Black Raspberry Necrosis Virus Research Articles

Characterization of the first Rubus yellow net virus genome from blackberry.

Rubus yellow net virus (RYNV) is a badnavirus that infects Rubus spp. Mixed infections with black raspberry necrosis virus and raspberry leaf mottle virus cause raspberry mosaic, a disease that leads to significant losses and even plant death. RYNV has been reported in several European countries and the Americas yet there is substantial lack of knowledge, especially when it comes to virus diversity and the evolutionary forces that affect virus fitness outside its primary host, raspberry. Herein, we report the first RYNV episomal genome isolated from blackberry and this is the first report of the virus in Bosnia and Herzegovina. The isolate has five open reading frames (ORFs) and, when compared with other fully sequenced counterparts, showed 82-97% nucleotide pairwise identity. This communication adds to our limited knowledge on RYNV and addresses some of the gaps in RYNV genetics when it comes to the coding capacity of episomal isolates and the probability of the first fully sequenced isolate of the virus being integrated in the raspberry genome.

First report of black raspberry necrosis virus and raspberry leaf mottle virus in Bosnia and Herzegovina

First report of black raspberry necrosis virus and raspberry leaf mottle virus in Bosnia and Herzegovina

First report of Raspberry leaf mottle virus infecting raspberry in Poland.

Raspberry leaf mottle virus (RLMV) in Europe has been associated with raspberry mosaic disease (Martin et al. 2013) and crumbly fruit disease (Quito-Avila et al. 2014) in red raspberry (Rubus idaeus L.) beside Rubus yellow net virus (RYNV) and Black raspberry necrosis virus (BRNV). RLMV has also been reported infecting blackberry (Jones and McGavin 1998; Thekke-Veetil et al. 2016). A survey of virus diseases was conducted from 2016 to 2018 in 34 raspberry commercial plantations in Central and southeastern Poland. Some of the plants showed chlorotic spots, vein yellows, mosaic patterns and deformation of leaves and fruits. Leaf samples from 146 plants were tested using RT-PCR for RLMV, RYNV, BRNV, Raspberry vein chlorosis virus (RVCV), Raspberry leaf blotch virus (RLBV), and Raspberry bushy dwarf virus (RBDV). The pairs of primers CPhF and CPhR (Tzanetakis et al. 2007) as well as 1436F and 1437R (McGavin and MacFarlane 2010) were used to amplify a 452-bp fragment of the coat protein homologue (CPh) gene and a 681-bp of the 1 a helicase gene, respectively. RT-PCR products were obtained for five samples from cultivars: Malling Promise (MPrOK1 and MPrOk2; plantation A), Canby (CanKop; plantation B), Polka (PolKop; plantation B) and Malling Seedling (MSeWa; plantation C) grown in southeastern Poland. MPrOK1 and MSeWa were co-infected with RYNV while the other three samples were mixed infected with RBDV. Each of these plants showed chlorotic spots and mosaic symptoms of different intensity, leaf deformation and reduced growth. The RLMV-specific amplicons obtained for all five positive samples were directly sequenced at Genomed company, Warsaw, Poland. The obtained sequences were aligned using ClustalW of the Lasergene 7.1 software (DNASTAR Inc., USA) and were compared with sequences available in GenBank using the BLASTn algorithm. The identity of nucleotide (nt) sequences of Cph gene of RLMV isolates found in Poland was revealed. They shared 97.7% and 99% nt sequence similarity with 'HCRL Glen Clova' from USA (DQ357218) and 'SCRI stock' isolate from United Kingdom (FN391551) strains respectively The nucleotide sequence of isolates from Poland indicates a closer relationship with the strain found in UK. However, the amino acid (aa) sequence of both reference strains was identical and shared 99.2% identity with the corresponding fragment of the isolates from Poland. The representative sequence of PolKop isolate was deposited in GenBank under accession No. MT241265. The similarity of nucleotide sequence of the 1 a helicase gene ranged from 98.5% (between MseWa and four other isolates) to 100% (between MPrOk1 and MPrOk2). The amino acids sequences of MPrOk1, MPrOk2 and MSeWa isolates were identical whereas they shared 99.5% similarity with CanKop and PolKop isolates. The nt and aa sequences within this region of all five isolates were in 98% homologous with the sequences of 'HCRL Glen Clova' strain. Nucleotide sequences of the 1 a helicase gene of the CanKop, PolKop, MseWa, MPrOk1, MPrOk2 isolates were deposited in GenBank (acc. Nos. MT847633-MT8347637). Considering the low incidence of RLMV (five out of 146 positively tested), it can be assumed that there is no emergency of the RLMV large-scale occurrence in Poland. However, as RLMV is transmitted by Amphorophora idaei aphids found in our country, infected plants near raspberry plantations may play an important role in virus spread. This is the first report of RLMV infecting red raspberry in Poland. Acknowledgments This work was performed in the frame of multiannual programme 2015-2020 "Actions to improve the competitiveness and innovation in the horticultural sector with regard to quality and food safety and environmental protection" (task 2.1), financed by the Polish Ministry of Agriculture and Rural Development. I would like to thank Mrs. Dorota Starzec for technical assistance. References Jones, A. T, and McGavin, W. J. 1998. Ann. Appl. Biol. 132:239. https://doi.org/10.1111/j.1744-7348.1998.tb05200.x. Martin, R. R. et al. 2013. Plant Dis. 98:176. http://dx.doi.org/10.1094/PDIS-04-12-0362-FE. McGavin, W. J. and MacFarlane, S. A. 2010. Ann. Appl. Biol. 156:439. doi:10.1111/j.1744-7348.2010.00401.x. Quito-Avila, D. F., et al. 2014. Plant Dis. 98:176. http://dx.doi.org/10.1094/PDIS-05-13-0562-RE. Thekke-Veetil, T., et al. 2016. Plant Dis. 101:265. https://doi.org/10.1094/PDIS-07-16-1014-PDN Tzanetakis, I. E., et al. 2007. Virus Res. 127:26. doi:10.1016/j.virusres.2007.03.010.

