Cycas necrotic stunt virus isolated from gladiolus plants in Japan

An undescribed spherical virus ca. 30 nm in diameter was isolated from gladiolus (Gladiolus spp.) plants in Japan. The virus had a moderate host range within eight families. Purified virus preparations contained two large RNA components and one coat protein with mobility similar to Cycas necrotic stunt virus (CNSV) from cycas (Cycas revolute). The virus was serologically closely related to CNSV. Its nucleotide sequence of the coat protein gene had 89% common identity with that of CNSV. These results indicated that the virus isolated from gladiolus is a new strain of CNSV. The nucleotide sequence data reported are available in the DDBJ/EMBL/Gen Bank databases under the accession number AB237656.     

侵染紫松果菊的黄瓜花叶病毒分离物鉴定

从表现黄花叶症状的紫松果菊病株上获得分离物2-1-2,电镜下可见直径约30 nm的球状病毒粒体,其与黄瓜花叶病毒抗体呈强的阳性反应,ds-RNA的谱带类型与本实验室保存的标准黄瓜花叶病毒株系相同。通过生物学、病毒粒体观察、血清学以及病毒核酸双链试验结果,确定该病毒分离物为黄瓜花叶病毒。     

Tomato infectious chlorosis virus — a new clostero-like virus transmitted byTrialeurodes vaporariorum

A previously undescribed virus disease of tomato, other crops and weed hosts was found in California. Affected tomato plants exhibited interveinal yellowing, necrosis and severe yield losses. Leaf dips and purified preparations contained closterovirus-like long flexuous, filamentous particles approximately 12×850–900 nm. The virus, designated as tomato infectious chlorosis virus (TICV), is transmitted in a semipersistent manner by the greenhouse whitefly,Trialeurodes vaporariorum. The host range of the virus is moderate (26 species in 8 plant families) but includes some important crops and ornamental species including tomato, (Lycopersicon esculentum), tomatillo (Physalis ixocarpa), potato (Solanum tuberosum), artichoke (Cynara scolymus), lettuce (Lactuca sativa) and petunia (Petunia hybrida). The virus has been found in a number of different locations in California and has a number of potential vehicles of movement including greenhouse grown ornamentals, tomato transplants, artichoke cuttings and potato seed. The virus has the potential to spread to other growing regions with resident populations of the greenhouse whitefly. The host range, particle size, insect transmission, and serology clearly distinguish TICV from previously described viruses.     

