of study. TBZ, fludioxonil, and pyrimethanil were effective in controlling decay at artificial wounds inoculated with Penicillium expansum up to 14 d after inoculation. Application of TBZ at harvest followed 3 weeks later by application of fludioxonil was superior to application of TBZ at harvest alone. Three yeast and one bacterial biocontrol agents reduced decay at pear wounds inoculated with P. expansum up to 14 d after inoculation with P. expansum, but were ineffective when applied at 28 d after inoculation. Of possible sequential arrangements of fungicide and biocontrol treatments, application of the most effective material promptly after harvest generally resulted in the highest level of decay control.     

Improving quality of greenhouse tomato (Solanum lycopersicum L.) by pre- and postharvest applications of hexanal-containing formulations

From harvest to consumption, tomato (Solanum lycopersicum L.) fruit are exposed to several exogenous factors that enhance product deterioration. Phospholipase D is a key enzyme involved in membrane deterioration that occurs during fruit ripening and senescence. Hexanal, an inhibitor of phospholipase D has been successfully used for pre- and postharvest treatment of fruit, vegetables and flowers. In this study, effectiveness of pre- and postharvest application of an aqueous hexanal formulation and an enhanced freshness formulation (EFF) containing hexanal and other ingredients were evaluated by monitoring changes in quality parameters during postharvest storage of greenhouse tomatoes. Tomatoes subjected to preharvest spray with EFF containing 1 mM hexanal twice a week had better colour, and firmness than untreated fruit and hexanal formulation treated fruit. EFF treated tomatoes also showed low hue angle values indicative of enhanced red colour. Preharvest spray with 1 mM hexanal twice a week resulted in higher levels of ascorbic acid and soluble solids in fruit than those subjected to EFF treatment, and the control. Postharvest dip application of harvested tomatoes in 2 mM hexanal as EFF resulted in enhanced brightness and hue angle values, reduced red colour, increased fruit firmness and ascorbic acid content after 21 days of storage, indicative of better quality. The results suggest that hexanal has the potential to enhance shelf-life and quality of greenhouse tomatoes.     

Effects of the yeast Pichia guilliermondii against Rhizopus nigricans on tomato fruit

The yeast Pichia guilliermondii was examined for its ability to control Rhizopus nigricans on tomato fruit during storage, and in order to highlight the reason for biocontrol, a possible mode of action is discussed. Results showed that autoclaved yeast culture and culture filtrate had no effect on controlling the postharvest disease caused by R. nigricans, although inoculation of P. guilliermondii prior to R. nigricans resulted in enhanced biocontrol efficacy. Moreover, rapid colonization of the yeast on wound sites was observed during the initial 3 days at 20 °C, and then the population stabilized for the remaining 4 days. This phenomenon indicated that at room temperature, P. guilliermondii could acclimatize itself to the environment of tomato fruit wounds and occupy the living space quickly. The results indicate that P. guilliermondii did not produce an antifungal substance, however, competition for nutrients and space on wounds appeared to play a role in the activity of the biocontrol and could be one of the mechanisms. In addition, the fruit inoculated with P. guilliermondii demonstrated changes in peroxidase (POD), polyphenoloxidase (PPO), superoxide dismutase (SOD), catalase (CAT), phenylalanine ammonia-lyase (PAL), chitinase (CHI) and β-1,3-glucanase activities, all of which were correlated with the onset of induced resistance. This result suggests that tomato fruit is capable of responding to the yeast P. guilliermondii, which could activate defensive enzymes and thereby induce host disease resistance.     

Metschnikowia pulcherrima strain MACH1 outcompetes Botrytis cinerea, Alternaria alternata and Penicillium expansum in apples through iron depletion

