甘肃省南瓜及西葫芦小西葫芦黄花叶病毒病鉴定

利用双抗夹心酶联免疫吸附测定(DAS-ELISA)的方法对甘肃出入境南瓜、西葫芦种子及采自河西地区显症病株叶片进行检测,在种子及病叶组织中均检测到ZYMV病毒,其中南瓜种子带毒批次占12.5%,西葫芦种子带毒批次占11.8%。根据已报道的小西葫芦黄花叶病毒(Zucchini yellow mosaic virus)基因组核苷酸序列,设计引物扩增其外壳蛋白(CP)基因,以ELISA阳性种子或病叶组织总RNA为模板,进行RT-PCR扩增,对预期大小的扩增产物进行测序,结果表明扩增获得的核苷酸序列与世界各地的ZYMV分离物CP基因具有高度一致性,综合ELISA检测和RT-PCR的结果,确定南瓜、西葫芦种子可携带ZYMV,且ZYMV是侵染甘肃瓜类作物的重要病毒种类。     

Comparison of the nucleotide and amino acid sequences of parental and attenuated isolates of Zucchini yellow mosaic virus

To identify possible sites of viral attenuation, the complete nucleotide sequences of two isolates of Zucchini yellow mosaic virus (ZYMV) were determined; a severe isolate Z5-1 and an attenuated isolate from Z5-1 (designated ZYMV-2002). The viral genome of both isolates consisted of 9593 nucleotides in size and contained an open reading frame encoding a single polyprotein of 3080 amino acids. Comparison of the nucleotide sequences for Z5-1 and ZYMV-2002 revealed 14 nucleotide mutations, resulting in seven amino acid substitutions with four in the HC-Pro region, two in the CI region, and one in the NIb region. These results provide a genetic basis for future manipulation of the ZYMV reverse genetics system. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession numbers AB188115 and AB188116     

2b Protein is essential to induce a novel gradual cell death in Zucchini yellow mosaic virus-inoculated cucumber cotyledon co-infected with Cucumber mosaic virus

Cucumber cotyledons inoculated with Cucumber mosaic virus (CMV, Pepo strain) or Zucchini yellow mosaic virus (ZYMV, Z5-1 isolate) developed either mild chlorotic spots or no symptoms. Cotyledons treated with CMV plus ZYMV also developed mild chlorotic spots. However, plants ZYMV-inoculated cotyledons had veinal yellowing and gradual cell death by 20 days postinoculation (dpi) when co-inoculated with CMV on the other cotyledon. When analyzing this synergism, an enzyme-linked immunosorbent assay showed that CMV gradually increased in CMV-inoculated cotyledons of plants, with the other cotyledon mock- or ZYMV-inoculated. However, CMV significantly increased at 9 to 14 dpi in the ZYMV-inoculated cotyledons of plants co-infected with CMV. ZYMV similarly increased in cotyledon pairs of both co-infected and singly infected plants. Inoculation with PepoΔ2b, a modified Pepo-CMV that lacks translation of the 2b protein, revealed that PepoΔ2b without the 2b protein systemically infected cucumber but induced no symptoms on cotyledons or true leaves. Plants with a ZYMV-inoculated cotyledon and co-infected with PepoΔ2b did not undergo cell death; nevertheless, PepoΔ2b was at high levels comparable to levels of CMV in the ZYMV-inoculated cotyledon. The 2b protein thus seems essential for induction of the novel gradual cell death in ZYMV-inoculated cotyledons of cucumbers co-infected with CMV.     

Occurrence of pepper yellow vein in the Netherlands

Samenvatting Het verschijnsel van geelnervigheid bij paprika (Capsicum annuum) kon door verenting en met de schimmelOlpidium brassicae worden overgebracht. Hierdoor bleek de ziekte identiek te zijn met een eerder in Engeland gemelde ziekte. Door inoculatie met zoösporen of rustsporen vanO. brassicae werden ook symptomen verkregen inC. baccatum, C. chacoense enC. frutescens. S. villosum bleek een waardplant te zijn voor het geelnervigheidsagens, waarbij zwakke nerfchlorosen werden waargenomen.Seconded to the Glasshouse Crops Research Station, P.O. Box 8, 2670 AA Naaldwijk, the Netherlands.     

