Disease Note.

Occurrence of Peach Latent Mosaic Viroid in Commercial Peach and Nectarine Cultivars in the U.S. L. J. Skrzeczkowski, Department of Plant Pathology, Washington State University, Prosser 99350 . W. E. Howell, and G. I. Mink. Department of Plant Pathology, Washington State University, Prosser 99350. Plant Dis. 80:823. Accepted for publication 13 May 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0823A.

Peach latent mosaic viroid (PLMVd) was detected in field- and greenhouse-grown peach and nectarine cultivars obtained from various growing regions of the U.S. The viroid originally described in Spain (1) was recently reported to be distributed worldwide (2). This prompted a survey of peach and nectarine cultivars collected from Virginia, Colorado, Oregon, California, and Washington. Our detection procedure was based on dot-blot hybridization using a cRNA probe developed by Shamloul et al. (2). Isolate D168 of PLMVd (1), obtained under permit from France and propagated on GF305 rootstock, served as a positive control for biological assay and for hybridization. Negative controls included healthy GF305 peach and several viroids other than PLMVd. A total of over 1,000 trees from the field and 291 trees grown in screenhouses were tested. Over 50% of the trees were infected with PLMVd. PLMVd was detected in trees of both peach and nectarine from all states but not in plants of four other Prunus species (P. tomentosa Thunb., P. salicina Lindl., P. avium (L.) L., and P. serrulata Lindl.) from Washington. The viroid was detected in leaf petioles, stem pieces, and dormant buds. This is the first report of PLMVd in commercial varieties of peach and nectarine grown in these states.