核酸酶保护试验在黄瓜花叶病毒株系鉴定中的初步应用

采用黄瓜花叶病毒（ＣＭＶ）亚组Ⅰ株系Ｆｎｙ－ＣＭＶＲＮＡ＿２的１２０９～１６２６核苷酸片段和亚组Ⅱ株系Ｌｓ－ＣＭＶＲＮＡ＿２的２００２～２４３３核苷酸片段的ｃＤＮＡ克隆,体外转录,同时掺入￣（３２）Ｐ获得负链ＲＮＡ探针,与纯化的番茄和甜椒上的ＣＭＶ中国分离物的ＲＮＡ杂交,结果表明：ＣＭＶ番茄和甜椒中国分离物与Ｆｎｙ－ＣＭＶ的核苷酸有高度同源性,隶属于Ｆｎｙ－ＣＭＶ为代表的亚组Ⅰ株系。并利用Ｋ－ＣＭＶ株系（亚组Ⅰ,源于中国）的ＲＮＡ＿２全长ｃＤＮＡ克隆的两个ＥｃｏＲＩ位点间的核苷酸序列（１６５７～２１２５ｎｔ）作探针,与上述两种ＣＭＶ中国分离物的ＲＮＡ杂交,进一步比较分析了这两个分离物和Ｋ－ＣＭＶ株系的关系。讨论了核酸酶保护法在ＣＭＶ株系鉴定中的作用。     

刺槐上分离的花生矮化病毒的研究

刺槐花叶病是我国北方刺槐（Ｒｏｂｉｎｉａｐｓｅｕｄｏａｃａｃｉａ）常见病害。１９８７～１９９５年对河南、河北、山东和北京部分地区刺槐进行调查,刺槐花叶病发病率为４％～８７．５％。该病害主要特征是：叶片出现浅绿与绿色相间带有疱疹的花叶症状,叶缘波状扭...     

侵染香蕉的黄瓜花叶病毒株系的血清学特征

香蕉花叶病三类不同症状,即断续条纹类（BS）、连续条纹类（CS）和斑驳类（MM）在田间广泛存在,经过血清学、生物学、核酸斑点杂交和反转录聚合酶链反应,已确定它们都由黄瓜花叶病毒（Cucumberm。。i。virus,CMV）所弓愧f’］。这三类症状分离物在鉴别寄主、粒子形态、粒子电泳相对迁移率以及在西葫芦（CI;curbitafor）和烟草（Nicotianatabacumcv．HV38）上增殖和运转动力学的特征也表现不同［’］。这些不同可能揭示了香蕉三类分离物分属不同的株系。血清学是鉴定和研究CMV株系间亲缘关系的重要依据。大量文献【’,‘1报道…     

侵染番茄的黄瓜花叶病毒（CMV）株系特性的比较研究

从山东省主要番茄种植区病毒样本中分离到111个黄瓜花叶病毒(CMV)分离物,根据病毒的寄主范围和症状,初步鉴定为三个株系:番茄蕨叶株系(CMV-ToF)、番茄花叶株系(CMV-ToM)和番茄轻花叶株系(CMV-ToL)。三株系除在生物学特性存在明显差异外,其病毒粒体形态大小,电泳迁移率,病毒外壳蛋白亚基分子量、核酸组分以及病毒粒体血清学特性亦存在差别。     

Transmission Studies with Cucumber Green Mottle Mosaic Virus

Cucumber green mottle mosaic virus may spread in bottlegourd under field conditions through soil contaminated with infected plant debris followed by contact. No seed transmission was noticed in bottlegourd (Lagenaria siceraria) or vegetable marrow (Cucurbita pepo) although pollen grains and cotyledons from infected bottlegourd flowers or seeds, respectively, contained negliginle amounts of virus. Cucumber leaf beerles (Raphidopalpa fevicollis) are probable vectors since their regurgitated fluid and excretes contained infective virus particles. No vector fungi were found in the soil around infected bottlegourd plants.     

Photosynthesis in Sugarcane Varieties Infected with Strains of Sugarcane Mosaic Virus

Symptoms of sugarcane mosaic virus disease caused by strains B and D were accompanied by a reduction in the rate of photosynthesis per unit area; the severe symptoms of strain A and the mild symptoms of strain I produced rates no different from those of healthy plants of variety C.P. 31-588. All four strains decreased chlorophyll content and increased the amount of light transmitted by the leaf. Photosynthetic rates were reduced less than the reduction of chlorophyll would indicate. Symptoms moderated on older leaves, but rates of photosynthesis per dm² were less in older leaves of both healthy and diseased plants. Sugarcane varieties differed in their rates of photosynthesis in both healthy and in virus-infected plants; a significant reduction in photosynthetic rate by sugarcane mosaic occurred in three of the four varieties.     

