Some hosts and properties of bulbous iris mosaic virus

Iris mosaic virus (IMV) was the only virus isolated from forty-six bulbous iris plants of twenty-two cultivars tested; it was common also in Iris danfordiae and I. reticulata but was not detected in any of fifty-two rhizomatous iris plants with mosaic symptoms. IMV was transmitted to healthy irises with difficulty by mechanical inoculation but was transmitted efficiently by Myzus persicae. IMV infected eight of forty-six plant species inoculated mechanically with partially purified virus preparations. Characteristic local lesions without subsequent systemic infection were produced in Amaranthus caudatus, six Chenopodium spp., and Tetragonia expansa; of these, C. quinoa and T. expansa were the best indicator and assay hosts. The virus was moderately stable in vitro and, unlike some similar filamentous viruses, was best purified by differentially centrifuging infective sap clarified with n-butanol. Partially purified preparations from several hosts were infective, produced one specific light-scattering zone after centrifuga-tion in sucrose density-gradient columns, were antigenic and contained particles of 760 mμ model length. IMV was not serologically related to any of nine similar aphid-transmitted, filamentous viruses.     

Complete genome sequence of garlic latent virus,a member of the carlavirus family

The complete genome sequence of the garlic latent virus (GLV) has been determined. The whole GLV genome consists of 8,353 nucleotides, excluding the 3'-end poly(A)+ tail, and contains six open-reading frames (ORFs). Putative proteins that were encoded by the reading frames contain the motifs that were conserved in carlavirus-specific RNA replicases, NTP-dependent DNA helicases, two viral membrane-bound proteins, a viral coat protein, and a zinc-finger. Overall, the GLV genome shows structural features that are common in carlaviruses. An in vitro translation analysis revealed that the zinc-finger protein is not produced as a transframe protein with the coat protein by ribosomal frameshifting. A Northern blot analysis showed that GLV-specific probes hybridized to garlic leaf RNA fragments of about 2.6 and 1.5 kb long, in addition to the 8.5 kb whole genome. The two subgenomic RNAs might be encapsidated into smaller viral particles. In garlic plants, 700 nm long flexuous rod-shaped virus particles were observed in the immunoelectron microscopy using polyclonal antibodies against the GLV coat proteins.     

Some hosts and properties of dahlia mosaic virus

Dahlia mosaic virus (DMV) infected twenty-five of the eighty-five plant species from four of eighteen families inoculated, but only dahlias were found naturally infected. DMV infected fourteen members of the Solanaceae, Amaranthaceae and Chenopodiaceae, and eleven of twenty-nine Compositae. Verbesina encelioides was the best plant for diagnosis, assay and source of virus. Systemically infected hosts contained ovoid intracellular inclusions 2–5–10 μm in diameter which were shown by electron microscopy to consist of a finely granular, vacuolated matrix containing numerous virus particles. V. encelioides sap was sometimes infective after dilution to 1/2000 but not 1/3000, after heating for 10 min to 75 °C but not 80 °C, and after 4 days at 18 °C or 32 days at 2 °C. Sap from infected dahlia, Zinnia elegans or Ageratum houstonianum rapidly became non-infective, but extracts made with 0·05 M sodium thioglycollate or 0·03 M sodium diethyldithiocarbamate remained infective for 24–48 h at 18 °C. Some purified preparations remained infective for up to 3 years at 2 °C. DMV was best purified from V. encelioides by one or more cycles of differential centrifugation, followed by density-gradient centrifugation and further concentration. Composition, molarity, and pH of the extracting buffer had little effect on yield of virus. Best yields were obtained from extracts stored with 8-5% (v/v) n-butanol at 2 °C for 10–14 days. Purified preparations were infective at dilutions up to 1/5000, had ultraviolet absorption spectra typical of a nucleoprotein (Å 260/280 = 1·47), probably contained DNA, and had a single sedimenting component having isometric particles c. 50 nm in diameter with a sedimentation coefficient of 254 S. The cryptogram of DMV is (D)/*:*/(16):S/S:S/Ap. DMV is serologically closely related to cauliflower mosaic virus, but the viruses are distinct pathogens. The two viruses have similar properties, size, shape and other characteristics, and together with at least three others form a small but apparently homogeneous group of aphid-borne viruses.     