A new strain of Metschnikowia pulcherrima (MACH1) was studied for its efficacy as a biocontrol agent against Botrytis cinerea, Penicillium expansum and Alternaria alternata on apples stored for 8 months at 1 °C. The results of two semi-commercial trials demonstrated the efficacy of the biocontrol strain MACH1. In order to understand the mechanism of action involved, the yeast strain was investigated for its competitive ability for iron against postharvest pathogens of apple. M. pulcherrima strain MACH1 was cultivated on PDA with different concentrations of iron (supplemented as FeCl₃) against A. alternata and B. cinerea. The yeast strain MACH1 produced a wider pigmented inhibition zone against both pathogens in low iron amendments while less inhibition was measured with increased iron concentrations. At the coloured inhibition zone, B. cinerea and A. alternata conidia did not germinate and mycelial degeneration was observed. In addition, a high reduction in infection by both pathogens was recorded in apples treated with M. pulcherrima strain MACH1 supplemented with low iron amendments compared to higher iron concentrations. The same experiments were carried out in vivo and in vitro against P. expansum. M. pulcherrima strain MACH1 amended with low iron concentration (5 μg mL⁻¹ FeCl₃), showing modest lesion diameter reduction and no effect on P. expansum under increased iron and without iron amendments. This study illustrated that iron depletion by the yeast strain MACH1 under low iron conditions could reduce the growth of some postharvest pathogens in vitro and in vivo. Although, iron depletion seems to be a primary mode of action against the postharvest pathogens studied, other mechanisms of action cannot be excluded in the biocontrol employed by M. pulcherrima strain MACH1.     

Effect of high-pressure hot water washing treatment on fruit quality, insects, and disease in apples and pears: Part II. Effect on postharvest decay of d’Anjou pear fruit

A hot water pressure process (HWP) was evaluated for its effect on conidia of Penicillium expansum and on development of blue mold, gray mold, and mucor rot of d’Anjou pear fruit. Spores were removed from the water system through dilution and also as a result of hot water in the system that was lethal to the spores. When the system was heated, viable spores were not detected after 2–4 h of operation. Reductions in decay in the HWP system were 36, 29, and 13% for Botrytis cinerea, Mucor piriformis, and P. expansum, respectively. The response of P. expansum appeared related to the length of time fruit was in cold storage. Heat injury was observed on fruit treated with 40 and 50 °C water but not on fruit at 30 °C nozzle temperature. The HWP system described in this study should be considered as a component of an integrated decay control strategy.     

Phospholipase A2 and postharvest peel pitting in citrus fruit

The role of phospholipase A₂ (PLA₂) activity in development of postharvest peel pitting in mature ‘Fallglo’ tangerines [Bower citrus hybrid (Citrus reticulata Blanco × C. reticulata Blanco × C. paradisi Macf.) × Temple (C. reticulata Blanco × Citrus sinensis L.)] and ‘Navel’ oranges (Citrus sinensis L. Osbeck) was investigated. Changes in RH from 30% to 90% followed by fruit waxing increased electrolyte leakage and PLA₂ activity in flavedo, and induced pitting. Treatment with an aqueous dip of aristolochic acid (AT), a specific inhibitor of secretory phospholipase A₂ (sPLA₂) activity, immediately before transfer from 30% to 90% RH storage, markedly reduced peel pitting symptoms. Five genes encoding various phospholipase As isolated from citrus (three patatin-like and two sPLA₂-like sequences) differentially accumulated in healthy areas, areas with developing lesions and necrotic lesions of disordered fruit. Other PLA₂, phospholipase C, and phospholipase D inhibitors also reduced peel pitting; however, PLA₂ inhibitors were the most effective in preventing the disorder. In addition, phospholipase inhibitors promoted fruit decay, suggesting that innate resistance is impacted by phospholipase action. Together, the results provide evidence for involvement of phospholipase activity in development of postharvest peel pitting symptoms in citrus fruit.     

产紫青霉对烟草根结线虫病的生物防治研究

为评估产紫青霉对烟草根结线虫病的生防潜质,采用产紫青霉K1对南方根结线虫二龄幼虫及卵的活性进行了室内生测,同时利用了产紫青霉K1生物菌剂对烟草根结线虫病进行了2年2地的田间防效测定。结果表明：（1）产紫青霉K1菌株对南方根结线虫具有较强的毒杀活性,48 h对根结线虫2龄幼虫的校正致死率高达94.53%,对卵孵化的相对抑制效率达90.75%;（2）3种用量的产紫青霉对烟草根结线虫的防治效果及烤烟综合农艺性状、产质量和均价均优于33.00 kg/hm²的淡紫拟青霉,其中以41.25 kg/hm²产紫青霉的防治效果、综合农艺性状、产值量和均价最好,平均防效为80.60%,烟叶产量、产值和均价分别为2119.50 kg/hm²、56762.77元/hm²和26.78元/kg。因此,产紫青霉K1在烟草根结线虫生物防治领域具有较大的潜能,可作为攀枝花烟草根结线虫病生防菌加以开发应用,推荐使用方法及用量为在烟草移栽时使用41.25 kg/hm²产紫青霉K1一次。     

