A domain of the readthrough protein of barley yellow dwarf virus (NY-RPV isolate) is essential for aphid transmission

Luteoviruses are obligately transmitted by aphids and contain two capsid proteins, the coat protein (CP) coded for by open reading frame (ORF) 3, and the readthrough protein (RTP), produced by readthrough of the amber termination codon of ORF 3 into the contiguous ORF 5. Previous studies have suggested that it is the RTP that determines transmissibility and vector specificity. To investigate which capsid protein or protein part contains determinants for the transmission of the NY-RPV isolate of barley yellow dwarf virus (BYDV) by its vectorRhopalosiphum padi, we produced three fusion proteins by expressing NY-RPV cDNA inE. coli. These respectively represented the CP alone (P3), a region of the RTP immediately following the amber termination codon (P5a), and the remainder of the RTP (P5b). Polyclonal antisera raised against the P3, P5a and P5b proteins each gave distinctive reactions against purified NY-RPV on Western blots. Also, in ELISA tests, antisera raised against all three fusion proteins detected purified intact virions. When mixed with purified virions and fed toR. padi through Parafilm membranes, immunoglobulins (Igs) from antisera raised against P3 and P5b had no effect on transmission, whereas Ig from antiserum against P5a interfered with transmission. P5a antiserum Ig had no effect on the transmission of the P-PAV isolate of BYDV byR. padi. The results demonstrate that while neither the CP itself nor the terminal region of the RTP are key determinants for transmission, a specific domain in the central part of the RTP is an important determinant in the transmission of NY-RPV byR. padi, though apparently not of P-PAV.     

Identification of barley yellow dwarf virus and cereal aphid Infestations In winter wheat by aerial photography

In 1976 distinctive patterns were identified on aerial photographs of winter wheat crops in East Anglia. The patterns consisted of numerous dark foci which were found to be associated with sooty moulds (mostly Cladosporium spp.) in the crops. Both green and mature crops were photographed in 1977 and the patterns were matched with crop inspection data. These suggested that barley yellow dwarf virus (BYDV) was the cause of the patterns and that sooty moulds secondarily invaded the infected plants. A different type of focal pattern appeared to be associated with damage caused by aphid feeding. All crops showing the pattern associated with BYDV were sown before 13 October but there was no relationship with sowing date for the crops damaged directly by aphids. Yield losses within foci were estimated by sampling and the total crop areas affected were calculated using an image analysis computer: yield losses were estimated to range from 10% (BYDV) to 2% (aphid feeding). The epidemiology of BYDV is discussed and reasons are suggested for the development and appearance of the foci.     

A simple test for evaluation of transmission efficiency of barley yellow dwarf virus by aphids

Barley yellow dwarf virus (BYDV) transmission test systems involve the use of clip-cages or of whole plants in cages, which are both labor-intensive methods and require large controlled environment units. Employing detached leaves for assessment of the inoculation efficiency of aphids proved reliable for assessing transmission of a BYDV PAV-like isolate byRhopalosiphum padi. One use of the system could be for the rapid determination of the infectivity of field-collected aphids, an essential part of any epidemiological study of BYDV. http://www.phytoparasitica.org posting Aug. 14, 2002.     

Reservoirs of plant virus disease: Occurrence of wheat dwarf virus and barley/cereal yellow dwarf viruses in Sweden

