Epidemiology of three viruses infecting the rose in the United Kingdom

Studies on the epidemiology of arabis mosaic (AMV), prunus necrotic ringspot (PNRSV) and strawberry latent ringspot (SLRV) viruses were made in relation to commercial production of standard and bush roses. AMV or SLRV apparently induced either symptomless infection in rose cultivars and Rosa spp., or leaf symptoms ranging from small chlorotic flecks to severe chlorotic mosaic and, occasionally, plant death. Infection of R. canina ‘inermis’ or R. corymbifera by an isolate of SLRV from R. corymbifera also severely depressed flowering and hip formation. In addition, whereas this isolate could be graft-transmitted to all Rosa spp. tested, isolates from R. rugosa and R. multiflora failed to be graft-transmitted to R. canina ‘inermis’ or R. corymbifera. No difference was detected in graft-transmission tests of Rosa spp. with several isolates of AMV or PNRSV. In plantings of up to 7 yr none of the viruses was transmitted through pollen to healthy roses grown in nematode-free soil, and only SLRV was readily seed-transmitted, particularly in R. rugosa. Nevertheless, in soil containing viruliferous nematodes, AMV and/or SLRV were transmitted to c. 80% of healthy plants. AMV and particularly SLRV were each damaging to field-grown maiden rose bushes cv. Fragrant Cloud. SLRV delayed the onset of flowering, and reduced the number and size of blooms. Diseased bushes were less vigorous, and half or none of the AMV- or SLRV- infected bushes respectively, conformed to the British Standards Institution specifications for maiden bush roses. These results are discussed in relation to the commercial production of field-grown roses in the UK.     

Studies on rose mosaic disease in field-grown roses produced in the United Kingdom

Arabis mosaic virus (AMV) and prunus necrotic ringspot virus (PNRSV), separately or together, caused in field-grown roses the range of symptoms recognised as rose mosaic disease. PNRSV infection alone generally induced chlorotic line patterns, ring-spots or mottles in the leaves at some time during the growing season; AMV plus PNRSV normally caused chlorotic vein-banding. However, during prolonged periods of high temperatures (c. 21 °C or more) vein banding occurred in some roses infected only with PNRSV. Isolates of PNRSV from rose had particles which were similar in shape, protein mol. wt, density and sedimentation coefficients to previously described isolates of PNRSV from cherry, plum and rose; all were cherry serotypes. In graft-inoculated roses, apple serotypes of PNRSV induced stunting and chlorosis, puckering and distortion of leaves, which closely resembled symptoms associated with rose mosaic in the USA and chlorotic mottle rose mosaic in New Zealand. To avoid possible confusion in using the name rose mosaic it is suggested that the virus(es) present in roses should be named.     

The isolation and identification of rhubarb viruses occurring in Britain

Virus-like symptoms were common in British crops of rhubarb. All plants tested of the three main varieties, ‘Timperley Early’, ‘Prince Albert’ and ‘Victoria’, were virus-infected. Turnip mosaic virus and a severe isolate of arabis mosaic virus (AMV) were obtained from ‘Timperley Early’; and ‘Prince Albert’ contained turnip mosaic virus, cherry leaf roll virus (CLRV), a mild isolate of AMV and, infrequently, cucumber mosaic virus (CMV). The main commercial variety ‘Victoria’ contained turnip mosaic virus, CLRV, a mild isolate of AMV and, infrequently, strawberry latent ringspot virus (SLRV). All the viruses were identified serologically. The rhubarb isolates did not differ markedly from other isolates of these viruses in herbaceous host reactions, properties in vitro or particle size and shape. A rhubarb isolate of CLRV was distinguished serologically from a cherry isolate of the virus. Turnip mosaic virus, CLRV and SLRV, were transmitted with difficulty, but AMV isolates were readily transmitted by mechanical inoculation. Turnip mosaic virus was also transmitted to rhubarb by Myzus persicae and Aphis fabae. CLRV was transmitted in 6–8% of the seed of infected ‘Prince Albert’ and ‘Victoria’ rhubarb and in 72% of the seed of infected Chenopodium amaranticolor. Mild isolates of AMV were also transmitted in 10–24% of the seed of infected ‘Prince Albert’ and ‘Victoria’ plants.     

