Detection of Potato Viruses X and Y in Sap Extracts by a Modified Indirect Enzyme-Linked Immunosorbent Assay on Nitrocellulose Membranes (NCM-ELISA). Charlotte Lizarraga, Research Assistant, International Potato Center, Aptdo. 5969, Lima, Peru. E. N. Fernandez-Northcote, Virologist, International Potato Center, Aptdo. 5969, Lima, Peru. Plant Dis. 73:11-14. Accepted for publication 27 June 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0011.

Potato virus X (PVX) and potato virus Y (PVY) were detected in sap extracts from potato leaves by a modified indirect form of enzyme-linked immunosorbent assay on nitrocellulose membranes (NCM-ELISA). The procedure used monoclonal antibodies (MAs) originating from hybridoma clone C-9 for PVY and from clones 58, 59, and 67 for PVX. These MAs performed well in NCM-ELISA, reacting with similar virus and strain specificity in direct or indirect forms of ELISA. Sensitivity of NCM-ELISA was similar to that obtained with the direct double antibody sandwich form of ELISA when 10 and 200 ?l of sap extracts, respectively, were used. Addition of 0.02 M disodium ethylenediaminetetraacetate in the extraction buffer increased sensitivity of NCM-ELISA. PVY was detected satisfactorily on NC membranes spotted with PVY-infected samples, sent airmail to Lima, Peru, from Guatemala, Brazil, and Uruguay, as well as on those kept locally at room temperature up to 20 wk before processing. The simplicity of this NCM-ELISA procedure allows its use in modestly equipped laboratories.