Influence of calcium pretreatment on pectic substance evolution in cucumber fruit (cucumis sativus) duringbotrytis cinerea infection

The role of calcium in protecting plant tissue from infection byBotrytis cinerea was studied in cucumber fruit. A self-defense reaction, consisting of an increase in cell-wall-bound Ca, occurred in the plant tissue after an injury or an infection. However, it was not sufficient to protect the tissue from the spread of the fungus, which is accompanied by pectic substance digestion. The degradation induced mainly a decrease in acid- and chelator-soluble pectin levels, and an increase in water-soluble pectin. Ca treatment of the fruit prior to infection could amplify the cell-wall-bound Ca and therefore lessen pectin digestion by fungal pectinolytic enzymes.     

Molecular,biological and serological variability of Zucchini yellow mosaic virus in Tunisia

A study was conducted to better understand the population structure of Zucchini yellow mosaic virus (ZYMV), a severe virus affecting cucurbit crops worldwide, in Tunisia and to estimate whether the use of resistant cultivars may provide durable control. Analysis of the polymerase and coat protein (NIb‐CP) partial sequences of 83 isolates collected in the three main cucurbit‐growing areas in Tunisia showed that ZYMV grouped into two distinct clusters within ZYMV molecular group A. An important variability was observed in the MREK motif of the P3 protein, a motif associated with tolerance breaking in ZYMV‐tolerant zucchini squash cultivars. Interestingly, significant differences were found in the distribution of the MREK variants in the two clusters defined by the partial NIb‐CP sequences, MREK and MKEK sequences being more common in cluster 1 and cluster 2, respectively. When combining NIb‐CP and P3 sequence information, ZYMV molecular variability was shown to be significantly higher in the Cap Bon region than in the Bizerte area. An important biological variability was observed in a subset of 23 isolates regarding symptomatology in susceptible or resistant cucurbits. Some isolates overcame ZYMV tolerance or resistance in zucchini squash and melon, but not in cucumber. Three serotypes were differentiated using a set of 13 monoclonal antibodies (MAbs). Seven parameters characterizing the 23 isolates, including molecular, serological and biological properties, were used for a multiple component analysis (MCA). This analysis revealed that symptom intensity of a given isolate was similar in different susceptible cucurbit hosts, suggesting similar degrees of aggressiveness in different hosts.     

马拉硫磷在西葫芦中的残留行为及膳食摄入风险评估

利用气相色谱-火焰光度检测器 (GC-FPD) 测定了马拉硫磷在西葫芦中的残留量,根据2016年湖南、山东、北京、安徽、山西和黑龙江6地马拉硫磷在西葫芦中的规范性残留试验,对中国各类人群和不同作物中的马拉硫磷进行了膳食风险评估。样品用乙腈提取,丙酮置换乙腈后,GC-FPD检测。结果表明:在0.02~8.0 mg/kg添加水平下,马拉硫磷在西葫芦中的回收率在88%~109%之间,相对标准偏差 (RSD) 为5%,定量限 (LOQ) 为0.02 mg/kg。湖南和山东的消解动态试验结果显示,马拉硫磷的半衰期为2.74~4.65 d,属于易降解农药;6地的最终残留试验结果表明,距最后一次施药3、5、7 d后,西葫芦中马拉硫磷的最终残留量在 < 0.02~0.049 mg/kg之间。针对西葫芦的膳食风险评估结果显示,中国各类人群对马拉硫磷的国家估计每日摄入量 (NEDI) 为0.115~0.207 μg/(kg bw·d),风险商值 (RQ) 为0.000 4~0.000 7;全膳食暴露风险评估结果显示,马拉硫磷在各类食物中的NEDI值为82.251 μg/(kg bw·d),RQ值为0.275 1,表明马拉硫磷在西葫芦中的长期膳食摄入风险较低。推荐中国马拉硫磷在西葫芦上的最大残留限量值 (MRL) 为0.1 mg/kg,可确保中国西葫芦的食用安全性。     

