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.     

Diversity and occurrence of chickpea chlorotic dwarf virus on legumes from Iran

Chickpea chlorotic dwarf virus (CpCDV; genus Mastrevirus, family Geminiviridae) is one of the most important legume-infecting viruses with a wide host range and geographic distribution in Africa and Asia. In Iran, CpCDV is common in chickpea (Cicer arietinum), but there is limited information about diversity and infections in plants of other legume species. In the current study, a total of 1671 leaf samples from different pulse crops with symptoms were collected in nine provinces of Iran, and the CpCDV infection status was tested by PCR and/or rolling circle amplification (RCA), resulting in the detection of CpCDV in samples of chickpea, lentil (Lens culinaris) and faba bean (Vicia faba) from different regions. Sequence analysis of complete genomes of 18 isolates recovered by digestion of RCA products revealed infection with isolates of the strains CpCDV-A and CpCDV-F in chickpea, lentil and faba bean. Phylogenetic analysis showed that the Iranian isolates of CpCDV were closely related to previously sequenced isolates of CpCDV-A and CpCDV-F. To the authors' knowledge, this is the first report of CpCDV-F in Iran. Using agroinoculation with infectious clones for one isolate each of CpCDV-A and CpCDV-F, infectivity was confirmed in both faba bean and chickpea, with plants developing leaf curling and/or yellowing. Both infectious clones also successfully infected Nicotiana benthamiana resulting in mild yellowing and intensive leaf curling for CpCDV-A, and dark-green mosaic, dwarfing and mild leaf curling for CpCDV-F.     

Sequence analyses of Wheat dwarf virus isolates from different hosts reveal low genetic diversity within the wheat strain

Wheat dwarf virus (WDV) causes disease in wheat (Triticum aestivum) and barley (Hordeum vulgare) in many parts of Europe. The host range also includes many species of the family Poaceae. WDV is only transmitted by the leafhopper Psammotettix alienus. During a five‐year period (2001–2005), grass samples were collected in central Sweden in the vicinity of fields with WDV‐infected winter wheat. Screening with ELISA and PCR identified WDV in a low number of samples (8/1098) from only three grass species: Apera spica‐venti, Avena fatua and Poa pratensis. In addition, triticale was found to be positive. Fourteen WDV isolates from Avena fatua, Apera spica‐venti, Triticum aestivum, Lolium multiflorum, Poa pratensis, triticale and the insect vector Psammotettix alienus, were partially sequenced (ca. 1200 nucleotides), providing the first published WDV sequences from the insect vector. All isolates belonged to the wheat strain of WDV and the genetic diversity was low. Phylogenetic analyses showed no clear grouping according to geographical location or host species. The results suggest that the same WDV genotypes are infecting both wheat and grasses in Sweden. Interestingly, one group of isolates (subtype B) formed a distinct clade in the phylogenetic tree. Subtype B was always found in mixed infection with the main genotype. Complete sequencing of a subtype B isolate showed that it was 98·6% identical to a typical wheat isolate from the same plant.     

马铃薯Y病毒在种薯中检出率及其株系鉴定

 马铃薯是我国重要粮食和经济作物。马铃薯Y病毒(potato virus Y,PVY)是危害马铃薯生产的重要病害。种植脱毒种薯是防治PVY最有效的途径。马铃薯种薯携带PVY问题严重,但种薯中PVY株系还不清楚。本研究利用PVY特异性抗体检测了7个马铃薯品种362个种薯,发现不同品种种薯带毒率差异较大,最高达12%。通过RT-PCR方法扩增获得了7个PVY分离物编码区全序列。重组分析发现7个分离物基因组均为重组型,根据重组位点的差异可以分为PVY^NTN-NW(SYR-II型)、Rec-1、Rec-2和Rec-3等4种重组类型,后3种为新重组类型。系统进化分析发现,分离物HQH18G3-10与PVY^NTN-NW(SYR-II型)处于同一个大的分支,但与中国PVY大田分离物聚集在一起形成一个相对独立的组,命名为PVY^NTN-NW(CN型);其余6个分离物与数据库中的中国分离物聚集在PVY^N-Wi组。这暗示PVY中国分离物具有相对独立的进化过程,PVY马铃薯大田分离物和种薯分离物进化上相近。所有分离物均能在珊西烟上引起典型叶脉坏死症状,HQH18G3-10引起的坏死症状最为严重。本研究首次报道了我国种薯内PVY发生情况,对分析病毒发生发展规律和防控具有借鉴作用。     