Tests for Transmission of Prunus Necrotic Ringspot and Two Nepoviruses by Criconemella xenoplax

In two of three trials, detectable color reactions in ELISA for Prunus necrotic ringspot virus (PNRSV) were observed for Criconemella xenoplax handpicked from the root zone of infected peach trees. Criconemella xenoplax (500/pot) handpicked from root zones of peach trees infected with PNRSV failed to transmit the virus to cucumber or peach seedlings. The nematode also failed to transmit tomato ringspot (TomRSV) or tobacco ringspot viruses between cucumbers, although Xiphinema americanum transmitted TomRSV under the same conditions. Plants of peach, cucumber, Chenopodium quinoa, and Catharanthus roseus were not infected by PNRSV when grown in soil containing C. xenoplax collected from root zones of PNRSV-infected trees. Shirofugen cherry scions budded on Mazzard cherry seedling rootstocks remained symptomless when transplanted into root zones of PNRSV-infected trees. Virus transmission was not detected by ELISA when C. xenoplax individuals were observed to feed on cucumber root explants that were infected with PNRSV and subsequently fed on roots of Prunus besseyi in agar cultures. Even if virus transmission by C. xenoplax occurs via contamination rather than by a specific mechanism, it must be rare.     

The association of Xiphinema diversicaudatum (Micoletsky) with strawberry latent ringspot and arabis mosaic viruses in a raspberry plantation

An outbreak of strawberry latent ringspot virus (SLRV) in a plantation of Mailing Jewel raspberry coincided with the greatest abundance of the nematode vector, Xiphinema diversicaudatum. Arabis mosaic virus (AMV) was not detected in the crop but was, together with SLRV, in many weed species present. AMV was transmitted through the seed of Poa annua, Capsella bursa-pastoris and Senecio vulgaris and SLRV through the seed of Mentha arvensis. X. diversicaudatum were more numerous within the rows than between them and vertical sampling showed that most occurred between 4 and 12 in depth in both locations. Monthly sampling showed that egg laying occurred from April to July; populations increased to a peak in late autumn but declined during the winter, resulting in about a twofold annual increase in numbers. Females, males and juveniles transmitted AMV and SLRV to cucumber seedlings, and in the absence of plants the nematode retained AMV for 112 days and SLRV for 84 days.     

Use of protein A to improve sensitisation of latex particles with antibodies to plant viruses

Protein A-coated latex (PAL) was compared with uncoated latex (L) for sensitisation with antibodies to five plant viruses: apple mosaic virus (ApMV), arabis mosaic virus (AMV), plum pox virus (PPV), potato virus Y ordinary strain (PVY°) and prunus necrotic ringspot virus (NRS V). A range of globulin concentrations was used with each antiserum and detection end points determined in serial dilutions of infective sap. When sensitised with antibodies to ApMV, PAL detected ApMV readily, whereas L did not. When sensitized with antibodies to PVY° and AMV, PAL gave higher detection end points than L. However, PAL gave little increase in sensitivity with the antisera to PPV and NRSV. Non-specific aggregation of latex, which sometimes occurred in very dilute sap with PAL, could be dispersed by adding 0.02% Tween-20 to the extraction buffer. Globulins of PVY° and AMV could be used at higher dilutions with PAL than with L, giving a saving in antiserum. Both types of latex sensitised with PVY° antibody globulins readily detected the tobacco veinal necrosis and C strains of this virus.     

建立基于TaqMan探针的李坏死环斑病毒实时荧光RT-PCR检测方法

李坏死环斑病毒(Prunus necrotic ringspot virus, PNRSV)是世界部分范围内分布的有害生物, 亦是我国重点关注的检疫对象。根据PNRSV各株系衣壳蛋白基因的保守序列, 设计特异性引物和TaqMan荧光探针, 进行了探针、引物和Mg2+浓度等反应体系和条件的优化实验, 确定最佳的引物浓度为400 nmol/L、探针浓度为333 nmol/L、Mg2+离子浓度为5 mmol/L和dNTPs浓度为0.43 mmol/L时, 其灵敏度达23个拷贝数。利用建立的实时荧光RT-PCR检测方法对PNRSV樱桃分离物进行了成功检测。这个方法具有灵敏、准确、简便、快速的特点, 适合于李坏死环斑病毒的检测和鉴定。     

