Phylogenetic relationships between rice dwarf phytoreovirus isolates from five countries

Rice dwarf virus isolates were collected from several locations in Japan, the Philippines, China, Nepal and Korea. Genomic dsRNA segment profiles in polyacrylamide gel electrophoresis differed among the isolates. There were less differences in the profiles between isolates from Japan and Korea than in those between these two Countries and others. Nucleic acid hybridization was used to examine the extent of genomic variation. Full-length cDNAs to all genomic segments encoding non-structural proteins (S4, S6, S9, S10, S11 and S12) were synthesized from two Japanese isolates, and were used for dot-blot hybridization. Hybridizations using probes generated from the full-length cDNA clones failed to differentiate isolates from different geographical areas. However, cDNA probes covering a variable region of S12 were able to distinguish Japanese and Korean isolates from those of other countries. Phylogenetic tree analysis based on the amino acid sequence of P12 encoded by S12 grouped Japanese and Korean isolates together. The Chinese isolates from two different locations (Yunnan and Fujian) were closely related to each other, and were the most distantly related to Japanese and Korean isolates.     

不同温度下转换寄主对桃蚜生态学特征的影响

在5种温度、4组寄主与蚜源组合处理条件下研究了温度对转换寄主后的桃蚜的影响。同一寄主间移植的桃蚜在有效积温、发育起点温度、生殖率、死亡率、寿命以及抗逆性上与不同寄主间移植的桃蚜有明显的差异;寄主对桃蚜生物学、生态学特征有明显的影响,表明长期生活在一种寄主上的桃蚜获得了一定的专化性。若将其移植到另一种寄主上,则会表现出种种不适反应,但这种反应还未进化至型或寄主生殖隔离。     

双季稻区稻水象甲的生物学特性研究

稻水象甲在浙江双季稻区每年发生２代，以成虫滞育越冬。春季越冬成虫迁入早稻田繁殖，形成１代致害种群；夏季１代成虫生殖滞育，绝大部分个体（９５％以上）迁出早稻田行夏蛰并越冬；秋季２代成虫羽化后，大部分迁飞山上草地越冬。     

茭儿菜(野茭白)的生物学特性

茭儿菜 ,别名野茭白、野茭瓜 ,属禾本科菰属。须根系 ,茎分地上茎和地下茎 ,叶分叶鞘和叶片两部分 ,圆锥状花序 ;茭儿菜在春季发芽、生根 ,随温度升高生长加快 ,夏、秋季抽穗、开花、结实 ;以地下匍匐茎和地上茎作为繁殖材料 ,生长发育对环境条件的要求 :适温范围 10～ 2 8℃ ,生长期间不能缺水 ,需 2 5～ 5 0cm深厚土层 ,以粘壤土或壤土为宜 ,生长期间需要充足的阳光 ,不耐遮荫     

The re-emergence of indigenous forest in an urban environment, Christchurch, New Zealand

Christchurch, the second largest city in New Zealand is a planned city on a coastal plain on the east coast of the South Island. The birth of the city and the subsequent century of development was characterised by colonial values and tree and garden planting with familiar European species along with those from Australia, North America, and eventually all other continents. The image of an “English garden city” with classical parks of oaks and willow-lined rivers became the accepted norm and the way in which the city has been promoted to potential tourists. Gardening is one of the top two recreational activities and exotic species greatly outnumber native species in the flora and in gardens. This has had serious consequences for the highly fragmented and degraded indigenous vegetation and its co-adapted wildlife. A few hardy indigenous species continued to regenerate through this period, but since the 1970s, there has been a progressive change of attitude and interest in reclaiming the natural heritage of the city, manifest in widespread private and public planting of indigenous species and active habitat restoration. In this article we examine the indigenous and exotic shrub and tree components of the Christchurch flora as planted street trees, in domestic gardens, and in parks. We also present data on shrub and tree regeneration in parks and domestic gardens in the city. Indications are that the more sensitive, less intrusive management of urban environments, combined with the greater density of indigenous seed sources, has allowed regeneration of a wide range of indigenous species across a broad spectrum of habitats – from neglected gardens to pavement cracks to exotic plantations. This is despite the competition from the prodigious seed banks and density of exotic trees, shrubs, and ground covers and albeit minimal impacts of introduced browsing and seed eating mammals. If the present trends continue through appropriate management and facilitation, these tentative signs of native forest regeneration should eventually proliferate into a sustainable mixed origin urban forest that resurrects and preserves the natural character of the region.     

