HIGH-INCIDENCE OF TRANSMISSION AND OCCURRENCE OF A VIROID IN COMMERCIAL SEEDS OF COLEUS IN CANADA

A survey of 16 ornamental plants indicated widespread infection of Coleus scutellarioides with a viroid similar to that reported in Coleus from Brazil and of goldfish (Hypocyrta mummularia) plants with a new viroid. Because Coleus plants in Canada originated from seeds obtained from Japan, the United States, and European countries, attempts were made to determine if the viroid was transmitted through the Coleus seed. The viroid from Coleus was transmissible to Ocimum sanctum plants by mechanical and graft inoculation but not through the seeds. Seeds produced by infected Coleus plants tested by return-polyacrylamide gel electrophoresis (R-PAGE) contained the viroid, however. The viroid was detected in dormant (about 325-mu-g) as well as in sprouted single seeds. Transmission rates were 71.4% in sprouted seed and 67.3% in seedlings. The viroid was present in the flower parts and endosperm of Coleus but not in the seed coat. The viroid could have been introduced into Canada by infected seeds imported from the United States, seeds that probably were produced in Costa Rica. Infection rates in seed lots from four commercial sources of Coleus ranged from 16 to 68%. The Coleus viroid was not transmissible to potato (Solanum tuberosum) or tomato (Lycopersicon esculentum) plants by mechanical or grafting inoculation.