Release of acetaldehyde from beta-cyclodextrins inhibits postharvest decay fungi in vitro

Many naturally occurring plant volatiles are known to have antifungal properties. However, they have limited use because they diffuse rapidly in air. In this in vitro study, acetaldehyde was chosen as a prototype volatile in order to study the controlled release of antifungal volatiles from cyclodextrins (CD). The major postharvest pathogens Alternaria alternata, Botrytis cinerea, and Colletotrichum acutatum were exposed to the pure volatile for 7 days at 23 degrees C. Acetaldehyde was most effective against A. alternata, followed by C. acutatum, and B. cinerea, with 0.12, 0.56, and 1.72 microL/L in air being required to inhibit fungal growth, respectively, according to the bioassay developed. Second, the effectiveness of the new beta-CD-acetaldehyde release system was evaluated against A. alternata for 7 days at 23 degrees C. Sufficient volatile was released from 0.7 g of beta-CD-acetaldehyde to prevent fungal growth in vitro.     

Off-vine grape drying effect on volatile compounds and aromatic series in must from Pedro Ximénez grape variety

Changes in 36 volatile compounds of must from ripe grapes dried by direct exposure to sun and must from ripe grapes were studied. Compounds not dependent on sampling site in both musts were selected, and their concentration/Brix degree ratio values, were subjected to variance analysis. Only butan-1-ol and isoamyl alcohols showed no differences, while (E)-hex-3-en-1-ol, (Z)-hex-3-en-1-ol, (E)-hex-2-en-1-ol, (E)-hex-2-enal, hexanoic acid, isobutanol, benzyl alcohol, 2-phenylethanol, gamma-butyrolactone, gamma-hexalactone, and 5-methylfurfural, showed significant differences between the two must types, which may be ascribed to the drying process. An approach to describe must odor has been carried out by grouping volatile compounds in aromatic series, increasing their values in the fruity, solvent, sweet, and roasted series and diminishing the herbaceous as a consequence of the drying process.     

草莓叶主要挥发性物质的测定及其对草莓球腔菌的抑菌效果

为探究草莓叶片中挥发性物质对草莓球腔菌的抑菌作用,本研究测定了草莓叶片中主要挥发性物质,并以草莓球腔菌为处理对象,研究草莓叶片主要挥发性物质对其孢子萌发、菌丝生长以及线粒体膜电位的影响。结果表明,草莓叶片挥发性物质中的萜类化合物主要组分为芳樟醇、桃金娘烯醇,C6醛类化合物主要组分为己醛、2-己烯醛、反式-2-己烯醛、顺式-3-己烯醛等。当芳樟醇、桃金娘烯醇浓度为50 μL·L^-1,己醛浓度为5 μL·L^-1, 反式-2-己烯醛浓度为0.5 μL·L^-1,顺式-3-己烯醛浓度为5 μL·L^-1 熏蒸处理草莓球腔菌时,能显著抑制病原菌孢子的萌发和菌丝生长,并能使病原菌线粒体膜电位下降,从而抑制草莓球腔菌的生长且对草莓叶片无明显损伤。研究表明利用适宜浓度的芳樟醇、桃金娘烯醇、己醛、反式-2-己烯醛、顺式-3-己烯醛熏蒸处理,能够有效抑制草莓球腔菌的生长。本研究为研制新型天然植物病害抑菌剂提供了依据。     

