Possible Root Infection of Cercospora beticola in Sugar Beet

A potential primary infection site of the foliar pathogen Cercospora beticola in sugar beet is described. Sugar beet seedlings of the susceptible cv. Auris were grown in a standard soil for 14 days. A monoconidial culture of a C. beticola isolate was grown to produce conidia. In experiment 1, roots were immersed in a conidial suspension of isolate code IRS 00-4, or in tap water (control), for 2 days. After incubation seedlings were potted in a peat – fine river sand mixture and placed at low relative humidity (RH) (<80%) or high RH (100%). Twelve days after infection, seedlings at high RH showed more disease incidence (90%) than seedlings grown at low RH (disease incidence = 25%), whereas no disease symptoms developed in the control seedlings. Cercospora leaf spots (CLSs) developed on the cotyledons, leaves, petioles and stems of the seedlings. In experiment 2, roots were immersed in a conidial suspension of isolate code IRS 00-2 for 5 h. Thirty-four days after infection at high RH, 100% disease incidence was observed in the treated seedlings and one CLS in the control treatment. First indications of leaf spot development were observed as reddish purple discolouration of individual parenchymatic cells. Because splash dispersal and symptoms due to infested soil were excluded, we showed that it is possible to obtain CLS symptoms in sugar beet seedlings when their roots were immersed in conidial suspensions of C. beticola, thus demonstrating that roots can be a primary infection site.     

大鳞副泥鳅人工繁殖技术研究

用专塘培育大鳞副泥鳅亲鳅,采用人工催情注射、产卵、授精,水泥池网箱孵化、培育等方法,催产大鳞副泥鳅5 200组,人工繁殖受精率和孵化率均在70%以上,繁育大鳞副泥鳅鳅苗2 600万尾。     

溴隐亭和克罗米芬对乌鸡生殖激素水平及产蛋性能的影响

研究溴隐亭和克罗米芬对乌鸡血液中生殖激素水平、就巢时间和产蛋性能的影响。将36只就巢的丝羽乌鸡随机分成3组,Ⅰ组为对照组;Ⅱ组第1～2天每只口服溴隐亭1.25mg/d,第3～7天每只口服克罗米芬12.5mg/d;Ⅲ组第1～2天每只口服溴隐亭0.625mg/d,第3～4天每只口服溴隐亭1.25mg/d,第5～6天每只口服克罗米芬25mg/d,第7天每只口服克罗米芬12.5mg。试验结果表明,Ⅱ组血液中雌激素水平显著高于Ⅰ组(P<0.05),Ⅲ组血液中雌激素水平极显著高于Ⅰ组和Ⅱ组(P<0.01);Ⅰ组平均就巢时间最长,为8.58d,Ⅱ组为6.67d,Ⅲ组为6.83d;Ⅰ～Ⅲ组处理后1个月内的平均产蛋率分别为37.72%、59.65%和53.51%,Ⅱ组和Ⅲ组的产蛋率显著高于对照组(P<0.05);3个组的平均蛋质量分别为43.86、44.65和44.16g,蛋形指数分别为1.306、1.312和1.323,蛋壳厚度分别为0.327、0.338和0.332mm,溴隐亭和克罗米芬对后3项指标的作用效果差异不显著(P>0.05)。     

影响猪精子介导基因转移效果的因素研究

为优化猪精子载体法技术参数,利用荧光定量PCR、荧光显微镜检测和精液常规检测方法,分析不同DNA转染剂、不同孵育温度和不同形态DNA对猪精子转染外源DNA的影响。结果表明,PEI和TransFast转染剂能极显著提高猪精子转染效果,且PEI优于TransFast,而NanoFect转染剂包裹DNA不能转染精子。随着转染温度的升高,精子的活力和活率均明显下降,而转染率和内化外源DNA量基本保持稳定,而吸附外源DNA量呈下降趋势。环状DNA和线性化DNA在与精子共孵育后,两者的精子活力、活率、转染率和内化外源DNA量差异均不显著,精子吸附线性化DNA量极显著高于环状DNA量。综合分析表明,外源DNA形态对猪精子转染效果无显著影响;PEI和TransFast能够显著提高猪精子转染效果;共孵育温度以17℃为最佳,本结果为开展精子载体法制备转基因猪研究提供了基础试验依据。     