马铃薯Y病毒在种薯中检出率及其株系鉴定

马铃薯是我国重要粮食和经济作物。马铃薯Y病毒(potato virus Y,PVY)是危害马铃薯生产的重要病害。种植脱毒种薯是防治PVY最有效的途径。马铃薯种薯携带PVY问题严重,但种薯中PVY株系还不清楚。本研究利用PVY特异性抗体检测了7个马铃薯品种362个种薯,发现不同品种种薯带毒率差异较大,最高达12%。通过RT-PCR方法扩增获得了7个PVY分离物编码区全序列。重组分析发现7个分离物基因组均为重组型,根据重组位点的差异可以分为PVY^NTN-NW(SYR-II型)、Rec-1、Rec-2和Rec-3等4种重组类型,后3种为新重组类型。系统进化分析发现,分离物HQH18G3-10与PVY^NTN-NW(SYR-II型)处于同一个大的分支,但与中国PVY大田分离物聚集在一起形成一个相对独立的组,命名为PVY^NTN-NW(CN型);其余6个分离物与数据库中的中国分离物聚集在PVY^N-Wi组。这暗示PVY中国分离物具有相对独立的进化过程,PVY马铃薯大田分离物和种薯分离物进化上相近。所有分离物均能在珊...     

马铃薯Y病毒中国分离物的分子株系组成

 马铃薯Y病毒(potato virus Y,PVY)主要侵染马铃薯和烟草等茄科作物,给世界农业造成巨大经济损失。本文对测定的23个及GenBank中注册的52个中国PVY分离物ORF序列进行了系统发育、重组和选择压等分析。系统发育分析表明,根据ORF序列可把我国75个PVY分离物和国外30个参比分离物分成O、C、E、NTN-NW(SYR-I型)、NTN-NW(SYR-II型)、NTN(NTN-a型)、NTN(NTN-b型)、NA-N/NTN、Eu-N、N-Wi(N:O型)和N-Wi(N-Wi型)等11个分子株系,其中中国PVY分离物属于除E和C株系外的9个分子株系。除ME162、guiyang、PVYzu、SD-G、WA-13和CN:JL-1:17等 6个分离物基因组中未检测到重组,其余69个分离物均存在明显重组。根据重组位点的不同,中国PVY可分为11种重组类型,其中5种为新的重组类型。选择压分析表明,中国PVY分离物的11个基因均处于负选择,其中核内含体b基因受到的选择压最大,PIPO受到的选择压最小。基因流分析表明,黑龙江、河南和山东PVY分离物间基因交流频繁,马铃薯与烟草PVY分离物之间基因交流频繁。本研究的结果明确了中国PVY分离物的分子株系组成,对指导PVY的检测和防控具有积极作用。     

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.     

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。     

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...     

