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Disease Note.

First Report of Potato Leafroll Virus in Ulluco (Ullucus tuberosus Caldas). C. Lizarraga, International Potato Center (CIP), Apartado 1558, Lima 100, Peru. M. Santa Cruz, and L. F. Salazar. International Potato Center (CIP), Apartado 1558, Lima 100, Peru. Plant Dis. 80:344. Accepted for publication 24 January 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0344B.

Ulluco (Ullucus tuberosus Caldas) is an Andean tuber crop often cultivated in close association with native potato (Solanum tuberosum L. subsp, andigena (Juz. & Buk.) Hawkes and other species) cultivars. Three hundred accessions from the ulluco in vitro germ plasm collection maintained at the International Potato Center (CIP) were tested by the double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) for potato viruses X, Y, S, Andean potato mosaic (APMV), and potato leafroll (PLRV). PLRV was detected in 5/189, 30/64, 3/4 and 21/40 accessions from Peru, Bolivia, Colombia, and Argentina, respectively, using gamma globulin for Andean PLRV isolate 029 and a commercial monoclonal conjugate (BIOREBA). Healthy ulluco plants grafted with the PLRV-positive Bolivian accession MH-295 became infected after 4 months, as determined by DAS-ELISA and the nucleic acid spot hybridization assay (NASH) using the probe pBR322-LR (donated by D. Baul-combe), routinely used for PLRV detection at CIP. The distribution of the virus in ulluco is irregular and samples must be collected from the upper, middle, and lower levels of the plant. None of the other potato viruses was detected in ulluco by DAS-ELISA. This is the first report of PLRV naturally infecting a tuber crop other than potato and it could have epi-demiological implications. The presence of PLRV in ulluco also supportsthe premise that viruses infecting one plant species can eventually become adapted to infect other species growing in close associations for extended periods of time.