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Detection of Potato Spindle Tuber Viroid in Avocado Growing in Peru. M. QUERCI, The International Potato Center (CIP), P.O. Box 1558, Lima, Peru. R. A. OWENS, USDA-ARS, Molecular Plant Pathology Laboratory, Plant Sciences Institute, Beltsville, MD 20705; C. VARGAS, Estacion Exp. Agric. Inst. Nac. Inv. Agrop. La Molina, Lima, Peru; and L. F. SALAZAR, The International Potato Center (CIP). Plant Dis. 79:196-202. Accepted for publication 4 October 1994 . This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1995. DOI: 10.1094/PD-79-0196.

Potato spindle tuber viroid (PSTVd) was detected in avocado trees growing at several locations in Peru by using nucleic acid spot hybridization assays. A viroidlike nucleic acid with a mobility similar to that of PSTVd was also found by return polyacrylamide gel electrophoresis analysis of RNA extracted from several trees, and a mild strain of PSTVd was recovered from Nicandra physalodes inoculated with leaf sap from affected avocados. Sequence analysis of cDNAs obtained using the polymerase chain reaction with primers to PSTVd indicated the presence of three different sequence variants of PSTVd in the avocado trees. The PSTVd infections were often latent, but some trees coinfected with avocado sunblotch viroid showed symptoms that included bunchiness of the inflorescence, decrease in both fruit size and number, and eventual decline and death. This is the first report of the isolation of PSTVd from a natural host other than potato.