碳酸铵对意大利青霉的作用机制及对不同柑橘果实品质的影响

为了寻求一种安全有效的方法防治由意大利青霉（Penicillium italicum）引起的柑橘青霉病，该研究分析了碳酸铵作为通常认为安全的药剂抑制意大利青霉生长的可能作用机制及对脐橙、皇帝柑、沃柑3种不同类型柑橘贮藏品质的影响。结果表明，碳酸铵能抑制意大利青霉孢子萌发和菌丝生长，且呈现剂量依赖效应，在质量浓度分别为 0.4 g/L和0.8 g/L时可完全抑制孢子萌发和菌丝生长。结构观察表明，碳酸铵引起菌丝生长节点稀疏和分支减少；超微结构观察发现菌丝严重皱缩，菌丝线粒体结构异常。生理生化分析表明，碳酸铵处理，引起线粒体的钠/钾离子ATP酶（Na+/ K+-ATPase）、钙离子ATP酶（Ca2+-ATPase）和镁离子ATP酶（Mg2+-ATPase）活性下降，导致还原型谷胱甘肽（Reduced Glutathione，GSH）含量及谷胱甘肽还原酶（Glutathione Reductase，GR）活性降低，活性氧清除体系超氧化物歧化酶（Superoxide Dismutase，SOD）、过氧化氢酶（Catalase，CAT）、过氧化物酶（Peroxidase，POD）活性紊乱，促进H2O2积累。添加活性氧清除剂半胱氨酸（Cysteine，Cys）能部分恢复碳酸铵处理的病菌孢子萌发。活体接种表明，16 g/L碳酸铵处理显著减小了柑橘果实接种意大利青霉的病斑直径（P<0.05），减轻果实发病。碳酸铵处理能降低3种类型柑橘果实自然发病率，且对果实失重率、色泽、可溶性固形物、可滴定酸、维生素C、还原糖含量无不良影响。结果表明，碳酸铵通过损伤意大利青霉菌丝线粒体结构和功能，促进活性氧积累来发挥抗真菌活性，碳酸铵可以作为杀菌剂的绿色有效替代方法，研究结果为碳酸铵防治柑橘果实采后腐烂提供参考。     

Possible contributions of volatile-producing bacteria to soil fungistasis

Soil fungistasis can adversely affect the germination and growth of most fungal species in the field. Among the inhibitors, volatiles of microbial origins are potentially very important. In this study, we investigated the frequency and identity of bacteria producing fungistatic volatiles. Among the 1018 bacterial isolates tested, 328 were found to produce antifungal volatiles that could inhibit spore germination and mycelial growth of two nematicidal fungi Paecilomyces lilacinus and Pochonia chlamydosporia. A phylogenetic analysis based on restriction fragment length polymorphism (RFLP) and 16S rDNA sequence placed the 328 bacteria in five groups: Alcaligenaceae, Bacillales, Micrococcaceae, Rhizobiaceae and Xanthomonadaceae. Volatile compounds of 39 bacterial isolates were identified by gas chromatography/mass spectrum (GC/MS). Tests with commercially available antifungal compounds suggested that seven volatile compounds of bacterial origins (acetamide, benzaldehyde, benzothiazole, 1-butanamine, methanamine, phenylacetaldehyde and 1-decene) likely play important roles in soil fungistasis.     

Identification and use of potential bacterial organic antifungal volatiles in biocontrol

Bacteria, isolated from canola and soybean plants, produced antifungal organic volatile compounds. These compounds inhibited sclerotia and ascospore germination, and mycelial growth of Sclerotinia sclerotiorum, in vitro and in soil tests. Ascospore germination in cavity slides was inhibited 54-90% by the volatile producers. When mycelial plugs or the sclerotia, exposed to these volatiles, were transferred to fresh agar plates, the pathogen could not grow, indicating the fungicidal nature of the volatiles. Head space volatiles, produced by bacteria, were trapped with activated charcoal, by passing nitrogen continuously over shake cultures for 48 h. The compounds were eluted from the charcoal with methylene chloride and identified using Gas Chromatography-Mass Spectrometry (GC-MS). The volatile compounds included aldehydes, alcohols, ketones and sulfides. Of the 23 compounds assayed for antifungal activity in divided Petri plates, with filter-disks soaked with these compounds (100 and 150 μl), only six compounds completely inhibited mycelial growth or sclerotia formation, suggesting their potential role in biological control. The compounds are benzothiazole, cyclohexanol, n-decanal, dimethyl trisulfide, 2-ethyl 1-hexanol, and nonanal. Volatiles may play an important role in the inhibition of sclerotial activity, limiting ascospore production, and reducing disease levels. Studies are under way to understand this phenomenon under field conditions. This is the first report on the identification and use of bacterial antifungal organic volatiles in biocontrol.     