Spinach latent virus,a new ilarvirus seed-borne in Spinacia oleracea

During 1977 and 1978 an apparently new virus was isolated from samples of 12 out of 142 lots of spinach seed from a number of countries which did not produce symptoms in spinach. In one sample seed infection was over 50%. The virus was later found to be identical with a virus encoded GE36, earlier presumed to have been isolated from apple and pear (Van der Meer, 1968; Maat and Vink, 1971). It has now been further characterized and named spinach latent virus.Seventeen out of 36 plant species tested were susceptible, most without producing symptoms.Myzus persicae did not transmit the virus, but rates of seed transmission in artificial hosts were high: 53% inCelosia cristata, over 90% inChenopodium quinoa, 30% inNicotiana rustica, 72% inN. tabacum Samsun, 90% in White Burley and 94% in Xanthi. Infection is in the embryo. The virus can also be detected in dry seeds.Purified virus contained three components sedimenting at 87, 98 and 108 S. In the electron microscope the virus particles were irregularly spherical and c. 27 nm in diameter. They were hard to detect in crude plant sap. Some particles were bacilliform. The buoyant density in cesium sulphate was 1.269×10³ kg.m^–3. Five RNA components were detected having relative molecular masses of 1.30, 1.18, 0.91, 0.35 and 0.27×10⁶, respectively. To induce infection the three largest components are required plus the two smallest components or the coat protein. Molecular mass of the coat protein subunit was 28000. These characters are typical of ilarviruses.The virus proved weakly immunogenic. An antiserum with a titre of 64 was produced. No serological differences could be found between the type isolate from spinach and GE36. The virus did not react with antisera to any of 36 spherical viruses and alfalfa mosaic virus.Samenvatting In 1977 kon uit 5 van de 43 en in 1978 uit 7 van de 99 getoetste partijen spinaziezaad afkomstig uit een aantal landen een klaarblijkelijk nieuw virus worden geïsoleerd zonder dat in de uit zulk zaad opgekweekte planten afwijkingen konden worden geconstateerd. Eén zaadherkomst was voor meer dan 50% geïnfecteerd. Het virus werd aangetoond in zaad van in totaal 12 verschillende spinazierassen. Tevens werd in enkele zaadmonsters komkommermozaïekvirus en in één het tabaksratelvirus aangetroffen.Biologisch, biofysisch en serologisch onderzoek heeft aangetoond dat het virus identiek is aan een eerder onder de code-naam GE36 beschreven virus, dat naar eerst werd vermoed, via toetsplanten was geïsoleerd uit appel en peer. Dit virus is nu vooral aan de hand van het spinazie-isolaat Sp20-9 uitvoerig gekarakteriseerd en beschreven als hetlatente spinazievirus (spinach latent virus). Zeventien van de 36 getoetste plantesoorten bleken vatbaar, de meeste echter symptoomloos. InChenopodium amaranticolor ontstonden karakteristieke, voornamelijk droge puntlesies en op de primaire bladeren vanPhaseolus vulgaris Bataaf opvallende necrotische lokale lesies, terwijl inC. quinoa de systemische reactie meer opviel dan de lokale. Ook bieteblad reageerde soms met lokale symptomen.De houdbaarheid van het infectievermogen in uitgeperst plantesap was bij verdunning 10³–10⁴, bij verhitting 60–65°C, en bij bewaring 4–5 dagen en éénmaal zelfs langer dan 13 dagen.MetMyzus persicae kon het virus niet op non-persistente wijze worden overgebracht. Zaadoverdracht werd ook aangetoond bij vier van de zes hierop onderzochte kunstmatige waardplanten. BijC. quinoa enN. tabacum White Burley en Xanthi bedroeg dit percentage zaadoverdracht zelfs meer dan 90. GE36 ging minder gemakkelijk over met zaad.Zuivering door butanol-klaring, differnetiële en dichtheidsgradiëntcentrifugering leverde aanvankelijk nog met celbestanddelen verontreinigd virus op. Afzondering van de viruszone, concentrering en verdere dichtheidsgradiëntcentrifugering verschafte echter zeer zuiver virus. Dit virus sedimenteerde in een suikergradiënt in twee zones en bij lage concentratie in drie zones. De drie componenten hadden sedimentatiecoëfficienten van 87, 98 en 108 S. De zweefdichtheid van het virus in een cesiumsulfaatgradiënt bedroeg 1,269×10³ kg. m^–3.Bij polyacrylamidegel-elektroforese ontstonden vijf nucleïnezuurbanden, elk bestaand uit RNA met een relatieve moleculaire massa van respectievelijk 1,30, 1,18, 0,91, 0,35 en 0,27 × 10⁶. De moleculaire massa van het eiwit bedroeg 28000. Intacte deeltjes verplaatsten zich in 2,5% polyacrylamide-gel als twee banden.Met de elektronenmicroscoop konden virusdeeltjes met moeite in ruw sap worden waargenomen, wel echter iets beter na fixatie en gemakkelijk in gezuiverde preparaten. De deeltjes waren onregelmatig van vorm, c. 27 nm in diameter, en soms bacilvormig.Bij infectieproeven met de verschillende groepen RNA-componenten en viruseiwit verkregen na SDS-afbraak bleek dat voor infectie de componenten 1, 2 en 3 nodig zijn tezamen met de componenten 4 en 5 òf het eiwit.Het virus bleek slechts zwak immunogeen (antiserumtiter 64) en in agargel vormden zich tenminste twee lijnen, indien de agar was bereid in een fysiologische zoutoplossing, doch slechts één lijn indien de agar was bereid in 0,05 M fosfaat-citroenzuurbuffer pH 7. Het bleek serologisch identiek aan GE36 en was niet verwant aan 36 verschillende bolvormige plantevirussen en aan luzernemozaïekvirus.De relatieve moleculaire massa's van de RNA-componenten, de uniforme zweefdichtheid in cesiumsulfaat, de aantoonbaarheid van meer dan één component in polyacrylamide-gel en bij suikergradiëntcentrifugering, het tripartite genoom en de eiwitafhankelijkheid ervan voor infectie, alsmede de onregelmatige deeltjesvorm en de kleine aantallen bacilvormige deeltjes rechtvaardigen plaatsing van het virus in de ilarvirusgroep.     

