PPRI GOS 03
Study of association of RSPaV-SY and GVB with Shiraz decline-affected Shiraz clone 99B
Goszczynski, D E Burger, J T
ARC Plant Protection Research Institute University of Stellenbosch. Department of Genetics
Goszczynski, D E
Burger, J T
Shiraz cultivar earns its popularity worldwide from the exceptional quality of the wine it produces. Recently, a new disorder severely affecting Shiraz plants has been observed in vineyards. The disorder is characterized by the development of swollen and cracked graft unions, followed by reddening of leaves. After peeling the bark away, deep grooves in the wood of the scion are observed. Progression of the symptoms leads to graft failure followed by death of the grafted plant in 4-10 years. This disorder does not affect the rootstock. The symptoms usually develop in 4-6-year-old grapevines but sometimes the disorder affects plants as young as 3 years old. The production and quality of fruit in declining plants is reduced to such an extent that vineyard replacement becomes necessary (Stamp, 2004). In South Africa, the disorder can be observed in vineyards planted with grapevine cv. Shiraz clone 99 imported from France (Spreeth, 2005).
Although Shiraz decline disorder was first discovered in France almost 16 years ago (Renault-Spilmont and Boursiquot, 2002), its exact cause is still unknown. Studies have failed to show any correlation between the disorder and climate, soil type, clone, rootstock or viral, bacterial or fungal pathogens. A new molecular variant of Rupestris stem pitting associated virus, RSPaV-SY, was identified in a Shiraz decline affected plant at the University of California laboratory, Davis, United States. (Lima et al., 2006). Positive PCR amplification of RNA from Shiraz decline-affected plants using primers specific to RSPaV-SY was also obtained by Habili et al. (2006). However, neither American nor Australian researchers have reported a clear-cut association between the RSPaV-SY variant and Shiraz decline. These results point to an urgent need to address the problem of this deadly disease of grapevines cv. Shiraz in different laboratories from all wine-producing countries.
My one-year study of Shiraz decline revealed that nucleus plant of Shiraz clone 99B (Vititec, KWV) is infected with viruses related to RSPaV-SY and GVB. Despite this intriguing finding, results of detection of RSPaV-SY and GVB in field-collected plants did not lead to clear-cut association of these viruses with the disease (see Research Report Gos-2). The results revealed, however, that Shiraz plants are infected with a population of extensively variable variants of GVB. GVB variants of five molecular groups were identified. This strongly suggests that some molecular variants of the virus may not be detected by standard RT-PCR (Habili and Symons 1999). The same may apply to RSPaV-SY.
Goszczynski, D E. 2007. Investigation of association of viruses of Viti-and Foveavirus genera with Shiraz disease and Shiraz decline in South Africa. Paper presented at the Syrah Vine Health Symposium. 6 November 2007, University of California, Davis, United States.
Goszczynski, D E. 2008. Detection of an extensively variable population of Apple stem pitting virus (ASPV) in grapevines cv. Shiraz clone 99B in South Africa. Paper presented at the International Syrah Symposium. 13-14 May, Lyon, France.
Goszczynski, D E. 2008. Flexi-viruses that were identified in clone 99B of grapevine cultivar Shiraz affected by Shiraz decline and clones 9C, 22B and 22F free of this disease in South Africa, using analysis of sequences amplified by RT-PCR based on degenerate primers for simultaneous detection of members of the Foveavirus and Vitivirus genera. Presentation at the Winetech Information Day. 19 September, Stellenbosch, South Africa.
2010. Rugose wood-associated viruses do not appear to be involved in Shiraz decline in South Africa, Archives of Virology, Mnth Sep v. 155 (9) (p. 1463-1469)
Goszczynski, D E. 2007. Investigation of association of viruses of Viti- and Foveavirus genera with Shiraz disease and Shiraz decline in South Africa, IN: Proceedings of the Syrah Vine Health Symposium. (p. 5-7) 6 November 2007, University of California, California, Unites States.
2008. Detection of an extensively variable population of Apple stem pitting virus (ASPV) in grapevines cv. Shiraz clone 99b in South Africa, IN: Proceedings of the International Syrah Symposium. (p. 118-120) 13-14 May,
Noach, L C. 2010. The molecular characterisation of South African isolates of grapevine Rupestris stem pitting associated virus. MSc (Genetics) University of Stellenbosch, Stellenbosch, South Africa.