Olive latent ringspot virus, a newly recognised virus infecting olive in Italy

A manually transmissible virus, for which the name olive latent ringspot virus (OLRV) is proposed, was isolated from a symptomless olive tree. The virus was mechanically transmitted to test plants. Purified preparations of OLRV contained three classes of isometric particle, c. 28 nm in diameter, with sedimentation coefficients of 525 (T), 975 (M) and 1325 (B) and containing 0, 30 and 43% nucleic acid respectively. At equilibrium in CsCl gradients, the buoyant densities of T and M components were 1–29 and 1–43 g/cm³ respectively, whereas B component separated into two sub-components with buoyant densities of 1–51 g/cm³ (BJ and 1–52 g/cm³ (B₂). Particle preparations contained two species of single-stranded RNA with mol. wt 1–40 times 10⁶ and 2–65 times 10⁶, both necessary for infectivity. The coat protein of OLRV, dissociated under strong denaturing conditions, separated into four components in polyacrylamide gel electrophoresis. Over 75% of the protein was found in a band with mol. wt 57 600, but all four components were recognised as oligomers of a monomeric form with mol. wt 14 300. OLRV was serologically unrelated to 26 different isometric plant viruses including 17 recognised nepoviruses. Its properties strongly indicate that it is a hitherto undescribed member of the nepovirus group.     

Some properties of grapevine Bulgarian latent virus

Grapevine Bulgarian latent virus (GBLV), obtained from symptomless vines grown in Bulgaria, was readily transmitted by inoculation of sap to a restricted range of hosts. The virus was re-inoculated into virus-free rooted cuttings and seedlings of several grapevine cultivars without inducing symptoms. Purified preparations of GBLV contained isometric particles c. 30 nm in diameter which sedimented as three components at 52 , c. 120 and 1275, respectively. The slow-sedimenting component (T) contained non-infective protein shells, whereas the two heavier classes of particles (J5_X, B₂) each contained one molecule of single-stranded ribonucleic acid (RNA) with mol. wts of 2.1 and 2.2 times 10⁶ daltons. The RNA content of B₁ and B₂ components were 39 and 41 % by particle weight respectively. The capsid was composed of one type of protein with a mol. wt of 54000. GBLV did not react with antisera to any of twenty-eight viruses with isometric particles. Its present cryptogram is R/1: 2-2/41 +2-1/39:S/S:S/*.     

Occurrence, purification and properties of narcissus tip necrosis virus

Narcissus tip necrosis virus (NTNV), a previously undescribed virus, was detected in the Netherlands and the United Kingdom in plants of twenty-one cultivars of trumpet, large-cupped, small-cupped, double, tazetta and poeticus narcissus. In some cultivars distinct leaf symptoms were sometimes associated with infection but in others infected plants remained symptomless and detection was dependent on serological tests. The virus was readily transmitted by manual inoculation to narcissus, but it failed to infect any of forty-six other plant species from fourteen families. Up to 50 mg of virus/kg of tissue were obtained by differential centrifugation of narcissus leaf extracts previously clarified with either diethyl ether, n-butanol or a mixture of n-butanol and chloroform. The virus particles are isometric, c. 30 nm in diameter, have a sedimentation coefficient (^s°₂₀ w) Of 123 S a buoyant density of 1·356 g/cm³, migrate as a single component in polyacrylamide gel electrophoresis, and contain a single RNA species of mol. wt 1·6×10⁶ and two major polypeptides of mol. wt 42000 and 39000. Although NTNV resembles tombusviruses it showed no serological relationship to the type member or six putative members of this group or to thirty-four other viruses with isometric particles. Its present cryptogram is R/*:1.6/(18):S/S:S/*.     

