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Etiology

Detection of the Mild Strains of Potato Spindle Tuber Viroid from Single True Potato Seed by Return Electrophoresis. R. P. Singh, Agriculture Canada Research Station, P.O. Box 20280, Fredericton, New Brunswick, Canada E3B 4Z7; A. Boucher, and J. E. A. Seabrook. Agriculture Canada Research Station, P.O. Box 20280, Fredericton, New Brunswick, Canada E3B 4Z7. Phytopathology 78:663-667. Accepted for publication 24 November 1987. Copyright 1988 Department of Agriculture. Government of Canada. DOI: 10.1094/Phyto-78-663.

A modified procedure of return polyacrylamide gel electrophoresis (R-PAGE) was used to detect mild strains of potato spindle tuber viroid (M-PSTV) from single true potato seeds (TPS). Seed lots obtained from field-grown PSTV-infected potato plants varied in their PSTV content. The viroid was detected in both dormant and germinated individual TPS. Dormant TPS contained approximately 0.8–10 ng of viroid RNA per seed. PSTV was detected by R-PAGE in nucleic acid extracts of single seed, diluted to 1:16 (about 500 pg). Germinated seed and TPS seedlings grown in vitro at 19 C showed similar rates of seed transmission. There was no change in PSTV detection in TPS seedlings grown for 4–10 wk. In composite samples of infected and healthy TPS, PSTV was detected when one infected TPS was combined with 90–100 healthy seeds. PSTV detection by R-PAGE was comparable or superior to that obtained by nucleic acid hybridization.