Analysis of volatiles in porcine liver pâtés with added sage and rosemary essential oils by using SPME-GC-MS

The effect of the addition of two natural antioxidant extracts (sage and rosemary essential oils) and one synthetic (BHT) on the generation of volatile compounds in liver patés from Iberian and white pigs was analyzed using SPME-GC-MS. Lipid-derived volatiles such as aldehydes [hexanal, octanal, nonanal, hept-(Z)-4-enal, oct-(E)-2-enal, non-(Z)-2-enal, dec-(E)-2-enal, deca-(E,Z)-2,4-dienal] and alcohols (pentan-1-ol, hexan-1-ol, oct-1-en-3-ol) were the most abundant compounds in the headspace of porcine liver patés. Patés from different pig breeds presented different volatiles profiles due to their different oxidation susceptibilities as a probable result of their fatty acid profiles and vitamin E content. Regardless of the origin of the patés, the addition of BHT successfully reduced the amount of volatiles derived from PUFA oxidation. Added essential oils showed a different effect on the generation of volatiles whether they were added in patés from Iberian or white pigs because they inhibited lipid oxidation in the former and enhanced oxidative instability in the latter. SPME successfully allowed the isolation and analysis of 41 volatile terpenes from patés with added sage and rosemary essential oils including alpha-pinene, beta-myrcene, 1-limonene, (E)-caryophyllene, linalool, camphor, and 1,8-cineole, which might contribute to the aroma characteristics of liver patés.     

Effect of 1-methylcyclopropene on volatile emission and aroma in cv. Anna apples

The rapidly ripening summer apple cultivar Anna was treated with 0.1 micro L(-1) and 1 microL L(-1) 1-methylcyclopropene (MCP) at harvest and kept at 20 degrees C, or stored for 5 weeks at 0 degrees C and then transferred to 20 degrees C. Total volatiles were not reduced by treatment with 0.1 microL L(-1) MCP, but were 70% lower in fruits treated with 1 microL L(-1) MCP than in untreated fruits. Ethylene production was 50% and 95% inhibited by 0.1 microL L(-1) and 1 microL L(-1) MCP, respectively. The volatiles produced by fruit at harvest were predominantly aldehydes and alcohols, with some acetate esters as well as 2-methyl butyl acetate and beta-damascenone. During ripening, the acetate and butyrate esters increased greatly and alcohols and aldehydes decreased. MCP-treated apples retained more alcohols, aldehydes, and beta-damascenone volatiles than did untreated apples. Sensory evaluation found that control and 0.1 microL L(-1) treated apples developed more fruity, ripe, and overall aromas, but the preference was for the 1 microL L(-1) treated apples with a less ripe aroma.     

pH modulation of zopfiellin antifungal activity to Colletotrichum and Botrytis

Zopfiellin, a novel cyclooctanoid natural product isolated from Zopfiella curvata No. 37-3, was evaluated in a 96-well microtiter assay for fungicidal activity against Botrytis cinerea, Colletotrichum acutatum, Colletotrichum fragariae, Colletotrichum gloeosporioides, and Fusarium oxysporum. Zopfiellin exhibited pH-dependent activity, with the most mycelial growth inhibition demonstrated at pH 5.0. Mass spectrometry and nuclear magnetic resonance spectroscopy studies indicated that zopfiellin undergoes structural changes with changes in pH. At pH 5.0, zopfiellin showed the greatest activity against B. cinerea (IC(80) = 10 microM), C. gloeosporioides (IC(80) = 10 microM), and C. fragariae (IC(80) = 10 microM) and intermediate activity against C. acutatum (IC(80) = 30 microM), and was not active against F. oxysporum (IC(80) > 100 microM).     