加拿大进口大麦中小麦线条花叶病毒检疫鉴定

小麦线条花叶病毒(WSMV)是我国进境植物检疫性有害生物。2018年5月秦皇岛海关利用反转录PCR(RT-PCR)和双抗体夹心酶联免疫吸附法(DAS-ELISA), 从加拿大进口的大麦中检出WSMV。同时利用实时荧光定量PCR (Real time RT-qPCR)和序列比对分析方法进行了验证。这是我国首次在进境加拿大大麦中截获WSMV。     

小麦矮缩病毒外壳蛋白基因的原核表达、抗体制备及应用

 小麦矮缩病毒(Wheat dwarf virus,WDV)引起的小麦矮缩病是近年来我国小麦生产中的一种重要病毒病害,急需研发快速精准的检测技术用于预测预报和病毒-介体相互作用的研究。本研究应用Gateway重组技术构建了外壳蛋白基因(Coat protein, CP)的原核表达载体,将重组表达载体转化大肠杆菌Rosetta,经IPTG诱导获得CP基因原核表达蛋白。以重组蛋白为抗原免疫新西兰大白兔制备得到了相应的抗体,Western blot检测表明制备的抗体能与CP重组蛋白、感病小麦和带毒叶蝉特异性结合,说明获得的抗体特异性高。用获得的抗体进行免疫荧光标记,观察到病毒分布在介体叶蝉的前中肠和中中肠部位,为WDV的预测预报和介体条沙叶蝉传毒机制的研究奠定了基础。     

Observations on the host range of an isolate of Septoria nodorum from wheat

An isolate ofS. nodorum from wheat was inoculated onto grasses in the field. Re-isolates from these grasses were tested in a cross-inoculation experiment, performed in a growth chamber. The wheat isolate was pathogenic to each element of a set consisting ofElytrigia repens, Hordeum vulgare, Lolium perenne, Poa annua, andTriticum aestivum. Re-isolates from any of the elements of this set were pathogenic to all other elements. The effects of hosts and inoculum-density treatments were statistically significant. A significant isolate x host interaction suggests a form of specialization, which is possibly due to a passage effect. These observations may contribute to a better understanding of the epidemiology ofS. nodorum in the Netherlands.Samenvatting Grassen en granen te velde werden geïnoculeerd met eenS. nodorum isolaat van tarwe. Symptomen van aantasting door de schimmel werden gevonden opElytrigia repens, Hordeum vulgare, Lolium perenne, Poa annua enTriticum aestivum. Van deze vijf waardplanten werden her-isolaten gewonnen, die vervolgens in een klimaatkamer geinoculeerd werden op ieder van de vijf waardplanten. Aldus ontstond een kruisinoculatiematrix van bladaantastingspercentages (Tabel 2), die aan een variantieanalyse (Tabel 3) kon worden onderworpen. De volgende effecten waren significant: waardplanten, inoculumdichtheden, interactie herisolaat x waardplant, en interactie herisolaat x waardplant x inoculumdichtheid. De interacties suggereren beïnvloeding door de waardplant, dus een passage-effect. Bij passage over een waardplant zou enige mate van fysiologische specialisatie kunnen optreden. Dit wordt bevestigd door gegevens van Weber (Tabel 5). Deze waarnemingen over de waardplantreeks kunnen van belang zijn voor een beter begrip van de epidemiologie vanS. nodorum in Nederland.     

The invasive weed Ventenata dubia is a host of Barley yellow dwarf virus with implications for an endangered grassland habitat

Ventenata dubia (African wiregrass), a winter annual weed, is a non‐native species invading grasslands, rangelands and pastures throughout the USA. Limited information is available on its suitability as a host to pathogens and insects in its invaded range. The barley/cereal yellow dwarf virus (B/CYDV) complex occurs ubiquitously in Poaceae species. In non‐managed grasslands, BYDV infection influences competitive dynamics between native and invasive grasses and facilitates invasion by non‐native annual weeds. The Palouse prairie of south‐eastern Washington and northern Idaho, USA, is an endangered ecosystem. Surveys of V. dubia in Palouse prairie and neighbouring Conservation Reserve Program (CRP) habitats were conducted to determine whether B/CYDV viral species are present. Laboratory tests examined the suitability of V. dubia to host BYDV‐PAV and serve as an inoculum source. Plant growth and weight parameters were measured to gauge the impact of BYDV‐PAV on V. dubia. Infection of V. dubia in Palouse prairie and CRP habitats with two species of BYDV, PAV and SGV, was detected for the first time. The ability of BYDV‐PAV to infect V. dubia in the laboratory and transmission from infected V. dubia to barley were demonstrated. BYDV‐PAV‐infected V. dubia showed reductions in plant height, number of leaves and tillers per plant, and above‐ground dry weight, suggesting that V. dubia is sensitive to BYDV. Results demonstrate that V. dubia is a host to BYDV and may serve as a virus inoculum source with potential implications for its management, competitive dynamics between invasive and native grasses and future conservation of endangered grasslands.     