Some hosts, properties and possible affinities of a labile virus from Hypochoeris radicata (Compositae)

Hypochoeris mosaic virus (HMV) is common in Hypochoeris radicata (‘cat's ear’) in western Canada. It infected 10 of 53 mechanically inoculated species in five of twelve families, but was not transmitted by aphids or through seed or soil. Sap from infected Nicotiana clevelandii was sometimes infective after dilution to 10^-1 and occasionally 10², after 10 min at 45 but not 50°C, and after 1 but not 2 days at 20°C. Infectivity of crude nucleic acid extracts from infected leaves was rapidly abolished by RNase but not by DNase. Host sap contained very few rod-shaped particles or particle fragments mostly 21.0–22.5 nm in diameter, and up to 420 nm long but with predominant lengths of 120–140 and 240–260 nm. Many rods in purified virus preparations were less than 240 nm long, and the majority were c. 140 nm or shorter. The particles had a helical substructure with a pitch of 2.58 nm and contained a single type of protein of estimated mol. wt 24.5 × 10³. HMV showed no serological relationship to eight morphologically similar viruses (beet necrotic yellow vein, broad bean necrosis, barley stripe mosaic, peanut clump, potato mop-top, Nicotiana velutina mosaic, wheat soil-borne mosaic and defective strains of tobacco mosaic). It is probably a hitherto undescribed tobamovirus.     

Purification and properties of lucerne Australian symptomless virus, a new virus infecting lucerne in Australia

A virus with isometric particles c. 26–28 nm in diameter isolated from naturally infected lucerne (Medicago sativa) in Australia and reported there to be a strain of lucerne Australian latent virus (LALV), is shown to be a distinct virus. The virus, called lucerne Australian symptomless (LASV), was mechanically transmitted to 10 of 22 plant species inoculated, but only induced symptoms in three Chenopodium species and Gomphrena globosa. Virus particles occurred in relatively low concentrations in plant sap, and the virus could not be reliably maintained in culture by serial transmission to plants during winter (October-April). During the summer, sap of infected C. quinoa remained infective after diluting 10^-2 but not 10^-3, after heating for 10 min at 50 but not 55 ^oC and after storage for 24 days (the longest period tested) at 20, 4 and -15 ^oC. LASV was seed-borne to 6% of C. quinoa seedlings. Partially purified preparations of virus particles contained one nucleoprotein component with a sedimentation coefficient of c. BOS. Particles contained two polypeptide species of estimated mol. wts 26 000 and 40 000, and two ssRNA species which, when denatured in glyoxal, had apparent mol. wts of 2–5 times 10⁶ and 1–4 times 10⁶. The infectivity of virus RNA was abolished by incubation with proteinase K. Purified particles of LASV reacted with homologous antiserum (gel diffusion titre 1:256) but not with antiserum to LALV or to 13 other plant viruses with isometric particles including arracacha B (AVB), broad bean wilt, rubus Chinese seed-borne (RCSV) and strawberry latent ringspot (SLRV) viruses, and five comoviruses. These properties distinguish LASV from LALV and from all recognised nepoviruses and comoviruses. Its closest affinities are with SLRV, RCSV and possibly AVB; these viruses may comprise a distinct virus group or nepovirus subgroup.     

