吉林、黑龙江毛葱病毒病调查

本研究为明确吉林和黑龙江省毛葱病毒病发生率,从两省5个地区共采集255份毛葱样品。根据毛葱4种主要病毒基因组序列设计特异性引物,对胡葱黄条病毒Shallot yellow stripe virus(SYSV)和青葱X病毒Shallot virus X (SVX)、洋葱黄矮病毒Onion yellow dwarf virus (OYDV)和葱潜隐病毒Shallot latent virus (SLV)进行双重RT-PCR检测。结果表明,229份样品检出病毒,带毒率为89.8%,SLV的检出率最高,达87.06%,OYDV次之,为36.86%,SYSV检出率偏低,为0.78%;同时存在病毒复合侵染,其中双病毒复合侵染为SLV和OYDV,检出率为33.3%;三病毒复合侵染为SYSV、OYDV和SLV,检出率为0.78%,未发现4种病毒复合侵染。本研究为吉林和黑龙江种植区毛葱病毒病防治提供了参考依据。     

Survey and characterization of potyviruses and their strains of Allium species

Nearly 5700 plants of 14 cultivated and 8 wildAllium species and varieties from the Netherlands and other parts of the world, were tested for infection with aphid-borne potyviruses by ELISA, electron microscope decoration tests and/or inoculation onto test plants. This resulted in the detection of two known viruses, viz. leek yellow stripe virus (LYSV) and onion yellow dwarf virus (OYDV), and the discovery and characterization of two new viruses, viz. shallot yellow stripe virus (SYSV) and Welsh onion yellow stripe virus (WoYSV), and of six strains of these viruses. ‘Garlic mosaic’, ‘barlic yellow streak’, ‘onion mosaic’, ‘shallot mosaic’, ‘shallot X’, and ‘shallot yellows’ viruses, incompletely described in the literature, are now reidentified as well-known viruses or as strains or mixtures of such viruses. ‘Garlic yellow stripe virus’ is also a complex containing a potyvirus possibly differing from the viruses found in this survey. The symptoms of the potyviruses studied varied widely and ranged from mild to severe chlorotic to yellow striping of leaves, and they are of little diagnostic importance.LYSV was found in vegetatively propagated pearl onion (A. ampeloprasum var.sectivum) from Europe and Asia. It has decreased in leek crops (A. ampeloprasum var.porrum) in the Netherlands since the 1970, apparently due to resistance in new cultivars. OYDV was common in onion (A. cepa var.cepa) from the former USSR and North Africa, and in European cultivars of shallot (A. cepa var.ascalonicum), with the exception of the highly resistant ‘Santé’, but was not detected during this survey in Asian shallot. European samples of ever-ready onion (A. cepa var.perutile), multiplier onion (A. cepa var.aggregatum) and tree onion (A. cepa var.viviparum) contained OYDV. It was also found in sand leek (A. scorodoprasum) from european gene collections. A strain of OYDV from onion and shallot in Morocco and Spain was virulent on onion and shallot cultivars resistant to common OYDV, as reported early for a similar isolate in the USA.Asian shallot appeared generally infected with the new SYSV, similar to OYDV in host range and symptoms but serologically distinct. It was not detected in onion and shallot from Europe or North Africa. A virulent strain of this virus caused striping in sap-inoculated garlic (A. sativum) and Formosan lily (Lilium formosanum). The new WoYSV, infecting Welsh onion in Indonesia and Japan, was earlier described in Japan as OYDV from rakkyo and Welsh onion. It appeared serologically closely related to SYSV and distantly to OYDV, but differed in its host range.Host-specific strains of LYSV and OYDV were detected in garlic, wild garlic (A. longicuspis), an unidentifiedAllium species (suffix-G), and great-headed garlic (A. ampeloprasum var.holmense) (suffix-GhG)., LYSV-G and OYDV-G infected on average 45% and 73%, respectively, of the garlic samples of worldwide origin. Symptoms of isolates of both strains varied in severity, implying the necessity of serological tests for disease diagnosis and health certification. LYSV-GhG was the cause of yellow striping in 93% of the great-headed garlic plants tested, mainly from the Mediterranean area. One sample was also infected with OYDV-GhG.Many samples from vegetatively propagated crops grown from non-certified planting stock contained a few plants free of potyviruses, implying the possibility to obtain healthy (and possibly resistant) selections of such cultivars avoiding meristem-tip culture. Cross-protection of garlic sets by a mild potyvirus isolate seems to be an alternative to the use of vulnerable virus-free sets.Generally, viruses and virus strains could not be transmitted to anyAllium species other than their natural host, except to the highly susceptible crow garlic (A. vineale). This species, and other predominantly vegetatively propagating wildAllium spp. (field garlic,A. oleraceum; ramsons,A. ursinum; sand leek), were found not to be reservoirs of viruses that might infectAllium crops in the netherlands. Streaking in vegetatively propagated wild leeks (A. ampeloprasum and closely related species) originating from the Mediterranean area and Asia was due to an undescribed miteborne virus. The survey confirmed that spread of potyviruses inAllium crops in the Netherlands is from planting sets, and from a neighbouring crop only if of the same species.     