Characterization of two distinct Polish isolates of Pepino mosaic virus

In Poland in 2002 and 2005 two different isolates of Pepino mosaic virus signed PepMV-SW and PepMV-PK were obtained. Both isolates were compared on the basis of their symptomatology on a series of plant species. In addition, the isolates were characterized by the nucleotide sequence analysis of the triple gene block, coat protein and a part of the polymerase genes. The studies showed that the Polish isolates differ from each other and belong to two strains. PepMV-SW was highly similar to European isolates, showing extensive sequence identity, ca. 99%. Pairwise comparisons of PepMV-PK with other PepMV isolates from the GenBank database showed that the highest nucleotide sequence identity was with two isolates: Ch2 from Chile and US2 from the USA.     

Further suppression of<Emphasis Type="Italic">Botrytis cinerea</Emphasis> disease in cucumber seedlings by chitosan-copper complex as compared with chitosan alone

Chitosan-copper complex compared with chitosan alone enhanced suppression ofBotrytis cinerea rot development on four-true-leaf cucumber seedlings in controlled growth chambers. This paper constitutes the first report of such enhancement. The optimal concentrations for the most effective suppression ofBotrytis development were 0.2 gl ⁻¹ chitosan and 1.6 mmole copper. After 12 days’ incubation, marked and significantly better disease suppression was obtained with chitosan-copper complex (75% suppression) than with chitosan alone. The chitosan-copper complex could be a very promising decay control agent for use in both conventional and organic agriculture. http://www.phytoparasitica.org posting Dec. 18, 2002.     

Infection and necrosis of cowpea mesophyll cells by tobacco necrosis virus and two strains of tobacco mosaic virus

When cowpea mesophyll tissue with or without any epidermal layer was inoculated with tobacco necrosis virus (TNV), local necrotic lesions were produced. In epidermal strips isolated after inoculation of intact leaves local lesions were never observed. Homogenates of epidermal strips removed within 30 min after inoculation of the leaf with the cowpea strain of tobacco mosaic virus (Cp-TMV) or with TNV and incubated on agar for 2 or 4 days were not infectious. However, when clusters of mesophyll cells or vein pieces were still attached to the epidermal strips after stripping, the homogenates showed virus activity. When cowpea leaves were inoculated with Cp-TMV or a common strain of TMV (TMV-U) infective virus material was present in the mesophyll tissue as measured in the homogenates, at the moment of stripping, i.e. within 10 min after inculation.It may be concluded that cowpea mesophyll cells can act as primary sites of viral ingress into the leaf and that the epidermis is not required for necrosis production after virus inoculation.Samenvatting De mogelijkheid werd onderzocht om cowpea-mesofylcellen zonder de aanwezigheid van epidermiscellen met TNV te infecteren. Kleine lokale necrotische lesies werden 40–72 uur na inoculatie zichtbaar waaruit blijkt, dat bij cowpea de epidermis niet noodzakelijk is voor de vorming van TNV-lesies. Geïsoleerd epidermisweefsel vertoonde nooit lokale lesies. Homogenaten van met TNV geïnoculeerde en daarna geïsoleerde cowpea-epidermisstukjes werden getoetst op virusactivitiet. Als de stukjes volledig vrij waren van mesofylcellen of nerfweefsel, dan vond daarin geen virusvermeerdering plaats tijdens een incubatie van 2 of 4 dagen op agar. Als na het strippen nog enkele mesofylcellen of nerfstukjes aanwezig waren, kon wel enige virusactiviteit in de homogenaten worden aangetoond.In cowpeabladeren die geïnoculeerd werden met de cowpea-stam van TMV of de normale stam van TMV had infectieus virusmateriaal al binnen 10 min na inoculatie het mesofyl bereikt. Blijkbaar is in cowpeabladeren de epidermis niet noodzakelijk voor de binnenkomst van virus of voor de necroseproduktie na virusinoculatie.     

