Genetic Structure of Mycosphaerella graminicola Populations from Iran, Argentina and Australia

Restriction fragment length polymorphism (RFLP) markers were used to assess the genetic structure of populations of Mycosphaerella graminicola collected from wheat fields. A total of 585 isolates representing 10 field populations were sampled from Iran, Argentina and Australia. The genetic structure of M. graminicola populations from Iran and Argentina is described for the first time. Results were compared to previously investigated populations from Israel, Uruguay and Australia. Populations from Iran exhibited high clonality and low gene diversity, suggesting an inoculation event. Populations from uninoculated fields in Argentina had gene and genotype diversities similar to previously described European and North American populations. Genotype diversity was high for populations from Australia and tests for multilocus associations were consistent with sexual recombination in these populations. Gene diversity was low and fixed alleles were found for several loci. These findings are consistent with a relatively small founding population for Australia. These 10 new populations were integrated into a genetic distance comparison with 13 global populations that were characterized earlier.     

湖南永顺杉木河林场三类楠木林群落的调查分析

湖南永顺杉木河有较成片的以利川润楠(Machilus lichuanensis)、宜昌润楠(Machilus ichangensis)、闽楠(Phoebe bournei)为优势种的3类群落。笔者通过对这3类群落的调查分析,认为这3类群落具有4大特点:群落的珍稀性,组成种类的丰富性,生态环境的脆弱性,演替的相对稳定性。建议在杉木河林场建立自然保护区,严格加以保护。     

三维轴心轨迹法在输油泵机组状态评价中的应用

定性分析了输油泵机组转子在不同状态下轴心轨迹的运行状况,提出了融合相位及轴心轨迹半径两个指标的多测点、三维轴心轨迹法,从整机角度对输油泵机组进行了整体评价,并定量提取了多个评价指标。通过现场检测试验证明了该状态评价方法的有效性,并分析了运行变化趋势。     

How can research on pathogen population biology suggest disease management strategies? The example of barley scald (Rhynchosporium commune)

Barley scald fungus, Rhynchosporium commune, belongs to a host‐specialized species complex infecting grasses. Coalescent analyses of several genes indicate that R. commune originated c. 2500 years ago, after the domestication of barley. Phylogeographical analyses identified a diversity hotspot in Scandinavia, indicating an origin in northern Europe. After its emergence, R. commune became distributed globally on infected seeds, eventually invading the Fertile Crescent and infecting wild barley progenitors. Analyses of gene flow identified historical routes of migration out of Scandinavia and indicate a high degree of modern gene flow among South Africa, Australia and New Zealand. About 76% of global species diversity is found within barley fields, with all field populations showing a genetic structure consistent with sexual recombination. High levels of regional gene flow suggest wind‐dispersed ascospores and movement of infected seed. Quantitative traits, including pathogen aggressiveness, thermal sensitivity and fungicide resistance, showed high heritability and high levels of diversity within nine globally representative populations. Field experiments provided evidence for a fitness cost associated with complex virulence and a trade‐off between pathogenic and saprophytic fitness. All findings indicate that global R. commune populations have significant potential to evolve rapidly in response to environmental changes, including deployment of resistant cultivars, fungicide applications and global warming. Specific recommendations to improve management of barley scald include: (i) focus resistance breeding efforts in northern Europe, which offers the best location to screen germplasm and may provide useful sources of scald resistance; (ii) improve seed treatment, certification and quarantine programmes to limit long distance pathogen movement; (iii) manage barley stubble to decrease pathogen population size, limit production of sexual inoculum and reduce the pathogen's evolutionary potential.     

中国稻谷生产的重心演变路径及偏移分析

本文利用1949-2009年全国31个省(市,自治区)稻谷种植面积、总产量及单产资料,分析全国稻谷种植面积重心、总产量重心以及单产重心的移动轨迹、偏移距离等。结果表明:(1)1949-2009年,稻谷种植面积重心、总产量重心,整体上均呈现出向东北方向移动的趋势。(2)稻谷单产重心偏移轨迹从东西方向来看,20世纪50、60年代先向东偏移,此后逐渐向西回归;从南北方向上来看,单产重心呈现波动上升、下降趋势,大约在33°N-34°N之间移动。(3)从重心总偏移距离来看,种植面积最小,总产量次之,单产最大;从偏移方向来看,三者均是向东北、西南方向偏移的年份居多,说明稻谷生产东北、西南方向的发展不平衡状态较西北、东南方向的严重。(4)稻谷种植面积和总产量在南北方向上的动态变化相对东西向的变化剧烈,而单产则是东西向的变化比南北向的变化剧烈。     

应用茜素-β-D-半乳糖苷快速检验食品中的大肠菌群

用茜素 β D 半乳糖苷琼脂和行标SNO16 9- 1992指定的结晶紫中性红胆盐琼脂 (VRBA)对比检测 13种相关标准菌株和 70份食物样品。二者对标准菌株的检测结果完全一致 ,对食物样品检测结果的符合率也较接近。大肠菌群在茜素 β D 半乳糖苷琼脂中 2 4h内可长成较大的鲜明红色 ,轮廓清晰 ,易于辨认 ,可作为计数食品中大肠菌群的任选方法加以应用     

用填充法巧解物理问题

以实例介绍了用填充法求解非安全对称性物理量的解题思路及解题技巧。     

关于半导体中深中心位形坐标图的几个问题

位形坐标图是描述固体中杂质缺陷中心上的电子与晶体耦合引起的多种物理效应的有力工具,在半导体深中心行为的统一描述中常被使用。本文给出了由实验数据建立半导体中深中心位形坐标图的简便方法,分析了位形坐标图中各有关能量值的物理意义和容易混淆之处,指出了由实测数据建立位形坐标图时应注意温度效应这一因素。     

貉中枢神经系统形态结构特点研究

采用大体解剖学方法，观察研究了２０只健康成年貉的中枢神经系统结构特点。     

周边进水辐流式二沉池出水方式研究

通过计算流体力学FLUENT6.3.26软件,分别对周边进水辐流式二沉池三种出水方式(中间出水、周边出水和周边和中间同时出水)的沉淀区流态进行了数值模拟,系统研究了三种出水方式沉淀区的速度分布、漩涡形态、驻流区和慢流区的体积分数等。结果表明:为有利周边进水辐流式二沉池污泥沉降,三种出水方式中,周边和中间同时出水最优,周边出水其次,中间出水最差。