香蕉分生小球体途径胚性细胞悬浮系的建立

 以7 个香蕉品种未成熟雄花为外植体均获得了分生小球体(meristematic globules) 。分生小球体的诱导率因基因组型和品种而异, 为15 %～81 % , 分生小球体的特点及开始出现的时间也受基因组型和品种的影响。以分生小球体为起始材料, 建立了‘广东2 号’、‘华农7 号’及‘河口龙牙’3 个品种的胚性细胞悬浮系, 并通过体胚发生途径获得了前两个品种的再生植株。     

江汉平原水稻白叶枯病菌致病型的变异研究

 从水稻和稻田周围常见的10种杂草上来集梨孢属菌株,以涂沫法作交互接种,分离自牛筋草、狗尾草、法氏狗尾草、李氏禾、罗氏草、铺地黍、稗和马唐的梨孢菌与分离自水稻的梨孢菌可以交叉侵染其寄主,茭白和碎米莎草梨孢菌与稻梨孢菌不能交互侵染;自然诱发条件下来自牛筋草和狗尾草的梨孢菌与来自水稻的梨孢菌对其寄主同样发生交叉侵染。直接从杂草寄主上分离的梨孢菌株对水稻的致病性较弱,接种到水稻感病品种发病后再分离的菌株,对水稻致病性增强,对原寄主的致病性基本保持不变。推断稻瘟病区稻田周围牛筋草、狗尾草、法氏狗尾草、李氏禾、罗氏草、铺地黍、稗和马唐等杂草寄主上的梨孢菌在稻瘟病菌的积累和传播方面具有作用。     

春麦田除草剂的应用与杂草群落演替

作者采用定点定位试验,对春麦田除草剂应用与杂草群落演替趋势进行研究。结果表明:在杂草群落多样性麦田,小麦连作并分别连续5年施用同一种除草剂,原杂草群落中占优势的靶标杂草得以控制,而非靶标杂草和抗、耐药性杂草因失去竞争和制约对象而猖獗发展,发生量较原来增加几倍至几十倍,并形成优势种群,对小麦造成新的更严重的危害。一种除草剂在同田块连续施用4年,由于杂草群落演替,抗、耐药杂草兴起,除草效果显著下降而失去其使用意义。作者提出除草剂配套使用、轮用、混用等措施,并配合以合理的轮作制度,以减轻杂草群落长期受到单一的定向选择性压力。     

遗传与环境在生物进化中的关系

本文讨论了在生物进化的过程中遗传与环境的关系及遗传物质的范围和生物可塑性的问题。遗传物质的变异是进化的内因，环境对遗传物质的变异起到诱发与筛选的作用，进化后的生物对环境又有反作用。     

浅谈我国猪伪狂犬病的净化

伪狂犬病是由伪狂犬病毒(Pseudorabies vires，PRV)引起的多种家畜、野生动物、伴侣动物和实验动物的一种急性传染病。PRV在自然条件下能感染猪、牛、羊、犬、猫、兔、鼠、野猪、貂、熊、狐等动物。除猪以外，其它动物感染PRV后，出现发热、奇痒和急性脑脊髓炎等典型症状。猪是PRV的储藏者和传染     

猪附红细胞体病的诊断和防治

近年我县发生了一种类似猪瘟症状的疾病 ,表现为高热、嗜睡、全身发红等 ,导致猪群 (特别是仔猪 )大批死亡。经采用注射青霉素、链霉素、磺胺类药、退烧解毒药等治疗 ,效果不理想。特别是在使用磺胺类药物后 ,会加重病情。该病在我县呈蔓延趋势 ,给广大养殖户造成了很大的经济损失。后与省畜牧研究所联合研究 ,根据临床症状、病理剖检、实验室检查等 ,确诊为猪附红细胞体病。经对症下药 ,很快控制了该病的流行和蔓延 ,确保养殖业的健康稳定发展。1流行病学特点本病一年四季均可发生 ,但以夏秋多发。蚊等吸血节肢昆虫可传播该病 ,各种年龄、…     

