Detection of squash mosaic virus in seeds of melon (Cucumis melo) by enzyme-linked immunosorbent assay (ELISA)

Squash mosaic virus (SqMV, comovirus) is seed-transmitted in severalCucurbitaceae. Therefore, the use of virus-free seed is important to prevent establishment of this virus in the Netherlands and to avoid spread to other countries.This study was undertaken to develop an enzyme-linked immunosorbent assay (ELISA) for the detection of SqMV in melon seeds. An antiserum was produced to a serotype 1 isolate from melon. Two ELISA variants were investigated viz. an ELISA variant with simultaneous incubation of sample and enzyme conjugate (ELISA 1) and an ELISA variant with successive incubation of sample and enzyme conjugate (ELISA 2). The sensitivity of ELISA was tested by mixing fluor of ground infected and non-infected seeds in different proportions. SqMV was detected by both ELISA variants at dilutions of 1 160 (1 part of infected flour mixed with 159 parts of non-infected flour) or higher after a substrate incubation period of 4 h. However, ELISA 1 gave relatively higher absorbance values than ELISA 2 for nearly all dilutions. Since ELISA 1 is also faster than ELISA 2, ELISA 1 is advised for routine testing. In these test, using subsamples of 100 melon seeds SqMV is detected reliably. ELISA 1 is now used in the Netherlands for routine-indexing of melon seed lots for SqMV.Samenvatting Het pompoenemozaïekvirus gaat over met het zaad van verscheideneCucurbitaceae. Het gebruik van virusvrij zaad is belangrijk om te voorkomen dat het virus zijn intrede doet in Nederland en zich naar andere landen verspreidt.Een antiserum werd geproduceerd tegen een serotype 1 isolaat van meloen. Met behulp van dit antiserum werd een ELISA ontwikkeld om pompoenemozaïekvirus in zaden van meloen aan te tonen. Twee varianten van ELISA werden vergeleken, namelijk een variant waarbij monster en enzymconjugaat gelijktijdig geïncubeerd werden (ELISA 1) en een variant waarbij monster en enzymconjugaat na elkaar geïncubeerd werden (ELISA 2). De gevoeligheid van de ELISA varianten werd uitgetoetst door meel van zieke zaden in verschillende verhoudingen te mengen met meel van gezonde zaden. Het pompoenemozaïekvirus werd met beide ELISA varianten aangetoond in verdunningen van 1 160 (1 deel meel van zieke zaden gemengd met 159 delen meel van gezonde zaden) of hoger na 4 uur incubatie met substraat. ELISA 1 gaf doorgaans hogere extinctiewaarden dan ELISA 2 voor bijna alle verdunningen. Omdat ELISA 1 ook nog sneller is dan ELISA 2, wordt ELISA 1 aanbevolen voor routinematig gebruik. Wanneer voor routinematig gebruik 100 meloenezaden per submonster getoetst worden, kan het pompoenemozaïek virus betrouwbaar worden aangetoond. In Nederland worden momenteel per zaadpartij 20 submonsters van 100 zaden getoetst.     

A seroepidemiological study on bluetongue virus in dairy cattle in the central valley of California

A seroepidemiological study on bluetongue virus (BTV) infection in California dairy cattle was conducted to estimate the prevalence and distribution by age and season of BTV group-reactive antibodies and to look for possible associations between the presence of antibodies and cattle age or breed and farm. Between December 1985 and March 1987, a sample of cattle was tested at approximately two-month intervals for BTV group-reactive antibodies using an enzyme-linked immunosorbent assay (ELISA). Data taken during the month of December 1986 were used to evaluate possible associations between a positive antibody test and certain intrinsic (age, breed) and extrinsic (farm) factors.Univariate and multivariate statistical analyses using the -square test for associations and multiple logistic regression, respectively, were carried out for possible associations between positive antibody tests to BTV and each factor of interest. The strengths of the associations were determined using estimates of the odds ratio.Of the 3774 serum samples tested, 238 (6.3%) were from calves, 1045 (27.6%) were from heifers and 2492 (66.0%) were from cows. Seroprevalence varied from nil in calves on two occasions to over 90% on several occasions in cows. Cows consistently had higher prevalence rates than heifers or calves across all test dates (p<0.05). The seroprevalence of BTV group-reactive antibodies also showed a seasonal fluctuation, with the highest rates occurring during the warmer months of the year. These highest prevalence rates coincided with heavy activity of the known vector of BTV, Culicoides spp. Breed and farm effects were not statistically significant (p>0.05). With the exception of one farm, all cattle were of the Holstein breed, which reduced confidence in assessing any breed effect in this study. Relative estimates of the sensitivity and specificity of BTV ELISA were 87% and 100% respectively, compared to the standard agar gel immunodiffusion (AGID) test.The observations support previous findings of seasonal distribution of BTV antibodies and suggest an age relationship, whereby older cattle are more likely to be positive to BTV group-reactive antibodies than younger cattle.     