中华鳖病毒的血清学检测

中华鳖病毒（ＴＳＶ）是从病鳖中分离到的一种病毒病原。经细胞培养和差异离心制备ＴＳＶ抗原,肌注家兔获ＴＳＶ抗体（ＴＳＶ－Ａｂ）,中和效价为１：２０,用ＴＳＶ－Ａｂ进行双向免疫扩散和间接ＥＬＩＳＡ检测,被检样品有健康和病鳖组织匀浆液、ＴＳＶ细胞培养液、提纯的ＴＳＶ,以及鱼传染性胰脏坏死病毒（ＩＰＮＶ）、草鱼呼肠孤病毒（ＧＣＶ）、鱼病毒性出血败血症病毒（ＶＨＳＶ）、鲁痘疮病毒（Ｃａｒｐ ｐｏｘ ｖｉｒｕ     

Comparative expression profiling of Nicotiana benthamiana leaves systemically infected with three fruit tree viruses

Plant viruses cause a wide array of disease symptoms and cytopathic effects. Although some of these changes are virus specific, many appear to be common even among diverse viruses. Currently, little is known about the underlying molecular determinants. To identify gene expression changes that are concomitant with virus symptoms, we performed comparative expression profiling experiments on Nicotiana benthamiana leaves infected with one of three different fruit tree viruses that produce distinct symptoms: Plum pox potyvirus (PPV; leaf distortion and mosaic), Tomato ringspot nepovirus (ToRSV; tissue necrosis and general chlorosis), and Prunus necrotic ringspot ilarvirus (PNRSV; subtle chlorotic mottling). The numbers of statistically significant genes identified were consistent with the severity of the observed symptoms: 1,082 (ToRSV), 744 (PPV), and 89 (PNRSV). In all, 56% of the gene expression changes found in PPV-infected leaves also were altered by ToRSV, 87% of which changed in the same direction. Both PPV- and ToRSV-infected leaves showed widespread repression of genes associated with plastid functions. PPV uniquely induced the expression of large numbers of cytosolic ribosomal genes whereas ToRSV repressed the expression of plastidic ribosomal genes. How these and other observed expression changes might be associated with symptom development are discussed.     

Deep sequencing reveals a novel closterovirus associated with wild rose leaf rosette disease

A bizarre virus‐like symptom of a leaf rosette formed by dense small leaves on branches of wild roses (Rosa multiflora Thunb.), designated as ‘wild rose leaf rosette disease’ (WRLRD), was observed in China. To investigate the presumed causal virus, a wild rose sample affected by WRLRD was subjected to deep sequencing of small interfering RNAs (siRNAs) for a complete survey of the infecting viruses and viroids. The assembly of siRNAs led to the reconstruction of the complete genomes of three known viruses, namely Apple stem grooving virus (ASGV), Blackberry chlorotic ringspot virus (BCRV) and Prunus necrotic ringspot virus (PNRSV), and of a novel virus provisionally named ‘rose leaf rosette‐associated virus’ (RLRaV). Phylogenetic analysis clearly placed RLRaV alongside members of the genus Closterovirus, family Closteroviridae. Genome organization of RLRaV RNA (17 653 nucleotides) showed 13 open reading frames (ORFs), except ORF1 and the quintuple gene block, most of which showed no significant similarities with known viral proteins, but, instead, had detectable identities to fungal or bacterial proteins. Additional novel molecular features indicated that RLRaV seems to be the most complex virus among the known genus members. To our knowledge, this is the first report of WRLRD and its associated closterovirus, as well as two ilarviruses and one capilovirus, infecting wild roses. Our findings present novel information about the closterovirus and the aetiology of this rose disease which should facilitate its control. More importantly, the novel features of RLRaV help to clarify the molecular and evolutionary features of the closterovirus.     

Disease intensity of some tomato viroses in Serbia

In this paper we present the data on the disease intensity of the tomato plants grown in glass and plastic-houses, and in the open field. The infection was caused by the following viruses: Tomato mosaic virus (ToMV), Tobacco mosaic virus (TMV), Tomato spotted wilt virus (TSWV), Alfalfa mosaic virus (AMV), Potato virus X (PVX), Potato virus Y (PVY), Tomato black ring virus (TBRV), Tomato ringspot virus (ToRSV), Tomato aspermy virus (TAV), and Cucumber mosaic virus (CMV). These viruses represented most frequent tomato pathogens in Serbia. According to the obtained results, it could be concluded that 92.94% of the tested tomato plants grown in glass and plastic-houses, and 89.82% grown in the open field were infected by one of the above viruses. Most of the plant samples were infected by two or more viruses. The most frequent viruses — tomato pathogens in Serbia were ToMV, PVY and TMV.     