High proportion of mixed virus infections in raspberry plantations in Serbia

Samples of red raspberry (Rubus idaeus L.) from the most important growing areas in Serbia were analyzed for the presence of four most important raspberry viruses: raspberry leaf blotch virus (RLBV), raspberry leaf mottle virus (RLMV), black raspberry necrosis virus (BRNV) and Rubus yellow net virus (RYNV), and their incidence in individual and mixed infected samples. Seventy-four samples of eight raspberry cultivars, selected from 32 main cultivation sites were tested, of which 62 leaf samples showed symptoms that could be caused by viruses and 12 samples were asymptomatic. The presence of viruses was tested by appropriate RT-PCR and PCR methods, using virus-specific primers. All four viruses were detected with highly significant differences of incidence in a total of 61 infected symptomatic samples. Infection with one of the four tested viruses was detected in 59.0% of all infected samples. The most prevalent was RLBV, which was associated with raspberry leaf blotch disorder in coexistence with its vector raspberry leaf and bud mite P. gracillis, and it was detected in 70.5% of the infected samples. It was followed by RYNV with an incidence of 42.6%, BRNV with 36.1% and RLMV with 9.8% incidence, considering all infected samples. The obtained results for the first time in Serbia showed a high proportion (41.0%) of mixed infections involving between two and four viruses. The most common were infections with two viruses, 68.0% of all mixed-infected samples, and among them coinfections with RLBV and RYNV (44.0%). Viruses of the raspberry mosaic complex, BRNV, RYNV and RLMV, including coinfections of 2-3 listed viruses along with RLBV, were found in a high joined proportion of 14.7% of all infected samples, i.e. 36.0% of mixed infected samples.

Proposed revision of the family Secoviridae taxonomy to create three subgenera, “Satsumavirus”, “Stramovirus” and “Cholivirus”, in the genus Sadwavirus

We present a taxonomic proposal for revision of the family Secoviridae, a taxon of plant viruses in the order Picornavirales. We propose the reorganization of the genus Sadwavirus to create three new subgenera and to update the classification of five existing species. The proposed subgenera are "Satsumavirus" (one species: Satsuma dwarf virus), "Stramovirus" (two species: Strawberry mottle virus and Black raspberry necrosis virus) and "Cholivirus" (two species: Chocolate lily virus A and Dioscorea mosaic associated virus).

