Inhibition of Leucoagaricus gongylophorus with Carica papaya: an alternative to control the leaf-cutter ant Acromyrmex octospinosus

Abstract

The symbiotic association of the leaf-cutter ants with the fungus Leucoagaricus gongylophorus implies that the negative impact on the fungi will affect the survival of the ants. After a promising antifungal bioactivity, Carica papaya was studied leading to the bioassay-guided isolation of squalene, 4,5-dihydrohumulen, the flavanol-glycosides quercetin, kaempferol, and rutin, and the alkaloid carpaine. Carpaine and squalene were found to have a moderate individual activity, which increased when evaluated together. Based on the presence of these compounds, standardized extracts were formulated for field tests on nests of Acromyrmex octospinosus. All the nests treated were negatively affected evidencing a promising lead for the integrated management of leaf-cutter ants.     

Implications of Azospirillum brasilense inoculation and nutrient addition on maize in soils of the Brazilian Cerrado under greenhouse and field conditions

The combination of nitrogen and Azospirillum can ensure greater nutrient absorption and crop yield in agricultural areas using high technology. Thus, the objective was to evaluate maize response to Azopirillum brasilense (AZ) inoculation and nutrient (macronutrients and micronutrients) application under greenhouse and field conditions in clay and sandy soils of the Brazilian Cerrado. In the greenhouse assays, the following parameters were measured: shoot dry weight (SDW), root dry weight (RDW), and root volume (RV). In the field experiments, the maize yield was determined after drying the grains at 60 °C for 48 h. In clay soil, there was a significant increase in the SDW, RDW and RV in the treatment with AZ concentrated (10¹¹ cells ml⁻¹ of inoculum) when compared with the control treatment and the treatment with AZ diluted (10⁶ cells ml⁻¹ of inoculum). In this soil, adding micronutrients did not affect the maize response under greenhouse conditions. In sandy soil, there was no difference between the AZ treatment and the control, except for treatments where nutrients and AZ were both added leading to a significant increase in the maize response. In both soils, the RV:RDW ratio was higher in the treatment with AZ concentrated compared to that in the treatment with AZ diluted, but the yield response depended on the addition of nutrients. Inoculation with A. brasilense gave comparable yield to the nitrogen treatment. The grain production was increased by 29% in the treatment with A. brasilense and nitrogen compared to nitrogen fertilization alone. In this study, the yield response was affected significantly when maize was inoculated with A. brasilense, but this response was dependent on the soil type under greenhouse conditions.     

沥滤液中低分子量有机酸对小麦种子的急性毒性

沥滤液来源于生活垃圾焚烧厂贮坑，富含垃圾中的各种有害物质，其处理与再利用过程中可能引起的生态毒性受到人们的关注。采用小麦种子为受试物，通过种子萌发抑制试验对低分子量有机酸（C2-C5）的急性毒性进行评价，并结合液液萃取和减压蒸馏的方法考察低分子量有机酸对沥滤液总体生物毒性的贡献。结果表明，分子态乙酸对小麦种子萌发的急性抑制毒性高于离子态，低分子量有机酸对小麦种子发芽和根伸长的急性抑制毒性，均随低分子量有机酸碳链的增长而增加。5种有机酸贡献了沥滤液稀释液总体急性抑制毒性的20．25％（根）和12．75％（芽）；短链有机酸由于具有较低的辛醇-水分配系数（kow），对酸性有机萃取物总体急性抑制毒性的贡献较低；减压蒸馏馏分总体毒性较低，5种低分子量有机酸对其的毒性贡献为24．6％（根）和21．9％（芽）。     

高亲和力的农药克百威单克隆抗体的制备及鉴定

【目的】制备高亲和力农药克百威单克隆抗体，建立克百威残留免疫检测方法，控制克百威残留，保障人民身体健康与保护环境。【方法】合成克百威半抗原BFNB，用人工抗原BFNB－BSA免疫Balb/c小鼠，取脾细胞与骨髓瘤细胞在PEG4000作用下融合，经间接ELISA筛选及显微克隆法亚克隆，分离出阳性细胞株，腹水诱导法及辛酸－硫酸铵沉淀法大量制备及纯化单克隆抗体，间接ELISA法测定抗体滴度及亲和力，间接竞争ELISA法测定抗体特异性。【结果】获得1株稳定分泌抗克百威单克隆抗体的杂交瘤细胞株5D3，其培养上清和腹水抗体滴度分别为1﹕2.048×103和1﹕1.024×106，其抗体亚类为IgG1，亲和力常数为2.54×109 L•mol-1，IC50为1.18 ng•ml-1，最低检测限为0.01 ng•ml-1。与克百威降解产物呋喃酚的交叉反应率为4.59×10-4％，另外几种结构类似的氨基甲酸酯类农药的交叉反应率均小于3.0×10-4％。【结论】此抗克百威的单克隆抗体亲合力高、特异性强，为建立克百威简便、快速、特异的免疫检测方法奠定了基础。     

