生防细菌复配对苹果主要病原真菌抑菌活性筛选及其稳定性

采用生长速率法测定4种生防细菌及其复配对5种苹果主要病原菌的抑制效果，并将筛选出的最佳复配生防细菌发酵液进行稳定性测定。结果表明，单一生防细菌发酵液中多粘类芽孢杆菌FS-1206对苹果树腐烂病菌的抑菌效果最好，为78.19%；当多粘类芽孢杆菌FS-1206与解淀粉芽孢杆菌TS-1203复配比例为 2∶1时，其对苹果树腐烂病菌的抑菌率高达86.64%，抑菌效果显著优于单一生防细菌发酵液。稳定性测定结果表明，复配生防细菌（FS-1206∶TS-1203= 2∶1）发酵液在紫外照射、高温和强酸强碱环境条件下，其抑菌活性均具有良好的稳定性。     

九里香层析物的抑菌活性及成分分析

以石油醚为洗脱液，对九里香氯仿萃取物进行硅胶柱层析分离，得到27个组分。采用生长速率法测定九里香层析物对5种供试病原菌的抑制作用。结果表明，在质量浓度为0.5 g/L时，组分26对5种供试病原菌有较好的抑制活性，对香蕉炭疽菌的抑制率达到89.46%，对香蕉炭疽菌的EC50为0.078 6 g/L。GC-MS分析表明，组分26的主要成分是7-甲氧基-8-异戊烯基香豆素，占92.00%。     

Synergism between potassium sorbate dips and brief exposure to high CO2 or O2 at curing temperature for the control of citrus postharvest green and blue molds

Synergistic effects and very effective control of citrus postharvest green and blue molds, caused by Penicillium digitatum and Penicillium italicum, respectively, were observed on artificially inoculated ‘Valencia’ oranges and ‘Clemenules’ and ‘Ortanique’ mandarins after a potassium sorbate (PS) treatment was followed by 2 days of storage in atmospheres of elevated CO₂ or O₂ at a curing temperature. A combined treatment consisting of 60-s dips in aqueous solutions of 3% PS heated to 62 °C was followed by 48-h exposure to air, 15 kPa CO₂ or 30 kPa O₂ at 33 °C. Control treatment was a 60-s water dip at 20 °C followed by 24-h exposure to air at 20 °C. Synergism was observed on citrus fruit either incubated at 20 °C for up to 22 days, simulating direct commercialization, or stored at 5 °C for up to 45 days, simulating commercial cold storage. This research offers potential new tools to the citrus industry for implementation of nonpolluting integrated postharvest disease management programs, especially devoted to high added value organic markets or export markets with zero residue tolerance.     

Chemical composition and antifungal activity of cuticular wax isolated from Asian pear fruit (cv. Pingguoli)

In order to understand the cuticular wax properties of Asian pear fruits (cv. Pingguoli), a series of assays was conducted on extraction, fractionation and determination of composition. The results showed that the maximum yield of wax from the fruit was obtained by chloroform/methanol (3:1), and then by chloroform extraction. Polar and low polar fractions occupied 64.3% and 26.9% of total crude wax by column chromatography. 54 and 22 components were identified in polar and low polar fractions by GC/MS, respectively. Long-chain fatty acids and triterpenoids predominated in polar fraction and n-alkanes were predominant in low polar fraction. In vitro tests indicated that polar fraction, low polar fraction and total crude wax inhibited spore germination and mycelial growth of Alternaria alternata, which is a causal agent of Alternaria rot of pears, and the maximum inhibition was obtained by polar fraction. These findings indicated that n-alkanes in low polar fraction and triterpenoids, fatty acid in polar fraction might have contributed to the antifungal properties of pear fruit cuticular waxes.     

Morphological evidences for onion-induced growth inhibition of Trichophyton rubrum and Trichophyton mentagrophytes

