First report of potato leafroll luteovirus in ulluco (Ullucus tuberosus Caldas).
Ulluco (U. tuberosus) is an Andean tuber crop often cultivated in close association with native potato cultivars. Three hundred accessions from the ulluco in vitro germplasm collection maintained at the International Potato Center (CIP) were tested by DAS-ELISA for several potato viruses. 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 monoclonal conjugate. Healthy ulluco plants grafted with the PLRV-positive Bolivian accession MH-295 became infected after 4 months, as determined by DAS-ELISA. Nucleic acid spot hybridization assay using the probe pBR322-LR was used routinely for PLRV detection at CIP. The distribution of the virus in ulluco was irregular and samples must be collected from the upper, middle and lower levels of the plant. This is the first report of PLRV naturally infecting a tuber crop other than potato.