中国番木瓜曲叶病毒南宁分离物的基因组结构特征

 从广西南宁田间表现曲叶症状的番木瓜植株上分离到病毒分离物G4,经三抗体夹心ELISA (TAS-ELISA)检测,G4与粉虱传双生病毒的抗体呈阳性反应。对G4 DNA-A全序列测定和分析表明,G4 DNA-A全长2 748个核苷酸,共编码6个ORFs。同源性比较及系统进化关系分析表明,G4 DNA-A与在亚洲发现的粉虱传双生病毒关系较近,其中与我国报道的中国番木瓜曲叶病毒(PaLCuCNV)同源性最高,达到98.0%。进一步比较发现,G4 DNA-A编码的AV1、AV2、AC1、AC2、AC3和AC4与PaLCuCNV相应ORFs的氨基酸同源性分别为98.4%、95.7%、97.5%、97.8%、94.1%和94.6%,表明G4应属于PaLCuCNV的一个分离物。G4编码的ORFs与中国胜红蓟黄脉病毒(AYVCNV)、辣椒曲叶病毒(PepLCV)及烟草曲茎病毒(TbCSV)有较高的氨基酸同源性,可能起源于共同的祖先。利用DNA-B及卫星DNAβ的保守引物均未能从G4分离物中扩增出相应的组分。     

侵染昆明玫瑰的李坏死环斑病毒的鉴定及其分子检测

采集昆明地区种植的花叶症状明显的玫瑰样品,运用现代分子生物学技术与常规技术相结合的方法,初步鉴定引起玫瑰花叶病的主要病毒病原为李坏死环斑病毒.该病毒引起玫瑰植株的系统花叶、畸形和皱缩等症状;电镜下病毒粒体为球形,直径为22～23nm;ELISA检测发现该病毒在植株芽、花粉和顶部叶片的浓度最高;同时,根据外壳蛋白的保守区利用Primer 5.0设计该病毒的特异引物,对该病毒进行分子检测,得到450bp的预期DNA片断,并在此基础上,进行了巢式RT-PCR的分子检测,表明巢式RT-PCR的检测能力最强.并通过序列的同源性分析得知该病毒的外壳蛋白与已知PNRSV的同源性为98.0%,进一步证明了该病毒为李坏死环斑病毒.     

Occurrence and transmission of sowbane mosaic virus in seed from naturally infected plants of spinach (Spinacia oleracea)

Sowbane mosaic virus was isolated as a single infectious component from seedlings and seeds from a seed-lot of spinach (Spinacia oleracea) propagated in Hungary, and was identified by experimental host-range, thermal-inactivation point, dilution end-point, electron microscopy and serology.Chenopodium quinoa was more susceptible and/or sensitive to infection thanC. amaranticolor and was a better indicator host, butC. amaranticolor is of diagnostic value. This is the first report on natural infection of spinach by the virus and on its natural seed-transmission in spinach. Growing-on tests on whole seeds and infectivity tests on separate embryos and seed-coats showed that over 30% of the seeds' embryos were infected and c. 80% of the seed-coats contained the virus. The incidence of infection in the spinach crop from which the seed was obtained must have been high.     

Biological and genetic characterization of carrot red leaf virus and its associated virus/RNA isolated from carrots in Hokkaido,Japan

Carrot motley dwarf (CMD) is caused by mixed infection of carrot red leaf virus (CtRLV) with either carrot mottle virus (CMoV) or carrot mottle mimic virus, and additional infection with CtRLV-associated RNA (CtRLVaRNA). Here, the author investigated the viruses or virus-like RNA isolated from carrots with reddening symptoms in Hokkaido, the northern island of Japan. Three types of infections were mainly detected: single infection with CtRLV, which was most prevalent; double infection with CtRLV and CMoV; and triple infection with CtRLV, CMoV, and CtRLVaRNA. Fields with the three agents were severely affected, with diseased plants showing mottling, whereas in fields where disease incidence was low and sporadic, CtRLV was often found alone in plants with mild symptoms. Inoculation tests using carrot plants showed that CMoV enhanced disease severity, and the RNA accumulation of CtRLV. However, in the presence of CtRLVaRNA (+ CMoV), distinct symptoms such as systemic mottling and stunting developed, while the enhancement of CtRLV accumulation was abolished. These results imply that CtRLVaRNA (+ CMoV) antagonizes CtRLV despite its dependence on CtRLV for aphid transmission, and that mixed infection with CtRLVaRNA is involved in the development of the conspicuous mottling. All agents detected in Hokkaido were very similar to European and American isolates in terms of their genomic sequences and host range. This represents the first report of CMD in Japan, and provides further information on the genetic and biological properties of CMD-associated agents, as well as the aetiology of the disease.     

