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%).     

Pasture ecology of barley yellow dwarf viruses at Sandford, Tasmania

Samples of cocksfoot ( Dactylis glomerata ), fescue ( Festuca arundinacea ), phalaris ( Phalaris aquatica ) and ryegrass ( Lolium perenne ) were collected every 4-6 weeks for 2.5 years from two sets of replicated plots, one on a heavy soil and the other on a light soil 200 m away. Rhopalosiphum padi was the predominant aphid species; it was more frequent at the heavy soil site. Sitobion fragariae and Metopolophium dirhodum occurred infrequently during the last 12 months of the survey.
Only PAV (57%), RPV (26%) and mixed infections (17%) of these barley yellow dwarf viruses were detected in the 4100 tillers sampled. Virus incidence increased over the sampling period and was consistently higher at the heavy soil site. RPV only became frequent during the last 12 months.
Virus incidence was higher in fescue (21%) and ryegrass (27%), in which PAV predominated, than in cocksfoot (6%) and phalaris (7%), in which RPV finally predominated.     

Barley yellow dwarf viruses in Japanese pasture grasses and lack of correlation with the presence of fungal endophytes

Pasture grasses from temperate Japan were tested for infection with barley yellow dwarf viruses (BYDVs) and fungal endophytes. BYDVs from both the MAV and RPV subgroups were detected, but no symptoms attributable to BYDV infection were observed. Not all isolates from the MAV subgroup could be clearly discriminated as MAV or PAV solely on ELISA results, and may have been intermediate serotypes or mixed infections. BYDVs were found to infect fescue ( Festuca arundinacea : 17%), ryegrass ( Lolium perenne : 41%), timothy ( Phleum pratense : 94%) and Poa spp. (20%). Fescue and ryegrass were predominantly infected with RPV and PAV, respectively. The small collections of Poa spp. were only infected with PAV, while timothy was only tested for MAV subgroup viruses. In fescue 26% of tillers were infected with Acremonium coenophialum , and 60% of ryegrass tillers from an ecotype collection were infected with Acremonium lolii. There was no correlation between BYDV infection and the presence of endophytes for the above species or for Epichloe typhina -infected (50%) timothy. An ELISA test for A. lolii did not detect A. coenophialum in fescue or E. typhina in timothy but showed good agreement with epidermal staining of A. lolii in ryegrass leaf sheaths.     

河北廊坊小麦穗期蚜虫优势度和生态位分析

为明确华北小麦穗期主要蚜虫种类及其生态位, 为京津冀地区小麦蚜虫预测预报和科学防控提供技术支持，采用五点式和棋盘式取样法系统调查了河北廊坊小麦穗期不同蚜虫种类的种群动态及其在植株上的分布, 利用生态位理论, 计算荻草谷网蚜Sitobion miscanthi (Takahashi)、禾谷缢管蚜Rhopalosiphum padi (Linnaeus)和麦无网长管蚜Metopolophium dirhodum (Walker) 3种优势蚜虫的生态位宽度和重叠度。禾谷缢管蚜的时空生态位最宽, 其次为荻草谷网蚜和麦无网长管蚜, 其中禾谷缢管蚜的生态位宽度随时间推移呈上升趋势, 其他两种蚜虫呈下降趋势。不同蚜虫种类之间存在生态位重叠, 其中荻草谷网蚜与禾谷缢管蚜的重叠度最大, 为2.073 0, 荻草谷网蚜与麦无网长管蚜的重叠度最低, 为1.656 4; 随时间推移, 荻草谷网蚜与禾谷缢管蚜之间的竞争趋于增强, 禾谷缢管蚜与麦无网长管蚜之间的竞争趋于减弱, 而荻草谷网蚜与麦无网长管蚜的竞争关系相对稳定。荻草谷网蚜是当地小麦蚜虫主要优势种群, 禾谷缢管蚜时空生态位宽度最大, 与荻草谷网蚜竞争激烈, 麦无网长管蚜时空生态位相对稳定。     

Variation in Transmission Efficiency Among Barley yellow dwarf virus-RMV Isolates and Clones of the Normally Inefficient Aphid Vector, Rhopalosiphum padi