Non-crop plants such as grasses and volunteer plants are an inseparable part of the flora of crop fields and can influence virus incidence in crop plants. The presence of grasses as virus reservoirs can lead to a higher probability of virus incidence in crop plants. However, the role of reservoirs as an inoculum source in agricultural fields has not been well studied for many viral diseases of crops. Grasses have been found to constitute potential reservoirs for cereal-infecting viruses in different parts of the world. This study revealed that cereal-infecting viruses such as wheat dwarf virus (WDV), barley yellow dwarf viruses (BYDVs), and cereal yellow dwarf virus-RPV (CYDV-RPV) can be found among ryegrass growing in or around winter wheat fields. Phylogenetic analysis showed that a WDV isolate from ryegrass was a typical WDV-E isolate that infects wheat. Similarly, a ryegrass isolate of barley yellow dwarf virus-PAV (BYDV-PAV) grouped in a clade together with other BYDV-PAV isolates. Inoculation experiments under greenhouse conditions confirmed that annual ryegrass of various genotypes can be infected with WDV to a very low titre. Moreover, leafhoppers were able to acquire WDV from infected ryegrass plants, despite the low titre, and transmit the virus to wheat, resulting in symptoms. Information from the grass reservoir may contribute to improving strategies for controlling plant virus outbreaks in the field. Knowledge of the likely levels of virus in potential reservoir plants can be used to inform decisions on insect vector control strategies and may help to prevent virus disease outbreaks in the future.     

紫外线、高压静电和大麦黄矮病毒胁迫下荻草谷网蚜SOD基因表达

为探索环境胁迫影响昆虫适合度的内在机制,通过cDNA末端快速扩增（rapid amplification of c DNA end,RACE）技术克隆得到荻草谷网蚜Sitobion miscanthi体内超氧化物歧化酶（superoxide dismutase,SOD）基因MnSOD和CuZnSOD的cDNA序列全长,对该序列进行分析,检测紫外线、高压静电和大麦黄矮病毒（barley yellow dwarf virus,BYDV）胁迫下荻草谷网蚜体内MnSOD和CuZnSOD基因表达量的变化。结果显示,荻草谷网蚜体内MnSOD和CuZnSOD基因的cDNA序列全长分别为1 517 bp和954 bp(GenBank登录号分别为MT533627和MT533626),开放阅读框分别为669 bp和459 bp,分别编码222个和152个氨基酸,预测蛋白质相对分子量分别为24.99 kD和15.84 kD。荻草谷网蚜体内MnSOD和CuZnSOD蛋白均与半翅目蚜科昆虫同源蛋白氨基酸序列相似性高,亲缘关系最近。0.50 m W/cm2（低强度）和0.70 m W/cm2（高强度）紫外线胁迫下...     

6种病毒抑制剂对西藏青稞上大麦黄矮病的防治效果

通过田间小区试验,开展了6种病毒抑制剂对西藏青稞上大麦黄矮病防治效果的研究.采用带毒蚜虫人工接种法,于青稞起身拔节期每株接种10～15头带毒麦长管蚜,7 d后灭蚜,灭蚜后3d喷施病毒抑制剂,在成株期出现黄矮病症状后调查病株率、病情指数、防治效果,以及长势和产量.结果表明,6种病毒抑制剂对青稞上大麦黄矮病有不同程度的防治...     

The occurrence and effects of barley yellow dwarf virus in maize in SW England

During 1975 and 1976 barley yellow dwarf virus was isolated, using the aphid Rhopalosiphum padi (L.) from five maize cultivars in the Exeter area. The isolates produced interveinal flecking, often accompanied by leaf reddening, in the maize cultivar Anjou 210 and several other susceptible cultivars. ln 1976 visual assessment of six commercial maize plantings indicated natural infections ranging from 11 to 14% of plants, whilst infection in a disease observation plot ranged from 0.8 to 27.5%. Population counts for the three aphid vectors Sitobion avenae (F.), Metopolophium dirhodum (W.) and Rhopalosiphum padi (L.), associated with the crop, corresponded closely with the Rothamsted Insect Survey results from Starcross, Devon.
The maize cultivars Anjou 210 and De Kalb 202 were grown in experimental plots with individual rows containing 0, 25, 50, or 100% barley yellow dwarf-infected plants. Infection caused severe stunting of Anjou 210 but had less effect on De Kalb 202. Dry matter yield losses of 50% for Anjou 210 and 27% for De Kalb 202 were recorded; there were also significant changes (p<0.05) in dry matter content, metabolisable energy, digestible crude protein and water soluble carbohydrate.     

