广西玉米纹枯病菌培养性状及其致病力研究

从广西玉米主产区的8个县市秋玉米的纹枯病病株中分离出8个玉米纹枯病菌株,经生物性状的观察和菌丝融合群测定表明,它们都属于立枯丝核菌AGk-1-IA融合群;腐生定殖能力和致病力测定表明,菌株GX4、GX1的腐生定殖能力和致病力最强。     

贺兰山高山草甸的群落生态学研究

在群落调查的基础上，对贺兰山高山草甸进行数量分析。主要的结果如下：（1）贺兰山高山草甸可分为三个群系，分别为珠芽蓼群系、高山嵩草群系和矮嵩草群系，而高山嵩草群系和矮嵩草群系可进一步划分为两个亚群系，不同群系（或亚群系）的群落结构和环境特征之间存在显著的差异；（2）高山嵩草群系和矮嵩草群系之间的界限约为海拔3200m，而珠芽蓼群系主要分布于研究区的偏阴坡，与海拔关系不大；（3）14个频次大于50％的物种在排序图上的空间分布反映了这些物种最适宜生境的位置，而且与群落类型的空间分布一致。     

山东地区三株鸽Ⅰ型副粘病毒的分离及鉴定

2005年在山东地区部分肉鸽养殖场出现鸽子大量死亡现象,从死亡鸽中分离到三株鸽Ⅰ型副粘病毒(SD05027,SD05028,SD05029),其鸡胚平均死亡时间(MDT)分别为69h,69.6h,81.6h;鸡脑内接种指数(ICPI)为1.31,1.43,1.48,证明此次分离的三株病毒株均属速发型新城疫病毒。应用RT-PCR技术对F基因重要功能区片段扩增后进行序列测定,分析表明,F蛋白裂解位点处的序列(112R/K-R-Q-K-R-117F)与新城疫强毒在这一区域的序列相符。与多株已报道的NDV参考株相应片段进行序列比对和基因进化树分析,将其鉴定为基因VIb型。     

O型口蹄疫病毒结构蛋白VP1的原核表达与抗原性分析

研究分析了O型口蹄疫病毒(FMDV)结构蛋白VP1与当前猪FMDV疫苗血清的免疫反应性.将VP1基因克隆至原核表达载体pET32c,并在大肠埃希菌BL21中得到了表达,Western blot分析表明该重组蛋白与豚鼠O型FMDV标准阳性血清具有良好免疫反应性.目的蛋白经纯化后用ELISA分析其与猪疫苗血清的免疫反应性,结果显示该重组VP1蛋白(rVP1)只能与部分O型FMDV疫苗血清反应.推测当前使用的不同O型FMDV疫苗毒株在VP1重要中和抗原位点G-H环(134 aa～158 aa)与C末端(200 aa～213 aa)存在较大差异.     

Changes of IFN-γ, IL-6 and TNF-α levels in rats with severe pneumonia

AIM:To study the variety of cytokines in severe bacterial pneumonia of Sprague Dawleg (SD) rats. METHODS:A total of 60 SD rats were randomly divided into three groups: model Ⅰ group (n=24), model Ⅱ group (n=24), and control group (n=12). Rats in the model Ⅰ group and the model Ⅱ group were intratracheally instilled with suspension of klebsiella pneumoniae at different doses. Rats in the control group were intratracheally injected with 1 mL saline. On the 2nd, 4th and 6th day after intratracheal instillation, 1/3 rats in each group were killed to determine the concentration of IFN-γ, IL-6 and TNF-α in blood. RESULTS:The levels of IL-6 and TNF-α in model groups were higher than those in control group, while the level of IFN-γ was lower. The change of cytokines was more significant in the model Ⅱ group (severe pneumonia) than those in the model Ⅰ group. CONCLUSION:The cytokines we studied may play an important role in the pathogenesis of severe pneumonia. The change of cytokines is more significant in severe pneumonia than those in common pneumonia.     