单性结实与自花结实柑橘果实发育中钙钾动态的研究

 对单性结实的‘国庆1 号’温州蜜柑和自花结实的‘华农本地早’橘从开花前子房发育至果实成熟采收期整个子房或幼果及果实的不同部位(果皮和果肉) 的钙与钾含量变化进行了测定。结果表明:1) ‘国庆1 号’花前及花期子房钙含量较高, 花后趋降; 而其钾含量在花前及花期相对较低, 花后上升;2) ‘华农本地早’花前子房钙含量相对较低, 花后有一上升过程; 而对应钾在花前及花期就已很高, 花后下降; 3) 两品种果肉的钙含量自花后65 d 后均呈下降趋势, 而‘国庆1 号’果皮的钙含量在花后80 d 有一显著上升, 对应的‘华农本地早’在花后125 d 才急剧增加, 之后直至果实成熟二者均维持在较高水平;4) 两品种果皮、果肉的钾含量在果实发育过程中均呈类似的下降趋势。     

Functional heterogeneity in resources within landscapes and herbivore population dynamics

Large mammalian herbivores are notorious for their propensity towards population irruptions and crashes, yet many herbivore populations remain relatively stable. I explore how resource heterogeneity within landscapes dampens population instability, using a metaphysiological modelling approach considering patch state distributions. Resource heterogeneity is functionally stabilizing through spreading consumption away from preferred resources before these become critically depleted. Lower-quality resources act as a buffer against starvation during critical periods of the seasonal cycle. Enriching resource quality is destabilizing, even if patch diversity is maintained, because food quantity then becomes the limitation. The potential consequences of landscape fragmentation are explored using the Serengeti ecosystem, characterised by broadscale resource gradients, as a hypothetical example. Further insights provided by the model are illustrated with specific examples concerning the effects of patch scales and waterpoint distribution. A metaphysiological modelling approach enables the basic consequences of landscape heterogeneity to be distinguished from further effects that may arise from specific patch scales and configurations, without the distracting detail of spatially explicit models.     

内蒙古沙尘暴的成因、趋势及其预报

本文利用内蒙古1961～2001年的天气气候资料,对内蒙古中西部地区沙尘暴作了统计分析,阐述了沙尘暴的危害并给出了沙尘暴的基本定义。分析了引起沙尘暴的天气和气候因子的变化趋势,研究了他们对沙尘暴的影响,结果表明近40年内蒙古的沙尘暴总体呈减少趋势,但从1998年开始有所增加;沙尘暴的空间分布以阿拉善盟偏北地区为最高发区;降水、气温、大风、寒潮、北半球极涡、西太平洋副热带高压、亚洲西风环流、东亚大槽和南方涛动等天气和气候因素均对该地区沙尘暴的发生有不同程度的影响。     

Validation of the specificity and sensitivity of species-specific primers that provide a reliable molecular diagnostic for <Emphasis Type="Italic">Xiphinema diversicaudatum</Emphasis>, <Emphasis Type="Italic">X. index</Emphasis> and <Emphasis Type="Italic">X. vuittenezi</Emphasis>

Xiphinema diversicaudatum and X. index are vector nematode species of economic importance in viticulture regions as they can transmit Arabis Mosaic, Grapevine Fanleaf and Strawberry Latent Ringspot viruses to grapevine. Wang et al. (2003) designed species-specific diagnostic primers from ribosomal genes for both these vector species as well as a vector and a non-vector species X. italiae and X. vuittenezi, respectively. Our study aimed to confirm the specificity and determine the sensitivity and reliability of the primers for the two vector species, X. diversicaudatumand X. indexwhen challenged with closely related longidorid species and general nematode communities typical of vineyard soil. With one exception, no PCR product was observed when the primers were tested against six Longidorus, one Paralongidorus and one Xiphinema non-target species. Occasionally (three out of eight replicate PCR reactions) a weak PCR product was noted when primers for X. index were tested with L. elongatus. Furthermore, when challenged with a range of non-target nematode species comprising the nematode community typical of viticulture soil, no PCR product was amplified. An experimental dilution series of extracted DNA rigorously demonstrated that DNA from an equivalent single specimen of the target virus-vector species, X. diversicaudatum and/or X. index, could be detected amongst 1000 equivalent non-targetX. vuittenezi. Also, extracted DNA from an equivalent single target specimen was detected when added to DNA extracted from the overall soil nematode community. The primers were assessed further by using serial mixtures of actual nematodes rather than extracted DNA to simulate field soil. Using this method, a single target nematode could be detected amongst 200 non-target specimens. Given their specificity, sensitivity and reliability, it appears that these diagnostic primers will be of great benefit to phytosanitary/quarantine services related to the viticulture industry.