Host range and some properties of potato mop-top virus

Potato mop-top virus (PMTV) was transmitted by inoculation of sap to twenty-six species in the Solanaceae or Chenopodiaceae and to Tetragonia expansa; species in eleven other plant families were not infected. The virus was cultured in inoculated leaves of Nicotiana tabacum cv. Xanthi-nc or in N. debneyi. Diagnostic local lesions were produced in Chenopodium amaranticolor. In winter, ten solanaceous species were slowly invaded systemically but the first leaves infected were those immediately above inoculated leaves. When transmitted to Arran Pilot potato by the vector Spongospora subterranea, PMTV induced all the main types of shoot and tuber symptoms found in naturally infected plants. Isolates of PMTV from different sources differed considerably in virulence. PMTV-containing tobacco sap lost infectivity when heated for 10 min at 80 °C, diluted to 10^-4, or stored at 20 °C for 14 weeks. Infectivity was partially stabilized by 0·02% sodium azide. When sap was centrifuged for 10 min at 8000 g, infectivity was mainly in the sediment. Infective sap contained straight rod-shaped particles about 20 nm wide, with lengths up to 900 nm and crossbands at intervals of 2·5 nm. Many of the particles were aggregated side-to-side, and the ends of most seemed damaged. The slight infectivity of phenol-treated leaf extracts was abolished by pancreatic ribonuclease. The present cryptogram of PMTV is R/*:*/*:E/E:S/Fu.     

Membrane-associated particle aggregates in extracts of plant: infected with some viruses of the potato Y group

Membrane-associated aggregates of filamentous virus particles were found occasionally in sap from plants infected with each of five distinct viruses of the potato Y group. The aggregates measured up to 960 × 700 nm and contained from four to twenty-four virus particles. Their occurrence is apparently specifically associated with potato Y and allied viruses, observations suggesting that they may be either fragments of virus-containing cytoplasmic strands or groups of particles enveloped during cellular disruption by pieces of tonoplast with which they are associated in vivo.     

Some properties of cocksfoot mottle virus

Cocksfoot mottle virus (CFMV) was transmitted by manual inoculation of sap to cocksfoot (Dactylis glomerata L.), wheat, oats and barley, but not to nineteen other monocotyledonous and thirteen dicotyledonous plant species. The virus was also transmitted by cereal leaf beetles (Lema melanopa L.). Adult beetles infected plants more frequently than larvae, and remained infective for up to 2 weeks after they had fed on infected plants. Seed from infected cocksfoot and oat plants produced virus-free seedlings. The infectivity of sap was lost during 10 min. at 65° C., and 2 weeks at 20° C., but survived many months at — 15° C. Purified virus preparations, made by various methods, contained numerous nearly spherical particles, about 30 mμ in diameter. In electron micrographs some of the particles were penetrated by negative stain though most appeared intact. However, all the particles migrated together in a centrifugal (sedimentation coefficient = 118 S) or electrophoretic field. The ultraviolet absorption spectrum, and the phosphorus and nitrogen contents of the virus preparations, were typical of a nucleoprotein containing about 25 % nucleic acid. Serological tests failed to show any relationship between CFMV and eleven other viruses with particles of similar shape and size.     

Properties of cocksfoot streak and cocksfoot cryptic, two viruses infecting cocksfoot (Dactylis glomerata) in Scotland