Properties of a carlavirus causing a latent infection of pepino (Solanum muricatum)

Pepino (Solanum muricatum) cuttings imported from Chile contained a latent virus which was transmitted by inoculation of sap to Chenopodium quinoa but not to 21 other species. The virus was transmitted by the aphid, Myzus persicae. In C. quinoa sap, the virus lost infectivity when diluted between 10^-3 and 10^-4, heated for 10 min between 65 and 70 °C, or stored at room temperature for 4 to 6 days. The virus particles were straight or slightly flexuous filaments 660 to 680 nm long. Up to 15 mg virus per 100 g C. quinoa leaves was obtained by clarification with a mixture of chloroform and carbon tetrachloride. Purified preparations had A_max/A_min= 1.11, A₂₆₀/A₂₈₀= 1–30, A^0.₂₆₀^1%= 2.8, and contained a single sedimenting component with a sedimentation coeficient of 149s and a buoyant density in CsCl of 1–318. The virus particles contained 5.5% of single-stranded RNA of mol. wt 2.4×10⁶ (estimated by gel electrophoresis of undenatured RNA) and sedimentation coefficient 38.5S, and a single polypeptide of mol. wt 33 000. The virus is distantly serologically related to potato S and carnation latent viruses and is considered a new member of the carlavirus group. The name pepino latent virus is proposed. The cryptogram for this virus is R/1: 2.4/5–5: E/E: S/Ve/Ap.     

Crimson clover latent virus - a newly recognised seed-borne virus infecting crimson clover (Trigolium incarnatum)

Crimson clover latent virus (CCLV) was detected in five seed lots of crimson clover (Trifolium incarnatum) from Europe and in one from the United States of America. Ninety-seven per cent of all crimson clover plants examined were found to be infected but were without symptoms. Keeping crimson clover plants at 32–38°C for 34 days failed to free them from CCLV. The virus was not transmitted by Myzus persicae, but was transmitted by inoculation of sap to Chenopodium album, C. amaranticolor and C. quinoa. Twenty-four other plant species from seven families were not infected. CCLV was best propagated in C. quinoa in which it caused stunting and systemic chlorosis. Sap from infected C. quinoa was infective after dilution to 10^-2 but not 10^-3, after 10 min at 60°C but not 65°C, and after 20 days at 20°C. In neutral phosphotungstate, CCLV had isometric particles c. 26 nm in diameter with a hexagonal profile. About 20 to 80 A_1cm,260 units of purified virus were obtained from 1 kg of infected C. quinoa or C. amaranticolor leaves by extraction in 0.5 M phosphate buffer, pH 7.5, containing 0.01 M ethylene diamine tetra-acetate and 0.4% 2–mercaptoethanol and clarification with chloroform-butanol followed by two precipitations with polyethylene glycol (mol. wt 6000) and several cycles of differential centrifugation. Purified virus sedimented as three components with sedimentation coefficients (s°_{20, w}) of 52S, 101S and 122S. The 101S and 122S components had buoyant densities in CsCl of 1.438 and 1.495 g/cm³ respectively. From these values the nucleic acid content of the 101S and 122S components was estimated to be 32–35% and 40–41% respectively. The virus contained a single protein with an estimated mol. wt of 52 000 and two single-stranded RNA species of estimated mol. wt 1.6 × 10⁶ and 2.2 × 10⁶. CCLV was serologically unrelated to 31 other morphologically similar viruses. Although its vector is unknown, CCLV seems to have affinities with nepoviruses. The cryptogram of CCLV is R/1:2.2/40–41 + 1.6132–35:S/S:S/*.     

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.     

Distribution, host range, properties and purification of cassava latent virus, a geminivirus

Cassava latent virus (CLV) is almost entirely confined in East Africa to upland cassava-growing areas west of the Rift Valley, where it is often associated with cassava mosaic disease (it was isolated from 27 of 38 cassava plants with mosaic, but not from 24 without mosaic). However, it is not the causal agent, because it was not recovered from any of 31 mosaic-diseased plants in coastal districts. All attempts to return CLV to cassava failed. The host range of CLV appears to be limited to Euphorbiaceae (Manihot) and Solanaceae (Nicotiana, Datura, Nicandra, Solanum). N. clevelandii proved the most useful assay and propagation host. The dilution end-point of CLV was about 10^-3, thermal inactivation point about 55°C, and longevity in vitro about 3 days. CLV was purified by clarification of leaf extracts with butanol/chloroform mixtures. Purified preparations (A 260/A 280 ratio c. 16) contained numerous 30 20 nm paired particles with a sedimentation coefficient (s₂₀w) of 76 S. Treatment with RNase and DNase showed that the viral nucleic acid is DNA; CLV closely resembles maize streak virus but is not related to it serologically. The cryptogram for CLV is D/1: 0.8/*: S/S: S/*, geminivirus group.     