Further Evidence that Shallot Yellow Stripe Virus (SYSV) Is a Distinct Potyvirus and Reidentification of Welsh Onion Yellow Stripe Virus as a SYSV Strain

ABSTRACT An antiserum to shallot yellow stripe virus (SYSV) was raised and used in combination with a range of other antisera to potyviruses of Allium spp. in electron microscopic decoration experiments. The serological results corroborated an earlier finding that the type isolates of SYSV and Welsh onion yellow stripe virus (WoYSV) are closely related to each other and only distantly related to onion yellow dwarf (OYDV) and leek yellow stripe (LYSV) viruses, the two other major potyviruses infecting Allium spp. Moreover, the decoration results indicated that Japanese potyviruses named OYDV and Wakegi yellow dwarf virus are isolates of SYSV. Sequence analysis of the 3'-terminal regions of the SYSV and WoYSV ge-nomes revealed coat protein (CP) amino acid and 3'-nontranslated region (3'-NTR) nucleotide sequence identities of 95 and 89%, respectively. The CP amino acid and 3'-NTR nucleotide sequences of these viruses differed from those of OYDV and LYSV by >25 and >67%, respectively. The serological and molecular studies showed that SYSV and WoYSV are different strains of a potyvirus distinct from OYDV and LYSV. For priority reasons, we propose that these strains together with the Wakegi-type isolates of OYDV described in Japan be referred to as SYSV and that SYSV isolates from Allium spp. other than shallot be designated as the Welsh onion strain of SYSV (SYSV-Wo).     

Double-edged effects of the cryogenic technique for virus eradication and preservation in shallot shoot tips

Plant virus eradication is a prerequisite for the use of virus-free propagules for sustainable crop production. In contrast, virus preservation is required for all types of applied and basic research of viruses. Shoot tip cryopreservation can act as a double-edged strategy, facilitating either virus eradication or virus preservation in cryoderived plants. Here, we tested the efficacies of shoot tip cryopreservation for virus eradication and preservation in shallot (Allium cepa var. aggregatum). In vitro stock shallot shoots infected with onion yellow dwarf virus (OYDV) and shallot latent virus were thermotreated for 0, 2, and 4 weeks at a constant temperature of 36℃ before shoot tip cryopreservation. Results showed that viruses were preserved in recovered shoots when thermotherapy was not applied. Although thermotherapy lowered the regrowth levels of cryotreated shoot tips, the efficiency of virus eradication increased from 5% to 54%. Immunolocalization of OYDV and histological observation of cryotreated shoot tips showed the high frequency of virus preservation was due to the viral invasion of cells close to the apical meristem and the high proportion of cells surviving. Four weeks of thermotherapy drastically decreased the distribution of OYDV, as well as the percentage of surviving cells within the shoot tips, thereby promoting virus eradication. Virus-free plants obtained from combining thermotherapy with cryotherapy showed significantly improved vegetative growth and bulb production. The present study reports how thermotherapy can act as a trigger to facilitate either the safe preservation of Allium viruses or the production of virus-free shallot plants.     

