Disease Note.

An Isolate of Potato Virus X Infecting Potato in Nigeria. A. M. Mih, International Livestock Center for Africa, P.O.Box 5689 Addis Ababa, Ethiopia. G. I. Atiri, Dept, of Agric. Biology, University of Ibadan, Nigeria H. W. Rossel, IITA, PMB 5320, Ibadan, Nigeria. Plant Dis: 79:83. Accepted 30 September 1994. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0083C.

An isolate of potato virus X (PVX) was identified in the first survey of potato (Solanum tuberosum L.) viruses in Nigeria. Host range studies showed that the virus infected species mainly in the family Solanaceae, usually causing very mild symptoms. Gomphrena globosa L., Chenopodium amaranticolor Coste & Reyn., and C. quinoa Willd. were also infected locally, while Citrullus lanatus (Thunb.) Matsum. & Nakai, Abelmoschus esculentus (L.) Moench, and Sesamum indicum L. were each infected systemically. The purified virus had a nucleoprotein-like absorption spectrum with a trough at 244 nm and a peak at 256 nm. The Amax/Amin and A260/A280 ratios (uncorrected for light scattering) were 1.095 ± 0.005 and I.578 ± 0.024, respectively. Homologous antiserum had a litre of 1/256 in lube precipitin test. Antibodies and alkaline phosphatase conjugate detected PVX in field-infected potato samples by DAS-ELISA. This PVX isolate is probably different from the resistance-breaking strain (PVXHB) from Bolivia that failed to incite local lesions in G. globosa (1). The relationship between our isolate and other commom PVX isolates was confirmed with monoclonal antibodies from Canada. PVX has not been previously reported from any crop in Nigeria, and might have been introduced along with potato, especially as regulatory schemes were not yet developed. Although the virus caused only mild symptoms in potato, it is potentially important in Nigeria since, as was observed in this survey, it causes more severe diseases when in mixed infection with other viruses such as PVY. This neccesitates emphasis on potato seed health testing in the production process.