Occurrence of barley yellow dwarf virus in autumn-sown cereal crops in the United Kingdom in relation to field characteristics

The incidence of barley yellow dwarf virus and of its aphid vectors was surveyed in untreated parts of autumn-sown cereal crops, mainly wheat and barley, in the United Kingdom in 1995-8. The incidence of virus in the spring was related to the incidence of aphids in the preceding autumn. Both virus and aphid incidences could also be related to a range of crop and field characteristics, in particular sowing date, regions as defined by their geographical position, topography and climate, the proximity of the field to the sea, the extent of arable land in the vicinity of the field, and the aspect and size of the field. Proximity of cropped fields to setaside areas had no significant effect on either aphid or virus incidence.     

RNA/cDNA hybridization studies of UK isolates of barley yellow mosaic virus

The RNA components of two isolates of BaYMV from Streatley and Wiltshire were analysed by agarose gel electrophoresis. Northern blots of extracts of both isolates analysed with random-primed cDNA probes to RNA1 and 2 of the Streatley isolate showed little or no sequence homologies between the two isolates, confirming other evidence that they should be considered as different viruses.     

Outbreak of MAV-type barley yellow dwarf virus on wheat in the Garhwal Hills in India

A serious outbreak of barley yellow dwarf luteovirus (BYDV, MAV-type) on wheat in the Garhwal Hills, Central Himalayas, India is reported. This is the first conclusive evidence based on serology for the presence of MAV-BYDV in India.     

Effects of barley yellow dwarf virus on some varieties of Italian, hybrid and perennial ryegrasses and their implication for grass breeders

With the exception of chlorotic streaks in a few plants, a severe strain of barley yellow dwarf virus (BYDV) transmitted by Rhopalosiplum padi caused no obvious foliar symptoms in 54 varieties of ryegrass when they were defoliated monthly. When defoliation ceased and yellow or red discoloration of the leaf tips was allowed to develop, it was a poor indicator of the seventy of disease effect on yield. Thus, some varieties which developed marked discoloration were less severely damaged than some with little or none While BYDV induced yield significant in some varieties of ryegrass, it increased it significantly in others. In some varieties these BYDV-induced yield increases occurred throughout the year, but in others they occurred in 1 month and were offset by a yield decrease in another. BYDV infection caused a greater yield reduction in roots than in shoots. Even varieties giving increased shoot yield gave decreased root yield. The possible disadvantages of the resulting increase in shoot to root ratio are discussed. It is concluded that breeding ryegrass for BYDV-induced yield increases may be easier and more rewarding than breeding for resistance or tolerance.     

Transmission of barley yellow dwarf virus by cereal aphids collected from different habitats on cereal farms

Cereal aphids were collected from cereal crops, from Poa annua within cereal fields, from Lolium perenne pastures and from wild grasses in hedge bottoms and around farm buildings. The frequency of barley yellow dwarf virus (BYDV) transmission was assessed by aphid transmission tests. There were differences in transmission rates between aphid species, between host species and between years. The transmission rates of Rhopalosiphum padi from the different host species were broadly similar whereas for Sitobion avenae, P. annua within cereal fields was significantly better than the other host species. Wild grasses other than P. annua were relatively poor sources of virus. A large percentage of aphids frequently transmitted more than one strain, suggesting that host plants are often infected with more than one BYDV strain.     

Occurrence of barley yellow dwarf virus in cereals and grasses of the low-rainfall wheatbelt of South Australia

South Australia is in the dry temperate zone where most cereal crops are grown in an area of low rainfall, with a crop-free season from December to April. The incidence of barley yellow dwarf virus (BYDV) was assessed by ELISA from 1989 to 1991 in wheat crops and irrigated pastures of South Australia. The incidence of BYDV was low in most wheat crops of the low-rainfall area in 1989 and 1990 (less than 1% of plants infected), but moderate levels of infection (1–10%) were observed in some early-sown crops. BYDV infection was more widespread in the high-rainfall area (south east of South Australia). A high incidence of BYDV was observed in the irrigated pastures of the three areas surveyed (4–86%). Of the five previously described strains, the Rhopalosiphum padi/Sitobion avenae strain (PAV) was the most common in wheat samples (> 90%). PAV and the R. padi-specific strain (RPV) were found in pasture grasses, alone or in mixed infection. Virus incidence was greater in Festuca spp. (56%) and Lolium perenne (30%) than in other species (2-–9%).     