C肉毒杀鼠素在高寒草甸地区灭鼠技术中的应用

综述C肉毒杀鼠素草原灭鼠应用技术,充分肯定了C肉毒杀鼠素毒力强、适口性好、对非靶动物毒性低、作用缓慢、无二次中毒、易降解和适合规模灭鼠的特点,为鼠害防治提供了新的思路。     

香蕉ACC氧化酶基因(MAO3)的克隆及其表达特性分析

 根据同源扩增得到香蕉(Musa acuminata) ACC氧化酶基因(MAO3) 的核心部分, 再通过3'和5'RACE扩增上、下游序列以及Genome-Walker的方法得到启动子部分, 共获得3 718 bp长度的序列。将所得结果进行聚类分析, 发现香蕉中ACC氧化酶的氨基酸序列非常保守, 各序列间的同一性高达99% ,与单子叶植物和双子叶植物中ACC氧化酶的氨基酸序列的同源性在66.7%～71.8%之间。组织原位杂交试验表明MAO3基因的表达具有组织特异性, 初步认为是在韧皮部筛管组织中特异表达。运用实时荧光定量PCR技术, 实时监测到了MAO3基因和香蕉乙烯受体基因ERS2受机械伤诱导的定量变化。     

硝酸钙和IAA对温州蜜柑果实钙含量及其品质的影响

在花期、花后1周、3周、采前2周对龟井蜜柑进行Ca(NO3)2、IAA和IAA+Ca(NO3)2喷布处理,同时测定了不同发育时期各处理果实钙含量及其采后果实的主要品质,并与采后浸钙处理和完熟采收果实品质进行了对比分析,结果表明:1)各处理的果皮钙含量在花后51d和112d均有所提高,但此期整个果实钙含量并无显著性差异,采收时各处理整个果实和果肉钙含量均显著高于对照;2)采收时各处理果实的可溶性固形物和可滴定酸均显著低于对照,可溶性糖、单果重、果皮色差值和相对电导率与对照无显著性差异,各处理糖酸比显著高于对照;3)采后30d时IAA+Ca(NO3)2喷布和采后浸钙处理果实的维生素C及完熟采收果实的可溶性固形物和可溶性糖均显著高于对照和其他处理。     

瓜类嫁接栽培技术探讨

从6个瓜类砧木品种中，选出了黄瓜适宜砧木为黑籽南瓜，苦瓜适宜砧木为黑籽南瓜和本地肉丝瓜，西瓜适宜砧木为超丰F1和欣京砧一号。瓜类嫁接方法以顶插接法和劈接法为宜，嫁接时期在3月初为宜。重病地黄瓜嫁接苗比自根苗枯萎病发病率降低95．8％，产量提高34．9％；嫁接苦瓜发病率降低83．7％，增产16．9％；嫁接西瓜发病率降低88．9％，增产13．7％。     

柑橘抗CTV转基因与分子标记研究进展

综述了柑橘抗衰退病基因工程中两方面的研究进展。介绍多种来源于柑橘衰退病毒(Citrustriztezavirus,CTV)核酸序列的转基因柑橘和抗性种质资源中抗性基因的分子标记,以及所涉及的方法和遇到的问题。目前研究表明,虽然已成功实现对病毒衣壳蛋白(CP)等基因的转化和Ctv等抗性基因的标记,但尚未获得对CTV有高度抗性的转基因柑橘,而抗性基因亦不能实现定点克隆和转化。因此上述两方面研究还有待深入。     

大蒜新品种成蒜早2号和成蒜早3号的选育

成蒜早2号和成蒜早3号是从温江蒜的自然变异株中,经系统选育而成的早熟新品种.成蒜早2号从播种到蒜薹始收需153～180 d(天),平均单薹质量12.7 g,单头质量10.7 g,多数蒜头由6～9瓣组成,蒜瓣紧密抱握蒜薹轴,一般蒜薹和蒜头产量分别为340和350 kg·(667 m2)-1,抽薹比温江蒜早,抗寒力比温江蒜弱;成蒜早3号从播种到蒜薹始收需153～186 d(天),平均单薹质量和单头质量分别为14.5和12.0 g,多数蒜头由5～8瓣组成.一般蒜薹和蒜头产量分别为320和410kg·(667 m2)-1,抽薹比温江蒜早,抗寒力与温江蒜相当.     

鸡传染性腔上囊病病毒VP2基因在昆虫细胞中的表达

为了深入研究鸡传染性腔上囊病病毒（IBDV）VP2基因的结构和功能,利用Bac-to-Bac系统研制出含有VP2基因的重组杆状病毒rBac-VP2,将rBac-VP2感染Sf9细胞,并用抗IBDV VP2特异性单克隆抗体经间接免疫荧光试验检测,证实感染重组病毒Sf9细胞能高效表达IBDV VP2基因产物;Western-blotting分析结果表明,VP2基因表达产物的分子质量约为40 ku.     

辣椒新品种镇江3号的选育

中晚熟杂交一代辣椒镇研3号是以江苏本地羊角椒自交系Y9007为母本,由甘肃酒泉引进的甜椒自交系T9218为父本配制的一代杂交组合。镇研3号为中熟辣椒品种,果形为牛角形,纵径15cm,肩横径5.0cm、肉厚0.40cm,单果平均重42g。果面光滑,青熟果绿色、味微辣,风味佳,适宜在长江流域或南方保护地栽培种植,667m2产量约为4200～5000kg。