Hippeastrum mosaic virus and another filamentous virus in Eucharis grandiflora

Two viruses were found in mosaic-diseased plants ofEucharis grandiflora in a glasshouse of the laboratory. One virus with a normal particle length of 733 nm caused local lesions onHyoscyamus niger and mosaic symptoms in leaves of healthy-lookingEucharis andHippeastrum plants. On the basis of its host range, physical properties and serology it was identified asHippeastrum mosaic virus, a member of the potyvirus group. This was confirmed by the presence of spherical nuclear inclusions and pinwheels in different tissues of diseasedEucharis plants. The second virus with a normal particle length of 598 nm was present in both healthy-looking and mosaic-diseasedEucharis plants, and it inconsistently induced local lesions onGomphrena globosa. According to its morphology and its reaction onGomphrena, it might be identical or related toHippeastrum latent virus. Crystal-like inclusions were observed in the cytoplasm of cells of both healthy-looking and mosaic-showingEucharis leaves. As no virus-free seedlings ofEucharis were available, the virus nature of these inclusions could not be established.     

Cucumber mosaic virus isolated from Aconitum spp. in Japan

Viruses were isolated from leaves of plants of Aconitum species with symptoms such as mottling and yellowing in Hokkaido and Gunma prefectures in Japan. These viruses were identified as Cucumber mosaic virus (subgroup II) based on particle morphology, host range, aphid transmission, and serology.     

A promising strain of endophytic <Emphasis Type="Italic">Streptomyces</Emphasis> sp. for biological control of cucumber anthracnose

In a survey for effective biocontrol agents of Colletotrichum orbiculare, causal agent of cucumber anthracnose, 43 (MBCu series) and 135 (MBPu series) endophytic actinomycete strains were recovered from surface-sterilized organs of cucumber (Cucumis sativus) and pumpkin (Cucurbita moschata) plants, respectively. The strains were cultured with C. orbiculare on IMA-2 agar medium to determine their in vitro antagonistic ability. Eleven strains that strongly inhibited hyphal growth of the pathogen were selected as potent antagonists. Detached cotyledons of cucumber were soaked in a spore suspension of an antagonistic strain 1 day before challenge-inoculation with the pathogen, and six of these antagonists (MBCu-32, 36, 42, 45, and 56, and MBPu-75) significantly reduced the number and size of the lesions on the cotyledons compared to the untreated control. In the same way, these six strains inhibited lesion development on attached leaves of 3-week-old cucumber seedlings. Strain MBCu-56, the most suppressive of the strains, was selected for further tests. Its suppressiveness increased as concentrations increased; pretreatment of leaves with the strain at 10⁷, 10⁸ and 10⁹ cfu/ml suppressed disease by 72, 79 and 93%, respectively. These results strongly indicated that MBCu-56 has strong potential for controlling cucumber anthracnose. Based on the taxonomic characteristics and 16S rDNA sequence, MBCu-56 was identified as Streptomyces sp. With scanning electron microscopy, the substrate mycelia of the strain were seen to colonize the surface of leaves above the cuticle. Some hyphae also penetrated and grew underneath the cuticle.     