Postharvest application of a new growth regulator reduces calyx alterations of citrus fruit induced by degreening treatment

Synthetic auxins, specially 2,4-dichlorophenoxyacetic acid (2,4-D), have been used as a postharvest treatment to retard calyx abscission, drying and browning, which occur as the result of degreening processes. Nevertheless, the use of 2,4-D is restricted by European Union (EU) legislation, which means that finding an alternative to this auxin in controlling calyx senescence is necessary. In the present research, the effect of postharvest application of a new growth regulator, S-ethyl-4-chloro-O-tolilooxytioacetate (HF-Calibra^®), currently registered for preharvest use, was used to investigate calyx senescence of early-season citrus varieties (‘Oronules’, ‘Clemenrubi’ and ‘Clemenules’ mandarins and ‘Navelina’ oranges) submitted to a commercial degreening treatment. After shelf-life, application of HF-Calibra^® treatment at different concentrations significantly reduced calyx changes. Although auxin treatments can retard color change, this delay had no negative effect from a commercial viewpoint since all the studied varieties reached a commercially acceptable color. The application of HF-Calibra^® at 10, 20, 40 or 60 mL/L affected neither weight loss nor sensory quality of the fruit (firmness, total soluble solids, titratable acidity, acetaldehyde and ethanol content and flavor). Postharvest application of HF-Calibra^® could be an alternative to 2,4-D to avoid calyx senescence of citrus fruit induced by a degreening treatment and to maintain fruit quality.     

Integration of pre- and postharvest treatments for the control of black spot caused by Alternaria alternata in stored persimmon fruit

In Israel, black spot caused by Alternaria alternata is the main postharvest factor that impairs the quality and reduces the storability of persimmon fruit (Diospyros kaki cv. Triumph). The fungus infects the fruit in the orchard and remains quiescent until harvest. After harvest, the pathogen slowly colonizes the fruit during storage at 0 °C, which elicits black spot symptom development 2–3 months after storage entry. A commercial postharvest dip treatment in chlorine at 500 mg L^?1, released from sodium troclosene tablets, effectively controlled black spot in fruit stored for up to 2 months. However, decay incidence increased as the length of storage was extended beyond 2.5 months. The long incubation period that precedes black spot symptom development after harvest enabled the development of a series of integrative approaches for application at the pre- and postharvest stages, in combination with the commercial chlorine dip treatment, to improve the control of black spot disease. Preharvest treatments included treatment with the cytokinin-like N₁-(2-chloro-4-pyridyl)-N₃-phenylurea (CPPU) 30 d after fruit set, or a single spray with the curative fungicide polyoxin B 14 d before harvest, and when one of these was applied in combination with the postharvest chlorine dip treatment, the black spot infected area was reduced by 3 and 60%, respectively, compared with the chlorine dip alone. At the postharvest stage, fogging during storage, or post-storage on-line spraying with sodium troclosene, when applied in combination with the postharvest chlorine dip, improved the percentage of marketable fruit by 2 or 10%, respectively, compared with the chlorine dip alone. The results indicate that postharvest pathogens that show a slow colonization pattern might enable the integration of pre- and postharvest disease control methods to improve quality and reduce postharvest disease development.     

采前喷施壳聚糖和油菜素内酯对葡萄采后落果的影响

以新疆无核白葡萄为试材,采前喷施油菜素内酯（BRs）和壳聚糖（CH）,观察贮藏期葡萄落果率变化,并分析对葡萄品质和衰老相关酶活的影响。结果表明,两种处理在贮藏前期均能有效降低贮藏期葡萄落果率,壳聚糖效果好于油菜素内酯。二者均降低了果实酸度,提高了果实糖酸比,对果实总维生素C（抗坏血酸）含量没有影响,但明显提高了VC的还原度,使PG、POD和LOX等果实成熟衰老相关酶的活力高峰向后推迟了15～30天。推论BRs和CH可能是通过延迟无核白葡萄果实成熟衰老进程来减少落果,也暗示了无核白葡萄迅速的成熟可能是导致果实过早脱落的原因。     

Effect of combined application of heat treatments and plastic packaging on keeping quality of ‘Oroblanco’ fruit (Citrus grandis L.×C. paradisi Macf.)

