Inhibitory influence of inorganic salts on banana postharvest pathogens and preliminary application to control crown rot

Lasiodiplodia theobromae, Thielaviopsis paradoxa, Colletotrichum musae, C. gloeosporioides, Fusarium verticillioides, and F. oxysporum were screened in vitro for sensitivity to Na₂CO₃, NaHCO₃, CaCl₂, NaCl, and NaClO. The spore germination of all pathogens was completely inhibited by Na₂CO₃ 4g/l, NaClO 5g/l, and NaHCO₃, CaCl₂, and NaCl 6g/l each. Dipping the bananas for 10–15min in these concentrations reduced the incidence of crown rot (compared with the untreated fruits) 17 days after harvest in fruits treated with NaClO by 67%, with NaHCO₃ by 62%, with NaCl by 38%, and with CaCl₂ by 33%. Na₂CO₃-treated fruits had the same incidence of crown rot as untreated fruits.     

Resistance to fusarium basal rot of onion in greenhouse and field and associated expression of antifungal compounds

Greenhouse and field evaluations of onion for resistance to Fusarium basal rot caused byFusarium oxysporum f.sp.cepae were conducted on cultivars ‘Akgün 12’ and ‘Rossa Savonese’ previously described as resistant at the seedling stage. In the greenhouse experiments inoculations were carried out on seeds or soil; in the field experiments evaluation was performed on onion sets from plants grown in naturally infested soils. Akgün 12 and to a lesser extent Rossa Savonese were resistant to the disease at the bulb stage in all experiments. Results were also consistent with those obtained from a previous screening at the seedling stage. Onion sets were also extracted and fractionated by thin layer chromatography to determine their content of antifungal compounds. Extracts were characterized by the expression of distinct antifungal components, which may be involved in resistance to the pathogen. http://www.phytoparasitica.org posting July 14, 2004.     

硅对瓠瓜酚类物质代谢的影响及与抗白粉病的关系

研究了硅酸盐和诱导接种白粉菌对瓠瓜叶片苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)、过氧化物酶(POD)活性的动态变化和木质素含量的影响.结果表明,诱导接种提高了瓠瓜叶片的PAL、PPO、POD活性,加硅后接种处理植株叶片酶活性更明显增加;接种后瓠瓜叶片中木质素含量增加,加硅处理植株叶片木质素含量是不加硅处理的1.43倍.说明酚类物质代谢在植物抗病机制中起着重要作用,硅能提高酚类代谢的酶活性.1.7mmol/L的硅能显著降低瓠瓜白粉病的病情指数,提高其对白粉病的抗病能力.     

Control of Penicillium expansum by plant volatile compounds

Nine plant volatiles were tested for their activity in vitro and in vivo against Penicillium expansum , the cause of blue mould of pear. In vitro spore germination and mycelial growth assay showed a consistent fungicidal activity by trans -2-hexenal, carvacrol, trans -cinnamaldehyde and citral, while hexanal (-)- carvone, p -anisaldehyde, eugenol and 2-nonanone exhibited a progressively lower inhibition. trans -2-Hexenal was the best inhibitor of conidial germination [MIC (minimum inhibitory concentration) = 24·6  µ L L⁻¹; ED₅₀ = 10·2  µ L L⁻¹], while carvacrol was the best inhibitor of mycelial growth (MIC = 24·6  µ L L⁻¹; ED₅₀ = 9  µ L L⁻¹). The four most active compounds in in vitro studies were tested in vivo as fumigants against blue mould on pear cv. Conference. Best control was achieved by trans -2-hexenal vapour treatments (12·5  µ L L⁻¹) when applied over a 24-h period, beginning 24 h after inoculation. In contrast, carvacrol (12·5–200  µ L L⁻¹), and trans -cinnamaldehyde (50–400  µ L L⁻¹) were ineffective and citral (200  µ L L⁻¹) showed only slight effect.     

