Viruses associations with plants often lead to growth and yield limiting disease symptoms, ultimately leading to economic losses and continue to pose a threat to food security, especially in the developing world. As there are no products which can be applied to plants in the field to control viral diseases in a manner equivalent to fungicides to control fungal diseases, control of viral diseases is generally achieved by the use of resistant plants or by controlling the spread of the virus between plants. In order to do this the epidemiology of the disease must be understood and control interventions applied at strategic points in the disease cycle. The Plant Virology Group focuses on determining the epidemiology and population dynamics of known viruses as well as the discovery of novel plant viruses and implementation of appropriate diagnostic assays for their detection. The plants under study are diverse and include species of agricultural importance and potential reservoir hosts, as well as native species. The majority of known plant viruses are associated with crops, however, even with important crop species, the associated viral diversity is likely to be grossly underestimated. While it is becoming apparent that not all plant virus infections result in severe, growth-limiting symptoms, especially on wild hosts, these viruses may pose a threat to agricultural crops through host jumps, leading to emerging viral diseases. Recent advances in DNA sequencing technologies have allowed for a paradigm shift for the discovery of novel plant virus diversity, as well as reshaping existing ideas of viral evolution and the interactions with their hosts.

Since the discovery of the first plant viruses, thousands of species have been characterised, a significant proportion of which have been characterised with the aid of metaviromics. In the last decade close to 500 new viruses have been recognised, with the genomic data of hundreds of “unclassified” viruses being deposited into public databases.  However, the number of viruses that are officially recognised has been described as the tip of the iceberg and it is only recently that plant virologists are starting to appreciate the diversity of viruses as they are beginning to emerge at an alarming rate from wild hosts and their spread exacerbated by a surge in the global trade of plants. 

In terms of public health, economics and virological research, SARS-CoV-2, which causes COVID-19, is arguably one of the most important viruses of the last century. The importance of the pandemic that has infected over 100 000 000 people cannot be understated. However, the fact that 822 000 000 people are currently facing food insecurity due to the effects of pests and diseases, 40% of which are viruses should not be dismissed. Therefore, at a time when food security on the African continent is coming under increasing threat from pests and diseases, including disproportionate pressure from plant viruses when compared with the developed world, increased surveillance and diagnostic development for their detection is crucial. The Plant Health Centre, being developed as part of Innovation Africa @UP, has identified capacity building within this space as critically important. Members of the Plant Virology Group are committed building the research and services we offer government and industry partners as part of FABI and Innovation Africa @UP’s Plant Health Centre.



New Publications

David A Read, Elrea Strydom, Bernard Slippers, Emma Steenkamp, Gerhard Pietersen. (2022) Genomic characterization of soybean blotchy mosaic virus, a cytorhabdovirus from South Africa. Archives of Virology 10.1007/s00705-022-05526-3
Otlotleng Moloto, Gerhard Pietersen, Dirk Swanevelder, Genevieve Thompson, David Read. (2022) First report of grapevine polerovirus 1 in South Africa. Australasian Plant Disease Notes 17(1) 10.1007/s13314-022-00459-x
David A. Read, Genevieve D. Thompson, Nathan Le Cordeur, Dirk Swanevelder, David Read. (2022) Genomic characterization of grapevine viruses N and O: novel vitiviruses from South Africa. Archives of Virology 10.1007/s00705-021-05333-2
Read DA, Thompson GD, Swanevelder D, Pietersen G. (2021) Detection and diversity of grapevine virus L from a Vitis cultivar collection in Stellenbosch, South Africa. European Journal of Plant Pathology 10.1007/s10658-021-02380-y
Read DA, Roberts R, Swanevelder D, Pietersen G, Thompson GD. (2021) Novel viruses associated with plants of the family Amaryllidaceae in South Africa. Archives of Virology 10.1007/s00705-021-05170-3
Read DA, Roberts R, Thompson GD. (2021) Genomic characterization of two novel viruses infecting Barleria cristata L. from the genera Orthotospovirus and Polerovirus. Archives of Virology 10.1007/s00705-021-05150-7
Welgemoed T, Pierneef R, Read DA, Schulze SE, Pietersen G, Berger DK. (2020) Next generation sequencing reveals past and current widespread occurrence of maize yellow mosaic virus in South Africa. European Journal of Plant Pathology 158(1):237-249. 10.1007/s10658-020-02070-1
