The Secretariat of the Pacific Community (SPC) has recently trained one of its staff on sweet potato virus diagnostics and elimination methods at the Queensland-based Gatton Research Station in the Australian Department of Employment, Economic Development and Innovation (DEEDI).Mr Amit Sukal, virus indexing research technician at the Centre of Pacific Crops and Trees (CePaCT) in SPC's Land Resources Division, attended a week of intensive training on sweet potato virus diagnostics and elimination methods.
'One of the major obstacles to sweet potato growth and production in the tropics is viral diseases, since it is a vegetatively propagated crop.'
'Viruses infecting sweet potato are spread and transmitted between cropping cycles by stem cuttings used as planting material.' He added that the viruses are also transmitted from one plant to another by sap-sucking insects such as aphids and white flies.
'Some viruses show very few or no symptoms at all, but they may still cause considerable yield reductions.'
'As more than 14 viruses have been reported to infect sweet potato, their diagnosis becomes a challenge. A combination of methodologies has to be used to ensure that all known viruses are detected,' Sukal said.
The one-week training focused on virus diagnostic methodologies, such as the use of indicator plants and the NCM-ELISA kit (a nitrocellulose membrane-enzyme-linked test), which the International Potato Centre designed. The kit can be used to test for ten viruses of sweet potato.
Due to low virus concentrations and the absence of symptoms from single infections in sweet potato by most viruses, grafting onto indicator plants is often required to boost concentration and detect viruses reliably.
Ipomoea setosa (Brazilian morning glory) is used as the indicator plant, as it is susceptible to most of the viruses infecting sweet potato.
Mr Sukal explained that sweet potato buds are grafted onto the I. setosa plantsand, if successful,the virus particles are transmitted from the sweet potato to I. setosa, which develops symptoms such as vein clearing, chlorotic spots, blistering, vein necrosis/necrotic spots, chlorosis/interveinal chlorosis and/or stunted growth, depending on the virus or virus combinations infecting the sweet potato.
Mr Sukal's attachment was supported by a project on validating and documenting a strategy for producing virus-free sweet potato material in Papua New Guinea (PNG). The project is funded by the Australian Centre for International Agricultural Research.
DEEDI staff have worked with partners to introduce and improve virus testing and planting material sanitation in PNG, which they hope to roll out to other Pacific Island countries and territories (PICTs).
Mr Sukal's training is expected to help CePaCT set up the sweet potato virus diagnostics protocols and procedures to facilitate the testing and safe exchange of sweet potato germplasm to PICTs and beyond.