猪圆环病毒2型ELISA抗体检测试剂盒的研制及初步应用

用PCV2 Cap蛋白单克隆抗体预包被酶标板,将杆状病毒表达系统表达的PCV2 Cap蛋白作为检测用抗原,利用捕获包被法建立了间接ELISA法用于猪圆环病毒2型抗体的检测.通过优化ELISA条件,研制试剂盒并应用于圆环病毒2型疫苗的免疫效果检验.利用研制的试剂盒与IFA、商品化进口和国产同类试剂盒对178份猪血清进行平行检测,总符合率分别为96.63％、97.75％和84.27％,与其他几种常见猪病毒抗体阳性血清无交叉反应.试剂盒批内、批间变异系数分别为2.35％ ～4.06％和4.87％ ～ 6.54％,2～8℃保存15个月稳定,适合于对不同来源猪圆环病毒2型疫苗人工免疫猪血清抗体进行检测.     

Nutrient release pattern of organic and inorganic resources used in cassava production (Manihot esculenta Crantz)

The major constraint in the promotion of organic farming, a safe and sustainable alternative, is lack of availability of quality organic resources in sufficient quantities. The quality of resources can be ascertained by monitoring its nutrient release pattern, which has not yet been attempted. A controlled condition pot experiment was conducted at ICAR-Central Tuber Crops Research Institute, Thiruvananthapuram, India, in completely randomized design to study the nutrient dynamics of various organic and inorganic resources, commonly used in cassava production, at monthly intervals up to six months. The release of almost all nutrients and activity of soil enzymes were higher at the middle (3 or 4?months) of the incubation period. The pH showed an increasing trend and electrical conductivity, organic C and Fe content declined from initial. Averaging over stages, organic practice favored the activity of soil enzymes and release of almost all nutrients over conventional system significantly, except N.     

Effects of rice husk biochar on selected soil properties and nitrate leaching in loamy sand and clay soil

Biochar is a product of pyrolysis of biomass in the absence of oxygen and has a high potential to sequester carbon into more stable soil organic carbon (OC). Despite the large number of studies on biochar and soil properties, few studies have investigated the effects of biochar in contrasting soils. The current research was conducted to evaluate the effects of different biochar levels (0 (as control), 1% and 3%) on several soil physiochemical properties and nitrate leaching in two soil types (loamy sand and clay) under greenhouse conditions and wet-dry cycles. The experiment was performed using a randomized design with three levels of biochar produced from rice husks at 500 °C in three replications. Cation exchange capacity increased significantly, by 20% and 30% in 1% and 3% biochar-amended loamy sand soil, respectively, and increases were 9% and 19% in 1% and 3% biochar-amended clay soil, respectively. Loamy sand soil did not show improvement in aggregate indices, including mean weight diameter, geometric mean diameter, water stable aggregates and fractal dimension, which was contrary to the results for the clay soil. Rice husk biochar application at the both rates decreased nitrate leaching in the clay soil more than in the loamy sand. Our study highlights the importance of soil type in determining the value of biochar as a soil amendment to improve soil properties, particularly soil aggregation and reduced nitrate leaching. The benefits of the biochar in the clay soil were greater than in the loamy sand soil.     

Filamentous fungi in wrapped forages determined with different sampling and culturing methods

The use of wrapped forage bales with high dry‐matter (DM) content implies risk of fungal growth inside the wrapping, and impaired feed quality. Since fungi may be unevenly distributed in bales, the method of sampling can influence the outcome of the analysis. Three common sampling methods for detection of fungi in wrapped forage were compared: direct plating of visible mouldy patches on bale surfaces (Method I), direct plating of pieces of foliage from drilled core samples (Method II) and quantitative analysis dilution series of drilled core samples (Method III). All samples were cultured on two media at two temperatures. Samples were collected from 124 farms in Sweden and Norway. Using Methods I, II and III, fungi were detected on 52%, 77% and 56% of the farms respectively. Fifty‐two fungal species were identified using a combination of culturing and molecular methods. The most predominant species were Arthrinium spp., found on 55% of the farms, followed by Penicillium roqueforti at 48% of the farms. Incubation at 25°C resulted in higher numbers of all genera, except Aspergillus, compared to incubation at 37°C. The different methods of sampling and culturing did not identify the same fungal species within the same bale. Analysing one bale per farm resulted in detection of less than half the number of species compared to analysing three bales. Of the sampling and culturing methods compared, direct plating of drilled core samples cultivated at malt extract agar at 25°C performed best in terms of qualitative analysis of fungi species.