The RMV strain of Barley yellow dwarf virus (BYDV-RMV) is an unassigned member of the Luteoviridae that causes barley yellow dwarf in various cereal crops. The virus is most efficiently vectored by the aphid Rhopalosiphum maidis, but can also be vectored with varying efficiency by R. padi and Schizaphis graminum. Field collections of alate aphids migrating into the emerging winter wheat crop in the fall of 1994 in central New York identified a high proportion of R. padi transmitting BYDV-RMV. This prompted a comparison of the BYDV-RMV isolates and the R. padi populations found in the field with type virus and aphid species maintained in the laboratory. A majority of the field isolates of BYDV-RMV were similar to each other and to the type BYDV-RMV isolate in disease severity on oat and in transmission by the laboratory-maintained population of R. maidis and a field-collected population of R. maidis. However, several field populations of R. padi differed in their ability to transmit the various BYDV-RMV isolates. The transmission efficiency of the R. padi clones was increased if acquisition and inoculation feeding periods were allowed at higher temperatures. In addition, the transmission efficiency of BYDV-RMV was significantly influenced by the aphid that inoculated the virus source tissue. In general, BYDV-RMV transmission by R. padi was higher when R. padi was the aphid that inoculated the source tissue than when R. maidis was the inoculating aphid. The magnitude of the change varied among virus isolates and R. padi clones. These results indicate that, under certain environmental conditions, R. padi can play a significant role in the epidemiology of BYDV-RMV. This may be especially significant in regions where corn is a major source of virus and of aphids that can carry virus into a fall-planted wheat crop.     

Plum pox in north america: identification of aphid vectors and a potential role for fruit in virus spread

ABSTRACT Thirteen aphid species were tested for their ability to transmit Pennsylvania isolates of Plum pox virus (PPV) collected in Columbia (PENN-3), Franklin (PENN-4), and York (PENN-7) Counties, PA. Four species, Aphis fabae, A. spiraecola, Brachycaudus persicae, and Myzus persicae, consistently transmitted PPV in preliminary transmission tests. Two species, Metopolophium dirhodum and Rhopalosiphum padi, were occasional inefficient vectors. Toxoptera citricida, from Florida, also was an effective vector but it does not occur in major stone-fruit-growing states. Species not transmitting PPV in parallel tests included Acyrthosiphon pisum, Aphis glycines, Aulacorthum solani, Macrosiphum euphorbiae, Rhopalosiphum maidis, and Sitobion avenae. When given a 3-day probing access period simultaneously on PPV-infected peach seedlings and healthy peach seedlings, Myzus persicae, Aphis spiraecola, A. fabae, and B. persicae transmitted PPV to 63, 31, 38, and 32% of the healthy peach seedlings, respectively. When given a similar probing period on PPV-infected peach fruit and healthy peach seedlings, the same aphid species transmitted PPV to 50, 35, 0, and 0% of seedlings, respectively. Results support the hypothesis of secondary PPV spread by indigenous aphids in Pennsylvania, and suggest that PPV-infected fruit has the potential to function as a virus source for long-distance dispersal.     

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.     

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.     

异色瓢虫显明变种对荻草谷网蚜和禾谷缢管蚜捕食选择性研究

在实验室条件下,在特定空间内,测定异色瓢虫显明变种对两种蚜虫荻草谷网蚜和禾谷缢管蚜不同密度值下的捕食量。结果表明,荻草谷网蚜和禾谷缢管蚜种群数量同步增加时,EG-S值和EI值变化是从1到∞,EI值是在0到+1范围内依次增加,表明异色瓢虫显明变种喜好捕食荻草谷网蚜明显高于禾谷缢管蚜;荻草谷网蚜数量不变,禾谷缢管蚜数量增加时,EG-S值和EI值是从+1到0,EI值从-1到0范围内依次减少,表明异色瓢虫显明变种明显喜好捕食禾谷缢管蚜;禾谷缢管蚜数量不变,荻草谷网蚜数量增加时,EG-S值和EI值变化从+1到∞,EI值在0到+1范围内依次增加,表明异色瓢虫显明变种明显喜好捕食荻草谷网蚜。捕食量结果同选择指数。     

茉莉酸诱导小麦幼苗对麦蚜取食行为的影响

茉莉酸可诱导小麦品种郑州891的防御反应，使麦长管蚜Sitobion avenae(F.)和禾谷缢管蚜Rhopalosiphum padi(L.)的取食行为发生明显改变。尽管此两种蚜虫在正常的小麦相干株上取食的EPG各波型参数出现的次数及历时变化较大，但经茉莉酸诱导后，都再现了NP波次数和历时显著增加、E1与E2波历时明显缩短、首次出现E1波时间显著延长以及口针在细胞间穿刺频率明显升高等变化。这说明茉莉酸诱导后，郑州891的取食适合度降低，其机理与茉莉酸诱导产生挥发性的蚜虫取食拒避剂及诱导维管液营养成份的改变有关。试验还证实；麦长管蚜和禾谷缢管蚜的嗅觉和味觉感受器在其对寄主植物适合度的鉴别中共同起作用；植物适合度不能仅由1－2个EPG波形参数作为指示因子，要视具体情况全面分析，才能得出可靠的结论。     