Characterization of Tomato curly stunt virus: a new tomato‐infecting begomovirus from South Africa

The biological and molecular characterization of a virus recognized as a distinct begomovirus species, Tomato curly stunt virus (ToCSV), first observed in South Africa in 1997, is reported here. Whitefly‐transmission and host‐range studies were carried out using a Bemisia tabaci colony identified as the B‐biotype. The experimental host range of ToCSV spanned primarily species in the Solanaceae and Fabaceae. The complete ToCSV genome (2·766 kb) was amplified by PCR, cloned, and the DNA sequence determined. Phylogenetic analysis revealed that ToCSV was most closely related to Tobacco leaf curl Zimbabwe virus (TbLCZV), at 84% nucleotide identity, indicating that ToCSV is a new species in the genus Begomovirus that is probably endemic to southern Africa. The ToCSV genome sequence contained all of the hallmark coding and non‐coding features characteristic of other previously recognized monopartite begomoviruses. ToCSV is only the second begomovirus described from southern Africa that infects solanaceous species. Neither a begomoviral DNA‐B component nor a satellite‐like DNA molecule was detected by PCR in extracts of ToCSV‐infected plants.     

Uneven distribution of two potyviruses (feathery mottle virus and sweet potato latent virus) in sweet potato plants and its implication on virus indexing of meristem derived plants

Abstract

The distribution of two sweet potato potyviruses, FMV and SPLV, was assessed in three plants infected with both viruses and in one plant infected with FMV only. All leaves, the top and basal sections of the main stem, and branch sections were tested by ELISA. Both symptomless leaves and leaves showing symptoms including purple rings, chlorotic spots, mottle or discoloration were found to contain the viruses. However, neither could be detected in every leaf or stem piece. SPLV was found in a lower proportion of leaf and stem samples than FMV. This indicates that the two viruses are either very unevenly distributed within sweet potato plants or that the virus concentration in some parts is below the detectable level. Testing of each leaf is recommended for reliable virus indexing of small, meristem‐derived sweet potato plantlets, if the ELISA method is used. Additional indexing of all ELISA‐negative materials by grafting to susceptible indicator plants is nevertheless still necessary.     

基于外壳蛋白基因的湖南烟草黄瓜花叶病毒遗传多样性分析

为探明湖南烟草上发生的黄瓜花叶病毒Cucumber mosaic virus(CMV)的遗传多样性及分子进化特征,对来自湖南烟区的303份疑似感染病毒的烟草样品进行检测,分析CMV系统发育、遗传变异和群体结构等特征。结果表明：部分分离物的外壳蛋白(coat protein, CP)基因与NCBI上登录的CMV分离物的一致性为86.34%～98.42%;系统发育分析发现湖南烟草CMV分离物属ⅠB组,不同组间的分离物地理特征不明显,无重组现象,进化的主要驱动力是负选择;组间遗传变异比较明显,基因交流频率较低,受到遗传漂变影响,遗传多样性高,群体趋于扩张。研究结果为烟草抗CMV育种提供了理论依据,对病害防治具有重要意义。     

Lack of synergistic effects in tomato plants co-infected with tomato severe rugose virus and tomato chlorosis virus

The begomovirus Tomato severe rugose virus (ToSRV) and the crinivirus Tomato chlorosis virus (ToCV), in single and co-infections, are very common in tomato crops in Brazil. Both viruses are transmitted by the whitefly Bemisia tabaciMEAM1 (biotype B). The objective of this study was to analyse the interaction between ToSRV and ToCV in tomato plants of cultivars Santa Clara and Kada. Plants at 15, 30 and 45 days after emergence were inoculated with 30 viruliferous B. tabaci per plant. The following treatments were compared: plants inoculated with ToSRV, ToCV, ToSRV + ToCV, and healthy (control). The interaction between these viruses was analysed by measuring the virus titre by qPCR and the fresh and dry weights of the aerial parts of the tomato plants. Based on two independent assays, no significant effects for co-infection of ToSRV and ToCV on virus titres and plant development were observed compared to single infections. The dry weight of tomato plants of both cultivars infected with ToSRV, ToCV, or co-infected did not differ significantly. However, the dry weight of Santa Clara tomato plants infected with ToSRV, ToCV and ToSRV + ToCV showed mean reductions of 21.5%, 25.5% and 32%, respectively, compared to healthy plants, and mean reductions for Kada were 31.7%, 37.5% and 38%, respectively.     

