Viruses are also a major constraint to potato production and yield losses are between 60% and 80%, especially when seed potatoes are infected. Potato virus Y, genus Potyvirus, belonging to the largest plant virus family, Potyviridae and Potato leaf roll virus, a luteovirus, are among the most important viruses of potatoes. Different strains of PVY including the tuber necrotic strain of Potato virus Y (PVYNTN) are prevalent in South Africa. PVYNTN causes tuber necrotic ringspot disease on the surface of the tubers, and the internal blemishes. This disease has an economic impact on all the potato market sectors. Viruses such as Potato virus A, Potato virus X, Potato virus S, Tomato spotted wilt virus etc. are some of the viruses reported to infect potatoes in South Africa.
The ARC-VIMP conducts research to investigate and characterize known, emerging and novel viruses of sweet potato, potato and cassava crops. Techniques such as the antibody-based enzyme linked immunosorbent assay (ELISA), nucleic-acid methods such as reverse transcription polymerase chain reaction (RT-PCR) and PCR are used. This also includes DNA sequencing of part of the virus genome and the use of High throughput sequencing. The work also includes routine diagnostics of viruses for both smallholder, emerging and commercial farmers, in order to assist with the implementation of management strategies to prevent loss of quality and yield.
Identification and genetic characterization of viruses of sweet potato.
Sweet potato is prone to virus infections, which are associated with substantial yield and quality loss. Recent research at the Agricultural Research Council (ARC) has shown that mixed infections of viruses have a detrimental effect on sweet potato production. Virus-free planting material can yield 20 to 25 t/ha while infected material can only yield 1 to 4 t/ha, if multiple virus species are involved. Viruses of sweet potato are mostly restricted to members of the genus Ipomoea, which includes the morning glory and sweet potato. Viruses occur naturally worldwide in sweet potatoes and more than one virus species can be found infecting a single sweet potato plant. Sweet potato feathery mottle virus, Sweet potato virus C, Sweet potato virus 2, Sweet potato virus G, Sweet potato chlorotic stunt virus, Sweet potato leaf curl virus etc. are among other viruses that threaten sweet potato production in South Africa (Mulabisana et al. 2015). As a vegetative propagated crop, viruses are carried from one crop cycle to the next through stem cuttings that are used as planting material. Field trials at the ARC showed that the marketable yield of almost all tested cultivars were severely reduced by a combination of above viruses. In trial 1 yield loss was between 67% (Ribbok) and 98% (Bophelo) and in trial 2 between 58% (Ribbok) and 100% (Bophelo, Blesbok, Bosbok) (Mulabisana et al., 2019).
The ARC-VIMP conducts research to investigate and characterize known, emerging and novel viruses of sweet potato, potato and cassava crops. Techniques such as the antibody-based enzyme linked immunosorbent assay (ELISA), nucleic-acid methods such as reverse transcription polymerase chain reaction (RT-PCR) and PCR are used. This also includes DNA sequencing of part of the virus genome and the use of High throughput sequencing. The work also includes routine diagnostics of viruses for both smallholder, emerging and commercial farmers, in order to assist with the implementation of management strategies to prevent loss of quality and yield.
Contact: Dr Julia Mulabisana, Dr Michele Cloete and Kenneth Mabasa.
References:
Mulabisana, J., Cloete, M., Mabasa, K., Laurie, S.M., Oelofse, D., Rey, M.E.C. 2015. Genetic characterization of viruses infecting sweet potato in South Africa. Acta Horticulturae 1105: 155-161. ISHS. DOI 10.17660/ActaHortic.2015.1105.22.
Mulabisana, M.J., Cloete, M., Laurie, S.M., Mphela, W., Maserumule, M.M., Nhlapo, T.F., Cochrane, N.M., Oelofse, D., Rey, M.E.C. 2019. Yield evaluation of multiple and co-infections of begomoviruses and potyviruses on sweet potato varieties under field conditions and confirmation of multiple infection by NGS. Crop Protection 119: 102-112. doi: https://doi.org/10.1016/j.cropro.2019.01.009.
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