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.     

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。     

肉用禽育种中应使用的主要屠宰性状指标的探讨

通过对不同周龄、品种的肉鸡、肉鸭屠宰数据进行分析,发现体重、屠宰重、全净膛重、半净膛重、胴体重这几个指标之间呈高度相关(R＞0.94,P＜0.0001),说明可以把这几个指标合并为一个指标,考虑到育种公司测定的实际需求,建议用屠宰重代替全净膛重、半净膛重.由于腿肌重与腿重呈显著相关,用腿重来代替腿肌重,可以大幅度简化育种工作,提高育种效率.本研究认为可以用宰前体重、腿重、胸肌重、腹脂重作为肉用禽屠宰测定的主要指标,为了计算相关的率,可以考虑测量屠宰重指标.     

饲粮中添加抗菌肽对肉鸭增重及血清尿素氮、总蛋白水平的影响

240只1日龄肉鸭随机成分4组,每组设3个重复,对照组用基础日粮,试验组在基础日粮上每千克分别添加1、2、3mL抗菌肽制剂。结果显示:1)2、3mL/kg添加量组增重效果显著(P<0.05),3mL/kg添加量组最佳;净肉率升高,达到显著水平(P<0.05),其中主要是胸肌率上升;腹脂率降低但差异不显著(P>0.05);料重比无显著变化(P>0.05)。2)血清总蛋白浓度差异不显著(P>0.05),但尿素氮浓度下降,2、3mL/kg添加量组达显著水平(P<0.05),3mL/kg添加量组最低。     

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.     

番鸭在南京地区的适应性观察

番鸭在南京地区进行冬、夏两批饲养,均有较强的适应性。试验结果表明:冬、夏两 批饲养的番鸭只平均重量差异不显著(P>0．05)。夏季与冬季的料重比分别为1:2．62和1: 3．07,冬季饲养的鸭子饲料利用率低,料重比大于夏季。冬季在塑料大棚中饲养番鸭精饲料减 少1／3,添加青粗饲料能达到同样的增重效果。温度与增重无相关关系,相对湿度与番鸭的增 重呈负相关(P<0．01)。鸭舍内平均温度在11．05℃-30．93℃之间,相对湿度在76．28％以 下,番鸭能正常生长发育。环境温度在9．8℃以下,番鸭的生长发育受阻,饲料利用率降低。相 对湿度在77％以上,其增重受到影响。特别在低温高湿的环境中,严重地影响番鸭的生长。在 相同的饲养期内,周平均温度9．8℃,平均相对湿度91％,番鸭周平均增重22 g,周平均温度 27．42℃,平均相对湿度71．29％,番鸭周平均增重355 g,相差333 g(P<0．01)。     

Effects of Latent Infection of Stock Plants and Abundance of Thrips on the Occurrence of <Emphasis Type="Italic">Tomato spotted wilt virus </Emphasis>in Chrysanthemum Fields

DAS-ELISA proved to be reliable enough to detect a latent infection by Tomato spotted wilt virus (TSWV) in asymptomatic stock plants of chrysanthemum. A high density of Frankliniella occidentalis, the predominant vector, in the presence of latently infected stock plants resulted in a high incidence of disease in the chrysanthemum production field. The incidence of disease was low when the vector thrips were not abundant in spite of the presence of latently infected stock plants. These results suggest that an infestation of the vector thrips causes severe secondary spread of TSWV originating from latently infected stock plants in chrysanthemum production fields. Received 27 July 2001/ Accepted in revised form 27 November 2001     

A Cucumber mosaic virus Isolated from Silene armeria

A Cucumber mosaic virus was newly isolated from Silene armeria and was characterized by biological, serological and molecular biological methods. Received 4 July 2001/ Accepted in revised form 28 August 2001