Evaluation of key aroma compounds in hand-squeezed grapefruit juice (Citrus paradisi Macfayden) by quantitation and flavor reconstitution experiments

Twenty-five odor-active compounds were quantified in the fresh, hand-squeezed juice of White Marsh seedless grapefruits using stable isotope dilution assays. By calculation of the odor activity values of the odorants (ratio of their concentrations in the juice to their odor thresholds in water) it was shown that the fruity esters ethyl 2-methylpropanoate, ethyl butanoate, and (S)-ethyl 2-methylbutanoate, and the fruity, sweet winelactone, as well as the grassy smelling (Z)-hex-3-enal, and trans-4,5-epoxy-(E)-dec-2-enal with metallic odor, were among the most potent odorants of the fresh grapefruit juice. The typical sulfurous, grapefruit-like odor quality was mainly due to the catty, blackcurrant-like 4-mercapto-4-methylpentan-2-one and the grapefruit-like smelling 1-p-menthene-8-thiol. These findings were confirmed by reconstitution experiments to simulate the aroma of the fresh grapefruit juice.     

Effects of cyclamen mite (Phytonemus pallidus) and leaf beetle (Galerucella tenella) damage on volatile emission from strawberry (Fragaria x ananassa Duch.) plants and orientation of predatory mites (Neoseiulus cucumeris, N. californicus, and Euseius finlandicus)

Volatile emission profile of strawberry (Fragaria x ananassa Duch.) plants (cvs. Polka and Honeoye) damaged by cyclamen mite (Phytonemus pallidus Banks) or leaf beetle Galerucella tenella (L.) (cv. Polka) was analyzed to determine the potential of these strawberry plants to emit herbivore-induced volatiles. The total volatile emissions as well as emissions of many green leaf volatiles (e.g., (Z)-3-hexen-1-ol and (Z)-3-hexenyl acetate) and methyl salicylate were greater from cyclamen mite-damaged strawberry plants than from intact plants. Leaf beetle feeding increased emissions of monoterpenes (Z)-ocimene and (E)-beta-ocimene, sesquiterpenes (E)-beta-caryophyllene, (E,E)-alpha-farnesene, and germacrene-D, and a homoterpene (3E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) significantly. Nevertheless, the na?ve generalist predatory mites, Neoseiulus cucumeris, Neoseiulus californicus, and Euseius finlandicus did not prefer P. pallidus- or G. tenella-damaged plants over intact plants in a Y-tube olfactometer, suggesting that these predatory mite species are not attracted by the herbivore-induced volatiles being released from young strawberry plants.     

Identification of the Solanum nigrum extract component involved in controlling cabbage black leaf spot disease

In this study, we discovered that an ethanol (EtOH) extract of Solanum nigrum inhibited spore germination of Alternaria brassicicola, the causative agent of cabbage black leaf spot disease. At a concentration of 500 mg/L, this ethanol extract also caused the germ tubes to become completely swollen. Detached cabbage leaves were then used to evaluate the effects of the extract in controlling the disease. It was observed that the extract-induced swelling of A. brassicicola germ-tube spores did not cause the symptoms of black spot disease on cabbage leaves. Furthermore, an n-butanol fraction of the EtOH extract exhibited strong antifungal activity; at a concentration of 25 mg/L, a derived subfraction (Bu-11-13) showed complete inhibition of spore germination. A white powder was collected from fraction Bu-11-13, and its minimum inhibitory concentration was determined to be 8 mg/L. Using NMR and LC-MS/MS analysis, this white powder compound was identified as degalactotigonin.     

Antimycotic activities of selected plant flora,growing wild in Lebanon,against phytopathogenic fungi

