Characterisation of cucumber leaf spot virus isolated from recycled irrigation water of soil-less cucumber cultures

Greenhouse‐grown cucumber plants showed mosaic‐type symptoms and irregular yellow spots on their leaves. The disease did not affect plant growth and the fruits remained symptom free. A virus having isometric particles, 30 nm in size, was isolated from the infected tissues and from recycled drainage water collected from tuff (volcanic rock) raised beds on which plants were grown. The virus was identified as a variant of cucumber leaf spot virus (CLSV) that has a host range similar but not identical to that of a previously described CLSV isolate. The overall nucleotide sequence identity between the RNAs of the Israeli isolate and the type isolate virus (accession numbers: DQ227315 and AY571334, respectively) amounts to 96%.     

Some properties of an isolate of tobacco rattle virus from Northern Ireland

A virus obtained from soil in which potato plants had shown severe spraing symptoms induced symptoms on indicator plants typical of tobacco rattle virus (TRY). Purified virus preparations of a local-lesion isolate contained particles of two modal lengths, 192 nm and 94 nm containing RNA molecules of mol. wt 2.4 × 10⁶ and 1.23 × 10⁶. Virus coat protein had a mol. wt of c. 21 500. The virus was serologically distantly related to TRY (SYM) and pea early browning virus (PEBV) SP5, but did not react with TRY (CAM) or TRY (PRN) antisera. However, cDNA hybridisation indicated that the virus was more closely related to TRY (PRN) than either TRY (SYM) or PEBV (SP5). The virus isolate has been designated TRY (NI).     

The Natural Occurrence of Turnip Mosaic Potyvirus in Allium ampeloprasum

An isolate of turnip mosaic potyvirus (TuMV) was obtained from Allium ampeloprasum grown in commercial greenhouses in Israel. Symptoms on infected plants include systemic chlorosis and yellow stripes, accompanied by growth reduction. Leaves were distorted, often showing necrotic flecking. The virus was readily transmitted mechanically, and in a non-persistent manner by aphids, among Allium, Chenopodium. Gomphrena and some Nicotiana spp. Purified preparations contained numerous filamentous particles similar to those observed in crude extracts of infected leaves. Particles from crude plant extracts had a normal length of 806 nm. Cells of infected plants contained cylindrical cytoplasmic inclusions with pinwheel, scrolls and laminated aggregates which indicated the presence of a potyvirus of Edwardson's subgroup III. and which resemble those of turnip mosaic virus (TuMV), The virus reacted strongly with antiserum to typical isolates of TuMV in immunoelectron microscopy and western blotting but not with antisera to several other potyviruses. Based on serological reactivity, electron microscopy, aphid transmission and cytopathology, the virus was identified as an isolate of TuMV.     

Versuche zur Ausarbeitung einer Laborprüfmethode zwecks Feststellung der Knollenresistenz gegenüber Phytophthora infestans

Beim routinemäßigen Nachweis mechanisch übertragbarer Viren in Bäumen des Kern‐ und Steinobstes kann die Probeentnahme das Testergebnis u. U. nachhaltig beeinflussen. Die Kenntnis der Verteilung dieser Erreger in der Baumkrone ist deshalb von entscheidender Bedeutung. Folgende Viren wurden in die Untersuchungen einbezogen: Chlorotisches Apfelblattfleckungs‐Virus (apple chlorotic leaf spot virus, CLSV), Apfelstammfurchungs‐Virus (apple stem grooving virus, SGV) und Apfelmosaik‐Virus (apple mosic virus, ApMV) (Kernobst) bzw. Nekrotisches und Chlorotisches Kirschenringflecken‐Virus (Prunus necrotic ringspot virus, PNRV; prune dwarf virus, PDV), ApMV, CLSV, Scharka‐Virus der Pflaume (plum pox virus, PPV), Petunia asteroid mosaic virus (PAMV) und Kirschenblattroll‐Virus (cherry leaf roll virus, CLRV) (Steinobst). In der Regel kam der ELISA, nur in Einzelfällen der Latextest, zur Anwendung. Die genannten Viren lassen sich hinsichtlich der Verteilung in der holzigen Wirtspflanze 3 Gruppen zuordnen:

• Viren mit systemischer Verteilung: CLSV, SGV, PNRV, PDV, PPV in hochanfälligen Pflaumensorten und Pfirsich

• Viren mit teilsystemischer Verteilung: ApMV, PPV in weniger anfälligen Pflaumensorten