Roberts R, Pietersen G. (2016) A novel subspecies of ‘Candidatus Liberibacter africanus’ found on native Teclea gerrardii (Family: Rutaceae) from South Africa. Antonie van Leeuwenhoek :1-8. 10.1007/s10482-016-0799-x
Kleynhans J, Pietersen G. (2016) Comparison of multiple viral population characterization methods on a candidate cross-protection Citrus tristeza virus (CTV) source. Journal of Virological Methods 237:92-100. 10.1016/j.jviromet.2016.09.003
Read DA, Pietersen G. (2016) PCR bias associated with conserved primer binding sites, used to determine genotype diversity within Citrus tristeza virus populations. Journal of Virological Methods 237:107-113. 10.1016/j.jviromet.2016.09.004
New SA, van Heerden SW, Pietersen G, Esterhuizen LL. (2016) First report of a Turnip Yellows virus in association with the Brassica Stunting Disorder in South Africa. Plant Disease 100(11):2341. 10.1094/PDIS-12-15-1443-PDN
Lin H, Pietersen G, Han C, Read DA, Lou B, Gupta G, Civerolo EL. (2015) Complete genome sequence of “Candidatus Liberibacter africanus,” a bacterium associated with Citrus Huanglongbing. Genome Announcements 3(4):e00733-15. 10.1128/genomeA.00733-15 PDF
Read DA, Pietersen G. (2015) Genotypic diversity of Citrus tristeza virus within red grapefruit, in a field trial site in South Africa. European Journal of Plant Pathology 142(3):531-545. 10.1007/s10658-015-0631-x
Roberts R, Steenkamp ET, Pietersen G. (2015) Three novel lineages of ‘Candidatus Liberibacter africanus’ associated with native rutaceous hosts of Trioza erytreae in South Africa. International Journal of Systematic and Evolutionary Microbiology 65:723-731. 10.1099/ijs.0.069864-0
Zablocki O, Pietersen G. (2014) Characterization of a novel citrus tristeza virus genotype within three cross-protecting source GFMS12 sub-isolates in South Africa by means of Illumina sequencing. Archives of Virology 159(8):2133-2139. 10.1007/s00705-014-2041-3
Almeida RPP, Daane KM, Bell VA, Blaisdell GK, Cooper ML, Herrbach E, Pietersen G. (2013) Ecology and management of grapevine leafroll disease.. Frontiers of Microbiology 4(94):1-13. 3389/fmicb.2013.00094 PDF
Pietersen G, Spreeth N, Oosthuizen T, Van Rensburg A, Van Rensburg M, Lottering D, Rossouw N, Tooth D. (2013) A case study of control of Grapevine Leafroll Disease spread at a commercial wine estate in South Africa. American Journal of Enology and Viticulture 64:296-305. 10.5344/ajev.2013.12089 PDF
Scott KA, Hlela Q, Zablocki ODJ, Read DA, Van Vuuren SP, Pietersen G. (2013) Genotype composition of populations of Citrus tristeza virus grapefruit cross-protecting GFMS12 in different host plants and aphid-transmitted sub-isolates. Archives of Virology 158(1):2-37. 10.1007/s00705-012-1450-4 PDF
Walsh HA, Pietersen Gerhard. (2013) Rapid detection of Grapevine leafroll-associated virus type 3 using a reverse transcription loop-mediated amplification method. Journal of Virological Methods 194:308-316. PDF
Phaladira MNB, Viljoen R, Pietersen G. (2012) Widespread occurrence of “Candidatus Liberibacter africanus subspecies capensis” in Calodendrum capense in South Africa. European Journal of Plant Pathology 124:39-47. PDF
Rey MEC, Ndunguru J, Berrie LC, Paximadis A, Berry S, Cossa N, Nuaila VN, Mabasa KG, Abraham N, Rybicki EP, Martin DP, Pietersen G, Esterhuizen L. (2012) Diversity of Dicotyledenous-Infecting Geminiviruses and Their Associated DNA Molecules in Southern Africa, Including the South-West Indian Ocean Islands.. Viruses 4(9):1753-1791. 10.3390/v4091753 PDF
Jooste AEC, Pietersen G, Burger JT. (2011) Distribution of grapevine leafroll associated virus-3 variants in South African vineyards. European Journal of Plant Pathology 131(3):371-381. PDF
Kruger K, De Klerk A, Douglas-Smit N, Joubert J, Pietersen G, Stiller M. (2011) Aster yellows phytoplasma in grapevines: identification of vectors in South Africa. Bulletin of Insectology 64:S137-S138. PDF
Van Vuuren SP, Cook G, Pietersen G. (2011) Lack of Evidence for Seed Transmission of . Plant Disease 95(8):1026-1026. 10.1094/pdis-02-11-0104 PDF
Jooste A, Maree H, Bellstedt D, Goszczynski D, Pietersen G, Burger J. (2010) Three genetic grapevine leafroll-associated virus 3 variants identified from South African vineyards show high variability in their 5'UTR. Archives of Virology :1-10. PDF
Lamprecht RL, Kasdorf GGF, Stiller M, Staples SM, Nel LH, Pietersen G. (2010) Soybean blotchy mosaic virus, a New Cytorhabdovirus Found in South Africa. Plant Disease 94(11):1348-1354. 10.1094/pdis-09-09-0598 PDF
Pietersen G, Arrebola E, Breytenbach JHJ, Korsten L, Le Roux HF, La Grange H, Lopes SA, Meyer JB, Pretorius MC, Schwerdtfeger M, Van Vuuren SP, Yamamoto P. (2010) A Survey for . Plant Disease 94(2):244-249. 10.1094/pdis-94-2-0244
De Graca JV, Pietersen G, Van Vuuren SP. (2009) Research on HLB in South Africa. Phytopathology 99:S157.
