Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 19, 1999
Publication Date: N/A
Interpretive Summary: Potato spindle tuber viroid (PSTVd) is a common and serious pathogen in the growing areas of several countries, however, many countries consider PSTVd to be a phytosanitary risk. In some countries where it occurs, seed potatoes must be grown in a production system shown to be free of PSTVd. PSTVd is readily transmitted through botanical seed and pollen of potato and is easily mechanically transmitted during cultivation. PSTVd is also insect transmitted in double infections with potato leafroll virus, having important implications for disease spread. Primary control of the disease is by the prevention of the introduction of infected materials into the field. We have identified and report for the first time the occurrence of PSTVd in the principal potato production region of Costa Rica. This report has important phytosanitary and marketability implications for the Costa Rican potato industry and the information will be of use to scientists, producers, and action agencies who are concerned with phytosanitary certification and prevention of yield losses to the disease caused by PSTVd.
During 1997-1998, symptoms of leaf roll, dwarfism, chlorosis and occasional leaf necrosis were observed on Solanum tuberosum cultivars Atzimba, Floresta, Idiafrit and Birris, in several plots in Cartago, the principal potato production region of Costa Rica. Because of the known association between potato leafroll virus (PLRV) and viroids, and previous reports of PLRV in Costa Rica, the presence of potato spindle tuber viroid (PSTVd) was suspected. Leaf samples from 120 symptomatic potato plants were collected from 10 different plots. Total nucleic acids (TNAs) were extracted and purified from collected symptomatic samples and six healthy potato controls. TNAs were spotted onto nylon membranes and hybridized to a DIG-labeled DNA probe specific for PSTVd. Of the 120 symptomatic plants, 61 were positive for PSTVd by dot blot hybridization. TNAs from twelve positive potato samples were used to inoculate Lycopersicum esculentum cv. Super Marmande. Eleven of twelve inoculated tomato plants showed symptoms of dwarfism, leaf deformation and grayish foliage, often with a dull surface. TNAs were extracted from inoculated tomato and hybridized to the PSTVd probe. All inoculated plants were positive for PSTVd by dot blot hybridization. This is the first report of PSTVd in Costa Rica.