Purification and properties of Australian lucerne latent virus, a seed-borne virus having affinities with nepoviruses

An isolate of Australian lucerne latent virus (ALLV) from lucerne in New Zealand was mechanically transmitted to a few herbaceous hosts. It induced diagnostic symptoms in several species of the Chenopodiaceae, but was symptomless in most other hosts including lucerne and Trifolium subterraneum. It was seed transmitted in lucerne. When assayed to Chenopodium quinoa, infective C. quinoa sap lost infectivity after diluting to 10^-4, heating for 10 min at 55°C and storage for 4 days at 4°C. ALLV was purified from infected C. quinoa or pea plants by extracting sap in 0.1 m borate buffer (pH 7) containing 0.2% 2-mercaptoethanol and clarifying with 15% bentonite suspension, high and low speed centrifugation and sucrose density gradient centrifugation. Purified virus preparations contained isometric particles about 25 nm in diameter and sedimented as three virus components with sedimentation coefficients (s_20-w⁰) of 56 S, 128 S and 133 S. The 56 S component appeared to consist of nucleic acid-free protein shells. Polyacrylamide gel electrophoresis of virus preparations showed that ALLV contained a single protein species of mol. wt 55 000 and two RNA species of mol. wt 2.1 × 10⁶ and 2.4 × 10⁶. An antiserum to ALLV had an homologous titre of 1/256 to purified virus but failed to detect ALLV in infective sap of C. quinoa, pea or lucerne. Purified ALLV failed to react to antisera to 28 distinct isometric plant viruses including those to 10 nepoviruses.     

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.     

Host range, purification and serological properties of heracleum latent virus

Heracleum latent virus (HLV occurs commonly in wild plants of Heracleum sphondylium (hogweed) in Scotland without causing symptoms. It was transmitted manually or by aphids (Cavariella aegopodii, C. pastinacae or C. theobaldi) to 37 of 105 species in 11 of 18 families (especially to members of the Amaranthaceae, Chenopodiaceae, Solanaceae and Umbelliferae), but was not transmitted through seed of four species tested. It has very flexuous filamentous particles c. 730 × 12 nm in phosphotungstate, with obvious cross-banding of pitch 3–8 nm. Leaf extracts lost infectivity after 1–2 days at 22°C, 10 min at 40–50°C and after dilution 10^-4-10^-5. Infectivity in leaf extracts was not stabilised by addition of Mg²⁺, Ca²⁺ or Ni²⁺, but was abolished by EDTA. HLV was purified by bentonite clarification, precipitation with polyethylene glycol (mol. wt 6000), and differential centrifugation. Its properties resemble those of the tentative closterovirus, apple chlorotic leaf spot (ACLSV), but no serological relationship was detected to this or to any of 18 other filamentous viruses, including six definitive closteroviruses. No cross-protection was observed between HLV, ACLSV and apple stem grooving virus.     

Some properties of peanut clump, a newly discovered virus

A mechanically transmissible soil-borne virus causing peanut clump disease in Upper Volta is described. It infected mainly species of Chenopodia-ceae and was propagated in Chenopodium amaranticolor. Infectivity was lost from sap of C. amaranticolor after 10 min at 64 °C, and after dilution to 10^-5 but not io^-4. A purification procedure is described. The particles are rod-shaped and of two predominant lengths, 190 and 245 nm. The virus is not serologically related to tobacco rattle, pea early-browning, or soil-borne wheat mosaic viruses, or to a virus associated with a rhizomania-like disease of beet.     