Aphid Abundance on Cereals in Autumn Predicts Yield Losses Caused by Barley yellow dwarf virus

ABSTRACT Barley yellow dwarf virus (BYDV) damage to winter cereals and population dynamics of the aphid Rhopalosiphum padi during fall were monitored in fields during 10 years at various locations in the northern half of France. Logistic regression was used to examine whether a simple risk probability algorithm based only on the autumnal population dynamics of R. padi can accurately predict yield losses caused by BYDV and, therefore, the need for insecticide treatment. Results showed that the area under the curve of the percentage of plants infested by R. padi during autumn was highly significantly related to BYDV yield losses. Then, a cost/benefit analysis was performed to estimate the optimal decision threshold resulting in the lowest annual average costs of BYDV damage and control. A "model use" strategy allowed a reduction in the annual average costs of BYDV disease and control of up to 36% when compared with a "prophylactic spraying" strategy. The optimal decision threshold was highly sensitive to variation in disease prevalence. This property was used to propose an easy way to adapt the model to any production situation through the determination of the most accurate decision threshold.     

主要次生物质对麦蚜的抗性阈值及交互作用

用麦蚜全纯人工饲料加不同浓度次生物质的薄膜饲养技术,研究了8种次生物质对麦长管蚜(Sitobion avenae)及禾谷缢管蚜(Rhopalosiphum padi)生长、发育及若蚜增重等生命参数的影响和4种次生物质对麦长管蚜的复合作用。结果表明,除芸香苷外其余几种次生物质具不同程度的抗蚜性,统计分析得到不同次生物质抗蚜阈值。单宁与总酚对麦长管蚜有明显增效作用,单宁与门布存在一定的增效作用,总酚与丁布有一定的拮抗作用。单宁酸、总酚、香豆素和单宁酸、儿茶素、香豆素、门布分别是抗麦长管蚜和禾谷缢管蚜的次生物质。     

Occurrence of barley yellow dwarf viruses in some common grasses (Gramineae) in south west England

The incidence and distribution of aphid transmitted barley yellow dwarf (BYD) viruses (PAV-, RPV- and MAV-like isolates) are described in 14 species of common pasture and hedgerow grasses from five localities of south-west England during 1987 and 1988. Isolates were identified by indirect 'sandwich' ELISA using the monoclonal antibodies MAC91, MAC92 and MAFF2. More infection was detected in 1987 than in 1988 but this was mainly due to a sharp decline at one site. Intensity of infection was greater in Poa annua and Lolium perenne populations than in most other species. BYD was not detected in Arrhenatherum elatius Elymus repens Agrostis canina and A. stolonifera . All three isolates of BYD were widespread. MAV was associated more with localities further north and RPV more with those further south. PAV was common only at the southern-most site. This geographical distribution was reasonably consistent in both years. Given these trends, susceptible grass species fell broadly into three groups with respect to isolate frequency, those predominently infected by RPV and MAV (seven spp.), those equally infected by all isolates (two spp.) and a single species, Poa annua , infected mainly by PAV. Some implications of these findings for the epidemiology and control of BYD viruses are briefly considered.     

BYDV PREDICTOR: a simulation model to predict aphid arrival, epidemics of Barley yellow dwarf virus and yield losses in wheat crops in a Mediterranean-type environment

BYDV PREDICTOR, a simulation model, was developed to forecast aphid outbreaks and Barley yellow dwarf virus (BYDV) epidemics in wheat crops in the grainbelt region of southwest Australia, which has a Mediterranean-type climate. The model used daily rainfall and mean temperature to predict aphid ( Rhopalosiphum padi ) buildup in each locality before the commencement of the cereal-growing season in late autumn, and to forecast the timing of aphid immigration into crops. The introduction of BYDV by aphid immigrants, aphid buildup within the crop, spread of BYDV, and yield losses were predicted for different sowing dates. The model simulations were validated with 10 years' field data from five different sites in the grainbelt, representing a wide range of scenarios. When first aphid arrival dates ranging from 1 June to 2 September were compared with predictions, 65% of the variation between sites and years was explained. Progress curves for the predicted percentage of plants infected with the serotype BYDV-PAV closely resembled the starting point and shape of those recorded in 14 out of 18 scenarios. Sensitivity analysis confirmed that the combination of a high proportion of immigrants vectoring BYDV, early sowing of crops and early start to aphid arrival relative to sowing date led to the most BYDV spread and greatest yield loss. The model was incorporated into a decision support system used by farmers in targeting sprays against aphids to prevent virus spread in autumn and winter. BYDV PREDICTOR could serve as a template for modelling similar virus/aphid vector pathosystems in other regions of the world, especially those with Mediterranean-type climates.     