A Scottish isolate of cocksfoot streak virus (CSV-S) was found to have flexuous filamentous particles which, in sap of infected cocksfoot plants, had a modal length of 712 nm. It was transmitted from infected to healthy cocksfoot plants in a non-persistent manner by Myzus persicae and by mechanical inoculation of infective sap extracts containing an anti-oxidant. Apart from cocksfoot, mechanical inoculation of infective sap succeeded in infecting only four of 22 plant species tested. The infectivity of sap extracts containing 0.2% thioglycerol was lost after heating for 10 min at 55^oC but not 50^oC, storage at room temperature for 48 but not 24 hours, and after diluting 10^-2to 10^-3. Highly purified preparations of CSV-S particles sedimented as a single component with a sedimentation coefficient of 139S and had a buoyant density in rubidium bromide of 1.31 g/cm³. Virus particles were composed of one protein and one ssRNA species with estimated M_r of 31 000 and 3.2 times 10⁶respectively. In ELISA, an antiserum prepared to CSV-S detected the virus in all aerial parts of infected cocksfoot plants and, when present in the ratio of 1 infected leaf: 1000 healthy leaves. Both CSV-S-infected and -uninfected cocksfoot also contained a previously undescribed virus with isometric particles c. 30 nm in diameter. This virus, named cocksfoot cryptic virus (CCV), was seed-borne in two cvs of cocksfoot tested and its particles contained two dsRNA species of estimated M_r of 1.14 times 10⁶and 1.27 times 10⁶. Despite the fact that particles of CSV-S were largely free from CCV particles following exclusion chromatography on agarose beads prior to immunisation, immunoelectron microscopy (IEM) showed that the antiserum prepared to CSV-S also contained some antibodies to CCV. Evidence from IEM suggested a possible distant serological relationship of CCV to ryegrass and beet (BCV 1 or BCV 2, or both) cryptoviruses, all members of sub-group A of crypto viruses.     

Leaf mottling of Spartina species caused by a newly recognised virus, spartina mottle virus

The cause of a previously undocumented leaf mottling of Spartina species was investigated. Negatively stained preparations of sap from mottled leaves revealed flexuous particles 725 × 12 nm. Pinwheels with associated laminar inclusion bodies were observed in thin sections of affected mesophyll cells. The virus was purified from infected Spartina anglica plants and had a sedimentation coefficient in 0·015 m borate of 150S. The virus was transmitted by inoculation of sap to healthy Spartina anglica, but not to a range of other graminaceous or dicotyledonous species tested. It was distantly serologically related to agropyron mosaic virus, but not to other viruses with similar morphology; the name spartina mottle virus is proposed.     

Purification and Partial Characterization of Isometric Virus-like Particles in Kalanchoe Species

Isometric virus-like particles (IVLP) were detected in crude sap from Kalanchoe pinnata, K. daigremontiana and K. tubiflora plants showing a mild mosaic on the leaves. These particles of 35 nm in diameter were transmitted mechanically to several test plants but not to healthy Kalanchoe. Air temperatures above 30 °C hindered the infection process. The IVLP were purified from systematically infected Nicotiana benthamiana using Triton X-100 as clarifying agent followed byP, EG precipitation. IVLP were degraded by organic solvents and formed aggregates in the presence of 2 mmol/1 CaCl₂. The particles occurred in relatively low concentration in plant sap and lost infectivity in leaves frozen at -70 °C for one week and in purified preparations kept at 4 °C. In buffer crude sap of N. benthamiana IVLP had a thermal inactivation point between 45 and 50 °C on a longevity in vitro of 20 h at 25 °C. Particles contained one nucleoprotein component witha molecular weight of 46,000 daltons and a ssRNA species which, when denatured, had a molecular weight of 1.2 × 10⁶. IVLP purified preparations exhibited a typical nucleoprotein absorption spectrum with a maximum at 254–260 nm and a minimum at 240,–243 nm and a A 260/280 ratio of 1.56. The buoyant density of the IVLP was 1.32 g/ml calculated by isopycnic centrifugation on CsCl. Ultrastructural studies in infected leaves of K. pinnata indicated that IVLP caused an increase in chloroplast volume, distortion of the grana and reduced the number of thylakiods per grana. IVLP infection also impared the diurnal pattern of synthesis and hydrolysis of starch, characteristic of CAM plants. The non-serological reaction of the IVLP with antisera specific to members of 7 different groups of spherical viruses as well as the combination of physicochemical properties and host range, exhibited by these particles impeded their taxonomic location. In nature, young Kalanchoe plantlets acquire the IVLP through their physical connections with the infected mature leaves.     

PROTEIN SYNTHESIS IN NORMAL AND SCRAPIE MOUSE BRAIN

Damage to the brain as a result of an intracerebral injection of physiological saline does not appreciably affect the rate of protein synthesis in mouse brain. The in vivo and in vitro incorporation of labelled amino acids into mitochondria and their in vivo incorporation into nuclei, microsomes, nerve ending particles, myelin and cell sap were compared in normal and scrapie-affected mice. No significant differences were found.     