Small-RNA analysis of pre-basic mother plants and conserved accessions of plant genetic resources for the presence of viruses

Pathogen-free stocks of vegetatively propagated plants are crucial in certified plant production. They require regular monitoring of the plant germplasm for pathogens, especially of the stocks maintained in the field. Here we tested pre-basic mother plants of Fragaria, Rubus and Ribes spp., and conserved accessions of the plant genetic resources of Rubus spp. maintained at research stations in Finland, for the presence of viruses using small interfering RNA (siRNA) -based diagnostics (VirusDetect). The advance of the method is that unrelated viruses can be detected simultaneously without resumptions of the viruses present. While no virus was detected in pre-basic mother plants of Fragaria and Ribes species, rubus yellow net virus (RYNV) was detected in pre-basic mother plants of Rubus. Raspberry bushy dwarf virus (RBDV), black raspberry necrosis virus (BRNV), raspberry vein chlorosis virus (RVCV) and RYNV were detected in the Rubus genetic resource collection. The L polymerase encoding sequence characterized from seven RVCV isolates showed considerable genetic variation. The data provide the first molecular biological evidence for the presence of RYNV in Finland. RYNV was not revealed in virus indexing by indicator plants, which suggests that it may be endogenously present in some raspberry cultivars. In addition, a putative new RYNV-like badnavirus was detected in Rubus spp. Blackcurrant reversion virus (BRV) and gooseberry vein banding associated virus (GVBaV) were detected in symptomatic Ribes plants grown in the field. Results were consistent with those obtained using PCR or reverse transcription PCR and suggest that the current virus indexing methods of pre-basic mother plants work as expected. Furthermore, many new viruses were identified in the collections of plant genetic resources not previously tested for viruses. In the future, siRNA-based diagnostics could be a useful supplement for the currently used virus detection methods in certified plant production and thus rationalize and simplify the current testing system.

Molecular detection and characterisation of black raspberry necrosis virus and raspberry bushy dwarf virus isolates in wild raspberries

AbstractVirus‐derived small interfering RNAs (siRNAs) were extracted from leaves of wild raspberries (Rubus idaeus) sampled from three different regions in Finland and subjected to deep sequencing. Assembly of the siRNA reads to contigs and their comparison to sequences in databases revealed the presence of the bipartite positive‐sense single‐stranded RNA viruses, raspberry bushy dwarf virus (RBDV, genus Idaeovirus), and black raspberry necrosis virus (BRNV, family Secoviridae) in 19 and 26 samples, respectively, including 15 plants coinfected with both viruses. Coverage with siRNA reads [21 and 22 nucleotides (nt)] was higher in BRNV‐FI (Finland) RNA1 (79%) than RNA2 (45%). In RBDV, the coverage of siRNA reads was 89% and 90% for RNA1 and RNA2, respectively. Average depth of coverage was 1.6–4.9 for BRNV and 16.5–36.5 for RBDV. PCR primers designed for RBDV and BRNV based on the contigs were used for screening wild raspberry and a few cultivated raspberry samples from different regions. Furthermore, the sequences of BRNV RNA1 and RNA2 were determined by amplification and sequencing of overlapping contigs (length 1000–1200 nt) except for the 3′ and 5′ ends of RNA1 and RNA2 covered by primers. RNA1 of the Finnish BRNV isolate (BRNV‐FI) was 80% and 86% identical to BRNV‐NA (USA) and BRNV‐Alyth (UK), respectively, whereas the identity of NA and Alyth was 79%. RNA2 of BRNV‐FI was 84% and 80% identical to BRNV‐NA and BRNV‐Alyth, respectively, whereas NA and Alyth were 82% identical. Hence, the strains detected in Finland differ from those reported in the UK and USA. Our results reveal the presence of BRNV in Finland for the first time. The virus is common in wild raspberries and nearly identical isolates are found in cultivated raspberries as well. The results show that wild raspberries in Finland are commonly infected with RBDV or BRNV or both viruses and thus are likely to serve as reservoirs of RBDV and BRNV for cultivated Rubus spp.