Plant community diversity influences vector behaviour and Barley yellow dwarf virus population structure

The species composition of a plant community can affect the distribution and abundance of other organisms including plant pathogens. The goal of this study was to understand the role of host diversity in the transmission of two Barley yellow dwarf virus (BYDV) species that share insect vectors and hosts. Greenhouse experiments measured the transmission rate of BYDV species PAV and PAS from infected oat plants to healthy agricultural and wild grasses and from these species back to healthy oat seedlings. In the field component of the study, the rate of spread of PAV and PAS was measured in monoculture plots planted with agricultural grasses. In greenhouse experiments, the aphid vector more readily transmitted PAV from agricultural grasses and more readily inoculated PAS to the wild grass species assayed. In the field experiment, disease prevalence was greater in wheat, but there was no difference in the rate of spread of PAV and PAS. These results indicate an interaction between vector and host genotype that selects for greater PAV transmission in grain crops, contributes to differences in disease prevalence between grass types, and maintains pathogen diversity within the larger plant community (i.e. agricultural and non‐agricultural hosts).     

麦无网长管蚜田间种群动态的研究

作者在田间系统调查的基础上对麦无网长管蚜空间分布格局，垂直分布动态和数量时序变化方面进行。组建了由气象因素和小麦生育期为自变量的数量预测模型。对三种主要麦蚜的空间生态位的定量计算，了解麦无网长管蚜，禾谷缢管蚜和麦长管蚜之间的种间竞争关系。用相关分析和通径分析方法寻找影响麦无网长管蚜种群消长的关键因子。认为该蚜在北京地区轻发生的原因是越冬虫源少和小麦生育阶段气温过高抑制作用所致。     

Role of acquisition and inoculation time in the expression of clonal variation for BYDV-PAV transmission in the aphid species Rhopalosiphum padi

Vector efficiency of 20 Rhopalosiphum padi clones, originating from Europe, North America and North Africa and exhibiting different types of life cycle, was evaluated by transmitting a French BYDV-PAV isolate to barley plants under five different acquisition/inoculation sequences (AAP/IAP). Differences between clones in transmission efficiency were found only when a short AAP was followed by a long IAP (6 h/120 h) and, to some extent, when a long AAP (48 h) was followed by a short IAP (6 h), but no differences were found when the conditions for virus transmission were optimal, i.e. long AAP followed by long IAP (48 h/120 h). There were no differences in transmission rates by clones of different geographical origins and with different life cycles. As a consequence, clonal variation is probably of little importance in the vector aspects of the epidemiology of PAV serotypes transmitted by R. padi , but the availability of a range of clones exhibiting transmission differences under limiting AAP or IAP conditions could be of interest for studies of virus–vector relationships.     

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。     

Variation in transmission of two BYDV-MAV isolates by multiple clones of Rhopalosiphum padi L.

Vector efficiency of up to 17 Rhopalosiphum padi L. clones originating from Europe, North America and North Africa, was evaluated by transmitting two isolates of the serotype MAV for which this species is normally an inefficient vector. When test plants were inoculated by batches of 3 aphids, both isolates were rather well transmitted by one clone (Rp5), isolate MAV2 was poorly transmitted by all other clones tested and isolate MAV11 was not transmitted by eight clones and poorly transmitted by two clones. When eight aphids were used by test plants, all clones transmitted both isolates. The epidemiological consequences of MAV transmission by some R. padi clones are discussed, as well as the interest of these clones for studying aphid-derived components of luteovirus transmission.     

麦蚜与天敌相互关系研究及麦蚜防治指标初报

试验结果表明:小麦产量损失率与麦长管蚜、七星瓢虫幼虫关系极显著,与禾缢管蚜关系显著。经对田间麦蚜防治指标初步试验探讨,揭示了在麦蚜、天敌共存的农田系统内,由于天敌捕食控制作用,原来仅以麦蚜为害单因素所制定的防治指标可有较大幅度的放宽。