南方水稻黑条矮缩病毒和水稻黑条矮缩病毒的单抗制备及其检测应用

 用与牛血清白蛋白偶联的南方水稻黑条矮缩病毒（Southern rice black-streaked dwarf virus,SRBSDV）衣壳蛋白的C端12个氨基酸多肽为抗原免疫BALB/c小鼠,经细胞融合、筛选、克隆,获得2株能稳定传代并分泌抗SRBSDV和水稻黑条矮缩病毒（Rice black-streaked dwarf virus,RBSDV）单克隆抗体（MAb）的杂交瘤细胞株3F1、5G1。3F1、5G1单克隆抗体腹水间接ELISA效价达10^-6,抗体类型及亚类均为IgG1, kappa链。 Western blot分析表明,2株单克隆抗体均与SRBSDV和RBSDV的外壳蛋白亚基有特异反应。利用单克隆抗体3F1建立的dot-ELISA检测方法能准确、特异、灵敏地检测田间稻飞虱及水稻样品中的SRBSDV和RBSDV。SRBSDV和RBSDV单克隆抗体的制备及检测方法的建立为水稻黑条矮缩病的诊断、预测预报及科学防控提供了技术支撑。     

The incidence of strains of barley yellow dwarf virus in perennial ryegrass crops in south-west and central Scotland

The incidence of barley yellow dwarf virus (BYDV) in perennial ryegrass ( Lolium perenne ) crops in four areas of south-west and central Scotland was investigated between March 1988 and February 1989. BYDV was detected in 93·8% of the grass swards using an indirect enzyme-linked immunosorbent assay (ELISA). This enabled the seasonal periodicity of the BYDV strains to be monitored over 12 months for the first time in Scotland. The incidence of the RPV, PAV and MAV strains of BYDV declined between March and July 1988, before gradually rising in August. Incidence increased markedly in September, especially of the RPV and MAV strains, and then gradually decreased over the winter months, before stabilizing in February 1989. The incidence of the different strains in perennial ryegrass leys varied between geographical areas and between fields within areas. Most ryegrass samples contained a mixture of the three strains of BYDV. RPV was the most common strain in Ayrshire, while the incidence of PAV was highest in Wigtownshire and that of MAV was highest in Dumfriesshire and Stirlingshire. The incidence of BYDV increased with the age of the sward. The role of perennial ryegrass as a source of virus for the infection of cereals is discussed.     

The characteristics of mineral oils in relation to their inhibitory activity on the aphid transmission of potato virus Y

