VIEW ARTICLE

Disease Detection and Losses

Detection of Potato Spindle Tuber Viroid in Field-Grown Potatoes by an Improved Electrophoretic Assay. M. A. Pfannenstiel, Research assistant, Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706; S. A. Slack(2), and L. C. Lane(3). (2)Associate professor, Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706; (3)Assistant professor, Department of Plant Pathology, University of Nebraska, Lincoln 68583. Phytopathology 70:1015-1018. Accepted for publication 23 April 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-1015.

An improved polyacrylamide gel electrophoresis (PAGE) procedure was developed for more efficient detection of potato spindle tuber viroid (PSTV). Modification in sample preparation permitted sample processing in 3 hr and completion of PSTV detection in one day. Inclusion of xylene cyanole, which comigrates with PSTV in gels, eliminated confusion due to the occasional appearance of extraneous RNA bands or uneven migration in individual gels. Photography of gels stained with ethidium bromide and illuminated with ultraviolet light enhanced PSTV detection. Reliability of the procedure was investigated by assaying 14 cultivars of field-grown potatoes (Solanum tuberosum) at monthly intervals. When potatoes were grown from infected tubers, PSTV was detected in all assays. Detection of current-season infections increased from 20% at 1 mo to 70% at 2 mo postinoculation. In current-season infections, PSTV detection was not affected by different PSTV strains (mild or severe). The concentration of PSTV in stem apices of the 14 cultivars varied from 0.64 to 2.20 μg per gram of tissue and was not correlated with symptom severity.