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PVY research in South Africa
ELISA testing for Potato virus Y (PVY), Potato Leaf Roll Virus (PLRV) and bacterial wilt (caused by Ralstonia solanacearum) infection in seed potatoes has been performed by the commercial potato growers association, Potatoes South Africa, for some 30 years now in an attempt to limit the spread of these pathogens. Although this has helped to control PVYand PLRV infections in South Africa, global warming has lead to an increase in aphid vectors and consequently higher infection rates in recent years. As a result, Potatoes South Africa have funded research aimed at the identification of aphid vectors, assessing aphid populations over different seasons and in different regions, and viral strain variation of PVY and PLRV.
The South African team of the PVY Wide Organization consists of Anel Espach and Marietta Botha of the Coen Bezuidenhout Seed Testing Centre, Pretoria, who perform routine disease testing for Potatoes South Africa. Viral testing is also performed at six other testing centres spread over South Africa. ELISA tests are performed for potato viruses and bacterial wilt and the results obtained are used in a disease certification scheme to supply disease free potato tubers to the South African farmer. Future realtime PCR testing is currently in the planning phases.
Other members of the South African team of the PVY Wide Organization are Chris Visser (Ph D student) and Prof Dirk Bellstedt of the Department of Biochemistry, University of Stellenbosch, Stellenbosch (near Cape Town). Dirk heads the South African team and is a specialist in antibody- and nucleic acid-based detection technologies and phylogenetic analysis.
From our research based on coat protein gene sequencing conducted in the period from 2003 to 2008 we have established which strains of PVY are present in South Africa (see publication). We have found that the current tendencies of viral evolution in South Africa are very similar to what is seen in Europe and the USA in that recombinant strains such as PVYWilga and in particularly PVYNTN have largely replaced the older PVYO and PVYN strains. Although imports of potato material are strictly regulated and are largely limited to tissue culture material, it is highly likely that these recombinant strains have been imported into South Africa. Currently our research is focussed on an in depth analysis of PVY evolution of South African strains by whole genome sequencing of isolates which we will follow up with biological testing on specific potato cultivars. Thanks to the establishment of the PVWide Organization we plan to contribute our whole genome sequences to a world-wide sequence data base in an effort to better understand global evolution of PVY.
We have used our large coat protein sequence database of PVY and PLRV coat protein sequences of South African isolates to develop realtime RT-PCRs for the detection of PVY and PLRV infection. All potato tissue culture material in South Africa has now been screened with these tests and newly imported material is also screened with these tests. An ELISA for Ralstonia solanacearum detection was developed in Prof Bellstedt’s laboratory and is supplied to the SA potato industry for the screening and certification of all potato mother tuber material in South Africa. Prof Bellstedt also collaborates with Prof Johann Burger of the Genetics Department, University of Stellenbosch on grape vine virus evolution.
Selected publications:
Bellstedt, D.U. Enzyme-linked immunosorbent assay detection of Ralstonia solanacearum in potatoes: the South African experience. (2009) In Methods in Molecular Biology, Volume 508: Plant pathology, techniques and protocols, in press, pp. 51-62, The Humana Press, New Jersey, USA.
Visser, J. C. and D. U. Bellstedt (2009) An assessment of molecular variability and recombination patterns in South African strains of Potato virus Y. Archives of Virology 154, 1891-1900.
Jooste A. E. C., H. J. Maree. D. U. Bellstedt, D. E. Goszczynski, G. Pietersen and J. T. Burger (2010) Three genetic Grapevine leafroll-associated virus-3 (GLRaV-3) variants identified from South African vineyards show high variability in their 5’UTR. In press, Archives of Virology.
Liebenberg, A., M-J. Freeborough, C. J. Visser, D. U. Bellstedt and J. T. Burger (2009) Genetic variability within the coat protein gene of Grapevine fanleaf virus isolates from South Africa and the evaluation of RT-PCR, DAS-ELISA and ImmunoStrips as virus diagnostic assays. Virus Research, 142, 28-35.
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Head of the team: Dirk Bellstedt
dub()sun.ac.za
University of Stellenbosch
Department of Biochemistry
7602 Stellenbosch
South Africa
Tel: +27 21 8085840
Fax: +27 21 8085863
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