• Viren mit sporadischer Verteilung: PAMV, CLRV

     

Properties of Scottish isolates of cocksfoot mild mosaic virus and their comparison with others

Two isolates of cocksfoot mild mosaic virus obtained from cocksfoot (Dactylis glomerata) in Scotland differed in symptomatology, and apparently in host range, from isolates obtained in Germany and Wales. They were serologically more closely related to a Dutch isolate from cocksfoot, and to a Scottish isolate from timothy (Phleum pratense), than was the German isolate from cocksfoot. The Scottish isolate from timothy was somewhat more virulent than, but serologically closely related to a Welsh isolate from timothy. Particles of Scottish isolates from cocksfoot and timothy were best preserved for electron microscopy by fixation with osmium tetroxide. In 1.0 m KCl or 0.01 m ethylene diamine tetraacetate they were stable at pH 5.2–5.3 but unstable above pH 7; they were disrupted by 0.5% sodium dodecyl sulphate. The particles contained major and minor RNA components of mol. wt c. 1.5. 10⁶(RNA-1) and 0.5. 10⁶(RNA-2) respectively, together with polydisperse RNA of intermediate mol. wt and protein of mol. wt c. 27 000. In CsCl gradients, major and minor nucleoprotein components of density 1.39 and 1.38 g/ml respectively were distinguished. The less dense particles contained a larger proportion of intermediate-sized RNA molecules and of RNA- 2 , and a smaller proportion of RNA- 1 , than did the denser particles. Particles seem to contain either RNA-1 or various combinations of smaller RNA molecules. Despite the differences in antigenic constitution, symptomatology and particle stability between virus isolates obtained from cocksfoot and timothy in different countries, these isolates seem sufficiently similar to be considered one virus.     

Properties of a tomato isolate of Pelargonium zonate spot virus

A manually transmissible virus isolated from tomato plants with stunting, unfruitfulness, malformation and yellow rings and line patterns of the leaves was indistinguishable from Pelargonium zonate spot virus (PZSV) in biological, physico-chemical and serological properties. The tomato isolate (PZSV-T) of PZSV was seed transmitted in Nicotiana glutinosa and was detected in the pollen of this host. In sap of N. glutinosa PZSV-T lost infectivity after diluting 10^-1 to 10^-2, heating for 10 min at 35 to 40 °C or storage at 25 °C for 7 h. Virus particles were quasi-spherical with a diameter ranging between 25 and 35 nm with a modal value of 29 nm. Particles sedimented as three components (TV, MV and BV) with sedimentation coefficients of 80S (TV), 90S (MV) and 118S (BV); component BV is probably an aggregate of TV. Particles were unstable in CsCl and CS₂SO₄ but formaldehyde-stabilised particles banded at a common density of 1–268 g/cm³ in Cs₂SO₄. Particles contained a single protein species with mol. wt of c. 23000 and c. 18% single stranded RNA present as two species with mol. wts of c. 1.25 × 10⁶ (RNA-1) and 0.95 × 10⁶ (RNA-2). Mixtures of RNA-1 + RNA-2 were infectious and this infectivity was not enhanced by the addition of coat protein. Virus particles had a Tf (mid point of extinction when heated) of 63 °C and were readily dissociated by 0.1% SDS. PZSV-T was serologically unrelated to alfalfa mosaic and to 32 isometric viruses including five ilarviruses. Some properties of PZSV resemble those of ilarviruses but others are sufficiently different to suggest that it may not be a member of this virus group.     

Properties of spinach yellow mottle, a distinctive strain of tobacco rattle virus

A virus (isolate SYM) obtained from spinach plants in England with a severe yellow mottle disease induced symptoms resembling those of tobacco rattle virus (TRV) in several indicator species but caused systemic necrosis in Chenopodium amaranticolor and C. quinoa. It was transmitted to bait plants grown in soil containing the nematode Trichodorus primitivus. Purified virus preparations contained rod-shaped particles that were predominantly of four modal lengths: 188 nm (L particles), 101 nm (S particles), 57 nm and 48 nm (together called VS particles), containing RNA with mol. wts of 2.4, 1.5, 0.7 and 0.6 million, respectively. L particles (s°₂₀= 300 S) and S particles (230 S) greatly outnumbered VS particles (c. 150 S). All particles contained a single polypeptide species with estimated mol wt of 24 700, slightly larger than those previously reported for tobraviruses. Purified L particles were infective but both L and S particles were needed to induce the production of virus nucleoprotein particles. VS particles were not infective and apparently had no qualitative or quantitative effect on infection by L or by L plus S particles. S particles carried determinants for serological specificity and ability to invade C. amaranticolor systemically. Isolate SYM produced pseudo-recombinants with isolate PRN of TRV. Also, isolates CAM, OR and PRN of TRV, and isolate SYM, were found to be distantly related by three kinds of serological test. No relationship was detected between these isolates and pea early-browning virus in gel-diffusion precipitin tests or electron microscope serological tests, but a distant relationship between isolate SYM and pea early-browning virus was found by micro-precipitin tests. Isolate SYM therefore has closer affinities with TRV than with pea early-browning virus and is considered to be a distinctive strain of TRV.     