Hazard tree liability in the United States: Uncertain risks for owners and professionals

The liability United States (U.S.) tree owners face from hazardous trees on their private properties has and continues to undergo a transformation. The traditional common law legal test focused upon whether a tree owner had acted to create a hazardous condition on the property. The modern trend is towards a test that imposes greater responsibility and greater uncertainty on tree owners and arborists. Abandoning the natural/artificial distinction, the modern test, adopted in half the U.S. jurisdictions, imposes general principles of negligence on tree owners. This paper discusses the U.S. legal context for hazardous trees, particularly the impacts on individual tree owners. It closes by addressing various practical means to minimize the risks associated with the modern legal standards, both for susceptible tree owners, and for professionals assessing the subject property.     

额济纳旗浅层地下水环境研究

通过 2 0 0 3年 4- 5月在黑河下游额济纳分两条路线 (a -a’和b -b’)采集水样 ,分析了额济纳现状水资源特征。远离河道区域水化学类型有HCO3·SO4-Na、Cl·SO4-Na·Ca、HCO3·Cl-Na·Ca和SO4·Cl-Na ;在河道附近或河道地区水化学类型主要是SO4·HCO3-Na ,类型单一 ;研究区矿化度和各离子含量随距离补给源的远近增减而升降 ,表明它们主要依赖于上游补给水量 ;同时 ,额济纳地处干旱区 ,降雨稀少 ,该区植被的生长发育主要依靠浅层地下水 ,地下水环境的改变直接导致了区域生态的变化。     

我国部分地区猪繁殖与呼吸综合征病毒分离株ORF5基因的遗传变异分析

参考Genbank发表的猪繁殖与呼吸综合征病毒（PKRSV）ATCC VR-2332的ORF5基因序列，设计并合成了一对引物．对来自福建、浙江、山东等地的PRRSV分离毒株进行RT-PCR扩增．获得约748bp的DNA片断，将其分别克隆入pMD18-T载体中，并进行测序。应用DNAStar软件分析所测序列，并与ATCCVR-2332、CH-1a、MLV、Lv等毒株的ORF5序列进行比较，结果表明：SHDl与F114、MLV、ATCCVR-2332同源性高达98．5％，与CH-1a同源性为91．0％，与其它毒株同源性为86．6％~88．4％；F114与MLV、ATCCVR-2332同源性为99．3％～99．7％．其余分离毒株在遗传关系上和CH-1a又分为明显的两个群．显示近年来各地PRRSV分离毒株与cH-1a株的遗传差异越来越大。     

北京油鸡胚胎成纤维细胞系建立与生物学特性研究

采取组织块直接培养法，对北京油鸡胚胎组织进行原代和继代培养，成功地建立了成纤维细胞系。并对培养细胞进行了形态学、细胞生长动力学观察，以及核型和乳酸脱氢酶、苹果酸脱氢酶的同工酶分析。结果表明，该细胞系的群体倍增时间(PDT)为24h；细胞染色体中二倍体占主体，为76％～88％；乳酸脱氢酶、苹果酸脱氢酶同工酶电泳图谱与本室其它细胞系有明显差别；细菌、真菌、病毒、支原体检测呈阴性。该细胞系的建立，使北京油鸡这一国家重要种质资源在细胞水平上保存下来，也为基因组文库和体细胞克隆等研究提供了理想的生物材料。     

一株鸭源禽流感病毒（H9N2）全基因序列分析及其排毒规律的研究

为研究一株鸭源H9N2亚型禽流感病毒(JN1株)全基因组的分子特征和遗传进化情况以及感染雏鸭后的排毒规律,对其生物学特性、全基因组序列以及遗传进化进行了分析,通过点眼滴鼻方式感染3周龄健康雏鸭,利用建立的实时荧光定量PCR(RT-PCR)检测鸭的排毒规律,并测定血清抗体效价。JNI株的鸡胚半数感染量为10~(-7.54)/0.2mL,鸡胚最小致死量的平均死亡时间为72h,静脉致病指数为0.266,抗原相关系数为0.47。系统发育分析表明,JN1株的HA与CK/HK/G9/97和DK/HK/Y280/97在同一分支上,NA、M、NP、PA、PB1、PB2基因与SH/F/98同源性较高,NS基因则与H5N1亚型禽流感病毒进化关系较近。HA的裂解位点为PSRSSR↓GL,存在6个潜在糖基化位点,在234位的氨基酸残基为L,NA基因颈部存在缺失。雏鸭在感染该病毒后,饮食正常,精神良好,3~17d均有排毒,咽拭子和泄殖腔棉拭子排毒规律基本一致,分别在第3天和第13天出现排毒高峰。该H9N2亚型禽流感病毒属欧亚大陆分支,为低致病性禽流感,病毒可通过呼吸道和泄殖腔向外界排毒,排毒时间较长。