Identification of Alfalfa Mosaic Virus in Greek Alfalfa Crops

Alfalfa mosaic virus (AMV) was found to be the prevalent virus disease in alfalfa crops in Central and Northern Greece. The virus was identified on the basis of the host symptomatology, aphid and seed transmission, particle morphology and serological tests. AMV was largely detected in commercial seeds of local grown alfalfa cvs by ELISA. Infected seed lots appear to be the main source responsible for the widespread distribution of the virus in Greek alfalfa fields.     

Biological and Serological Properties of Strains of Barley Mild Mosaic Virus

The biological and serological properties of two Japanese barley mild mosaic virus (BaMMV) strains (BaMMV-Kal and BaMMV-Nal) and a German BaMMV strain (BaMMV-M) were compared. Mechanical inoculation experiments showed that these three strains differed from one another in their ability to infect specific barley cultivars. BaMMV-Kal and BaMMV-M caused similar symptoms, but BaMMV-Nal clearly differed from them in its symptoms on some barley cultivars. The three BaMMV strains efficiently infected barley plants at 15°C, whereas at 20°C BaMMV-Kal and BaMMV-M also infected many plants but BaMMV-Nal infected only a few. BaMMV-Kal and BaMMV-M were indistinguishable by ELISA, while BaMMV-Nal was distinguished from both. The biological and serological variability reported shows that BaMMV occurs as two distinct strains in Japan.     

Non-Reciprocity of the Serological Relationship Between the Italian III Strain and Other Strains of Tobacco Mild Green Mosaic Virus

The Italian III strain (It III) of tobacco mild green mosaic virus (TMGMV) could not be distinguished from other strains of TMGMV using three antisera to this strain in precipitin, immunodiffusion gel tests, and ELISA. Antisera to the strains U2, PTMV, G-TAMV, and type TMGMV, however, were able to differentiate these strains from It III strain. The non-reciprocity of the serological relationship may be explained by assuming that It III lacks a specific epitope that the other strains have or that the, corresponding region in It III is not immunogenic.     

侵染香蕉的黄瓜花叶病毒株系的形态和生物学特征

对香蕉花叶病广东三个代表分离物的形态和生物学特征进行了较为全面的研究。在六种鉴别寄主上,斑驳类（ＭＭ）和断续条纹类（ＢＳ）分离物侵染较多的寄主种类诱导较为严重的症状,连续条纹类（ＣＳ）分离物侵染能力较弱。电镜观察表明：ＢＳ、ＣＳ和ＭＭ三个代表分离物的粒子呈球状、其粒子直径分别为２２．５、２４．３和２７ｎｍ,纯化的病毒粒子电泳相对迁移率分别为０．７２、０．５６和０．５１,在西葫芦上的增殖速度：不管在子叶或真叶,都是ＭＭ最快、ＢＳ次之、ＣＳ最慢。从西葫芦接种叶运转出接种叶的速度：ＭＭ和ＢＳ相似、ＣＳ明显较慢。在烟草上,三个分离物的运转速度和增殖速度以ＭＭ最快、ＢＳ次之、ＣＳ最慢;而且在烟草上随着接种后时间的延长,三个分离物除ＭＭ维持高浓度的时间较长外,ＢＳ和ＣＳ的都很短。在西葫芦和烟草上提纯产量,ＭＭ类最多、ＢＳ类次之、ＣＳ类最低。     

Identification of Yeast Factors Involved in the Replication of Mungbean Yellow Mosaic India Virus Using Yeast Temperature-Sensitive Mutants

正Dear Editor,The geminiviruses are small single-stranded plant DNA viruses belonging to the family Geminiviridae, which cause serious diseases in many economically important     

Reaction of Muskmelon Collections to Cucumber Green Mottle Mosaic Virus

Abstract In a preliminary trial 187 collections of muskmelon comprising dessert and non-dessert types and wild Cucumis species were screened against cucumber green mottle mosaic virus (CGMMV) under field conditions. Based on the reaction to CGMMV, 64 were studied further in detail. Thirteen collections were found to be resistant in two field screenings (summer and rainy seasons). Results on screening under artificial conditions against pure isolate of CGMMV indicated that Cucumis figarei , C. myriocarpus 1, C. myriocarpus 3, C. africanus 1, C. africanus 2, C. meeusii, C. ficifolius and C. zeyheri 2 were resistant to virus. Immune nature of resistance was later confirmed by back inoculation technique and, transmission electron microscopic study of C. figarei, C. ficifolius, C. meeusii, C. africanus 1 and C. zeyheri 2. Phoot ( C. melo var. momordica ) and Kachri (non-dessert types), FM 1 and FM 2 (Cornell breeding lines) and C,. myriocarpus 2 were also resistant to CGMMV with very mild symptoms.     