Morphological and molecular characterization of <Emphasis Type="Italic">Oidium</Emphasis> subgenus <Emphasis Type="Italic">Reticuloidium</Emphasis> (powdery mildew) newly occurred on cucumber in Japan

In 2002, a powdery mildew with catenate conidia lacking fibrosin bodies was found on cucumber in a greenhouse in Kanagawa Prefecture, Japan. Morphological observation revealed that the fungus belongs to Oidium subgenus Reticuloidium, anamorph of the genus Golovinomyces. Molecular phylogenetic analyses of the nucleotide sequences of the rDNA ITS regions and D1/D2 domains of the 28S rDNA indicated that the fungus belongs to the clade of G. orontii with other Golovinomyces fungi from a wide range of host plants, suggesting that the fungus was newly transported from abroad. Because there has been no prior report of cucumber powdery mildew caused by Reticuloidium, further research on the physiology, epidemiology, control and resistant cucumber varieties is required.     

Leaf-yellowing in combination with corm necrosis in freesia caused by bean yellow mosaic virus: Factors involved in syndrome development

In freesia cv. Aurora grown in the field for cutflower production, a disease occurred with symptoms of leaf-yellowing in combination with corm necrosis (LYCN). It is shown that this disease is caused by bean yellow mosaic virus (BYMV).No differences in symptoms of LYCN were observed between the freesia cultivars Aurora, Imperial and Rose Marie. Most BYMV isolates gave rise to LYCN; the isolates from crocus andIxia sp. did not. LYCN was stimulated by a high BYMV concentration in the inoculum, a temperature above 20°C, inoculation soon after emergence of the freesias, and by the absence of freesia mosaic virus. Freesias with mosaic symptoms and infected with a cross-protecting BYMV strain, did not show symptoms of leaf-yellowing and/or corm necrosis after inoculation with BYMV-Cm. The presence of the unknown agent causing leaf necrosis in freesias did not have an influence on symptom development after infection with BYMV.     

Further characterization of melon necrotic spot virus causing severe disease in glasshouse cucumbers in the Netherlands and its control

