Recent studies on Grapevine red blotch virus
Recent studies have brought new knowledge on the causative role of Grapevine red blotch virus (Grablovirus, GRBV – EPPO Alert List) in the red blotch disease of grapevine and on its geographical distribution.
- Fulfilment of Koch’s postulates
The etiological role of GRBV in red blotch disease of grapevine (Vitis vinifera) was investigated in the USA. Inoculation experiments demonstrated the causative role of GRBV in red blotch disease and the Koch’s postulates were fulfilled. In these studies, it is stressed that in North America, GRBV is causing severe losses. For example, its economic impact was estimated to range from 8 855 to 69 548 USD per hectare over a 25-year lifespan of a Cabernet Sauvignon vineyard in Napa Valley, California. In an infected vineyard in California, it was also observed that the disease incidence increased by 1 to 2% every year. It is finally noted that in the USA, some states are in the process of revising their certification programmes to include GRBV (Yepes et al., 2018).
- First detection in India
In India, GRBV has been detected in symptomless grapevine plants (Vitis vinifera) growing in Jind, Punjab. This is the first time that this GRBV is detected in India (Marwal et al., 2018).
- Absence in Switzerland
In Switzerland, surveys were conducted in the three major grape-growing regions (Valais, Vaud, Ticino) to determine the possible presence of GRBV. In total, 3062 plants were tested by PCR and all results were negative, thus suggesting that GRBV is absent from Swiss vineyards. Studies were also carried out in the grapevine virus collection at Nyon, which includes predominantly Swiss grapevine accessions but also international ones. Results showed that 6 accessions were infected by GRBV, all originating from the USA (some present since the 1980s). The absence of spread of GRBV in the grapevine collection for more than 30 years indicated the lack of vector or contact transmission. As a precautionary measure, all accessions infected with GRBV were eliminated from the collection. During these studies, it was also observed that GRBV had clear detrimental effects on grapevine physiology (vine vigour, leaf chlorophyll content, gas exchange) and fruit quality. The authors concluded that GRBV should be included in certification or quarantine programmes to avoid its dissemination (Reynard et al., 2018).
Sources
Marwal A, Kumar R, Khurana SMP, Gaur RK (2018) Complete nucleotide sequence of a new geminivirus isolated from Vitis vinifera in India: a symptomless host of Grapevine red blotch virus. VirusDisease. https://doi.org/10.1007/s13337-018-0477-x
Reynard JS, Brodard J, Dubuis N, Zufferey V, Schumpp O, Schaerer S, Gugerli P (2018) Grapevine red blotch virus: absence in Swiss vineyards and analysis of potential detrimental effect on viticultural performance. Plant Disease 102(3), 651-655.
Yepes LM, Cieniewicz E, Krenz B, McLane H, Thompson JR, Perry KL, Fuchs M (2018) Causative role of grapevine red blotch virus in red blotch disease. Phytopathology 108(7), 902-909.