In vitro elimination of Black raspberry necrosis virus from black raspberry (Rubus occidentalis) - Short Communication

Black raspberry necrosis virus (BRNV) is one of the most important viral pathogens of Rubus spp. In this study, a procedure combining in vitro culture and heat therapy on axillary buds of Rubusoccidentalis was developed to eliminate BRNV from infected plants. Axillary buds were grown aseptically at 4-h alternating periods of 29°C and 38°C with 14-h day length for 1–5 weeks. Shoots induced after thermotherapy were tested for the viruses by RT-PCR. BRNV was not detected in any shoots indicating that BRNV was heat labile. BRNV-free shoots were rooted in vitro and acclimatized in greenhouse. Regenerated plants remained virus-free after 2-month acclimatization, 3-month dormancy and 5-month growth periods.  

Raspberry viruses manipulate the behaviour of their insect vectors

AbstractMany insect herbivores and plant pathogens influence each other via plant‐mediated mechanisms. Although there is speculation that these interactions may be important in structuring terrestrial food webs, few studies have empirically demonstrated the mechanisms by which pathogens manipulate the behaviour of their insect vectors. We investigated how infection of red raspberry, Rubus idaeus L. (Rosaceae), with two viral pathogens, black raspberry necrosis virus (BRNV) and raspberry leaf mottle virus (RLMV), affected the behaviour of their vector, the large raspberry aphid, Amphorophora idaei Börner (Hemiptera: Aphididae: Macrosiphini). As semi‐persistently transmitted viruses, comparatively little is known about how such viruses affect vector biology. We also examined the effect of infection on plant volatile emissions and amino acid content, which could drive changes in aphid behaviour and performance. Virus‐infected plants were initially more attractive to the aphid and the insects remained on infected plants for 30 min, but were found equally on uninfected plants 12 h after inoculation. Twenty‐seven volatile compounds were identified. Two green leaf volatiles were emitted at higher concentrations by infected plants: (Z)‐3‐hexenyl acetate and 2‐hexenal. In dose‐response assays, (Z)‐3‐hexenyl acetate was attractive to the aphid at concentrations of 50 ng ml−1. When reared on infected plants, aphids took more than 3 days longer to reach adulthood compared with those on uninfected plants, although the number of offspring remained the same. Soluble amino acid (essential and non‐essential) concentrations in raspberry leaves increased more than two‐fold with virus infection. Amino acid composition was dominated by glutamate, accounting for 64 and 77% of the total in uninfected and infected leaves, respectively. Excessive glutamate may have underpinned the negative effects of viral infection on aphid performance. These results demonstrate the capacity of viruses to alter their host plant to manipulate vector behaviour, which may have evolved to be consistent with the transmission requirements of the virus.

The complete sequence of a UK strain of black raspberry necrosis virus

The complete nucleotide sequence of a UK strain of the sadwavirus Black raspberry necrosis virus (BRNV) was obtained by amplification and sequencing of virus RNA from infected plants grown in a raspberry plantation in Aylth, Scotland. The RNA1 was 7,572 nucleotides (nt) in size and RNA2 was 6,350 nt in size, each excluding the 3' poly-A tail. The RNA1- and RNA2-encoded polyproteins are predicted to be processed into (RNA1) a protease cofactor, an RNA helicase, the VpG, a 3C-like protease, an RNA-dependent RNA polymerase and an AlkB protein, and (RNA2) a movement protein and two capsid proteins.

