Submitted to: Acta Horticulturae
Publication Type: Proceedings
Publication Acceptance Date: 9/14/1998
Publication Date: N/A
Interpretive Summary: Plum spotted fruit is a disease which has been recently reported from Italy. In some orchards, more than 50% of the trees were affected. Diseased fruits are depreciated considerably in value. In Beltsville, we have characterized the infectious agent associated with the disease using recombinant DNA and polymerase chain reaction technologies as well as nucleotide sequence analyses. We have demonstrated that a strain of peach latent mosaic viroid (PLMVd) is associated with the disease. The nucleotide sequence of the Italian isolate of the viroid from plum is identical to that of a Romanian isolate characterized in our laboratory from infected, quarantined germplasm. Thus, in addition to peach, plum germplasm should also be tested for PLMVd in certification and quarantine programs world-wide.
Technical Abstract: A fruit disease of 'Angeleno' plum is described. The disease is characterized by the presence of a high number of discolored areas with an isodiametric shape (1-2 mm in diameter), irregular border, and scattered in an irregular manner on the fruit but more numerous in the petiole area. Discolored areas may merge to form spots 6-8 mm in diameter. The disease is widespread in the 'Angeleno' plum orchards of the Emilia-Romagna region of central Italy, affecting up to 50% in an orchard with as many as 60-70% of fruit showing disease symptoms. We propose the name "plum spotted fruit" to describe this disease. RT-PCR assays of nucleic acid extracts from diseased fruit using DNA primers specific for peach latent mosaic viroid (PLMVd)(Shamloul et al., 1995) revealed DNA fragments of the expected size which hybridized to PLMVd cRNA probe. Similar size products were also amplified from nucleic acid extracts of leaf and bark tissues from diseased plum trees. Nucleotide sequence analysis of cloned viroid molecules from infected plum trees indicated that the plum isolate of PLMVd is 338 nucleotides in length and is 92 % homologous to PLMVd isolates from peach. Identical nucleotide sequences were obtained with PLMVd plum isolates from Italy and Romania. The latter isolate was cloned and sequenced after transmission to Prunus tomentosa by grafting.