In greenhouse trials paraffinic mineral oils, characterized by a viscosity gravity constant (VGC) of 0.790–0.819, and with viscosities between 12 and 30 cSt at 37°C (66–150 SUS) proved to have the best aphid transmission inhibiting activity of potato virus Y to red peppers. The activity decreased rapidly with decreasing viscosities but only slowly with increasing values.Effective oils are further characterized by an unsulfonated residue (USR) of 95–100, indicating the near or total absence of aromatic structures, which are inactive and known to be phytotoxic. The paraffine-pourpoint should be below 0°C, indicating that n-paraffines do not form a very important part of the oil, since they are also inactive. Naphthenic structures seem equally inert, their percentage in the oil depending on the origin of the crude oil, because they cannot be separated from the paraffinic structures by refining procedures.Mineral oils which one commercialize for agricultural practice normally have an USR above 95 and a paraffine-pourpoint below 0°C. Therefore, the information on the classification, based on a VGC value and on the viscosity, is already sufficient to allow an evaluation of those oils of their suitability as inhibitor of the virus transmission by aphids.Samenvatting In kasproeven bleken minerale paraffine oliën, gekenmerkt door een VGC (viscositeits-dichtheidsconstante) van 0.790–0.819 en een viscositeit tussen 12 en 30 cSt bij 37°C (66–150 SUS) de beste werking te bezitten tegen de overdracht van aardappelvirus Y naar paprika door bladluizen. De werking verminderde snel bij afnemende viscositeiten beneden 12 cSt, slechts langzaam bij toenemende waarden boven 30 cSt.De minerale olie met de meest gunstige eigenschappen met betrekking tot verhindering van de virusoverdracht wordt verder nog gekenmerkt door een USR (nier-sulfoneerbare rest) van 95–100. Dit betekent het geheel of bijna geheel afwezig zijn van aromatische verbindingen, die bekend zijn om hun fytotoxische eigenschappen en bovendien niet werkzaam zijn. Het stollingspunt moet bij voorkeur onder 0°C liggen wat betekent dat n-paraffinen geen al te belangrijk bestanddeel van de olie vormen, aangezien deze eveneens onwerkzaam zijn. Naphthenische structuren bleken ook onwerkzaam te zijn. Het gehalte hiervan in de oliefractie hangt echter van de herkomst van de ruwe olie of, omdat ze niet door raffineren van de paraffinestructuren kunnen worden gescheiden.Minerale oliën die aanbevolen worden voor landbouwkundige doeleinden, bezitten normalerwijze een USR boven 95 en een stollingspunt onder 0°C. Dit betekent dat informatie over de aard der oliën op grond van een VGC waarde en over de viscositeit voldoende is om dergelijke oliën te beoordelen op hun geschiktheid de virusoverdracht door bladluizen te kunnen verhinderen.     

Effect of barley yellow dwarf virus on susceptibility of barley cultivars to net blotch (Pyrenophora teres) and leaf blotch (Rhynchosporium secalis)

The effect of barley yellow dwarf virus (BYDV) on the development of net blotch (Pyrenophora eves) and leaf blotch (Rhynchosporium secalis) was examined on seven barley cuitivars. Seedlings were infected with BYDV at the two-leaf stage (G.S. 12). Their susceptibility to three isolates of p teres and isolates of two races (U.K. 1, U.K. 2) of R. secalis was examined at the four-leaf stsge (G.S. 14) and when plants were more mature (G.S. 33/38). At G.S. 14 numbers of lesions produced by P. teres and R. secalis were reduced, on average, by 37 and 72% respectively, and at G.S. 33/38 by 61 and 74%.     

Evaluation of various methods for the detection of barley yellow dwarf virus by the tissue-blot immunoassay and its use for virus detection in cereals inoculated at different growth stages

Various modifications of the tissue-blot immunoassay (TBIA) for the detection of barley yellow dwarf virus (BYDV, luteovirus) were compared. Similar results were obtained by using three different labelled molecules; goat anti-rabbit antibodies conjugated to alkaline phosphatase, protein A conjugated with alkaline phosphatase and goat anti-rabbit antibodies conjugated with colloidal gold. Blocking the nitrocellulose membrane with polyvinyl alcohol for 1 min was effective and allowed the procedure to be shortened by one hour. TBIA was sensitive enough to detect BYDV in old dry tissue wich had been soaked in water for 1 h.BYDV was monitored by TBIA in wheat, oat and barley after inoculation at heading, flowering and grain filling growth stages. The later the inoculation date, the greater the chance of detecting the virus in stem bases rather than in the upper part of the stem. The later the inoculation the less virus moved, from the inoculated tiller to other tillers of the same plant.     

大麦黄矮病毒GPV与GAV株系间异源装配现象的初步研究

 以我国麦区的大麦黄矮病毒GPV、GAV株系为材料,利用它们的蚜传特异性,将由禾谷缢管蚜传播的GPV和由麦长管蚜传播的GAV混合侵染到岸黑燕麦上,并进行继代传毒。混合侵染后代蚜传表现型的变化初步表明存在异源装配现象,且表现型混合发生的比例较高。用DAS-ELISA和RT-PCR法对混合侵染后代进行了测定,进一步证明了异源包装现象的存在。部分基因的核苷酸序列分析初步显示所测定的混合侵染后代中没有发生基因重组。