Combinations of various heat treatments with individual fruit sealing, packaging in polyethylene liners or waxing were tested as means to control pathological and physiological spoilage of ‘Oroblanco’ fruit (Citrus grandis L.×C. paradisi Macf.). The following heat treatments were used: curing at 36°C for 72 h, hot water dip at 52°C for 2 min or ‘hot drench brushing’ at 52, 56 or 60°C for 10 s. The standard packinghouse treatment included waxing with addition of thiabendazole (TBZ) and 2,4- isopropyl ester. The fruit was stored for 2 weeks at 1°C (simulated low-temperature quarantine treatment), followed by 12–13 weeks at 11°C (simulated sea transportation to Japan) and 1 additional week at 20°C (simulated retail shelf-life period). The lowest weight loss and the highest firmness were observed with individually sealed fruit. Polyethylene liners were usually more efficient for weight loss control than waxing. However, the liner packaging enhanced the risk of postharvest disease development, if not accompanied by appropriate decay-controlling measures. Applying TBZ, hot water dip or curing controlled the development of postharvest pathogens, especially that of Penicillium molds. In another trial, both hot drench brushing at 56 or 60°C and hot water dip reduced decay incidence. Hot drench brushing at 60°C and hot water dip slowed fruit softening and reduced buttons abscission. In addition, the hot drench brushing at 60°C significantly delayed the loss of ‘Oroblanco’ green rind color, especially at the stylar and stem ends of the fruit. The hot dip at 52°C inhibited yellowing only when combined with individual seal-packaging.     

柑橘青霉病防治的研究进展

柑橘青霉病是柑橘采后在储藏和运输工程中的重要病害,可造成巨大的经济损失,主要由意大利青霉(Penicillium italicum)和指状青霉(P. digitatum)引起。为了更有效地预防和控制柑橘青霉病的发生和发展,为柑橘的运输和保存工作提供科学依据,本文归纳了柑橘青霉病的物理、化学和生物防治方法所采用的主要技术手段和制剂,分析并总结了不同防治措施的优缺点,提出了柑橘青霉病防治后续研究的方向及策略。指出深入探究柑橘青霉病菌的致病机制和生物源制剂对柑橘青霉病的防控机理,推进生物防治方法与化学或物理防治方法联用,能为新型药剂的开发和建立良好的综合防治管理策略奠定基础。     

Potassium sorbate effects on citrus weight loss and decay control

Potassium sorbate (PS) is a well-known and widely used food preservative. Among other applications, it is used as a GRAS fungistatic postharvest treatment for citrus, although its use is not free of significant adverse effects. In this paper, we study in detail the efficacy of wax containing increasing concentrations of PS to control Penicillium digitatum decay in citrus fruit, and its effect on fruit weight loss. Decay control and weight loss increased with the concentration of PS in the wax. Wax with typical amounts of 2–5% PS showed poor decay reduction indices (DRI), between 26% and 32%, whereas fruit weight loss increased compared with non-waxed controls. Waxing of fruit reduced weight loss by up to 40%, depending on wax formulation, but the addition of just 2% PS to the wax caused an increase in fruit weight loss of up to 65% compared with the waxed fruit. Similar results were observed for all the types of wax formulations tested. The hygroscopic effects of PS are even more damaging for citrus fruit with leaves. The leaves lose weight very rapidly when PS is added to the wax and they become desiccated in 24 h.We also present the results of a similar study where PS was applied to citrus as an aqueous treatment. When applied in water, PS was far more effective for decay control than when applied in wax, but there was also a considerable increase in fruit weight loss. A treatment combining aqueous PS with Fortisol^® Ca Plus biostimulant completely solved the problem of weight loss, these mixtures being commercially feasible treatments.     