Molecular diagnosis of apple virus and viroid pathogens from India

Apple is known to be susceptible to various virus and viroid pathogens. Symptomatic apple cultivars and rootstocks were collected and analyzed by ELISA and then through RT-PCR. The study reports the presence of Apple mosaic virus (ApMV), Apple stem grooving virus (ASGV), Apple stem pitting virus (ASPV), Apple chlorotic leaf spot virus (ACLSV), the major apple viruses and Prunus necrotic ringspot virus (PNRSV), a minor apple virus, at the molecular level in India. Apple scar skin viroid (ASSVd) infection was also confirmed at the molecular level. Sporadic incidences of Tomato ringspot virus and Arabis mosaic virus infections were also detected by ELISA in nursery plants.     

Influence of in vitro factors on titre and elimination of model fruit tree viruses

The titre of apple chlorotic leaf spot virus (ACLSV) was higher in microplants of Malus domestica cv. Jonagold than in 2-year-old grafted scions. Cytokinin concentration in the medium increased the titre of prunus necrotic ringspot virus (PNRSV) in the apex of microplants of Prunus insititia cv. Kozlienka but did not affect the titre of ACLSV in M .domestica.Virus titre of ACLSVwas higher in the haulms of autotrophically-grown compared with heterotrophically-grown microplants whereas as for PNRSV the results were the reverse. For both viruses, however, titre of the virus in the roots of autotrophically-grown plants was significantly higher than in haulm tissue from heterotrophic cultures. Ribavirin incorporation resulted in elimination of both viruses. Negative ELISA results were confirmed independently by PCR. The efficacy of Ribavirin in elimination of ACLSV was increased by increasing the concentration of cytokinin in the medium in parallel with decreasing the concentration of Ribavirin. These results are discussed in the context of the reliability of in vitro virus testing.     

Seed-transmission of nematode-borne viruses

Transmission through seed of crop and weed plants seems to be characteristic of nematode-borne viruses. It occurred with tomato black ring virus (TBRV) in nineteen species (thirteen botanical families), with arabis mosaic virus (AMV) in thirteen species (eleven families), with raspberry ringspot virus (RRV) in six species (five families), and also, in more limited tests, with tomato ringspot, cherry leaf roll and tobacco rattle viruses. A remarkable feature was that infected seedlings, except those containing tobacco rattle virus, often appeared healthy. The occurrence and extent of seed-transmission depended on both the virus and the host plant. In many progenies more than 10%, and in some 100%, of seedlings were infected. The viruses were transmitted through at least two or three generations of seed of those host species tested. After 6 years' storage, TBRV- and RRV-containing seed of Capsella bursa-pastoris and Stellaria media germinated to give infected seedlings. In controlled crossing experiments with strawberry and raspberry, virus was transmitted to seed from both male and female parents but, at least in raspberry, the presence of competing virus-free pollen much decreased the ability of pollen from infected plants to set seed. There was no evidence that healthy mother plants became infected when their flowers were pollinated with infected pollen.     

Host status of some plants for Xiphinema diversicaudatum (Micol.) and their susceptibility to viruses transmitted by this species

Forty plant species were grown in pots containing viruliferous Xiphinema diversicaudatum (Micol.) for 15 wk to assess the host range of the nematode in relation to infection with arabis mosaic (AMV) and strawberry latent ring-spot (SLRV) viruses. Host status for the nematode was determined mainly from changes in total populations, but the presence of eggs in the uteri of females and changes in the numbers of adults provided additional criteria. The nematode multiplied on relatively more woody perennials than on herbaceous crop plants or weeds. Chrysanthemum coronarium was the only plant on which numbers declined significantly below those on the controls. Most plant species became infected with either AMV or SLRV. Neither virus was detected in eight out of thirteen species of trees and shrubs although four were good hosts for the nematode. Galling or distortion of the terminal region of fine feeder roots, associated with X. diversicaudatum feeding, was seen on many of the experimental plants.     