植物青枯病高效生防菌株PBW1培养工艺研究

植物青枯病生防菌株PBW1对植物青枯病的防效可高达70%以上。本文首先获得了PBW1 500 mL摇瓶培养的最佳条件:30℃、初始pH7、接种量为1%、装液量为120 mL、摇床转速为220 r/min;在最佳条件下培养48 h的菌体浓度达4.2×10¹²cfu/mL;同时还对500 mL摇瓶培养过程中菌体生长、还原糖、总糖及pH变化特征进行了研究。此外,本文还在6L全自动发酵罐上对PBW1培养过程中的菌体生长、还原糖、氨基氮、pH和DO的变化特征进行了研究,培养48h的菌体浓度达4.76×10¹²cfu/mL。     

陕西韩城严重发生的小麦矮缩病病原鉴定与原因分析

2007年在陕西韩城发现一种新的小麦病毒病害,症状表现为严重矮缩、黄化、条斑和分蘖增多等,发病面积约0.07万hm²,病田减产达50%,严重地块甚至绝收。本研究通过对采集自我国陕西韩城的7个样品进行PCR鉴定、全基因组序列测定及比较,证实陕西韩城样品确是小麦矮缩病毒(WDV)侵染所致,并对发病原因及其流行趋势进行了分析。这是小麦矮缩病在我国麦田大发生的首次报道。     

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.     

Genetic diversity of the wheat yellow rust population in Pakistan and its relationship with host resistance

Yellow rust, caused by Puccinia striiformis f.sp. tritici (PST), is an important disease that threatens wheat production in Pakistan. This study was designed to explore the virulence and simple sequence repeat (SSR) diversity of the Pakistani PST population and the ongoing selective pressures of widely grown wheat cultivars. Analyses of 49 isolates sampled from the North‐West Frontier Province of Pakistan led to the identification of 12 distinct pathotypes. The virulence frequencies of v2 (virulent against Yr2), v6, v7, v9, vSU and v27 ranged from 63% to 100%. Virulences v3, v4, v17 and vSD were uncommon, whilst v5, v10, v15, v24, v32 and vSp were not detected. The pathotypes thus described were then classified into 27 distinct genotypes. Bayesian structure analysis clustered these genotypes into five groups (in addition to one hybrid isolate) which represent three distinct lineages of the SSR‐based phylogenetic tree. Of the studied isolates, 80%, represented by three predominant pathotypes (P1–P3), belonged to the same characteristic Pakistani lineage, whilst the other isolates were close to either a Mediterranean lineage or a Northern European lineage. Genetic recombination was detected within P2 isolates. Resistance genes postulated in 40 Pakistani wheat cultivars indicated the high frequency of Yr2, Yr6, Yr7, Yr9, Yr27 and YrSU. Only 11 cultivars were found to be resistant to P1–P3. Migration and varietal diversity factors might contribute to maintaining the currently high genetic diversity in Pakistani PST, and have serious regional implications for wheat improvement programmes.     

溶氧浓度对植物青枯病高效生防菌株PBW1生长影响的研究

青枯病是危害大、分布广、损失重的植物病害之一。生防菌株PBW1对植物青枯病的防效可高达70％以上。本文研究了溶氧浓度对PBW1生长的影响, PBW1生长的临界溶氧浓度为25.5%;摇瓶与发酵罐培养的结果均表明,溶氧浓度越高,越有利于菌体的生长。