Leek yellow stripe virus and its relationships to onion yellow dwarf virus; characterization,ecology and possible control

Since 1970 yellow stripe disease of leek (Allium porrum) has developed epidemically in the south-eastern part of the Netherlands coincident with increasing year-around cultivation of the crop. Many autumn and winter crops now become totally infected. Apparently similar attacks, first reported in Germany in 1937, are increasingly attracting attention in various European countries. This paper describes the leek yellow stripe virus (LYSV) as a new potyvirus related to onion yellow dwarf virus (OYDV), which was so far incompletely described. LYSV is hardly infectious to onion (A. cepa) and shallot (A. ascalonicum) and OYDV behaves similarly on leek. The leek virus further differs from OYDV in not being infectious toA. fistulosum and in causing distinct local lesions onChenopodium amaranticolor andC. quinoa. The two viruses closely resemble each other in external symptoms in their respective hosts, in persistence of infectivity in expressed sap, and in particle morphology and length (LYSV 820 nm; OYDV 833 nm). Intracytoplasmic inclusion bodies slightly differ. Further biophysical characters of the two viruses, such as sedimentation coefficient (OYDV 143 S), buoyant density in CsCl (LYSV 1.326; OYDV 1.306, or 1.258 in Cs₂SO₄), and molecular mass of coat protein subunit (LYSV 34000; OYDV 30000 dalton), are characteristic of the potyvirus group, but do not assist in judging their relationships. Serologically they are only distantly related if at all. The leek virus is not seed-borne. It is aphid-transmitted in the non-persistent manner and its main epidemic build-up is during late summer and autumn. The sole sources of infection are nearby leek crops. Awaiting the development of resistant leek cultivars, it is advised to avoid sowing leek seed beds and planting spring crops near overwintering leek, and to remove infected plants showing up during summer.     

Carlavirus isolates from cultivated Allium species represent three viruses

From 12 cultivated and mostly vegetatively propagatedAllium species and varieties tested for carlavirus infections, 94 virus isolates were obtained which varied greatly on indicator hosts.Chenopodium amaranticolor, C. quinoa, Celosia argentea var.plumosa Geisha,Nicotiana hesperis accession 67A andN. occidentalis accession P1 proved valuable for detection, isolation and propagation of part of the isolates. The latter three species are new experimental hosts for carlaviruses ofAllium species. Other isolates could only be transmitted toAllium species such as crow garlic (A. vineale) leek (A. ampeloprasum var.porrum) and onion (A. cepa var.cepa). The isolates were grouped into three viruses by differential hosts and host reactions and their reaction with four antisera.Shallot latent virus (SLV) was found in ever-ready onion (A. cepa var.perutile), grey shallot (unidentifiedAllium species), multiplier onion (A. cepa var.aggregatum), pearl onion (A. ampeloprasum var.sectivum), rakkyo (A. chinense), shallot (A. cepa var.ascalonicum), and Welsh onion (A. fistulosum). Virus isolates from garlic and Asian shallot, fully reacting with antiserum to SLV but differing in host reactions from the SLV type-isolate, are now described as garlic strain (SLV-G) and Asian shallot strain of the virus, respectively. The garlic latent virus from garlic described in Japan is now considered identical with SLV-G.A carlavirus almost universal in garlic, and also found in great-headed garlic (A. ampeloprasum var.holmense), in an unidentifiedAllium species, and occasionally in leek, did not react with the antisera to SLV and the Japanese garlic latent virus, and is now described as the new garlic common latent virus (GCLV). It appeared identical to a virus erroneously identified in Germany as garlic latent virus.The new Sint-Jan's-onion latent virus (SjoLV) from Utrechtse Sint-Jan's onion (unidentifiedAllium species) from the Netherlands and similar crops originating from other countries, did not induce reactions in test plants and could only be detected by electron microscope decoration tests. It reacted equally wellwith the antisera to SLV and GCLV. It was also present together with SLV in ever-ready onion, pearl onion, rakkyo, shallot, and Welsh onion. Garlic latent virus reported in Japan from hosts other than garlic should be regarded as SLV, SjoLV, or a mixture of these viruses.The carlaviruses were not detected in wild plants of ramsons (A. ursinum), and of the predominantly vegetatively propagated crow garlic (A. vineale), field garlic (A. oleraceum), and sand leek (A. scorodoprasum), collected in the Netherlands.Severe reactions in the indicator hosts incidentally revealed soil-borne viruses in shallot (the nepovirusesArabis mosaic virus (ArMV) and tomato black ring virus) and crow garlic (ArMV and the tobravirus tobacco rattle virus). Tobacco necrosis virus (necrovirus) was detected in roots of shallot.     