Aphid resistance in raspberry and feeding behaviour of Amphorophora idaei

The raspberry aphid Amphorophora idaei is a major pest of the raspberry plant and a vector of different viruses like Raspberry leaf mottle virus (RLMV), Raspberry leaf spot virus (RLSV), Black raspberry necrosis virus (BRNV) and Rubus yellow net virus (RYNV). Aphid resistant raspberry genotypes additionally show a reduced occurrence of viruses, thus the aim of this study was to investigate whether the feeding behaviour of A. idaei differs between aphid resistant and susceptible plants. In a biotest the cultivars (cvs.)‘Titan’,‘Rumiloba’,‘Nootka’,‘Schoenemann’,‘Williamette’ and‘Autumn Bliss’ show different levels of resistance. A significantly lower population was observed after 27 d on the resistant cvs.‘Rumiloba’ and‘Autumn Bliss’ in comparison to the other cultivars tested. The number of aphids on cv.‘Nootka’ was higher than on the resistant cultivars but significantly lower than on the susceptible cvs.‘Titan’,‘Williamette’ and‘Schoenemann’. The feeding behaviour was studied over a period of 12 h on plants of the cvs.‘Rumiloba’,‘Nootka’,‘Schoenemann’ and‘Autumn Bliss’ by using the electrical penetration graph (EPG) technique. Overall between 62% and 68% aphids tested per cultivar made probes on the leaves and penetrated into the phloem. On the resistant cv.‘Rumiloba’ the aphids started to probe considerably later (49.3 min) than on the other cultivars (12.1 to 33.1 min). In contrast, the first probe on‘Rumiloba’ was shorter (2.2 min) than on the resistant cultivars (23.9 to 63.5 min). On average the aphids attained the phloem on the susceptible cv.‘Schoenemann’ considerably earlier (221.1 min) than on the resistant cultivars (349.5 to 370.4 min). On the resistant cv.‘Nootka’ significant differences were found for the duration of phloem salivation (E1-pattern, 810.9 s in comparison to 24.3 to 176.9 s), the number of phloem salivation phases (2.7 in comparison to 0.1 to 0.2) and the number of phloem contacts before the sustainable phloem feeding (> 10 min) started (1.1 in comparison to 0.1 to 0.2). No differences were found between the cultivars for the number and duration of potential drops (cell penetrations) during the pathway to the phloem, analysed during the first 2 hours of the experiments. The obtained results indicate that the probing and feeding behaviour of A. idaei, which is responsible for virus transmission, is not sufficiently different between resistant and susceptible cultivars to be the reason for virus resistance.

Black raspberry necrosis virus. [Distribution map

Abstract A new distribution map is provided for Black raspberry necrosis virus. Hosts: Rubus spp. Information is given on the geographical distribution in Europe (France, Germany, Italy, Mainland Italy, Netherlands, Norway, Poland, Romania, Serbia, UK, Scotland), North America (Canada, British Columbia, USA, Michigan, Oregon, Pennsylvania, Tennessee, Wisconsin), Oceania (Australia, New Zealand).

PM 4/10(2): Certification scheme forRubus

Specific scopeThis standard describes the production of certified pathogen‐tested material ofRubus.Specific approval and amendmentFirst approved in 2004–09.Revised in 2009–09.

Biology of the European large raspberry aphid (Amphorophora idaei): its role in virus transmission and resistance breakdown in red raspberry

Abstract1 The European large raspberry aphid Amphorophora idaei Börner is the most important vector of viral diseases afflicting commercially grown red raspberry (Rubus idaeus L.) in Northern Europe, with European raspberry production amounting to 416 000 tonnes per annum. This review synthesizes existing knowledge on its biology and interactions with other organisms, including its host plant and the viral pathogens it vectors.2 Information about trophic interactions with other insect herbivores and natural enemies is reviewed. Vine weevils Otiorhynchus sulcatus compromise aphid resistance in some raspberry cultivars, increasing A. idaei abundance by 80%. Parasitoids show mixed success in parasitizing A. idaei, although Aphidius ervi attack rates more than doubled when A. idaei fed on a partially susceptible raspberry cultivar, compared with a resistant variety. These findings are discussed in the context of potential biological control as part of an integrated pest and disease management framework.3 Amphorophora idaei transmits four known viruses: Black raspberry necrosis virus, Raspberry leaf mottle virus, Raspberry leaf spot virus and Rubus yellow net virus, with A. idaei taking as little as 2 min to transmit some viruses.4 Existing control strategies, including resistant cultivars, insecticides and eradication of disease from parent plants, are described. In particular, strong selection pressures have resulted in A. idaei overcoming genetic resistance in many raspberry cultivars and most insecticides are now ineffective.5 Future directions for the sustained control of A. idaei are suggested, taking into consideration the possible effects of climate change and also changes in agronomic practices in U.K. agriculture.