A severe leaf necrosis, observed since 1978 in glasshouse cucumbers grown on rockwool and later also in crops on soil, is described. A virus could be isolated and the disease be reproduced in cucumber and melon. The virus could be transmitted by leaf inoculation with expressed sap and by pouring rockwool leakage water onto sterilized soil containing cucumber seedlings. Infectivity steeply declined in expressed sap between dilutions 10 and 100 (dilution endpoint ca 10⁶), at temperatures between 55 and 65°C (thermal inactivation point 75°C) and during storage between 1 and 1 1/2 month at room temperature.Out of 40 plant species tested only three species, viz. cucumber, melon and watermelon, were susceptible. All 21 cucumber cultivars and all 8 melon cultivars tested reacted severely with local lesions and some with systemic necrosis, but systemic infection and reaction were erratic under experimental conditions.Purified virus sedimented in sucrose and CsCl gradients and during analytical ultracentrifugation in a single peak. Thes ₂₀ was 134S and buoyant density in CsCl was 1.33 g.cm^–3. Virus particles in crude sap and purified suspensions were spherical and ca 30 nm in diameter. They contained one type of protein with a relative molecular mass of 46 000 and one RNA species. An antiserum with a titre of 1024 did not react with cucumber and tobacco necrosis viruses, nor did their antisera react with our cucumber virus. Serologically and in physicochemical properties the virus is similar to if not identical with the melon necrotic spot virus incompletely described in Japan.Disease control may be through improved hygiene, including steam sterilization of rockwool, soil disinfection by steam sterilization or with methyl bromide, and addition of a surfactant to nutrient solutions, and prevention may be by grafting cucumber ontoCucubita ficifolia rootstocks, immune to the virus.Samenvatting Sinds 1978 komt in de op steenwol en in grond geteelde kaskomkommer een ernstige bladnecrose voor, die vooral in het najaar tot afsterving van planten kan leiden en in wel 45% van de planten van een aangetast gewas is geconstateerd. Uit zieke planten kon een virus worden geïsoleerd dat gemakkelijk overging door sap-inoculatie en in lekvocht uit besmette steewol (waarschijnlijk door tussenkomst van eenOlpidium-soort), nadat dit werd gegoten op gesteriliseerde grond waarin komkommerzaailingen groeiden. Met dit virus konden de symptomen van de ziekte worden greproduceerd.Het infectivermogen van ruw platesap nam snel af bij verdunning tussen 10 en 100× (verdunningseindpunt ca 1 millioen), en bij warmtebehandelingen tussen 55 en 65°C (inactiveringstemperatuur 75°C) en bij bewaring bij kamertemperatuur tussen 1 en 1 1/2 maand.Slechts 3 van de 40 getoetste plantesoorten bleken vatbaar voor het virus, te weten komkommer, meloen en watermeloen. Alle 21 getoetste komkommercultivars en alle 8 getoetste meloenerassen reageerden hevig met lokale lesies en enkele, onder de heersende proeformastandigheden onvoorspelbaar, met systemische necrose. De wel als onderstam gebruikteCucurbita ficifolia is onvatbaar.Gezuiverd virus sedimenteerde in suiker- en CsCl-gradiënten en bij analytische ultracentrifugering in één piek. Des ₂₀ was 134S en de zweefdichtheid in CsCl 1.33 g.cm^–3. In ruw sap en gezuiverde suspensies deden de virusdeeltjes zich voor als bolletjes met een diameter van ongeveer 30 nm. Ze bevatten slechts éé soort eiwit met een relatieve moleculaire massa van 46 000 en één RNA-soort. Een antiserum met titer 1024 werd bereid. Het reageerde niet met komkommernecrosevirus en tabaksnecrosevirus. Wel reageerde het virus met een uit Japan ontvangen antiserum tegen het daar sinds 1966 bekende melon necrotic spot virus, terwijl het Japanse virus reageerde met het Nederlandse antiserum. Serologisch, zowel als in biologische en fysisch-chemische eigenschappen lijken de Nederlandse en Japanse isolaten identiek. Voor het virus wordt daarom de Nederlandse namm meloenenecrosevirus voorgesteld. Het verschilt van drie andere, onlangs min of meer gelijktijdig in Oost-Duitsland, op Kreta en in Libanese grond aangetroffen, via de bodem overgaande komkommervirussen, die evenals tabaks- en komkommernecrosevirus ook andere plantesoorten dan cucurbitaceeën kunnen infecteren.Waarschijnlijk is meloenencerosevirys al sinds 1967 bekend in Frankrijk als verwekker van criblure du melon. Het is ook nauw verwant aan de verwekker van een in een veredelingsprogramma van meloen in Californië opgedoken necrosevirus, waarvan echter wordt beweerd dat het overgaat met zaad van meloen en wordt overgebracht door bladkevertjes,Diabrotica-soorten. Het meloenenecrosevirus is in ons land voor het eerst geconstateerd als ziekteverwekker van kaskommer. Ook in England is het daarin onlangs aangetroffen. De ziekte kan op verschillende manieren bestreden, respectievelijk voorkomen worden. De grond dient gestoomd te worden of begast met methylbromide. Steenwolmatten kunnen bij hergebruik gestoomd worden, terwijl aan de voedingsoplossing uitloeier (Agral) toegediend kan worden. Zowel bij grond- als steenwolteelten is de ziekte te voorkomen door komkommerplante te enten op de onvatbare onderstamCucurbita ficifolia.     