Mite-borne virus isolates from cultivated Allium species,and their classification into two new rymoviruses in the family Potyviridae

While testing several samples of onion and of vegetatively propagated garlic, sand leek and shallot from a number of countries, virus isolates with unusually flexuous particles were obtained by mite (Aceria tulipae) or sap transmissions. No aphid-borne poty-or carlavirus was transmitted by mites, and mite-borne virus isolates could not be transmitted by aphids. The mite-borne isolates did not react with antisera to aphid-borne potyviruses ofAllium spp. or with the Agdia potyvirus group monoclonal. In contrast to the mite-borne onion and garlic mosaic viruses reported in the literature, our mite-borne isolates induced no visible or only very mild symptoms inAllium spp., except isolates from shallot ‘Santé’ which caused diffuse striping. Heavily mite-infested test plants or plant samples showed streaking and malformation due to mite feeding (tangle-top). The mite-borne virus isolates could be classified with test plants and a discriminating antiserum into three groups, representing two viruses and a strain of one of them. They are tentatively named onion mite-borne latent virus (OMbLV), garlic strain of this virus (OMbLV-G), and shallot mite-borne latent virus (SMbLV). Mite transmission, length of virus particles (ca. 700 to 800 nm), and the presence of granular inclusion bodies in infected tissue indicate that the viruses belong to the mite-borne genusRymovirus of the familyPotyviridae. OMbLV from shallot and onion, and OMbLV-G from garlic and sand leek, can be assayed onChenopodium murale but differ in their natural hosts. They are very common. SMbLV, to whichC. murale does not react, was isolated from shallot originating from Asia and Russia.     

Nucleotide sequence and symptom modulating analysis of a Peanut stunt virus-associated satellite RNA from Poland: high level of sequence identity with the American PSV satellites

Two peanut stunt virus isolates from Poland (PSV-Ag and PSV-P) have been studied. The isolates produce similar systemic symptoms onNicotiana tabacum plants but the symptoms onN. benthamiana, Pisum sativum andDatura stramonium plants are much stronger for the PSV-P isolate. Analysis of the RNA extracted from purified virions by gel electrophoresis and RT-PCR amplification allowed the detection of a satellite RNA in the PSV-P isolate. The nucleotide sequence of this European PSV satellite was determined and found to have a high degree of identity with the sequences of the four American PSV satellites previously studied, which were found to have either no effect or ameliorate the PSV symptoms in tobacco plants (Collmer et al., 1985; Naidu et al., 1991). The possible role of the European PSV satellite in the modulation of viral symptoms has been studied but no effect was observed when the purified satellite was used with the PSV-Ag isolate as helper virus on any of the three hosts cited above.     

Biological and molecular characterization of a novel carmovirus isolated from angelonia