Preparation and Characterization of a Monoclonal Antibody to Prunus necrotic ringspot virus

A cell line named PVRSV1D11 secreting monoclonal antibody (McAb) against the prokaryotically expressed coat protein (CP) of Prunus necrotic ringspot virus (PNRSV) was developed using hybridoma technology including animal immunization, cell fusion, cell line culture and enzyme‐linked immunosorbent assay (ELISA)‐based for screening. The specificity, titre and detection sensitivity of the McAb were determined by indirect ELISA to establish optimal conditions. The antibody reacted strongly with PNRSV and showed no cross‐reactions with the proteins of Plum pox virus, Prunus dwarf virus, Apple stem pitting virus, Apple stem grooving virus, Apple mosaic virus or Apple chlorotic leafspot virus. The ascites developed with PNRSV1D11 cell line showed high absorbance until it was diluted to over 6.6 × 10⁷ fold. The McAb belonged to IgG_2a isotype and was diluted by 1.28 × 10⁵ folds as an optimal detection concentration. The detection sensitivity of the monoclonal antibody was 11.7 ng/ml protein of PNRSV. The results indicated that the McAb against the CP of PNRSV is suitable for PNRSV detection in the plants and for monitoring the dynamics of the virus by using indirect ELISA.     

Apple mosaic virus isolated from hop plants in Japan

A strain of apple mosaic virus was isolated from hop plants in Japan. The virus was purified from young hop plants and back-inoculated to virus-free hop plants obtained by meristem tip culture. Inoculated plants developed chlorotic spots, ringspots and a band pattern accompanied by necrosis in the inoculated and systemically infected leaves. Shoot tips of infected plants sometimes became necrotic and these symptoms resembled those of a ring- and band-pattern mosaiclike disease prevalent in hop gardens in Japan. Since apple mosaic virus was recovered from infected plants, it is likely that the virus was the causal agent of this disease. Agar gel double diffusion tests and ELISA showed the hop virus to be serologically closely related to apple mosaic virus (ApMV), and distantly related to prunus necrotic ringspot virus (PNRSV). The virus had a narrow host range, and infected only cucumber of 18 species of Cucurbitaceae, Chenopodiaceae, Leguminosae or Solanaceae inoculated. It produced chlorotic spots on the inoculated cotyledons of cucumber, but no systemic infection. By contrast, ApMV from apple and PNRSV from peach had wide host ranges and infected cucumber plants systemically.     

Seed-transmission in the ecology of nematode-borne viruses

Virus-free populations of vector nematodes can acquire tomato black ring (TBRV), raspberry ringspot (RRV) and arabis mosaic (AMV) viruses from weed seedlings grown from virus-carrying seed. When soils from fields where nematode-borne viruses occurred naturally were air-dried to kill vector nematodes and then moistened, TBRV and RRV occurred commonly in the weed seedlings that grew, but AMV occurred only rarely. Similar tests did not detect tobacco ringspot, grapevine fanleaf or tobacco rattle viruses in weed seeds in the single soil studied in each instance, although these three viruses are also seed-borne in some of their hosts. Many weed species, when infected experimentally, readily transmit TBRV and RRV to their seed, but the viruses were much commoner in naturally occurring seed of some of these species than of others. These discrepancies between the frequency of seed-transmission of viruses from experimentally infected plants and the extent of natural occurrence of infected seed seem largely to reflect the host preferences of the vectors. Infective Longidorus elongatus kept in fallow soil retained TBRV and RRV only up to 9 weeks. When weed seeds in the soil were then allowed to germinate, the nematodes reacquired virus from the infected seedlings. Some weed species were better than others as sources of virus. Persistence of these viruses in fields through periods of fallow or fasting of the vector therefore depends on a continuing supply of infected seedlings produced by virus-containing weed seeds. This is probably less true of viruses like AMV and grapevine fanleaf, which persist for 8 months or more in their vectors (Xiphinema spp.). A few seeds containing TBRV and RRV were found in soils free of vector nematodes, suggesting that the viruses are disseminated in weed seed. This probably explains how TBRV and RRV have reached a large proportion of L. elongatus populations in eastern Scotland.