Parsnip mosaic virus, a new member of the potato virus Y group

Parsnip mosaic virus (PMV) occurs commonly in parsnip in Britain and is transmitted after acquisition access periods of 2–5 min by the aphids Cavariella aegopodii, C. theobaldi and Myzus persicae. It was transmitted by manual inoculation of sap, infecting parsnip, chervil, coriander and carrot plants systemically, and causing local lesions without subsequent systemic infection in eight Chenopodium spp., Spinacia oleracea, Gomphrena globosa, and Toreniafournieri. It lost infectivity in Chenopodium quinoa sap after dilution to 10^-3–10^-4, heating for 10 min at 55–58 °C, or storage at room temperature for 7–10 days. Preparations partially purified by n-butanol or chloroform clarification, followed by acid precipitation and/or chromatography on columns of 2% agarose beads, contained filamentous particles, many of which were aggregated or fragmented. Preparations made with chloroform and without acid precipitation contained unaggregated particles of 755 nm normal length, with a sedimentation coefficient of 149 S. PMV did not react with antisera to any of fourteen other viruses with filamentous particles. The present cryptogram for PMV is */*: */*:E/E:S/Ap.     

Effect of Fungicides on the Viability of Phylophthora cactorum Propagules m the Soil

Vein-clearing followed by downward rolling and necrosis of leaves and severe stunting of groundnut (Arachis hypogaea) plants were caused by cowpea mild mottle virus (CMMV). The virus was readily transmitted by mechanical sap inoculations to groundnut and to 10 plant species belonging to Leguminosae, Chenopodiaceae and Solanaceae. Chenopodium quinoa and Beta vulgaris were good diagnostic hosts. Diseased sap remained infective at 10^–3 but not 10^–4, when stored 8 to 9 days at 25 °C; for 10min at 75 °C but not 80°C. In limited tests, virus was not seed-transmitted m groundnut or soybean. Virus was transmitted by Bemisia tabaci but not by Aphis craccivora or Myzus persicae. An antiserum for CMMV was produced and virus was serologically related to CMMV reported on cowpea and groundnut crinkle virus (GCV) from West Africa. Employing carbon diffraction grating replica as a standard the modal length of virus particles to be 610 nm. Infected cells contained large number of virus particles associated with endoplasmic reticulum.     

A probable rhabdovirus infection of lemon-scented thyme

Bacilliform particles were found in the perinuclear space of phloem parenchyma cells of Thymus xcitriodorus (lemon-scented thyme) showing a marked leaf chlorosis. They were of typical rhabdovirus morphology, of mean dimensions 219 X72nm and composed of a bullet-shaped internal component surrounded by an envelope. A few unenveloped internal components were seen in the nucleus and the perinuclear space. The bacilliform particles were concentrated and partially purified from leaf material but were not easily detected by negative staining of leaf squashes. They were not transmitted by inoculation of infected sap and the evidence indicates that they were not the causal agent of the leaf chlorosis.     

Visualisation of xylem sap flow direction in isolated fine lateral roots and estimation of the xylem sap osmotic potential

Xylem sap outflow from fine lateral roots (FLRs) isolated from hydroponically grown young maize (Zea mays L.) plants was visualized by local brightening of test solutions contrasted with purified Indian ink particles. Flow into the vessels was indicated by the adsorption of Evans Blue in their walls. The fraction of the FLRs able to exude xylem sap in a mineral medium with 30 mM mannitol decreased with increasing incubation time. This change was strongly retarded, when the FLRs were incubated in a medium containing glucose instead of mannitol. There was a broad range of variation of the osmotic potential of the test solutions (Ψ_so), wherein the fraction of the FLRs showing an initially reversed flow of the xylem sap varied between zero and unity. A median (M) of the osmotic potential of the xylem sap in FLRs (Ψ_sx) was estimated. It represents the value of Ψ_so that was lower than Ψ_sx in half of the roots of a sample before their transfer to the test solutions (Ψ_sxo). M was dependent on the osmotic potential of the medium used for growth or pre-incubation of the FLRs. Its value was not dependent on the molecular size of the osmolytes used to adjust Ψ_so, including dextran 8, which is excluded from cell walls. In all of the studied plants, M was lower than the osmotic potential of the xylem sap collected from the root before isolation of the FLRs. To explain this finding it is assumed that FLRs with Ψ_sxo > M had a higher hydraulic conductivity and a larger volume contributed to the exuded sap than those with Ψ_sx < M.     