ABSTRACT A new carmovirus was isolated from Angelonia plants (Angelonia angustifolia), with flower break and mild foliar symptoms, grown in the United States and Israel. The virus, for which the name Angelonia flower break virus (AnFBV) is proposed, has isometric particles, approximately 30 nm in diameter. The experimental host range was limited to Nicotiana species, Schizanthus pinnatus, Myosotis sylvatica, Phlox drummondii, and Digitalis purpurea. Virions were isolated from systemically infected N. benthamiana leaves, and directly from naturally infected Angelonia leaves, using typical carmovirus protocols. Koch's postulates were completed by mechanical inoculation of uninfected Angelonia seedlings with purified virions. Isometric particles were observed in leaf dips and virion preparations from both Angelonia and N. benthamiana, and in thin sections of Angelonia flower tissue by electron microscopy. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis of dissociated purified virus preparations, a major protein component with a molecular mass of 38 kDa was observed. Virion preparations were used to produce virus-specific polyclonal antisera in both Israel and the United States. The antisera did not react with Pelargonium flower break virus (PFBV), Carnation mottle virus (CarMV), or Saguaro cactus virus (SgCV) by either enzyme-linked immunosorbent assay or immunoblotting. In reciprocal tests, antisera against PFBV, CarMV, and SgCV reacted only with the homologous viruses. The complete nucleotide sequence of a Florida isolate of AnFBV and the coat protein (CP) gene sequences of Israeli and Maryland isolates were determined. The genomic RNA is 3,964 nucleotides and contains four open reading frames arranged in a manner typical of carmoviruses. The AnFBV CP is most closely related to PFBV, whereas the AnFBV replicase is most closely related to PFBV, CarMV, and SgCV. Particle morphology, serological properties, genome organization, and phylogenetic analysis are all consistent with assignment of AnFBV to the genus Carmovirus.     

Comparative Cytopathology and Immunocytochemistry of Japanese, Australian and Brazilian Isolates of Orchid fleck virus

Cytopathic effects in orchid leaf tissues infected with Australian, Japanese and Brazilian isolates of Orchid fleck virus (OFV) were indistinguishable and like those previously described in the literature. Cells had an electron-lucent viroplasm with unenveloped rod-shaped virions in the nucleus and cytoplasm, often associated with the inner membrane of the nuclear envelope and the endoplasmic reticulum. Antiserum raised against a Japanese isolate of OFV reacted with Brazilian and Australian isolates in ELISA, and when used for immuno-gold labelling, also reacted in situ with the rod-shaped virions and the intranuclear viroplasm of all three isolates. These results suggest that the viroplasm is where structural proteins accumulate and virions are formed. Received 13 December 2000/ Accepted in revised form 13 April 2001     

大麦黄矮病毒GAV株系在麦二叉蚜体内的运行途径研究

 以生物学测定和酶联检测鉴定出的大麦黄矮病毒GAV株系为材料,研究了病毒在麦二叉蚜体内的运行途径。在麦二叉蚜不同组织的超薄切片中,只有在唾液附腺组织中观察到膜包被的病毒粒体,在后肠腔和血淋巴中的病毒粒体是游离的。说明病毒与唾液附腺膜上传毒蛋白(受体)的相互识别是介导传播的根本原因,而麦蚜的获毒过程不存在专化的识别过程。     

Characterization of a vector-non-transmissible isolate of Tomato spotted wilt virus

The characteristics of a thrips‐non‐transmissible isolate of Tomato spotted wilt virus (TSWV), designated TSWV‐M, were compared with those of a thrips‐transmissible isolate, designated TSWV‐T. TSWV‐M showed a narrower host range than TSWV‐T. Adult thrips failed to transmit TSWV‐M, although the vector acquired the virus during the larval stages. TSWV‐M was detected by RT‐PCR in adult thrips bodies, but not in thrips heads, suggesting that loss of thrips transmissibility was the result of the absence of virus in adult thrips salivary glands. Whereas N (nucleoprotein), NSs (non‐structural protein) and G_C (the C‐terminal portion of the glycoprotein precursor protein) were present in similar amounts in leaf tissue from TSWV‐M‐ or TSWV‐T‐infected plants, G_N (the N‐terminal portion of the glycoprotein precursor protein) was present at much lower amounts in TSWV‐M‐ than in TSWV‐T‐infected plants. SDS‐PAGE and immunoblotting analysis of TSWV‐M and TSWV‐T virion preparations with G_N‐ and G_C‐specific antibodies revealed similar amounts of the G_N and G_C glycoproteins in TSWV‐T virions, but lower amounts of G_N than G_C in TSWV‐M virions. This resulted in a statistically significant reduction in the G_N/G_C ratio in TSWV‐M virions. In affinoblots, the G_C and G_N glycoproteins of TSWV‐M exhibited weak binding with lectins showing affinity for N‐linked oligosaccharide structures. Sequence analysis of M RNA (medium segment of the TSMV genome) revealed no deletions or frameshift mutations in the G_N/G_C precursor of TSWV‐M. However, five amino acid changes were detected in the G_N/G_C precursor. A single, relatively conservative amino acid substitution (V→I) was observed in the NSm protein. Sequence analysis of S RNA (small portion of the TSMV genome) revealed a large intergenic region with no changes in the N protein and with three amino acid changes in the NSs protein.     