The antifungal activity of onion (Allium cepa L.) on two important dermatophytes, Trichophyton rubrum and Trichophyton mentagrophytes, with special reference to morphological aspects was studied. Growth of both fungi was found to be strongly inhibited by aqueous onion extract (AOE) as a dose-dependent manner. The extract showed fungicidal effect for both fungi at concentrations >3.12% (v/v). The fungus T. mentagrophytes was more affected by the onion as compared to T. rubrum at all concentrations used. Morphological effects of onion exposure were examined in correlation with fungal growth. Corresponding to the growth inhibition, light and electron microscopy observations revealed morphological anomalies in hyphal compartments. The results demonstrated that AOE targets the cell membrane of the fungi as breaking down of both inner and outer membranes with consequent extrution of materials into the surrounding medium. Cytoplasmic membranes and other membranous structures of organelles, such as nuclei and mitochondria, were also disrupted. In correlation to the fungal growth, morphological alterations occurred to a less content for T. rubrum compared with T. mentagrophytes. The hyphae of T. rubrum were found to be mainly affected by converting to resistant forms, i.e., chlamidospores as a consequence of phenotype switching response to AOE. Plasmolysis accompanied by an almost complete depletion and disorganization of cytoplasmic structures were found to be the final event which led to cell death. Ultrastructural evidences obtained from this study strongly support that morphological changes of T. rubrum and T. mentagrophytes caused by AOE are associated with its fungistatic and fungicidal activities. With respect to the morphological results and the preliminary data on fungal biochemistry, a mechanism of action by interacting of AOE with thiol (-SH) groups present in essential compartments of the fungal cells was postulated.     

Activity of Berberis aetnensis root extracts on Candida strains

The antifungal activity of methanolic extract and alkaloidal fraction of Berberis aetnensis against Candida species was investigated. The crude extract was active against Candida species, this activity being higher than that of the alkaloidal fraction and berberine.     

Comparison of chitosans with different molecular weights as possible wood preservatives

Fungi cause serious problems in wood utilization, and environmentally benign wood protection is required as an alternative to traditional chemicals. Chitosan has shown promising antimicrobial properties against several microorganisms. In this study, we present the characterization of and antifungal properties of a commercial chitosan formulation developed for impregnation of wood. A broad range of chemical and mycological methods were used to evaluate the uptake, fixation, and antifungal properties of chitosan for wood preservation. The results show that the higher the uptake of chitosan the lower the relative recovery of chitosan in wood after leaching, and the higher the molecular weight of chitosan the higher the recovery. Chitosan with high molecular weight proved to be more efficient against decay fungi than chitosan with low molecular weight. The fungi tested on chitosan-amended nutrient agar medium were totally inhibited at 1% (w/v) concentration. In decay studies using small wood blocks, 4.8% (w/v) chitosan concentration gave the best protection against brown rot fungi.     

苦参对辣椒枯萎病的抑菌活性

[目的]探讨苦参对辣椒枯萎病的抑菌活性。[方法]采用生长速率法和悬滴法测试不同溶剂、浓度苦参提取物对辣椒枯萎病菌的抑制作用。[结果]乙酸乙酯与丙酮提取苦参所得粗提物的抑菌率显著高于乙醇。随着苦参乙酸乙酯粗提液浓度的增大,其对枯萎病病菌菌丝生长及孢子萌发抑制作用均显著增强;在质量浓度为40 g/L时,其对辣椒枯萎菌菌丝生长、孢子萌发抑制率分别达到94.48%、89.01%。[结论]苦参根中所含活性物质对辣椒枯萎病的抑菌活性较强,具有进一步研究开发的价值。     

Effects of middle-viscosity chitosan on Ramularia cercosporelloides

The inhibitory properties of middle-viscosity Chitosan on the growth of fungus Ramularia cercosporelloides were studied in vitro. The inhibitory concentration that delayed 50% of the radial growth (IC₅₀) was 3.4 g l⁻¹ for middle-viscosity Chitosans with molecular weights of about 133 and 187 kDa (middle molecular weight) dissolved in lactic and acetic acids, respectively. At 96 h of incubation and under the same growing conditions, inhibitions of 91.79% and 73.13% of the radial growth of the fungus were observed when 3.4 g l⁻¹ of Chitosan was dissolved in 0.05 M acetic and 0.05 M lactic acid, respectively. The biomass production was significantly lower than that observed in the controls at 72 h. Based on these in vitro results; Chitosan could be a good alternative to control the disease caused by R. cercosporelloides on safflower.     

蒿属植物提取物对棉花枯萎病菌和红腐病菌的抑制活性研究

在实验条件下,采用菌丝生长速率测定法,以棉花枯萎病菌、棉红腐病菌为供试菌,对茵陈、黄蒿、艾蒿等3种蒿属植物提取物的抗菌活性进行了研究。结果表明,供试3种蒿属植物提取物对棉花枯萎病菌和棉花红腐病菌均具有较好的抗菌活性,其中尤以艾蒿提取物的抗菌活性强而稳定,48~96h对上述两病菌的菌丝抑制率均达80%以上;丙酮提取物的抗菌活性强于乙醇提取物,前者的EC50为1.4785 mg/L ,后者的为3.2090 mg/L。间歇振荡法、超声波法、冷浸法提取物对供试菌的72h菌丝抑制率分别为84.34% 、84.56%、88.7% ,可见同种溶剂不同提取方法所得提取物抗菌活性基本一致。