The Characterization of a Strain of Zucchini Yellow Fleck Virus Found in Southeastern France

A virus was isolated from squirting cucumber (Ecballium elaterium L.) collected in France (Alpes de Haute Provence). After mechanical inoculation, eight species belonging to the Cucurbitaceae were found susceptible to this virus with systemic symptoms of mosaic, chlorotic spots, and fruit deformations. The French ZYFV (ZYFV-Fr) isolate differed from the type strain in its ability to infect some differential host plants. Elongated flexuous particles with a modal length of 752 nm were observed by electron microscopy in leaf extracts. Cytoplasmic inclusions similar to those associated with infections by members of the potyvirus group were observed by light microscopy. The virus was found by SDS-immunodiffusion and DAS-ELISA to be serologically related but distinct from the type strain of zucchini yellow fleck virus from Italy (ZYFV-lt). ZYFV has not yet been found in cultivated cucurbit plants in France; this virus appears to be restricted to squirting cucumbers in a few localities. The distribution of ZYFV in France is discussed.     

The detection of apple chlorotic leafspot virus by a modified procedure of enzyme-linked immunosorbent assay (ELISA)

The technique of enzyme-linked immunosorbent assay (ELISA) was modified to enable detection of apple chlorotic leafspot virus (CLSV) both in herbaceous hosts and in several naturally infected fruiting and ornamental woody host species. Some of the characteristics of the modified method as used with different virus-host combinations are described.     

Association of different kinds of bacilliform particle with vein chlorosis and mosaic diseases of raspberry (Rubus idaeus)

Thin sections of diseased raspberry (Rubus idaeus) were examined by electron microscopy. Plants of the cv. Baumforth's B and of an aphid (Amphorophora rubi)-resistant breeding selection (6820/54), both infected with raspberry vein chlorosis virus (RVCV) but not with other detectable viruses, contained large bacilliform particles c. 430 × 65 nm. Particles occurred in the cytoplasm and perinuclear space of a small proportion of xylem parenchyma cells. They had an inner core c. 25–30 nm in diameter with cross-banding of periodicity 4·5 nm, and were bounded by an outer membrane. They are probably the particles of RVCV. Plants of cv. Mailing Jewel and of a selection (M14) both showing symptoms of raspberry mosaic (veinbanding) disease contained smaller bacilliform particles c. 125 × 30 nm, which occurred singly or in clusters in the cytoplasm of a small proportion of vascular parenchyma cells. It is not known which, if any, of the viruses associated with raspberry mosaic are represented by the particles.     

A yellow mosaic disease of horse chestnut (Aesculus spp.) caused by apple mosaic virus

A severe foliar yellow mosaic disease was observed in horse chestnut trees (Aesculus carnea and A. hippocastanum). Reactions in woody indicator plants grafted with diseased horse chestnut suggested the presence of an ilarvirus. Virus isolates obtained by mechanical inoculation of herbaceous test plants reacted with antisera to apple mosaic virus but not with antisera to its serotype prunus necrotic ringspot virus, or to prune dwarf virus. Yellow mosaic was induced in horse chestnut seedlings grafted with tissues from herbaceous hosts infected with horse chestnut isolates or with the European plum line pattern isolate of apple mosaic virus. Virus was detected by enzyme-linked immunosorbent assay (ELISA) in embryo and endosperm of immature seed from infected trees but not in mature seed, or progeny seedlings. Strawberry latent ringspot virus was detected in one of six A. hippocastanum trees with a leaf vein yellows disease.     