Plant proteases as interfering factors in the electron microscopic detection of alfalfa mosaic and bean yellow mosaic viruses inSolanum laciniatum Ait

Plant proteases rapidly destroy virus architecture in sap ofSolanum laciniatum Ait., with yellow mosaic symptoms but even under these conditions the partially digested amorphous nucleoproteins retain their immunospecificity and infectivity for a limited time. Homogenization with phenylmethylsulfonylfluoride inhibits efficiently host serine proteases and fully stabilizes the virus particles in plant sap and in partial purificates. During the electronmicroscopic examination of stabilized infectious saps in 12 out of 14 isolates of yellow mosaic ofS. laciniatum besides alfalfa mosaic virus a poty-virus was disclosed. This was identified serologically and by transmission tests as a weakly virulent type of bean yellow mosaic virus.     

喀斯特区天峨槭(Acer wangchii)树干液流特征及其与环境因子的相关分析

采用TDP(Thermal Dissipation Probe)热扩散探针法,于2012年2月—2014年3月,对喀斯特地区天峨槭(Acer wangchii)树干液流速率进行了长期连续的监测,并同步监测了林分空气温度(Ta)、相对湿度(RH)、太阳辐射(Solar)、风速(WS)、降雨量(Rainfall)、土壤含水量(SWC)等环境因子,探讨了不同时间尺度下天峨槭树干液流特征及其与环境因子的关系。结果表明:1)不同天气条件下的树干液流为晴天阴天雨天,且均呈明显的"昼高夜低"变化规律;2)天峨槭树干的日平均液流量为5.08kg/d,不同季节表现为夏季((8.38±5.32)kg/d)秋季((5.16±3.99)kg/d)春季((4.86±3.77)kg/d)冬季((1.94±1.40)kg/d);3)月平均液流量为153.64 kg,年平均液流量达1838.40 kg;4)小时尺度下,影响晴天、阴天、雨天全天树干液流的主要环境因子都是Solar,但各环境因子对树干液流的影响程度又因昼夜、季节及降雨量的不同而存在差异;5)从年度范围来看:小时尺度下,Solar、Ta、RH、SWC_(10cm)和WS可以共同解释树干液流的63.50%;日尺度下,Solar、Ta、SWC_(10cm)和Rainfall可共同解释其68.50%;月尺度下,单个因子Ta就能解释其74.80%;且随着时间尺度的缩小,各环境因子入选回归方程的个数有增加的趋势,而对树干液流的解释程度(R2)则有降低的趋势。对比其他地区研究结果,其环境因子对树干液流的影响差异都很大;但总的来说,无论在何种时间尺度上,Solar(或光合有效辐射(PAR))和Ta基本上都是影响树干液流的主要环境因子,且各环境因子对雨天树干液流的解释程度都不高,本研究亦如此;因此,以环境因子对雨天树干液流进行预测的时候可能会存在误差,应特别注意土壤含水量对其的影响。     

Properties of some defective strains of tobacco mosaic virus and their behaviour as affected by inhibitors during storage in sap

From the type strain of tobacco mosaic virus, defective strains were isolated that produced chlorotic or ringspot type symptoms in tobacco and were difficult to transmit without carborundum in the inoculum. Their concentration was less than 0–1 μg/ml of sap instead of the usual 2 mg/ml with the type strain. Phenol extracts of infected leaves were a little more infective than extracts in buffer, whereas phenol extracts of leaves infected with type strain were very much less infective than extracts in buffer. Electron microscopy of infective sap rarely showed any virus particles, but preparations concentrated by ultracentrifugation contained virus particles, many of which were broken or seemed inadequately assembled. Changing the ambient temperature at which infected plants were kept from 20 to 35°C did not increase the amount or improve the appearance of the virus. Some of the strains were inactivated during heating for 10 min between 70 and 80 °C. Undiluted sap lost its infectivity in 3 days at 20 °C, as did the type strain when diluted to 0–1 μg/ml in sap from healthy leaves. This is because substances that inhibit infection were produced by microbes in the sap. The ability of sap from healthy leaves to inhibit infection increased by more than twenty-five times when left 3 days at 20 °C. Infectivity of appropriate mixtures of type strain and aged sap was restored by diluting them in buffer. Sodium azide at 0·02% in sap prevented formation of the inhibitor. The infectivity of the defective strains increased when inoculated together with the type strain.     