Structural Analysis of A-Protein of Cucumber Green Mottle Mosaic Virus and Tobacco Mosaic Virus by Synchrotron Small-Angle X-Ray Scattering

The size and shape of A-protein of tobacco mosaic virus coat protein (TMVP) and cucumber green mottle mosaic virus coat protein (CGMMVP) were evaluated by means of small-angle X-ray scattering (SAXS) using a synchrotron radiation source, complemeted by electron microscopic observations. The results imply that TMV and CGMMV A-proteins are composed of three and two subunits, respectively, stacked in the shape of an isosceles triangular prism at lower ionic strength. Considering the difference of the A-protein structure at higher and lower ionic strength, the globular core structure was proposed as a subunit which might be modeled as a thin isosceles triangular prism composed of four globular cores joined by rather flexible segments. These cores correspond probably to four helical regions in a subunit, and rearrange their relative positions according to the external conditions. A slight rearrangement of core positions in a subunit may result in the formation of A-proteins of various shapes.     

Mixed Infections of Pepino Mosaic Virus Strains Modulate the Evolutionary Dynamics of this Emergent Virus

Pepino mosaic virus (PepMV) is an emerging pathogen that causes severe economic losses in tomato crops (Solanum lycopersicum L.) in the Northern hemisphere, despite persistent attempts of control. In fact, it is considered one of the most significant viral diseases for tomato production worldwide, and it may constitute a good model for the analysis of virus emergence in crops. We have combined a population genetics approach with an analysis of in planta properties of virus strains to explain an observed epidemiological pattern. Hybridization analysis showed that PepMV populations are composed of isolates of two types (PepMV-CH2 and PepMV-EU) that cocirculate. The CH2 type isolates are predominant; however, EU isolates have not been displaced but persist mainly in mixed infections. Two molecularly cloned isolates belonging to each type have been used to examine the dynamics of in planta single infections and coinfection, revealing that the CH2 type has a higher fitness than the EU type. Coinfections expand the range of susceptible hosts, and coinfected plants remain symptomless several weeks after infection, so a potentially important problem for disease prevention and management. These results provide an explanation of the observed epidemiological pattern in terms of genetic and ecological interactions among the different viral strains. Thus, mixed infections appear to be contributing to shaping the genetic structure and dynamics of PepMV populations.Pepino mosaic virus (PepMV; genus Potexvirus, family Flexiviridae) was identified in 1974 as the agent responsible for a viral disease of pepino crops (Solanum muricatum) in Peru (30). PepMV in tomato (Solanum lycopersicum) was first reported in The Netherlands in 1999 (74) but has since spread rapidly in Europe (3, 11, 38, 48, 51, 57) and beyond (20, 35, 36, 42, 68), causing epidemics and severe economic losses (27, 29, 36, 51, 67, 69). The PepMV host range is limited mainly to the Solanaceae (59), and the virus is easily transmitted from plant to plant by contact (30), vectored by bumblebees (65), or seedborne-transmitted (37). PepMV infections in tomato are associated with a wide range of leaf symptoms: mild and severe mosaics, bubbling, laminal distortions, and stunting (26, 27, 51). Fruit symptoms occur with or without leaf symptoms, and the main impact of PepMV is on fruit quality (irregular lycopene distribution [26]) but not on yield (69). Therefore, PepMV is currently considered a dangerous pathogen and is included in the European Plant Protection Organization alert list (15) as one of the most important tomato viruses worldwide (27, 51, 57, 68, 69).The PepMV genome consists of a single, positive-sense, ∼6,400-nucleotide (nt) RNA strand containing five open reading frames (ORFs). ORF1 encodes the putative viral polymerase (RdRp) (3). ORFs 2, 3, and 4 encode the triple gene block (TGB) proteins TGBp1, TGBp2, and TGBp3, which are essential for virus movement (46, 75, 78). Potato virus X TGBp1 is a multifunctional protein that induces plasmodesmal gating, moves from cell to cell, has ATPase and RNA helicase activities, binds viral RNAs, and acts as suppressor of RNA silencing (39, 76-78). ORF5 encodes the coat protein (CP) which, in addition to its structural role, is required for cell-to-cell and long-distance movement (12). Finally, two short untranslated sequences flank the coding regions, and there is a poly(A) tail at the 3′ end of the genomic RNA (3, 11, 48).Previous studies have shown that Spanish PepMV populations sampled between 2000 and 2004 were genetically very homogeneous (∼99% nucleotide identity), most comprising isolates highly similar to the so-called European tomato strain (PepMV-EU). However, a few isolates sampled in 2004 in the Murcia region (Southeastern Spain) were distinct and highly similar to the US2 strain reported in the United States (51). U.S. isolates (US1 and US2) and a Chilean isolate from infected tomato seeds (CH2) share only 79 to 86% nucleotide identity with European (EU) isolates (36, 42). The CH2 type has been reported recently in greenhouses for tomato production in Poland (29) and Belgium (27). In this last study, CH2 was predominant in single infections and also frequent in mixed infections with isolates of the EU type (27). However, all PepMV types (EU, US1, US2, and CH2) have been found in United States, where the PepMV-EU type has been the most prevalent, and mixed infections were found in samples collected from Arizona, Colorado, and Texas (35).Several studies of plant virus populations have reported a reduced genetic diversity of populations separated in time or space (19, 40, 56) with high virus genetic stability (23). Nevertheless, how genetic and ecological factors modulate the evolutionary dynamics of viruses and determine epidemiological patterns is still poorly understood (25, 47).We have characterized the population genetic structure of PepMV in infected samples of commercial tomato crops in the Murcia region (southeastern Spain) between 2005 and 2008. Phylogenetic analysis was performed, and genetic diversity values among PepMV isolates were estimated to determine the structure of the population and the strength and direction of selection. In addition, the biological properties (host range, fitness, and virulence) of two cloned isolates of the CH2 and EU types were studied to understand the evolutionary dynamics of natural PepMV populations.     

