大麦黄矮病毒(BYDV) cDNA的合成、克隆及初步应用

 以大麦黄矮病毒二叉蚜和麦长管蚜专化株的病毒核酸为模板,以小牛胸腺DNA为引物,合成cDNA的第一条链,再用缺口翻译法合成第二条链,然后采用加装BamH₁人工接头的方法将ds-cDNA插入到质粒载体pUC₈中,重组质粒于大肠杆菌JM—83中进行克隆,以克隆的颜色变化选择含有外源DNA的克隆,再用病毒核酸制备的探针筛选真正病毒cDNA插入的克隆。重组质粒中ds-DNA的插入长度在300—1600bp之间。用缺口翻译法制备质粒DNA分子探针检测同源病毒液,反应灵敏度在100pg-1ng之间。应用cDNA探针检测不同病毒和病毒株系,从中筛选出黄矮病毒株系专化克隆系,黄矮病毒专化克隆系和黄矮病毒组专化克隆系.     

Problems of control of insecticide-resistant Plutella xylostella

In the different regions of SE Asia, resistance problems in the diamondback moth (DBM), Plutella xylostella, are comparable, and depend on the type of insecticide used to control this pest. Resistance is especially high to insecticides metabolised by mfos (multifunctional oxidases), but since the detoxification of each such insecticide depends on different mfo(s), there is little cross-resistance between insecticides. Thus, carbaryl, carbofuran and the synthetic pyrethroids, all detoxified by mfos, show little cross-resistance. Resistance to cartap and some organophosphorus insecticides is much lower, and is often unstable. Those compounds are therefore essential in the rational control of DBM. The cross-resistance relationships within the traditional insecticides have mostly been worked out. It is thus possible to use alternate spraying schedules with insecticides conferring minimum cross-resistance potential. Alternating insecticides is better than using mixtures, because DBM can develop multiple resistance through treatment with mixtures. DBM has now developed resistance to the newly-introduced IGRs and other experimental control agents. Possible resistance to these as well as to future DBM control agents has been examined, and their resistance-inducing ability and cross-resistance characteristics examined. Experience in monitoring the spectrum together with the strength of resistance of field populations of DBM suggest that control can only be achieved by wellplanned rational chemical control programs.     

Susceptibility of Mastomys natalensis to Brugia malayi following pretreatment with antifilarials

Mastomys natalensis pretreated with diethylcarbamazine (DEC), levamisole or centperazine were exposed to the standard inoculum of infective larvae of Brugia malayi. Percentage 'take' of infection, duration of prepatent period, course of microfilaraemia and number of adult worms recovered were compared with those of untreated infected Mastomys (control). DEC and centperazine did not alter the 'take' (DEC/centperazine: 100%; control: 88.24%) and the average prepatent period (DEC: 105.44 days; centperazine: 105.18 days, control: 109.20 days). In levamisole pretreated animals on the other hand, the 'take' was much lower (68.18%) with extended prepatent period (125.87 days). However, unlike centperazine and control, the course of microfilaraemia was identical in DEC and levamisole pretreated animals. The average adult worm recovery was significantly high in centperazine pretreated animals being 14.09 as against 8.12, 7.46 and 8.42 in DEC, levamisole pretreated and control animals, respectively.     

气候因素对禾谷缢管蚜发生程度的影响及预测

小麦禾谷缢管蚜Rhopalosiphum padi(L.)是本省小麦主要害虫,其发生程度受诸多因素的影响。作者通过整理1979—1987年田间系统调查资料,应用通径分析方法,对影响小麦禾谷缢管蚜发生程度的气候因子进行了研究。试验选取3月中旬均温     

黄土高原地区草场资源与畜牧业的发展战略初探

本文根据黄土高原草场的特征、分布及其评价,对草场资源在发展畜牧业中的作用与地位进行了论述,确定了黄土高原畜牧业发展的战略目标、布局与措施,以及草场资源的保护与合理利用。     

温度对拟稻虱缨小蜂实验种群增长的影响

拟稻虱缨小蜂的世代发育起点温度为12.91℃,有效积温为198.89日度,未成熟期的发育速率与温度符合逻辑斯蒂曲线关系,低温对未成熟期的存活有明显的抑制作用。在供试温度范围内,成虫寿命随温度升高而缩短,而雌虫产卵历期则与成虫寿命呈正相关,30℃下的雌虫生殖能力最大,种群内禀增长能力与温度呈二次抛物线曲线关系。种群增长的理论最适温度31.84℃下,内禀增长能力γm=0.1021,种群数量加倍时问t=6.79天,该实验种群将逐日以1.1075倍的速率不断地作几何级数增长。     

福建省葡萄病毒病的调查和研究

１９９０～１９９２年作者对福建省葡萄产区进行了抽样调查，发现该省约３１％的果园有葡萄扇叶病（ＧＦＬＶ）和葡萄卷叶病（ＧＬＲＶ）。在调查的１１３００株葡萄中（６０２亩），ＧＦＬＤ株发病率为１３．２７％，造成葡萄减产２７．２％；ＧＬＲＶ株发病率为７．３％，减产２１．５％。病株表现为不同程度的种性退化，生长赢弱、停滞，果实品质下降，果粒成熟不齐。     

小麦梭条花叶病毒粒子特性及血清学

 小麦梭条花叶病是土壤真菌(禾谷多粘菌Polymyxa graminis)传播的一种低温型病害。现已广泛分布于长江、黄河中下游地区各省,对小麦生产造成严重危害。     

百合枯萎病发生规律及防治研究

百合枯萎病是甘肃省百合产区近年来新发生的一种重要病害。研究证明,百合枯萎病系由尖孢镰刀菌(Fusarium oxysporum Schlecht.)、串珠镰刀菌(F.moniliform Sheldon)和茄病镰刀菌[F.solani(Mart.)Sacc.]侵染所致。病菌以菌丝体在种球内,或以菌丝体、厚垣袍子及菌核随病残体在土壤中越冬,成为翌年的主要初侵染源。病害的发生与连作、线虫、栽培技术及气候因素等密切相关。多菌灵对此病有显著防治效果。     

连作晚稻三化螟为害损失与防治指标研究

三化螟幼虫在晚梗稻分蘖、圆秆、孕穗、破口期均能侵入,所形成的为害株数、为害类型和幼虫存活率与生育期有密切关系,为害丛、株增长呈S型曲线。分蘖期、孕穗—破口期引起丛、株为害率和损失率与卵块密度显著相关,每个卵块损失稻谷分别为59.11±2.99g、74.58±3.31g。考种结果表明,产量损失的主要原因是有效穗减少。在现有生产条件下,三化螟经济允许卵块密度为:分蘖期130—150块/666.7m~2,孕穗—破口期100—120块/666.7m~2;防治指标:分蘖期100—110块/666.7m~2,为害团50—60个/666.7m~2,丛为害率2.0％—3.0％,株为害率1.0％—1.5％。