Identification and characterisation of a newly described potyvirus in West Africa: Asystasia mottle virus

Asystasia mottle virus (AsMV) was detected serologically in samples of Asystasia gangetica with mottle symptoms, from several areas of tropical West Africa. It infected 12 species systemically and induced local lesions in a further four. The virus lost infectivity after dilution to 10^-4, after 10 min at 75 °C and after 3 days at 27°C. Purified virus had an A₂₆₀/A₂₈₀ ratio of c. 1·2 and a protein subunit mol. wt of c. 33 000. Particles were c. 750 nm long and cytoplasmic inclusions typical of potyviruses were seen in ultrathin sections of infected leaves. The antiserum prepared had a titre of 1/1024 in microprecipitin tests but purified virus failed to react with 31 antisera to known potyviruses. The virus was transmitted in the non-persistent manner by Aphis spiraecola but only very infrequently. On the basis of these properties, AsMV is considered to be a new member of the potyvirus group.     

The occurrence, hosts and properties of lilac chlorotic leafspot virus, a newly recognised virus from Syringa vulgaris

Lilac chlorotic leafspot virus (LCLV), a hitherto undescribed virus, was isolated from three of 65 lilacs (Syringa vulgaris) with chlorotic leafspotting symptoms growing in S.E. England. The virus was transmitted readily by sap-inoculation to 21 of 52 species from eight of 20 families, but it was not seed-borne in four hosts or transmitted in the semi-persistent manner by any of four aphid species. The virus was moderately stable in vitro; sap from Chenopodium quinoa was infective after 10 min at 60 but not 65 ^oC, after 8–16 days at 20 ^oC or 25–30 wk at 2 ^oC, and after dilution to 10^-3 but not 10^-4. Up to 180 mg of purified virus per kg leaf tissue were obtained from C. quinoa by clarification of buffered leaf extracts with 8% (v/v) n-butanol, followed by one cycle of differential centrifugation and molecular permeation chromatography on controlled pore glass beads (700 Å, 120–200 mesh). LCLV has fragile flexuous filamentous particles which, when intact, mostly measured c. 12-5 times 1500–1600 nm; the helical substructure (pitch c. 3–7 nm) was clearly visible on some particles mounted in uranyl acetate. The particles sedimented as a single component (sedimentation coefficient 96 S; buoyant density 1–302 g cm^-3) and contained c. 5% nucleic acid and a single polypeptide of mol. wt 27 times 10³. Although these properties place LCLV in the closterovirus group, the virus showed no serological relationship to any of six closteroviruses (beet yellows, beet yellow stunt, carnation necrotic fleck, apple chlorotic leafspot, apple stem grooving and potato virus T) and differed from other recognised or possible members of this group in host range and/or symptoms induced in indicator species. The infrequent occurrence of LCLV in lilac in S.E. England indicates that the virus could probably be eradicated by selecting only virus-free plant material for propagation.     

Hedgerow hawthorn (Crataegus spp.) and blackthorn (Prunus spinosa) as hosts of fruit tree viruses in Britain

Apple chlorotic leafspot virus (CLSV) was detected in 27 of 109 hawthorn and three of 67 blackthorn plants sampled in various parts of Britain. The CLSV isolates possessed similar properties to those isolated from other rosaceous species but differed in the severity of symptoms they induced in woody indicators. No seed or aphid transmission of CLSV was detected. Prunus necrotic ringspot (PNRV) and prune dwarf (PDV) viruses were detected in four and three respectively of 67 blackthorn plants. The PNRV and PDV isolates were serologically closely related to isolates from cherry. Arabis mosaic virus was detected in one blackthorn plant, but plum pox virus was not found in any of the tested plants.     

Narcissus latent, a virus with filamentous particles and a novel combination of properties

As previously reported, narcissus latent virus (NLV) has flexuous filamentous particles measuring c. 650 nm × 13 nm, is manually transmissible to Nicotiana clevelandii and Tetragonia expansa, and is transmitted by the aphid Myzus persicae following brief acquisition access periods. In contrast to previous reports the virus particle protein has an apparent mol. wt of c. 45 kD. Moreover, infected cells in N. clevelandii leaves contain cytoplasmic inclusion bodies resembling those of potyviruses. In vitro translation of NLV RNA produced only one major product (mol. wt c. 25 kD) which was not precipitated by antisera to virus particle protein or to cytoplasmic inclusion protein. Antisera to 12 potyviruses and nine carlaviruses failed to react with sap containing NLV particles. Similarly antiserum to NLV particles did not react with particles of seven potyviruses or four carlaviruses. A weak reaction was detected between NLV particles and antiserum to particles of maclura mosaic virus (MMV), a virus which resembles NLV in particle morphology and particle-protein size, and in inducing pinwheel inclusions. The cytoplasmic inclusion proteins (CIPs) of NLV, MMV and from narcissus plants with yellow stripe symptoms were serologically inter-related. These proteins were also serologically related to, and had mol. wt similar to, the CIP of members of the potyvirus group. Particles with the size and antigenic specificity of those of NLV were found consistently in narcissus plants with yellow stripe disease. Narcissus latent and narcissus yellow stripe viruses therefore seem to be synonymous and, together with MMV, have properties distinct from those of any previously described virus group.     