运用ELISA快速检测CPV抗体方法的建立与均衡性的研究 I.间接ELISA快速检测CPV抗体方法的建立

用蔗糖密度梯度离心和凝胶层析纯化犬细小病毒(CPV)作抗原，建立了检测CPV抗体的间接酶联免疫吸附试验(ELISA)，其特异性和稳定性良好，结果判定精确明显，易于把握。     

Transgenic Bt plants decompose less in soil than non-Bt plants

Bt plants are plants that have been genetically modified to express the insecticidal proteins (e.g. Cry1Ab, Cry1Ac, Cry3A) from subspecies of the bacterium, Bacillus thuringiensis (Bt), to kill lepidopteran pests that feed on corn, rice, tobacco, canola, and cotton and coleopteran pests that feed on potato. The biomass of these transgenic Bt plants (Bt+) was decomposed less in soil than the biomass of their near-isogenic non-Bt plant counterparts (Bt−). Soil was amended with 0.5, 1, or 2% (wt wt⁻¹) ground, dried (50 °C) leaves or stems of Bt corn plants; with 0.5% (wt wt⁻¹) ground, dried biomass of Bt rice, tobacco, canola, cotton, and potato plants; with biomass of the near-isogenic plants without the respective cry genes; or not amended. The gross metabolic activity of the soil was determined by CO₂ evolution. The amounts of C evolved as CO₂ were significantly lower from soil microcosms amended with biomass of Bt plants than of non-Bt plants. This difference occurred with stems and leaves from two hybrids of Bt corn, one of which had a higher C:N ratio than its near-isogenic non-Bt counterpart and the other which had essentially the same C:N ratio, even when glucose, nitrogen (NH₄NO₃), or glucose plus nitrogen were added with the biomass. The C:N ratios of the other Bt plants (including two other hybrids of Bt corn) and their near-isogenic non-Bt counterparts were also not related to their relative biodegradation. Bt corn had a significantly higher lignin content than near-isogenic non-Bt corn. However, the lignin content of the other Bt plants, which was significantly lower than that of both Bt and non-Bt corn, was generally not statistically significantly different, although 10-66% higher, from that of their respective non-Bt near-isolines. The numbers of culturable bacteria and fungi and the activity of representative enzymes involved in the degradation of plant biomass were not significantly different between soil amended with biomass of Bt or non-Bt corn. The degradation of the biomass of all Bt plants in the absence of soil but inoculated with a microbial suspension from the same soil was also significantly less than that of their respective inoculated non-Bt plants. The addition of streptomycin, cycloheximide, or both to the soil suspension did not alter the relative degradation of Bt+ and Bt− biomass, suggesting that differences in the soil microbiota were not responsible for the differential decomposition of Bt+ and Bt− biomass. All samples of soil amended with biomass of Bt plants were immunologically positive for the respective Cry proteins and toxic to the larvae of the tobacco hornworm (Manduca sexta), which was used as a representative lepidopteran in insect bioassays (no insecticidal assay was done for the Cry3A protein from potato). The ecological and environmental relevance of these findings is not clear.     

Microbial and soil parameters in relation to N mineralization in soils of diverse genesis under differing management systems

 Oregon soils from various management and genetic histories were used in a greenhouse study to determine the relationships between soil chemical and biological parameters and the uptake of soil mineralized nitrogen (N) by ryegrass (Lolium perenne L.). The soils were tested for asparaginase, amidase, urease, β-glucosidase, and dipeptidase activities and fluorescein diacetate hydrolysis. Microbial biomass carbon (C) and N as well as metabolic diversity using Biolog GN plates were measured, as were total soil N and C, pH, and absorbance of soil extracts at 270 nm and 210 nm. Potentially mineralizable N (N₀) and the mineralization rate constant (k) were calculated using a first order nonlinear regression model and these coefficients were used to calculate the initial potential rate of N mineralization (N₀ k). Except for Biolog GN plates, the other parameters were highly correlated to mineralized N uptake and each other. A model using total soil N and β-glucosidase as parameters provided the best predictor of mineralized N uptake by ryegrass (R ² =0.83). Chemical and biological parameters of soils with the same history of formation but under different management systems differed significantly from each other in most cases. The calculated values of the initial potential rate of mineralization in some cases revealed management differences within the same soil types. The results showed that management of soils is readily reflected in certain soil chemical and biological indicators and that some biological tests may be useful in predicting N mineralization in soils. Received: 31 January 1997     

大豆脂肪氧化酶缺失体鉴定方法研究

应用比色法和等电聚焦聚丙烯酰胺凝胶电泳法鉴定大豆脂肪氧化酶缺失体,得出结论：后者是一种简单明了的鉴定脂肪氧化酶基因缺失材料的方法,能够适应大豆育种工作要求（要使农艺性状和缺失脂肪氧化酶综合到某一个体中需要对成千上万的群体进行鉴定）;并同时筛选出了农艺性状优良,缺失脂肪氧化酶Lox2的稳定新品系F4-5。