DETECTION OF POTATO SPINDLE TUBER VIROID IN AVOCADO GROWING IN PERU

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