Evidence for a phytoreovirus associated with tobacco exhibiting leaf curl symptoms in South Africa

ABSTRACT Three forms of tobacco leaf curl (termed classes I, II, and III, based on symptomatology) recently have been described in southern Africa. Numerous attempts to isolate virus particles responsible for a nongeminivirus-induced leaf curl disease (class I) of tobacco in South Africa have been unsuccessful. Recently, 12 dsRNA segments were isolated from tobacco exhibiting class I leaf curl symptoms, suggesting a possible reovirus genome. The objective of our study was to confirm whether the dsRNA segments are associated with a reovirus. Isolation of icosahedral particles with an outer core 60 to 65 nm in diameter and an inner core 40 to 45 nm in diameter was achieved. Twelve distinct nonpolyadenylated dsRNAs were isolated from purified virions, and the total molecular masses of the dsRNAs ranged from 17.86 to 18.40 x 10(6) Da in polyacrylamide and agarose gels, respectively. Using hybridization analysis, dsRNAs were identified as non-homologous distinct segments. Comparisons with other known reoviruses revealed a unique banding pattern that was most similar to the wound tumor virus (WTV), the type species of the genus Phytoreovirus. Hybridizations of WTV cloned DNA probes (segments S4 and S6 to S9) and dsRNAs from infected tobacco indicated no significant sequence similarity, whereas indirect enzyme-linked immunosorbent assay with a polyclonal antiserum to WTV showed strong positive cross-reactivity to tobacco virions. Our results indicate a virus with features consistent with those of phytoreoviruses. This is the first report of a plant reovirus in tobacco, the first record in Africa, and the second example of a field-isolated dicot phytoreovirus.     

Geminate Particle Morphology of Sweet Potato Leaf Curl Virus in Partially Purified Preparation and Its Serological Relationship to Two Begomoviruses by Western Blotting

Sweet potato leaf curl virus (SPLCV) is a possible member of the genus Begomovirus; however, the presence of typical geminate particles in sap has not been confirmed. We attempted to observe SPLCV virions by partially purifying the virus using an enzyme-assisted procedure. The observed virions in the partially purified preparations were typical geminate particles with a size of ca. 18×30nm. This virus preparation was subjected to western blot analysis using antisera against Bean golden mosaic virus (BGMV) and Mungbean yellow mosaic virus (MYMV). SPLCV reacted with both antisera. Specific bands appeared to be slightly larger than the 30-kDa marker protein and were considered to be SPLCV coat protein. This western blot analysis revealed for the first time a serelogical relationship between SPLCV and the two well-characterized begomoviruses. Received 28 June 1999/ Accepted in revised form 17 November 1999     

Testing garlic cloves and bulblets for onion yellow dwarf virus by ACP-ELISA

Onion yellow dwarf virus (OYDV) was detected in cloves and aerial bulblets of garlic (Allium sativum) at levels as high as or higher than in leaves of plants grown from tested cloves. It is recommended to test bulblets or a few cloves per bulb before planting to determine if all cloves of a bulb are virus-free. This aids in early detection and allows a more thorough testing of stock than field testing.     

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.     