小西葫芦黄花叶病毒外壳蛋白基因的克隆及序列分析

 以小西葫芦黄花叶病毒(Zucchini yellow mosaic virus,ZYMV)的中国分离物(CH-87)接种发病的叶片中提取的总RNA为模板,经RT-PCR扩增获得ZYMV CP基因,将其克隆到pUCm-T质粒上进行序列分析。结果表明该CP基因由837个核苷酸组成,编码279个氨基酸。与已发表序列相比较,该CP基因与国际上已报道的4个基因型不同,应属于新的基因型,暂命名为基因型Ⅴ。     

Colonisation and histological changes in muskmelon and autumn squash tissues infected by <Emphasis Type="Italic">Acremonium cucurbitacearum</Emphasis> or <Emphasis Type="Italic">Monosporascus cannonballus</Emphasis>

Muskmelon (Cucumis melo cv. Temprano Rochet) and autumn squash (Cucurbita maxima) seedlings were inoculated either with Acremonium cucurbitacearum or Monosporascus cannonballus, two of the soil-borne fungi implicated in ‘melon collapse’. Inoculation was achieved in two different ways: by growing the plants in pots containing infested soil to study the histological changes produced in the infected tissues using light microscopy and by growing seedlings in Petri dishes together with fungal colonies in order to observe the colonisation of the plant tissues using scanning electron microscopy. Both muskmelon and autumn squash roots infected with A. cucurbitacearum showed a suberised layer in the epidermis and the outermost layers of the parenchymatic cortex, but these symptoms developed earlier in the muskmelon plants. Muskmelon plants infected by this fungus also presented hypertrophy and hyperplasia, which led to a progressive separation of the vascular bundles in the lower stems of the affected plants. This response was not observed in autumn squash during the study. On the other hand, few histological changes were observed in tissues infected with M. cannonballus and only a slight increase in the size of cortical intercellular spaces was noted in the lower stems of muskmelon plants, and infected autumn squash tissues remained free of these symptoms throughout the study. The scanning electron microscope observations revealed that both fungi were able to colonise the tissues of the two host plants which were studied. A. cucurbitacearum colonised the epidermis and cortex of both muskmelon and autumn squash. The hyphae grew both inter- and intracellularly, and the density of the colonisation decreased within the endodermis. The same colonisation of host plants was observed as a result of M. cannonballus infection. The xylem vessel lumina of both muskmelon and autumn squash showed hyphae and tylose formation as a result of both fungal infections. However, non-fungal structures were detected in the hypocotyl vascular tissues. The present study demonstrates that both fungi are capable of infecting the tissues of a species which is resistant (autumn squash) and a species which is susceptible (muskmelon) to melon collapse.     

Aubian wheat mosaic virus, a new soil-borne wheat virus emerging in France

The properties of Aubian wheat mosaic virus (AWMV), a new soil-borne wheat virus in France, were investigated. Symptoms include foliar mosaic and severe stunting of winter wheat. The vector of the disease is unknown but the plants infected carry Polymyxa graminis in the roots. AWMV was transmitted mechanically to wheat and to two dicotyledoneous species: Lactuca sativa and Vicia faba. This virus was transmitted by seed to three winter wheat cultivars tested. Purified preparations contained rod-shaped particles with a variable length of 150–700 nm. Certain particles are very long and appear flexible. Antiserum raised against AWMV reacted specifically with AWMV in both indirect and direct enzyme-linked immunosorbent assays (ELISA). The incidence of AWMV in 26 winter wheat cultivars was investigated in the field during the growing season of 1999–2000. AWMV was detected in roots and shoots of all cultivars regardless of the symptoms. Twelve virus species belonging to the genera Benyvirus, Bymovirus, Furovirus, Pecluvirus and Pomovirus did not react with the AWMV antisera. A new tubular virus described in winter wheat in Bedfordshire in England reacted strongly with AWMV in ELISA. It is concluded that AWMV and probably the Bedford-virus constitute a previously undescribed tubular virus biologically and serologically distinct from other soil-borne viruses of wheat.     

Zucchini yellow mosaic virus — incidence and sources of virus infection in field-grown cucumbers and pumpkins in the Spreewald,Germany

Journal of Plant Diseases and Protection - In a survey in field-grown cucumber (Cucumis sativus L.) of the Spreewald cultivation area, Germany, from 2001 to 2004, infection with zucchini yellow...