Parsley latent virus,a new and prevalent seed-transmitted,but possibly harmless virus of Petroselinum crispum

Parsley latent virus, a hitherto undescribed virus, was isolated from 38 out of 54 samples of seed of parsley (Petroselinum crispum) of 17 out of 24 cultivars and from all five European countries tested, but not from some samples from the USA. It could easily be detected in seedlings and also in seeds germinated on moist filter paper, but not in dry seeds or in seeds soaked in water. Strawberry latent ringspot virus was detected in five samples. The parsley virus is symptomless in parsley and caused latent systemic infection inGomphrena globosa, three cultivars ofSpinacia oleracea and weak and often transient systemic symptoms inChenopodium amaranticolor, C. giganteum, C. glaucum andC. quinoa, but did not infect any other species out of all 32 species of seven plant families tested in total.The virus could easily be transmitted mechanically but not by seven aphid species in the non-persistent manner. Dilution end-point was between 100 and 1000, thermal inactivation between 55 and 60°C and ageing in vitro between 7 and 10 days.Purification yielded a single infectious component. The particles were spherical, ca. 27 nm in diameter, with a sedimentation coefficient of 127.5 S, a buoyant density of 1.449 g/ml, an RNA content of 36% and one type of protein with a relative molecular mass of 22×10³. Purificition without Triton and urea resulted in preparations with aggregates each consisting of 12 particles in icosahedral array.The virus differs from all viruses described so far and did not show clear serological affinity with antisera to any of 34 widely differing viruses tested. It does not seem of direct practical importance and may be easily overlooked.Samenvatting In zaailingen van peterselie (Petroselinum crispum) werd een nog niet eerder beschreven virus aangetroffen. Het virus kon niet worden aangetoond door toetsing van droge of in water geweekte zaden opChenopodium quinoa maar wel in op filtreerpapier gekiemde zaden en vooral in zaailingen. Het werd aangetroffen in 38 van de 54 getoetste herkomsten, in 17 van de 24 getoetste rassen en in zaad vermeerderd in alle zes hierop onderzochte Europese landen maar niet in enkele zaadmonsters uit de USA. In sommige monsters bevatten nagenoeg alle zaden het virus. In vijf herkomsten werd eveneens het nog niet eerder in peterselie gerapporteerde latente aardbeikringvlekkenvirus geconstateerd. Dit virus kan bij toetsing gemakkelijk worden herkend door systemische symptomen inC. amaranticolor en komkommer.In geïnfecteerde peterselieplanten zijn geen afwijkingen waargenomen. Het virus kon niet op non-persistente wijze worden overgebracht met zeven bladluissoorten maar wel gemakkelijk met sap. Van 32 getoetste plantesoorten van zeven families, waaronder vier schermbloemigen, kon het virus slechts worden overgebracht op vierChenopodium-soorten,Gomphrena globosa en alle drie getoetste spinazierassen. AllenC. quinoa (Fig. 1),C. giganteum, C. glaucum en soms ookC. amaranticolor (Fig. 2) reageerden met vaak voorbijgaande systemische symptomen. Een lokalelesietoetsplant werd niet gevonden. Zaadovergang bijC. quinoa kon niet worden aangetoond.Voor de houdbaarheid van het infectievermogen werden de volgende waarden gevonden: verdunningseindpunt 100–1000, thermaal inactiveringspunt 55–60°C en houdbaarheid in vitro 7–10 dagen.Zuivering door homogenisatie in fosfaatcitroenzuurbuffer, behandeling met Triton X-100 en ureum en differentiële en daarna dichtheidsgradiëntultracentrifugering leverde preparaten op met uniforme deeltjes van ca. 27 nm diameter (Fig. 3B), een sedimentatiecoëfficiënt van 127,5 S, een zweefdichtheid van 1,449 g/ml, een RNA-gehalte van 36% en een relatieve moleculaire massa van de eiwitondereenheid van 22×10³. Bij zuivering zonder toepassing van Triton en ureum werd een extra zone verkregen met aggregaten van 12 deeltjes in icosaëdrische rangschikking (Fig. 4). In ruw plantesap waren slechts met grote moeite enkele deeltjes met behulp van de elektronenmicroscoop te vinden.Het virus reageerde niet met antisera tegen 33 bolvormige virussen en luzernemozaïekvirus (Tabel 1). Of de zwakke reactie verkregen met één antiserum tegen het tomate-aspermievirus een verre serologische verwantschap inhoudt, dan wel het gevolg is van een verontreiniging, werd niet vastgesteld.Het virus wordt beschouwd als een geheel nieuw virus waarvoor de naamlatent peterselievirus wordt voorgesteld. Het lijkt door zijn beperkte waardplantenreeks en symptoomloosheid in de vatbaar bevonden soorten, behalve in enkele als toetsplant te gebruikenChenopodium-soorten, nauwelijks van praktische betekenis.     