The occurrence of Indian peanut clump,a soil-borne virus disease of groundnuts (Arachis hypogaea) in India*

A disease characterised by severely stunted plants with small dark green leaves was found in groundnut (Arachis hypogaea) in sandy soils in Punjab State, India. The disease occurred in patches in the field and reappeared in the same positions in succeeding groundnut crops. Plants infected early did not produce mature pods. Seeds sown in soil collected from infected fields produced plants with typical disease symptoms. Phaseolus vulgaris cv. Local and Chenopodium quinoa were found to be good diagnostic hosts. The disease was shown to be caused by a rod-shaped virus c. 24 nm in diameter with predominant particle lengths of c. 249 and 184 nm when stained in uranyl acetate. The virus, named Indian peanut clump virus (IPCV), resembled peanut clump virus (PCV) reported from W. Africa in symptomatology on groundnuts, particle morphology and soil-borne nature. However, it is not serologically related to two W. African PCV isolates tested, or to tobacco rattle (PRN and CAM strains) or pea early browning virus (Dutch isolate) in microprecipitin, enzyme linked immunosorbent assay and immunosorbent electron microscopy tests.     

The P2 Protein of Rice Dwarf Phytoreovirus Is Required for Adsorption of the Virus to Cells of the Insect Vector

Intact particles of rice dwarf phytoreovirus adsorbed to and entered monolayer-cultured cells of the insect vector Nephotettix cincticeps and multiplied within the cells. Particles that lacked the P2 protein neither attached to nor infected such cells. Furthermore, P2-free particles obtained from a transmission-competent isolate of the virus were unable to infect insect vectors that had been allowed to feed on these virus particles through a membrane. However, when such virus particles were injected into insects via a glass capillary tube they successfully infected the insects, which became able to transmit the virus. These results support the hypothesis that, while P2-free particles can neither interact with nor infect cells in the intestinal tract of the insect vector, they do retain the ability to infect such cells when physically introduced into the hemolymph by injection.     

Some virus and virus-like diseases of tobacco,tomato, papaya,and rubber tree in vietnam and cambodia

In Vietnam a green strain of tobacco mosaic virus was isolated having TIP 89°C (10 min) and causing systemic necrosis in tobacoo ‘Xanthi-nc’ and sometimes also inDatura stramonium. In symptomless tomato plants an elongated virus belonging apparently to the Carlavirus group (NL 630 nm) was found. In papaya trees showing severe symptoms of mosaic and/or ringspot elongated virus particles (NL 730 nm) were observed; this virus being apparently a member of the Potyvirus group, resembled as far as its symptoms in papaya are concerned, the papaya ringspot or the distortion ringspot. In Cambodia some young rubber trees showed malformed leaves (esp. edges and veins) with yellow discolorations along the veins. Such leaves contained elongated virus-like particles (rigid or slightly flexible) of various length (60 to 880 nm), so that their normal length (NL) could not be established precisely. Particles 120 to 150 nm long occurred very frequently.     

Characterisation of a variant of zucchini yellow fleck virus (ZYFV), a potyvirus causing a wilt disease of melons in Israel*

A flexuous filamentous virus 750 nm in length was isolated from field-grown melons (Cucumis melo L.) and squirting cucumber (Ecballium elaterium L.). Infection of melon seedlings of most commercial varieties resulted in a lethal wilting, but late infections gave dieback. The virus infected systemically all economically important cucurbit crops. Its coat protein consists of a single polypeptide, 34 500 D in size, encapsidating a single stranded RNA genome of 10.1 kb. Antiserum against the Italian zucchini yellow fleck virus (ZYFV) reacted specifically with the Israeli isolate in both ISEM and Western blot. The virus was aphid transmissible in a non-persistent manner. Based on host range, host reaction and serological data, it is suggested that the virus described is an Israeli variant of ZYFV.