Strawberry vein banding virus
(vein banding of strawberry)

Reports of the occurrence of SVBV before 1995 have been based exclusively on the disease symptoms. Nucleic acid-based detection techniques (polymerase chain reaction and western hybridization) confirmed the presence of SVBV infection in samples from the USA (western type), Germany, Norway, the Czech Republic, Slovakia and Federal Republic Yugoslavia.

In Germany, old references are based on symptoms that might be strawberry vein banding. The German experts on strawberry viruses at the Landesanstalt für Pflanzenschutz in Stuttgart have never detected it. Mráz et al. (1996) detected SVBV in plants obtained from Germany.

In Norway, Mráz et al. (1996) detected SVBV in Danish strawberry plants (cv. Mimek) introduced to Norway for scientific purposes. Danish authorities report that the virus has never been detected in strawberry plants, inside or outside the compulsory certification system.

SVBV is listed as an A2 quarantine pest by EPPO (OEPP/EPPO, 1978) and is also of quarantine significance for IAPSC. The most important factors in evaluating the potential of SVBV in a new area are the presence of aphid vectors and their mobility. Because of the range of vector species, conditions can be defined only in so far as they affect aphids in general. For example, extremely low winter temperatures killing overwintering nymphs and adults; windy climates restricting activity of alatae.

Phytosanitary Measures

EPPO (EPPO, 1990) recommends that importing countries can require that Fragaria ananassa plants for planting, from countries where the pest occurs, should be derived from mother plants tested and found free from SVBV during the last three growing seasons and should have been maintained under conditions preventing their reinfestation; the consignment must come from a field found free (in the immediate vicinity) of the virus during the last growing season.

 

SVBV is known to occur only on species of Fragaria. The main host is Fragaria vesca (wild strawberry). Commercial strawberries may also be infected, but diagnostic symptoms are usually only apparent when Strawberry latent C virus is present simultaneously (EPPO/CABI, 1996). The garden burnet (Sanguisorba minor) has been established as a symptomless experimental host by graft inoculation and by the dark strawberry aphid vector Chaetosiphon jacobi (Mullin et al., 1980).
 

Acyrthosiphon pelargonii, Amphorophora rubi, A. idaei, Aphis idaei, A. rubifolii, Aulacorthum solani, Chaetosiphon fragaefolii, C. jacobi, C. tetrarhodum, C. thomasi, Macrosiphum rosae, M. pelargonii, Myzus ascalonicus, M. ornatus and M. persicae are vectors of SVBV. Of these, Chaetosiphon species are the most efficient vectors in glasshouse experiments, although other genera are probably important vectors when they occur in large numbers and frequently move from plant to plant. Aphids can acquire and transmit the virus in 30-120 minutes, but persistence in the vector is short, usually less than 8 h (semi-persistent type). There are differences in the efficiency of clonal lines of aphids, and evidence that some species will transmit only certain strains of SVBV. Aphis gossypii, A. fabae, Aulacorthum solani and Macrosiphum euphorbiae failed to transmit the virus in a limited number of trials.

SVBV is transmissible by grafting and by Cuscuta subinclusa. Attempts to transmit SVBV mechanically have been unsuccessful. The incubation period in the indicator host varies from 2 to 5 weeks depending on the strain.

 

Diagnosis must usually be made or confirmed by use of virus-free Fragaria vesca indicator plants. Research in California, USA, has shown that the F. vesca clone UC-6 and the F. virginiana clone UC-12 are superior for detecting and diagnosing SVBV. A modified leaf grafting technique is used (Frazier, 1974). F. vesca semperflorens Alpine is also a very sensitive diagnostic indicator clone for this virus (Frazier and Morris, 1987). An ELISA test can be performed using Cauliflower mosaic virus antisera (Morris et al., 1980; Honetslegrová et al., 1995). However, routine serological detection requires the production of an SVBV-specific antiserum. A combination of polymerase chain reaction (PCR) and southern blotting gives the best results: PCR alone can produce unclear or smeared bands in some samples. Treating PCR products with the corresponding SVBV probe clearly discriminates positive and negative samples. An amount of nucleic acid corresponding to 2 µg (50 µg) of fresh plant tissue could be detected in PCR (or in southern blots, respectively) (Mráz et al., 1999). Nucleic acid isolation from fresh plant tissue was the best template for PCR, and primers amplifying the shortest product should be recommended (Petrzik et al., 1998a). For further information on diagnosis and quantification of SVBV using molecular approaches, see Mahmoudpour (2004). Zhang et al. (2009) were able to detect SVBV using multiplex RT-PCR.

Vaskova et al. (2004) developed an assay for the detection of SVBV in Fragaria spp. based on nuleic acid sequence based amplification (NASBA) and real-time detection using molecular beacons (real-time NASBA). When compared with biological indexing and a PCR-based detection method, the assay was found to offer a fast, sensitive and reliable approach to the routine diagnosis of strawberry stock material. 

Visual examination of the symptoms of SVBV on commercial cultivars on strawberry is not reliable.

 

Phylogenetic data carried out on the amino acid sequence of the ORF V reveals that SVBV shows a close relationship to Cauliflower mosaic virus, Figwort mosaic virus and Carnation etched ring virus (Petrzik et al., 1998b).

A serological relatedness between SVBV and some Cauliflower mosaic virus isolates has been reported (Morris et al., 1980).

 

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

There are no specific control measures. SVBV is highly resistant to inactivation by heat therapy but it can be eliminated from plants by means of meristem tip culture. As a consequence, the use of certified planting material is the best control procedure, and certification schemes for the production of healthy planting material of strawberry are in operation in several EPPO countries. EPPO is at present (November 2000) preparing an internationally acceptable certification scheme for strawberries. Control of aphids with insecticides could reduce the incidence of the disease.

Elimination of the virus from mother plants by runner tip culture (Miller and Belkengren, 1963) or by heat treatment for 10 days at 42°C (Bolton, 1967) has been reported. The elimination of the type strain of SVBV from experimentally infected Hood plants by meristem tip culture was 100% whether or not the plants were preheat treated for 6 weeks at 37°C (Mullin and Schlegel, 1978). In these tests, the cultured plants were indexed and discarded after 6 months. This could prove to be an insufficient incubation period for cloned meristems, as some dahlia plants similarly treated to eliminate Dahlia mosaic virus remained symptomless for up to 10 months (Mullin and Schlegel, 1978).