Identification of a Strain of Peanut Chlorotic Streak Virus Causing Chlorotic Vein Banding Disease of Groundnut in India

A virus disease characterized by chlorotic vein banding, chlorotic line pattern along the margins or midrib of mature leaflets and chlorotic spots/rings was observed on commercial groundnut crops in Rayalaseema area of Andhra Pradesh with an incidence from 1% to nearly 60%. The virus was transmitted by mechanical inoculation in extracts prepared with 0.01 M potassium phosphate butter, pH 8.0 to 21 species from the Chenopodiaceae, Cruciferae, Leguminosae and Solanaceae, Chenopodium quinoa was found to be a good local lesion host. The virus was neither seed-transmitted through 1591 groundnut seeds nor aphid-transmitted by Aphis craccivora, Myzus persicae and Rhopalosiphum maidis either in non-persistent or semi-persistent manner. The virus remained infective in buffered tobacco leaf sap at a dilution of 10^?5; in a 10^?1 dilution of buffered sap the virus was infective for 2–3 days at 22–29°C or when heated to 65°C for 10 min but not to 70°C. Clarification treatments with organic solvents with 10% chloroform was least damaging. The virus was purified from Nicotiana rustica leaves. Purified virus contained isometric particles of 51 nm in diameter with an electron dense core of 22 nm and two major polypeptides of 76 kDa and 36 kDa. A polyclonal antiserum to this virus was produced. In agar gel double diffusion, enzyme-linked immunosorbent assay and in electro-blot immunoassay rests the virus was related to peanut chlorotic streak virus and not to cauliflower mosaic, figwort mosaic and soybean chlorotic mottle viruses.     

Variation of Cell-free Translation Profiles Among Pathogenic Strains of Soybean Mosaic Virus

Cell-free translation products from isolates representing soybean mosaic virus (SMV) strains G1 to G7 and G7a, along with several other SMV isolates, were analyzed. SMV RNAs were translated in both rabbit reticulocyte lysates and wheat germ extracts, yielding approximately 20 translation products for each strain from each translation system. Comparison of translation profiles by the presence or absence of proteins allowed for the formation of distinctive groups from each cell-free translation system. Groupings formed by analysis of products from rabbit reticulocyte lysates correlated with pathogenicity; groupings formed by analysis of products from wheat germ extracts had no apparent biological significance.     

Strains of Zucchini Yellow Mosaic Virus in Muskmelon (Cucumis melo L.)

According to the reaction of muskmelon line PI 414723, 22 natural isolates of Zucchini Yellow Mosaic Virus (ZYMV) were grouped into two pathotypes. When inoculated by isolates belonging to pathotype 0, most of the PI 414723 plants (over 70%) remained symptomless while few plants developed systemic chloronecrotic spotting and more rarely yellowing, stunting, mosaic and leaf deformations. When contaminated by pathotype 1 all PI 414723 plants developed systemic chloronecrotic spotting. Two variants were obtained from representative strains of these two pathotypes, able to induce yellowing, stunting, mosaic and leaf deformation on all inoculated PI 414723 plants. These variants could not be differentiated from their originating strains either by host range, serology or aphid transmission properties. Therefore they are regarded as belonging to a third group called pathotype 2. No relation was observed between the type of symptom developed on PI 414723 and the ability to induce a rapid wilting reaction of melon cv. Doublon (pathotype F).