First Report of Black raspberry necrosis virus in Rubus canadensis in Tennessee.

Symptoms that resembled virus infection were observed on several smooth blackberry (Rubus canadensis L.) plants in the Great Smoky Mountain National Park (GSMNP) during a project carried out in the summer and fall of 2006 as part of All Taxa Biodiversity Inventory (ATBI) activities (2). Diseased specimens showed chlorosis and mottling as well as deformation of younger leaves. Symptomatic leaves were collected, and preliminary screening by double-antibody sandwich (DAS)-ELISA did not detect Tobacco ringspot virus (TRSV), Tomato ringspot virus (ToRSV), Tomato spotted wilt virus (TSWV), Raspberry bushy dwarf virus (RBDV), or Impatiens necrotic spot virus (INSV) in these samples. Double-stranded RNA (dsRNA) extracted from symptomatic leaves of two diseased specimens (GSM-1 and GSM-2) revealed two bands with sizes estimated at 7.5 and 6.5 kb. Purified dsRNAs from specimen GSM-1 were used as a template to generate random-primed cDNA clones. Several clones were sequenced and analysis of approximately 3 kb of contiguous sequence (GenBank Accession No. EU419645) revealed the presence of a single open reading frame encoding a protein containing the complete proteinase and partial polymerase domains. BLAST analysis showed that the virus from R. canadensis shared 77 and 87% nucleotide and amino acid sequence identity, respectively, with the recently described putative sadwavirus Black raspberry necrosis virus (BRNV) (GenBank Accession No. NC_008182) (1), suggesting that this virus is a distinct isolate of BRNV. The virus shared a lower degree of identity with the analogous sequences of other viruses belonging to the genus Sadwavirus, with only 48 and 37% identity with Strawberry mottle virus (GenBank Accession No. NC_003445) and Satsuma dwarf virus (GenBank Accession No. NC_003785), respectively. To our knowledge, this is the first report of BRNV in GSMNP and Tennessee, indicating that it may be widespread in native Rubus spp. through the southeastern United States.

Identification, Characterization, and Detection of Black raspberry necrosis virus

ABSTRACT A serious disease was observed in black raspberry (Rubus occidentalis) in Oregon in the last decade. Plants showing mosaic symptoms declined rapidly and, in many cases, died after several years. Double-stranded RNA extraction from symptomatic black raspberry revealed the presence of two high molecular weight bands which were cloned and sequenced. Sequence analysis disclosed the presence of a novel virus that was tentatively named Black raspberry decline-associated virus (BRDaV). The complete sequences of the two genomic RNAs, excluding the 3' poly-adenosine tails, were 7,581 and 6,364 nucleotides, respectively. The genome organization was identical to that of Strawberry mottle virus, a member of the genus Sadwavirus. The C terminus of the RNA 1 poly-protein is unique within the genus Sadwavirus, with homology to AlkB-like domains, suggesting a role in repair of alkylation damage. A reverse-transcriptase polymerase chain reaction test was designed for the detection of BRDaV from Rubus tissue, and tests revealed that BRDaV was associated consistently with the observed decline symptoms. While this publication was under review, it came to our attention that scientists at the Scottish Crop Research Institute had molecular data on Black raspberry necrosis virus (BRNV), a virus that shared many biological properties with BRDaV. After exchange of data, we concluded that BRDaV is a strain of BRNV, a previously described yet unsequenced virus. The North American strain was vectored nonpersistently by the large raspberry aphid and the green peach aphid. Phylogenetic analysis indicates that BRNV belongs to the genus Sadwavirus.