光照对芦苇生物生产力及光合能力的影响

为研究水陆交错带优良造林材料芦苇(Phragmites australis)对光照环境的响应规律,选择水岸不同光照生境分布的芦苇种群为对象,测定分析光照强度对芦苇生长、生物量积累及光合能力的影响规律。本试验在野外原位观测全光照和林冠遮荫条件下芦苇株高、地径、叶片SPAD值以及叶绿素荧光参数的基础上,采用全株收获法进行不同器官生物量的室内测定。结果表明：（1）林冠遮荫条件下,芦苇株高、叶片生物量和茎生物量比全光照条件下分别高30.95%,56.08%和84.37%;芦苇株高与地径和茎干重达到极显著正相关水平,分别为0.692、0.875。（2）种光照条件下的芦苇叶片的SPAD值存在显著差异;林冠遮荫条件下,芦苇叶片SPAD值大于全光照条件下25.98%。（3）林冠遮荫条件下显著促进了芦苇叶绿素荧光参数Fm与PSII最大光化学量子产量Fv/Fm的值,分别高达34.14%、10.73%。     

Blue light alters infection by Penicillium digitatum in tangerines

The effect of blue light exposure on Penicillium digitatum infection of tangerines during postharvest storage was investigated. In citrus, P. digitatum is one of the most important fungi causing diseases that result in postharvest loss. There is increasing interest in development of environmentally sustainable and consumer-friendly strategies of decay control. Strategies based on a plant's immunity can minimize pathogen infection of fruit. Light signalling affects plant-pathogen interactions and blue light may modulate phospholipase activation, a key step in plant immune responses. Exposure of fruit to 410-540 nm blue light at a fluency of 40 μmol m⁻² s⁻¹ reduced infection by P. digitatum and induced phospholipase A₂ (PLA₂) gene expression. Inhibition of PLA₂ activity allowed infection, whereas inhibition of phospholipase D (PLD) expression by 580-670 nm red light at the same fluency was correlated with infection. These data strongly suggest that induction of lipid signalling by light reduces fungal colonization by P. digitatum in citrus fruit.     

Expression of expansin genes during postharvest lignification and softening of ‘Luoyangqing’ and ‘Baisha’ loquat fruit under different storage conditions

Four expansin cDNA fragments, EjEXPA1, EjEXPA2, EjEXPA3 and EjEXPA4, were isolated and characterized from loquat (Eriobotrya japonica Lindl.) fruit. EjEXPA1 mRNA accumulated consistently with the increase in fruit firmness in 0 °C storage of ‘Luoyangqing’ (LYQ) fruit, where chilling injury with increased fruit firmness due to lignification was observed. EjEXPA1 mRNA levels were lower in fruit that underwent low temperature conditioning (LTC, 6 d at 5 °C then 4 d at 0 °C), and in 1-methylcyclopropene (1-MCP) treated fruit, in both cases where chilling injury was alleviated. Fruit of the ‘Baisha’ (BS) cultivar soften after harvest rather than increase in firmness, and high expression levels of EjEXPA1 and EjEXPA4 accompanied the softening of BS fruit stored at 20 °C; such mRNA accumulation was much lower when fruit were stored at 0 °C, where softening was significantly inhibited by the low temperature. Very low expression of EjEXPA2 and EjEXPA3 was observed during storage of both LYQ and BS fruit under the different storage conditions. Our results showed that of the four genes characterized, EjEXPA1 might be associated with chilling-induced lignification while both EjEXPA1 and EjEXPA4 were closely related to softening of loquat fruit during the postharvest period.     

Essential oil amended coatings as alternatives to synthetic fungicides in citrus postharvest management

A new approach to the control of postharvest pathogens, while maintaining fruit quality, has been implemented by the application of essential oil amended coatings to citrus. This approach eliminates the need for synthetic fungicides, thereby complying with consumer preferences, organic requirements and reducing environmental pollution. In vitro studies indicated that the essential oils and some of the terpenoid components tested were active against Penicillium digitatum. In a series of subsequent semi-commercial and commercial trials, Mentha spicata and Lippia scaberrima essential oils, as well as pure (d)-limonene and R-(−)-carvone were incorporated into a variety of commercial citrus coatings. These amended coatings were applied postharvest to ‘Tomango’ oranges in the absence of the standard fungicide dip. Excellent disease control was achieved with the amended coatings, while measured quality parameters indicated that overall fruit quality was maintained. Moreover, moisture loss was decreased significantly in fruit treated with essential oil enriched coatings. The efficacy of amended coatings as a viable alternative or supplement to existing fruit protection strategies was demonstrated in a commercial trial.     