烟草坏死病毒A大豆分离物的分子鉴定

 对曹琦和濮祖芹早期分离到的烟草坏死病毒大豆分离物的生物学、血清学和外壳蛋白的序列进行了进一步研究。该分离物能侵染8科29种植物, 除系统侵染大豆和本生烟外, 其余寄主均为局部侵染。电镜下病毒粒子呈球状, 直径约28nm。基因组为单组分RNA, 大小约为3.7 kb, 具有2条亚基因组, 分别约为1.6 kb和1.3 kb。外壳蛋白亚基的分子量约为30 kDa。血清学试验表明, 该分离物与TNV柳树分离物的抗血清呈特异反应, 与同属坏死病毒属(Necrovirus)的烟草坏死病毒D(TNV-D)和甜菜黑色焦枯病毒(BBSV)无血清学关系。利用简并引物通过RT-PCR克隆了该分离物的外壳蛋白基因。序列分析表明, 该分离物与烟草坏死病毒A(TNV-A)、TNV-D和TNV-D^H的外壳蛋白分别具有88.77%、45.13%和45.49%的氨基酸序列一致性。因此, 该大豆分离物属于TNV-A的一个新株系, 命名为TNV-A^C。     

Low root‐to‐root transmission of a tobamovirus,yellow tailflower mild mottle virus,and resilience of its virions

Tobamoviruses are serious pathogens because they have extremely stable virions, they are transmitted by contact, and they often induce severe disease in crops. Knowledge of the routes of transmission and resilience of tobamovirus virions is essential in understanding the epidemiology of this group of viruses. Here, an isolate of the tobamovirus yellow tailflower mild mottle virus (YTMMV) was used to examine root‐to‐root transmission in soil and in a hydroponic growth environment. Root‐to‐root transmission occurred rarely, and when it occurred plants did not exhibit systemic movement of the virus from the roots to the shoots over a 30‐day period. The resilience of YTMMV virions was tested in dried leaf tissue over time periods from one hour to one year under temperatures ranging from ?80 to 160 °C. Infectivity was maintained for at least a year when incubated at ?80 or 22 °C, or at fluctuating ambient temperatures of 0.8 to 44.4 °C, but incubation under dry conditions at 160 °C for >4 days eliminated infectivity. Exposure of virions to 0.1 m sodium hydroxide or 20% w/v skimmed milk solution for 30 min, treatments recommended for tobamovirus inactivation, did not abolish infectivity of YTMMV.     

Helper component mutations in nonconserved residues associated with aphid transmission efficiency of a pepper isolate of potato virus y

ABSTRACT The aphid transmission properties of a pepper isolate of potato virus Y belonging to the pathotype 1-2 (PVY 1-2) have been characterized. PVY 1-2 was not transmitted in plant-to-plant experiments, although purified virus particles were efficiently transmitted when supplemented with heterologous helper component (HC) of the transmissible isolate PVY 0 AT through membrane acquisition assays, indicating that its coat protein was functional in transmission. Additionally, virions of PVY 1-2 were able to bind to different HCs in in vitro binding assays. Analysis of the sequence of the PVY 1-2 HC gene and comparison with that of PVY 0 AT revealed 19 nucleotide differences, but only 2 resulted in amino acid changes, one of which induced a change of charge. Neither of these two amino acid changes occurred within the cysteine-rich domain, nor did they coincide with conserved motifs of the HC protein known to be involved in aphid transmission and which are present in all known potyvi-ruses. However, both changes are located in positions highly conserved among PVY strains. The possible role of both mutations on the activity of the PVY 1-2 HC in aphid transmission is discussed.     

京郊大蒜病毒病的研究及其鳞茎中病毒的脱除

 京郊大蒜病毒病发生普遍,主要症状为条纹花叶、矮化和叶片扭曲畸形。病体细胞中含大量线状病毒粒体和风轮状内含物。线状病毒粒体长度范围为250-1875nm,以长度550-800nm粒体居多。其中长700-800nm的粒体被鉴定为大蒜花叶病毒(GMV),回接脱毒大蒜叶片产生条纹花叶症状。血清学鉴定表明GMV与洋葱黄矮病毒(OYDV)有近缘关系。长度500-600nm的粒体可能为大蒜潜隐病毒(GLV),回接脱毒大蒜不产生花叶症状。下述两种病毒为京郊大蒜的主要病毒。此外,个别标样含烟草花叶病毒,但不是大蒜的主要病毒。对800nm以下线状病毒粒体归属尚待研究。
应用营养茎尖、生殖茎尖和根尖分生组织培养技术,可以脱去上述主要病毒,获得脱毒大蒜。