The relationship between nutrients in extracted xylem sap and the susceptibility of fruit trees to silver-leaf disease caused by Stereum purpureum (Pers.) Fr.

Xylem sap was extracted from cut branches of stone-fruit and pip-fruit trees at different times of the year, and analysed for nitrogen and carbohydrate content. Growth of Stereum purpureum was measured in the different sap samples in vitro. Nitrogen and carbohydrate levels in xylem sap from peach trees were highest in late winter and early spring, and these samples supported most growth of S. purpureum. At full bloom the levels of nitrogen and carbohydrate in xylem sap from stone-fruits (peach, nectarine, plum, cherry) were several times greater than in sap from pip-fruits (apple, pear), and the growth of S. purpureum in sap from stone-fruits was approximately ten times that in sap from pip-fruits. The results suggest that seasonal variations in susceptibility of stone-fruits to silver-leaf disease, and the greater susceptibility of stone-fruits than of pip-fruits, are due to differential ability of their xylem saps to support growth of S. purpureum.     

Purification and Characterization of Indian Cassava Mosaic Virus

The Indian cassava mosaic virus (ICMV) was transmitted by the whitefly Bemisia tabaci and sap inoculation. ICMV was purified from cassava and from systemically infected Nicotiana benthamiana leaves. Geminate particles of 16–18 × 30 nm in size were observed by electron microscopy. The particles contained a single major protein of an estimated molecular weight of 34,000. Specific antiserum trapped geminate particles from the extracts of infected cassava and N. benthamiana plants in ISEM test. The virus was detected in crude extracts of infected cassava, ceara rubber, TV. benthamiana and N. tabacum cv. Jayasri plants by ELISA. ICMV appeared serologically related to the gemini viruses of Acalypha yellow mosaic, bhendi yellow vein mosaic, Croton yellow vein mosaic, Dolichos yellow mosaic, horsegram yellow mosaic, Malvastrum yellow vein mosaic and tobacco leaf curl.     

毛乌素沙地杨柴液流变化对气象因子的响应

采用FLOW32-1K (Thermal Dissipation Probe)热平衡包裹式液流仪对毛乌素沙地杨柴(Hedysarum leave)植株液流速率进行了连续监测,同步监测灌木林地内气温、太阳辐射、相对湿度和饱和水汽压差(VPD)等气象因子,探讨了在不同时间尺度下杨柴植株液流特征及其与气象因子的关系。结果表明：(1)不同径级(3—4 mm、4—6 mm和>6 mm)杨柴植株的日平均液流速率分别为5.61 g/h、9.29 g/h、35.30 g/h,平均日液流量分别为(134.72±82.48)g/d、(223.06±152.20)g/d、(847.23±403.38)g/d。不同天气条件下的树干液流速率晴天>阴天,液流速率变化呈“昼高夜低”,不同月份表现为8月>7月>9月。(2)影响晴天和雨天杨柴植株液流的首要气象因子都是太阳辐射,小时尺度下,太阳辐射、气温、相对湿度和饱和水汽压共同解释杨柴液流的75%以上,在日尺度下,气象因子可以共同解释其80.8%以上;且随着时间尺度增大,进入回归方程的气象因子个数呈减小趋势,但气象因子对杨柴液流变化的解释度呈增...     

Pepino mosaic virus, a new potexvirus from pepino (Solanum muricatum)