Petroleum ether (PE) and methanolic extracts of nine wild plant species were tested in vitro for their antimycotic activity against eight phytopathogenic fungi. The efficacy of PE extracts against all pathogens tested was higher than that of methanolic extracts. Wild marjoram (Origanum syriacum) PE extract showed the highest and widest range of activity. It resulted in complete inhibition of mycelial growth of six of eight fungi tested and also gave nearly complete inhibition of spore germination of the six fungi included in the assay, namely, Botrytis cinerea, Alternaria solani, Penicillium sp., Cladosporium sp., Fusarium oxysporum f. sp. melonis, and Verticillium dahlia. The other plant extracts showed differential activities in the spore germination test, but none was highly active against mycelial growth. Inula viscosa and Mentha longifolia were highly effective (>88%) in spore germination tests against five of six fungi tested, whereas Centaurea pallescens, Cichorium intybus, Eryngium creticum, Salvia fruticosa, and Melia azedarach showed >95% inhibition of spore germination in at least two fungi. Foeniculum vulgare showed the least antimycotic activity. Fractionation followed by autobiography on TLC plates using Cladosporium sp. as a test organism showed that O. syriacum PE extracts contained three inhibition zones, and those of Inula viscosa and Cichorium intybus, two, whereas the PE extracts of the remaining plants showed each one inhibition zone. Some of the major compounds present in these inhibition zones were identified by GC-MS. The possibility for using these extracts, or their mixtures, to control plant diseases is discussed.     

Plant growth promoting properties of a strain of Enterobacter ludwigii isolated from Lolium perenne rhizosphere

The capability of native bacterial strains isolated from Lolium perenne rhizosphere to behave as plant growth promoting bacteria and /or biocontrol agents was investigated. One strain (BNM 0357) over 13 isolates from the root tips of L. perenne resulted proved to be nitrogenase positive (ARA test) and an IAA producer. Conventional tests and the API 20E diagnostic kit indicated that BNM 0357 behaves to the Enterobacteriaceae family and to the Enterobacter genus. Molecular identification by 16S rRNA sequence analysis indicated that BNM 0357 had the highest similarity to Enterobacter ludwigii (EN-119). Isolate BNM 0357 had the capability to solubilize calcium triphosphate and to antagonize Fusarium solani mycelial growth and spore germination. Strain BNM 0357 also showed the ability to improve the development of the root system of L. perenne. This study disclosed features of E. ludwigii BNM 0357 that deserve further studies aimed at confirming its putative importance as a PGPR.     

High chlorogenic and neochlorogenic acid levels in immature peaches reduce Monilinia laxa infection by interfering with fungal melanin biosynthesis

Chlorogenic acid (CGA) and its isomer, neochlorogenic acid (NCGA), were found to be the major phenolic compounds in the flesh and peel of three peach cultivars. Their concentrations are especially high in immature fruits (CGA, 151-548 mg/kg; NCGA, 85-380 mg/kg), whose resistance to the brown rot fungus, Monilinia laxa , is very high. The concentrations of these two phenolic compounds decline in maturing fruits (CGA, 77-181 mg/kg; NCGA, 30-82 mg/kg), and this decline is associated with a concomitant increase in susceptibility to brown rot infection. Other phenolic compounds found in the same HPLC chromatograms at 340 nm from each peach extract at varying sampling dates in each of the three peach cultivars were not correlated with the incidence of brown rot and appeared only in some cultivars. The incidence of brown rot for each cultivar at each sampling date was significantly negatively correlated with the NCGA (r > -0.85) and CGA (r > -0.90) contents. At concentrations that are similar to those in peach fruit, CGA does not inhibit spore germination or mycelial growth of M. laxa in culture but markedly inhibits the production of melanin-like pigments in the mycelia of M. laxa in culture (42% melanin reduction). Accordingly, we propose that the high concentrations of CGA and NGA in immature fruits might contribute to their reduced susceptibility or increased resistance to brown rot infection by interfering with fungal melanin production.     

Impact of 1-methylcyclopropene and methyl jasmonate on apple volatile production.

Climacteric Fuji apples were treated with 10 microL x L(-1) MCP (1-methylcyclopropene), 2 mmol x L(-1) MJ (methyl jasmonate), or a combination of 10 microL x L(-1) MCP and 2 mmol x L(-1) MJ. Fruit were kept at 20 degrees C for 15 days after treatment. Production of ethylene and other volatile compounds was measured prior to and 3, 7, 11, and 15 days after treatment. Ethylene production decreased 3 days following MJ treatment and then increased. MCP treatment alone or in combination with MJ inhibited ethylene production. MJ and MCP inhibited production of many volatile alcohols and esters. The production of individual alcohols and esters appears to be differentially inhibited by MJ or MCP. MJ and MCP inhibited not only production of alcohols but also formation of esters from alcohols.     