Doddapaneni H, Liao H, Lin H, Bai X, Zhao X, Civerolo EL, Irey M, Coletta-Filho H, Pietersen G. (2008) Comparative phylogenomics and multi-gene cluster analyses of the Citrus Huanglongbing (HLB)-associated bacterium 'Candidatus Liberibacter'. BMC Research Notes 1(75) PDF
Lamprecht R, Pietersen G, Kasdorf G, Nel L. (2008) Characterisation of a proposed Nucleorhabdovirus new to South Africa. European Journal of Plant Pathology 123(1):105-110. 10.1007/s10658-008-9339-5 PDF
Meyer JB, Kasdorf GGF, Nel LH, Pietersen G. (2008) Transmission of activated-episomal Banana streak OL (badna)virus (BSOLV) to cv. Williams banana (Musa sp.) by three mealybug species. Plant Disease 92(8):1158-1163.
Saccaggi DL, Ger K, Pietersen G. (2007) A multiplex PCR assay for the simultaneous identification of three mealybug species (Hemiptera: Pseudococcidae). Bulletin of Entomological Research 98:27-33. PDF
Stewart K, Pietersen G. (2007) Dynamics and molecular characterization of citrus tristeza virus (CTV) strains within the South African GFMS 12 cross-protecting population. South African Journal of Science 103(1-2):II-II.
Pietersen G. (2004) Spread of grapevine leafroll disease in South Africa-a difficult but not insurmountable problem. Wineland (South Africa)
Pietersen G, Morris J. (2002) Natural occurrence of groundnut ringspot virus on soybean in South Africa. Plant Disease 86(11):1271.
Pietersen G, Smith MF. (2002) Tomato yellow leaf curl virus resistant tomatoes show resistance to Tomato curly stunt virus. Plant Disease 86(5):528-534.
Jooste AEC, Pietersen G, Kasdorf GGF, Goszczynski DE. (2001) Identification of three viruses from Pisum sativum in South Africa. African Plant Protection 7(2):59-65.
Pietersen G, Idris AM, Kruger K, Brown JK. (2000) Characterization of Tomato curly stunt virus: a new tomato-infecting begomovirus from South Africa. Plant Pathology 57(5):809-818. 10.1111/j.1365-3059.2008.01882.x PDF
Pietersen G, Idris AM, Kruger K, Brown JK. (2000) Tomato curly stunt virus, a New Begomovirus of Tomato Within the Tomato yellow leaf curl virus-IS Cluster in South Africa. Plant Disease 84(7):810-810. 10.1094/pdis.2000.84.7.810b
Cook G, Kasdorf GGF, Pietersen G. (1999) Synopsis of a virus survey on groundnut in South Africa. African Plant Protection 5(1):1-3.
Cook G, Miranda JR, Roossinck MJ, Pietersen G. (1999) Tobacco streak ilarvirus detected on groundnut in South Africa. African Plant Protection 5(1):13-19.
Higgins CM, Cook G, Pietersen G, Dietzgen RG. (1999) Molecular characterisation of a strain of peanut stripe potyvirus from groundnut germplasm imported into South Africa. African Plant Protection 5(1):5-12.
Cook G, Rybicki EP, Pietersen G. (1998) Characterization of a new potyvirus isolated from peanut Arachis hypogaea. Plant Pathology 47(3):348-354.
Pietersen G, Staples MS, Kasdorf GGF, Thomas JE. (1998) First report of cucumber mosaic cucumovirus subgroup 1 in South Africa, from banana with infectious chlorosis. Plant Disease 82(10):1171. PDF
Pietersen G, Staples SM, Kasdorf GGF, Jooste AEC. (1998) Relative abundance of soybean viruses in South Africa. African Plant Protection 4(2):65-70.
Goszczynski DE, Kasdorf GGF, Pietersen G. (1997) Production and use of an antiserum to grapevine virus B capsid protein purified from SDS-polyacrylamide gels. Vitis 36(4):191-194.
Liu L, Tonder TV, Pietersen G, Davies JW, Stanley J. (1997) Molecular characterization of a subgroup I geminivirus from a legume in South Africa. Journal of General Virology 78(8):2113-2117.
Goszczynski D, Kasdorf G, Pietersen G, Tonder H. (1996) Grapevine leafroll-associated virus 2 (GLRaV-2)- mechanical transmission, purification, production and properties of antisera, detection by ELISA. South African Journal for Enology and Viticulture 17(1)
Goszczynski DE, Kasdorf GGF, Pietersen G, Tonder HV. (1996) Detection of two strains of grapevine leafroll-associated virus 2. Vitis 35(3):133-135.
Goszczynski DE, Kasdorf GGF, Pietersen G. (1996) Western blots reveal that grapevine viruses A and B are serologically related. Journal of Phytopathology 144(11-12):581-583.