Pepino mosaic virus (PepMV), a previously undescribed virus, was found in fields of pepino (Solanum muricatum) in the Canete valley in coastal Peru. PepMV was transmitted by inoculation of sap to 32 species from three families out of 47 species from nine families tested. It caused a yellow mosaic in young leaves of pepino and either a mild mosaic or symptomless infection in 12 wild potato species, five potato cultivars and potato clone USDA 41956 but S. stoloniferum and potato cultivars Merpata and Revolucion reacted with severe systemic necrotic symptoms. The virus was transmitted by plant contact but not by Myzus persicae. It was best propagated and assayed in Nicotiana glutinosa. Sap from infected N. glutinosa was infective after dilution to 10^-1 but not 10^-6, after 10 min at 65°C but not 70°C and after 3 months at 20°C. PepMV had filamentous particles with a normal length of 508 nm; the ends of some seemed damaged. Ultra-thin sections of infected leaves of N. glutinosa revealed many inclusions containing arrays of virus-like particles some of which were banded or whorled; small aggregates of virus-like particles were also common. The virus was purified by extracting sap from infected leaves in a solution containing 0·065 M disodium tetraborate, 0·435 M boric acid, 0·2% ascorbic acid and 0·2% sodium sulphite at pH 7·8, adding silver nitrate solution to the extract, and precipitating the virus with polyethylene glycol followed by two cycles of differential centrifugation. Particles of PepMV normally yielded two proteins with molecular weights of 26 600 and 23 200, but virus obtained from infective sap aged overnight yielded only the smaller protein suggesting that it was a product of degradation of the larger one. The virus is serologically related to two potexviruses, narcissus mosaic and cactus X and its properties are typical of the potexvirus group.     

Host range, properties and purification of raspberry bushy dwarf virus

Raspberry bushy dwarf virus (RBDV) was found in all plants of Lloyd George raspberry with bushy dwarf disease and occurred occasionally in plants of some other cultivars. It was transmitted by inoculation of sap to fifty-five other species in twelve families of flowering plants and infected most of them symptomlessly. It caused systemic symptoms in some species of Amaranthaceae, Chenopodiaceae and Cucurbitaceae, and necrotic local lesions in some Leguminosae. It did not induce bushy dwarf disease when returned to Lloyd George raspberry. Chenopodium quinoa was used for propagating the virus and Vigna cylindrica for local lesion assay. In C. quinoa sap, RBDV lost infectivity when diluted 10^-4, heated for 10 min at 65 °C or stored for 4 days at 22 °C. Preparations made by twice precipitating the virus at pH 4·8 and resuspending it at pH 7·0, followed by ultracentrifugation and exclusion chromatography in columns of 2 % agarose beads, contained isometric particles about 33 nm in diameter, which sedimented as two components, with sedimentation coefficients of 111 and 116S. Only a few particles, all of them disrupted, were seen in preparations mounted in phosphotungstate, but the particles were well preserved in uranyl formate provided that they were first dispersed in a saxlt such as MgCl₂ instead of distilled water. Many particles were oval in outline as though distorted during drying. No serological relationship was detected between RBDV and twenty-four other isometric viruses nor between RBDV and the filamentous virus apple chlorotic leafspot, to which it was previously thought to be related. An isolate of loganberry degeneration virus was serologically indistinguishable from RBDV.     

Production and properties of monoclonal antibodies to Solanum nodiflorum mottle sobemovirus

Black raspberry necrosis virus (BRNV) reaches only very low concentrations in herbaceous plants and is difficult to maintain in culture. However, in a mixed culture with an unrelated virus, Solanum nodiflorum mottle (SNMV), in the genus Sobemovirus, the concentration of BRNV particles increases about 1000‐fold. In attempts to produce monoclonal antibodies (MAbs) to BRNV for diagnostic use, purified virus particles from the mixed virus culture were used as immunogen and the resultant antibodies screened against cultures of SNMV alone, BRNV+SNMV and healthy plant extracts. None of the virus‐specific MAbs obtained in this way was specific to BRNV but six were specific to SNMV. Although the original objective was not achieved, the SNMV MAbs were characterised and used to study serological properties of SNMV and other Sobemoviruses. Characterisation of the six SNMV MAbs showed that four were IgG3, one IgG1 and the other IgG2b. SNMV was detected by all six MAbs in ELISA, by five in Western blotting, by three in agarose gel double diffusion tests, but only one was suitable for trapping virus particles in immuno‐electron microscopy (IEM). In Western blotting using virus in sap extracts of Nicotiana clevelandii, each of the five MAbs detected a single major band of Mc. 31 000 in sap containing SNMV, and additional bands of lower mass attributed to degradation of coat protein. In various serological tests, no cross‐reactions were detected between SNMV and seven other viruses from the genus Sobemovirus. However, in IEM but not in Western blotting, significant cross‐reactions were observed between SNMV and Velvet tobacco mottle virus, another species from the genus Sobemovirus. The significance of these different findings is discussed.