VIRUS DISEASES OF RUBUS AND STRATEGIES FOR THEIR CONTROL

VIRUS DISEASES OF RUBUS AND STRATEGIES FOR THEIR CONTROL

Propagation, virus-screening and heat therapy of northern hemisphere imports ofRibes, Rubus, andVaccinium

Abstract In a plant quarantine station administered by the Department of Scientific and Industrial Research (DSIR) from 1954 to 1987, a system was developed whereby Ribes, Rubus, and Vaccinium plant material, imported from the northern hemisphere, was propagated and virus indexed in a little over 2 years with three simulated growing seasons. A virus indexing procedure, introduced in the early 1970s, showed that most cultivars were virus free. However, infections of cucmnber mosaic, raspberry bushy dwarf, black raspberry necrosis, raspberry vein chlorosis, and several unidentified viruses, were detected. Heat therapy was used to eliminate cucumber mosaic virus from cultivars of both Ribes and Rubus, and raspberry bushy dwarf virus and black raspberry necrosis virus from cultivars of Rubus. Tomato ringspot and tobacco streak were found in subsequent virus tests of earlier importations of Ribes and Rubus.

Propagation of black raspberry necrosis virus (BRNV) in mixed culture with solanum nodiflorum mottle virus, and the production and use of BRNV antiserum

SUMMARYThe concentration of particles of black raspberry necrosis virus (BRNV), which is normally extremely low in herbaceous plants, increased about 1000‐fold when Nicotiana clevelandii plants were inoculated with a mixture of BRNV and an unrelated virus, solanum nodiflorum mottle (SNMV). In sap from N. clevelandii infected with the mixed culture, BRNV infectivity survived dilution to 10˜4 but not 10˜5, and storage for 6 but not 8 days at 20 oC, for 6 but usually not 10 days at 4 oC and for more than 13 days at – 15 oC. When plants were inoculated with the mixed culture, BRNV induced typical symptoms in several Chenopodium species and infected several previously unreported hosts. Purified preparations of particles of the mixed culture contained only a small proportion of BRNV particles, which sedimented in sucrose density gradients as two components, one, probably non‐infective, of c. 505, and the other, infective, of 120‐130S. An antiserum prepared to purified particles of the mixed culture was cross‐absorbed with SNMV particles and used in indirect ELISA to detect BRNV in herbaceous plants infected with the mixed culture, and also in a wide range of Rubus species, cultivars and hybrids infected naturally, by grafting or by inoculation with the aphid Amphorophora idaei. The reliability of ELISA for detecting BRNV in raspberry leaves depended on the cultivar and time of year. Some cultivars, such as Glen Clova, had low concentrations of BRNV, which was detected reliably only in late spring/early summer, whereas other cultivars, such as Lloyd George and Mailing Enterprise, had greater BRNV concentrations.In small‐scale surveys in eastern Scotland, BRNV was detected by ELISA in many raspberry cvs, including some that contain major gene resistance to the vector, A. idaei; in five of nine raspberry stocks entered for the Standard grade certificate but in none of five stocks entered for the Stock Cane certificate; and in 40% of wild raspberry and 14% of wild bramble plants growing near commercial raspberry crops. The significance of these findings for the control of BRNV is discussed.

Effects of Raspberry Bushy Dwarf Virus on Yield and Cane Growth in Susceptible Red Raspberry Cultivars1

Abstract Virus-free (VF) plants of 6 cultivars of red raspberry (Rubus idaeus L.) were graft-inoculated with raspberry bushy dwarf (RBDV)-infected scions. Plants grown from root cuttings of the inoculated plants were established in a replicated field trial and their performance was compared with noninoculated plants for 4 years. ‘Haida’ and ‘Willamette’ did not become infected with the virus either by graft inoculation or by pollen transmission. The other cultivars, ‘Creston’, ‘Canby’, ‘Lloyd George’, and ‘Meeker’, were infected by graft inoculation. Moreover, after 4 years, all of the original VF plants of these cultivars were infected. Differences in virus effects between the original VF and RBDV-infected clones were greatest for ‘Meeker’ and least for ‘Creston’. Black raspberry necrosis virus (BRNV) was not associated with RBDV infection in Meeker although the cultivar is susceptible to the aphid vector of BRNV.