Partial purification and some properties of wineberry latent, a virus obtained from Rubus phoenicolasius

Wineberry latent virus (WLV) was obtained from a single symptomless plant of American wineberry (Rubus phoenicolasius) originally imported from the United States of America. On graft inoculation, WLV infected but induced no distinctive symptoms in several Rubus species including those used as indicators for known Rubus viruses. It was not seed-borne in wineberry. WLV was mechanically transmitted to several herbaceous species but induced local lesions in only a few; it was weakly systemic in some Chenopodium species. Infective C. quinoa sap lost infectivity after diluting to 10^-4, heating for 10 min at 70°C, and storage either for 8 days at 18°C or for 32 days at 4°C. Sap from infected plants contained flexuous filamentous particles c. 510°12 nm. WLV was partially purified by extracting infected C. quinoa leaves in 0·05 M tris-HCl buffer (pH ₇) containing 0·2% thio-glycerol and 10% (v/v) chloroform and concentrating virus by precipitation with 7% (w/v) polyethylene glycol (PEG, mol. wt 6000) and 0·1 NaCl. The virus was then pelleted through a 30% (w/v) sucrose pad containing 7% PEG+0·1 M NaCl and finally sedimented through a sucrose density-gradient. These preparations had A_260/280 ratios of 1·26, contained end to end aggregates of WLV particles and formed a partly polydispersed peak in the analytical ultracentrifuge. WLV did not react with antisera to four potex-viruses, or to apple chlorotic leaf spot or apple stem grooving viruses.     

Some properties of latent collagenase from human synovial fluid

Latent collagenase has been isolated in pure form from the rheumatoid synovial fluid. The final preparation, activated by trypsin, yielded a collagenase of specific activity 2,227 units/mg. Electrophoresis in sodium dodecyl sulfate polyacrylamide gels revealed a protein doublet of 54 and 50 kDa. Trypsin or HgCl2 activation resulted in disappearance of the doublet and emergence of a new doublet of 47 and 43 kDa. The latent collagenase could also be activated by leucocyte cathepsin G or plasmin. Neither the latent nor the active collagenase from synovial fluid showed any cross-reactivity with the antibodies against leucocyte collagenase. The trypsin activated collagenase degraded collagen type I, II, III giving typical cleavage products but did not degrade type IV and V collagen.     

Detection of multiple strains of latent herpes simplex virus type 1 within individual human hosts

One hundred and fifteen isolates of herpes simplex virus were recovered from parallel explant cultures of trigeminal and vagus ganglia and trigeminal nerve roots derived from 20 unselected human cadavers. Restriction enzyme patterns of strains recovered from 18 of 20 individuals could be differentiated from individual to individual, although all isolates from a single host were identical. Isolates from two individuals differed among themselves in the number and location of certain restriction enzyme sites.     

Further properties of black raspberry latent virus, and evidence for its relationship to tobacco streak virus

Purified preparations of an isolate of black raspberry latent virus (BRLV) contained quasispherical particles with a mean diameter of 28·5 nm; these particles were resolved into three sedimenting components (s_{20, w}= 82S, 95S and 104S), but when centrifuged to equilibrium in caesium chloride solution they formed a single infective band (σ= 1·35 g/cm³). During electrophoresis in polyacrylamide gels, virus particles separated into three classes, and virus RNA was resolved into three major (mol. wt 1·35, 1·10 and 0·85 × 10⁶) and one minor (mol. wt 0·4 × 10⁶) component. The protein from virus particles had an estimated mol. wt of 28000. Isolates of BRLV were found to be serologically related but not identical to some strains of tobacco streak virus. No symptoms developed in black raspberry seedlings infected with BRLV by mechanical inoculation, nor in eight red raspberry cultivars infected by graft inoculation. However, graft inoculation of BRLV to Rubus henryi, R. phoenicolasius and Himalaya blackberry induced symptoms typical of necrotic shock disease.