Neutral models for testing landscape hypotheses

Neutral landscape models were originally developed to test the hypothesis that human-induced fragmentation produces patterns distinctly different from those associated with random processes. Other uses for neutral models have become apparent, including the development and testing of landscape metrics to characterize landscape pattern. Although metric development proved to be significant, the focus on metrics obscured the need for iterative hypothesis testing fundamental to the advancement of the discipline. We present here an example of an alternative neutral model and hypothesis designed to relate the process of landscape change to observed landscape patterns. The methods and program, QRULE, are described and options for statistical testing outlined. The results show that human fragmentation of landscapes results in a non-random association of land-cover types that can be describe by simple statistical methods. Options for additional landscape studies are discussed and access to QRULE described in the hope that these methods will be employed to advance our understanding of the processes that affect the structure and function in human dominated landscapes.     

Linking Land-use, Water Body Type and Water Quality in Southern New Zealand

Land-use and vegetation cover have been linked to the nutrient levels (nitrogen, phosphorus) of surface waters in several countries. However, the links generally relate to streams and rivers, or to specific types of standing water, for example shallow lakes in a geologically defined region. We measured physical variables and nutrient chemistry of 45 water bodies representative of the wide range of lentic wetland environments (swamps, riverine wetlands, estuaries, reservoirs, shallow lakes, deep lakes) in Otago, New Zealand, and related these to catchment variables and land-use in order to assess the potential influence of catchment modification on water quality of these diverse wetlands. Catchment boundaries and land cover were derived from maps using ArcView GIS software. Our predictions that concentrations of nutrients and other components of water quality would correlate positively with the nature and intensity of catchment modification were confirmed in multivariate analyses. Physical and chemical measures were positively related to the extent of modification in the catchment (percentage of the catchment in pasture, planted forest, scrub and urban areas), and negatively related to lack of catchment modification (more of the catchment in bare ground, tussock grassland and indigenous forest). The strong negative correlations between nutrient concentrations, suspended sediment, water colour and the percentage of tussock cover in the catchment imply that increased conversion of the␣native tussock grassland to pastoral farming in␣Otago will increase nutrient concentrations and␣reduce water quality of the diverse lentic ecosystems.     

夏季覆盖盐碱地表面对土壤盐分和水分的影响

在干旱区土壤水分蒸发损失引起土壤盐分表聚是土壤次生盐碱化的一个重要原因.在夏季高温时节,采用塑料薄膜、麦草和沙子覆盖盐碱地表面,结果表明,具有较好地改良盐碱地的作用.塑料薄膜宜采用全地面覆盖,麦草的覆盖量应为2 934.8 kg/hm2;沙子的覆盖厚度以4 cm为宜.覆盖后对土壤中各离子的抑制作用顺序为:K Na ＞ Cl-＞ SO42-＞Mg2 ＞HCO3-＞Ca2 .3种覆盖材料以塑料薄膜效果最佳.     

Repeated grading of weed abundance and multivariate methods to improve the efficacy of on-farm weed control trials

We evaluated whether new information could be drawn from additional data collection and unconventional statistical analyses of an on-farm trial. First, we compared a conventional sampling method using a biomass estimate of weed abundance to repeated visual assessment of the percentage ground cover of weeds. The biomass was sampled once after the treatment, whereas the ground cover was repeatedly sampled once before weed control plus several occasions after weed control. Second, we contrasted the outcomes from analysis of variance ( anova ), taking samples from a single point in time with repeated measures (rm) anova and a multivariate method. As the outcomes and conclusions drawn were relatively similar, we conclude that the ground cover estimate of weed abundance was as reliable as the biomass estimate. The rm anova enabled us to follow the temporal trend in response to treatments in the most abundant species, including possible initial differences. Multivariate analysis went even further, by clearly displaying species-wise responses and treatment selectivity.