西安南郊不同深度土壤CO_2浓度变化研究

利用红外CO2监测仪对西安南郊不同深度条件下的土壤CO2浓度进行了多次昼夜观测。观测结果表明:在一昼夜内土壤CO2浓度具有从低到高再到低的变化规律,这种变化特点与昼夜温度变化基本一致;土壤CO2浓度从总体来看具有白天高,夜间低,夏季高,秋季低的特点;浅层土壤CO2浓度昼夜变化幅度明显大于深层土壤CO2浓度变化幅度;在厚层黄土的150cm深度范围内,土壤CO2浓度随着深度的增加而增加,在150~600cm深度范围内CO2浓度基本恒定,显示出与薄层土CO2浓度变化明显不同。     

非灌溉条件下不同年龄梭梭蒸腾耗水比较

通过野外的实际观测,研究2龄、3龄和4龄植物群落区的土壤水分差异及其对梭梭(Haloxylon ammodendron)蒸腾耗水的影响.结果表明:(1) 种群年龄增加,土壤水分显著降低,裸地、2龄、3龄、4龄种群0～200 cm土层年平均土壤水分含量分别为74.40,66.08,52.71 mm和49.23 mm;(2) 生长初期,不同年龄间梭梭蒸腾速率差异不明显,盛夏,3龄梭梭蒸腾速率最大,生长后期,梭梭蒸腾速率随群落年龄增加而减小;(3) 种群年龄增加,梭梭长势停滞,水分消耗减少,2龄、3龄和4龄梭梭平均株高分别为71,132,75 cm,平均冠幅分别为54 cm×57 cm,80 cm×123 cm,58 cm×63 cm,年均蒸腾耗水分别为33 603.0,98 827.1,32 231.5 g.选择合理的密度配置方式,对维持人工植物群落与土壤水分的相对稳定具有十分重要的作用.     

Comparison of three biological control agents against cucumber powdery mildew (Sphaerotheca fuliginea) in semi-commercial-scale glasshouse trials

The effect of three reported biological control agents, Ampelomyces quisqualis, Verticillium lecanii and Sporothrix flocculosa, was tested against cucumber powdery mildew (Sphaerotheca fuliginea). Two glasshouse experiments, one in the summer and one in winter/spring were conducted on a semi-commercial scale. In both experiments, a susceptible and a partially resistant cultivar were used. In the second experiment, the additional effect of integration of biological control and silicon amendments to the nutrient solution was also assessed. In both experiments, A. quisqualis did not control the disease. V. lecanii had a small effect on powdery mildew in the first experiment but not in the second. S. flocculosa gave the best control of powdery mildew in both experiments. In the first experiment, weekly application of S. flocculosa reduced disease in the partially resistant cultivar to the same level as a treatment in which the fungicides bupirimate and imazalil were each applied once. Addition of silicon in the nutrient solution in a concentration of 0.75 mM reduced disease by 10–16%, averaged over all treatments. There was no interaction between silicon and the biocontrol agents. Yield was recorded in the second experiment and was significantly increased by the fungicide treatment compared to the control in the partially resistant cultivar. Yield in the treatment with S. flocculosa was not significantly different from the fungicide treatment in this cultivar. Silicon had no effect on yield in either cultivar.     

The antifeedant effect of neem seed kernel extract and azadirachtin on nymphs ofEyprepocnemis plorans

Acridids belonging to different species and families exhibit large differences in their response to neem components. In this context the antifeedant effect of a methanolic neem seed kernel extract (NSKE) and of azadirachtin (AZA) on fourth-instar nymphs of the acrididEyprepocnemis plorans Charpentier (Saltatoria:Acrididae) was investigated. Nymphs were offered either saccharose-impregnated filter paper disks or leaves of broad beans, treated with neem components. The amount of substrate consumed was determined by weighing the filter paper or by measuring the leaf area. On filter paper both NSKE and AZA were highly active down to the 10⁻⁴% treatment. In the leaf treatment, however, AZA was definitely more active than NSKE, with 100% deterrence at 10⁻⁴% and 10⁻²%, respectively. The methanolic NSKE was somewhat more active than the commercial preparation ‘Neemark’.     

树脂法吸附分离苹果汁中多酚物质的研究

通过树脂的筛选、吸附和解吸条件的优化等对树脂法分离提取苹果汁中多酚物质进行了研究。结果表明,XDA-5树脂为吸附分离苹果汁中多酚物质的优良材料,其吸附最适温度为40℃,适宜的洗脱剂为80%乙醇溶液。在此基础上结合苹果浓缩汁加工工艺提出了一条分离提取苹果多酚的新途径。根据该方法制备的苹果多酚提取物中总酚含量可达到96.72%。该方法既能提高苹果浓缩汁的品质和稳定性,又实现了资源的充分利用。