Superoxide anion and hydrogen peroxide in the yeast antagonist–fruit interaction: A new role for reactive oxygen species in postharvest biocontrol?

The importance of reactive oxygen species (ROS) in plant defense responses against certain pathogens is well documented. There is some evidence that microbial biocontrol agents also induce a transient production of ROS in a host plant which triggers local and systemic defense responses to pathogens. The ability of biocontrol agents used to control postharvest diseases to induce defense-related oxidative responses in fruits, however, has not been explored. Here we show that the yeast antagonists, Metschnikowia fructicola (strain 277) and Candida oleophila (strain 182) generate greater levels of super oxide anion (O₂⁻) on intact fruit surfaces (poor in nutrients) then those applied on a nutrient-poor agar medium. Even though yeast antagonists show a high level of O₂⁻ on nutrient-rich media, when applied on fruits around wounds (areas abundant in nutrients) accumulation of O₂⁻, as detected by nitro blue tetrazolium staining, occurred much more rapidly on the latter. Using laser scanning confocal microscopy we observed that the application of M. fructicola and C. oleophila into citrus and apple fruit wounds correlated with an increase in H₂O₂ accumulation in host tissue. In citrus fruit, the level of H₂O₂ around inoculated wounds increased by 4-fold compared to controls (wounds inoculated with water) as early as 18 h after inoculation. Yeast continued to stimulate H₂O₂ production in citrus fruit up to 66 h after inoculation and H₂O₂ levels were still 3-fold above the control. Living yeast cells were detected in fruit wounds at this time point indicating the ability of M. fructicola to tolerate host ROS, which has been reported to be an intrinsic characteristic of efficient yeast antagonists. Similar increase in H₂O₂ accumulation around yeast-inoculated wounds was observed in apple fruit exocarp. The present data, together with our earlier discovery of the importance of H₂O₂ production in the defense response of citrus flavedo to postharvest pathogens, indicate that the yeast-induced oxidative response in fruit exocarp may be associated with the ability of specific yeast species to serve as biocontrol agents for the management of postharvest diseases.     

1-MCP结合自发气调包装对‘空心李’果实软化和细胞壁代谢的影响

探讨果实软化与细胞壁代谢之间的关系及1-甲基环丙烯(1-MCP)结合自发气调包装(MAP)对果实软化的调控机制,为生产中李果实软化问题提供理论依据和技术参考。笔者以贵州省特色果品‘空心李’为试材,通过测定果实的硬度、细胞壁代谢成分和细胞壁代谢酶活性的变化,研究1-MCP、MAP及两者结合(1-MCP+MAP)对(20±1)℃下果实软化的抑制效应。结果表明：（1）与对照（直接放于纸箱内）相比,1-MCP、MAP及1-MCP+MAP处理抑制了果实硬度下降,原果胶和纤维素降解,抑制了多聚半乳糖醛酸酶(PG)、果胶甲脂酶(PME)和纤维素酶(Cx)活性增加,抑制效果为1-MCP+MAP>1-MCP>MAP。（2）果实硬度的下降与原果胶和纤维素含量呈显著正相关,与可溶性果胶含量关系表现不一,1-MCP和1-MCP+MAP处理与可溶性果胶含量呈显著负相关,而对照和MAP处理与可溶性果胶含量没有表现出明显的相关性。1-MCP、MAP、1-MCP+MAP处理和对照果实硬度的下降与PG和PME活性存在显著负相关,对照和MAP处理的果实硬度与Cx活性表现显著负相关,1-MCP和1-MCP+MAP处理果实硬度与Cx活性没有表现相关性。1-MCP结合MAP对沿河‘空心李’果实硬度下降、细胞壁物质降解及其相关酶活性有显著抑制作用,能够抑制‘空心李’果实软化,延长保鲜时间,减少采后损失。