丁香精油对甜樱桃采后优势致腐真菌的控制及其抑菌机理

为探明植物精油对甜樱桃采后优势致病菌的抑菌效力及抑菌机理,以山东泰安地区主栽品种红灯为试验材料,从自然腐烂的甜樱桃果实上分离纯化优势致病菌,采用形态学方法并结合ITS序列法进行鉴定,选用丁香精油从体外熏蒸和接触2种作用方式研究其对主要病原真菌的抑菌效果。结果表明,甜樱桃采后的3种主要致腐真菌分别为灰葡萄孢菌(Botrytis cinerea)、链格孢菌(Alternaria alternata)和胶孢炭疽菌(Colletotrichum gloeosporioides);体外抑菌试验表明,一定浓度的丁香精油能显著抑制3种致病菌的菌丝生长和孢子萌发,熏蒸处理较接触效果更好,对B. cinerea、 A. alternata和C. gloeosporioides的最小抑菌浓度(MIC)分别为120、100和100 μL·L^-1;试验还表明丁香精油破坏了菌丝形态,其抑菌机理可能与精油疏水性造成的微生物膜系统结构破坏、及胞内主要内容物流失有关。综上所述,丁香精油作为甜樱桃贮藏前的熏蒸剂具有较好的应用潜力。     

Active package for wild strawberry fruit (Fragaria vesca L.)

An antimicrobial active package has been developed to improve the safety and quality of wild strawberries, as well as extending their shelf life. The fruits were packed in equilibrium-modified atmosphere packaging (EMAP), and the effect on Botrytis cinerea growth and on the quality parameters of the fruit by the addition of different amounts of 2-nonanone, an antifungal volatile compound naturally present in strawberries, was investigated during storage at 10 and 22 degrees C. The temperature of 10 degrees C was chosen as the temperature used at points of sale, and 22 degrees C was chosen as the control temperature. Fungal growth was inhibited in all cases, possibly due to the synergistic effect of high CO2 partial pressures and the presence of the antifungal compound. Weight, soluble solids, titrable acidity, and anthocyanin losses were retarded by the presence of 2-nonanone. This effect was more pronounced as the 2-nonanone concentration was increased at both temperatures. Therefore, an active package that releases 2-nonanone inhibits fungal decay and delays the senescence of highly perishable wild strawberry fruit.     

Lipoxygenase and hydroperoxide lyase activities in ripening strawberry fruits

The enzymes lipoxygenase and hydroperoxide lyase have been identified in strawberry (Fragariax ananassa Duch.) var. Camarosa. Their subcellular localization, substrate preference, and product specificity were determined in mature strawberry fruits. The activity of both enzymes was located mainly in the microsomal fraction. Linolenic acid was the preferred substrate for strawberry lipoxygenase, forming 13- and 9-hydroperoxides of this acid in the proportion 70:30. The strawberry hydroperoxide lyase cleaves 13-hydroperoxide of linoleic (13% relative activity) and linolenic (100% relative activity) acids to form hexanal and (3Z)-hexenal, respectively. Both enzyme activities and endogenous content of volatile aldehydes formed by sequential action of lipoxygenase-hydroperoxide lyase were evaluated during strawberry development and ripening. A sequential enzymatic pathway for the formation of green odor compounds in strawberry is proposed.     

土壤微生物制剂防治草莓连作病害的研究

木霉T42与枯草芽孢杆菌Bs-6对引起草莓连作病害的主要病原菌尖孢镰刀菌和立枯丝核菌有明显的拮抗作用.应用实验表明,由T42与Bs-6组成的复合生物制剂能显著促进连作草莓的营养生长和生殖生长,连作草莓的死苗率由52.9%降低到8.2%,产量增加111%,果实品质显著提高.