利用RNA介导的抗病性获得抗2种病毒的转基因烟草

 RNA介导的病毒抗性(RMVR)是近年发展起来的一种新的植物抗病毒基因工程策略,具有抗病性强、抗性持久、生物安全性高等特点。利用该策略培育多抗病毒植株具有广阔的应用前景和重要的实践意义。本研究将非翻译的马铃薯X病毒的衣壳蛋白(PVX-CP)基因和非翻译的马铃薯Y病毒的衣壳蛋白(PVY-CP)基因组成嵌合基因,构建植物表达载体pROKXY,利用农杆菌介导法转化烟草NC89,获得6株对PVX和PVY的混合侵染表现为免疫的转基因植株。分子分析表明,这种抗性为RNA介导的病毒抗性。这一研究结果为利用RMVR进行植物多抗病毒育种提供了重要数据和资料。     

白草花叶病毒承德玉米分离物3′-cDNA 片段序列分析

 采自河北承德11 个表现矮花叶症状的玉米样品,用甘蔗花叶病毒(Sugarcane mosaic virus, SCMV)和白草花叶病毒
(Pennisetum mosaic virus, PenMV)简并引物扩增了基因组3′ 端约2. 1 kb 的片段并进行测序。Blast 结果表明其中8 个样
品含有PenMV。扩增到的PenMV 序列均为2 135 nt,包括部分NIb 基因(985 nt)、完整的CP 基因(909 nt)和3′-UTR(241
nt)。这8 个分离物CP 基因和3′-UTR 与GenBank 上其他PenMV 分离物相应序列的核苷酸一致率分别为89. 8% ~ 93． 4%
和95. 9% ~ 97. 9% 。根据扩增的2 135 nt 序列和CP 基因序列构建系统发育树,8 个分离物与GenBank 上其他PenMV 分离
物都分为2 个组:山西组和承德组。重组分析表明CD9 的CP 基因存在重组。     

Changes in the glucosinolate content of oilseed rape plants following infection with turnip mosaic virus

Low and high glucosinolate cultivars of oilseed rape were analysed for variation in both individual and total glucosinolate content up to 27 days after inoculation with turnip mosaic virus. Both infected and control plants of the two cultivars differed in the concentration of aliphatic, aromatic and indole glucosinolates. The biggest differences in glucosinolate content between the cultivars were found in the aliphatic and aromatic glucosinolate groups. Infected plants of the high glucosinolate cultivar, Solida, possessed lower amounts of glucosinolates, than did healthy control plants. Similar results were obtained with a low glucosinolate cultivar, S1. No significant difference was found between the two cultivars in resistance to turnip mosaic virus, using qualitative and quantitative ELISA to determine virus content in their tissues.     

玉米粗缩病毒及抗病策略

玉米粗缩病毒属于植物呼肠孤病毒组的斐济病毒属，是一种有双层衣壳的球状病毒。该病毒基因组包含10条线状的双链RNA片段，近年来已经完成了其中4条RNA片段的测序工作。玉米粗缩病毒对我国玉米生产的危害最为严重。该病毒主要由介体昆虫传播，侵染的植株表现严重矮化和叶片浓绿等病症。玉米对该病毒的抗性表现出多基因控制的数量性状遗传的特征。作者描述了玉米粗缩病病原、病症及侵染循环的特点，对玉米粗缩病毒基因组的研究进展进行了评述，并对抗病策略进行了讨论。     

Localization of potato leafroll virus in leaves of secondarily-infected potato plants

Potato leafroll virus (PLRV) antigen was localized by immunogold labelling in semi-thin leaf sections of secondarily-infected potato plants cv. Bintje. Viral antigen was present in all cell types of the phloem tissue. but occurred most abundantly in the companion cells. Detectable amounts of PLRV antigen were found only in the sieve elements in veins with a large number of infected companion cells. Occasionally, parenchyma cells were also found to be infected. PLRV was not exclusively limited to the phloem tissue in the infected potato plants, but was also found in mesophyll cells neighbouring minor phloem vessles. Spread of virus from cell to cell in the mesophyll was not observed. The distribution of PLRV in the potato leaf tissue has implication on its availability, for acquisition by aphids.