Detection of potato spindle tuber viroid in avocado growing in Peru:

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.

Querci, M., Owens, R.A., Vargas, C., and Salazar, L.F. 1995. Detection of potato spindle tuber viroid iin avocado growing in Peru. Plant Dis. 79, 196-202.