Prunus necrotic ringspot virus (PNRSV) is a rose and stone fruit tree pathogen. Three different PNRSV isolates, originating from three rose cultivars were studied. These PNRSV isolates were characterized using molecular techniques. Nearly the complete nucleotide sequence (1,630 nucleotides) of RNA3 of the isolate PNRSV-R1 has been determined (GenBank Acc. No. DQ003584). The sequence of the MP gene of the PNRSV-R1 isolate was determined, the first such results for a rose-derived PNRSV isolate. The reaction of PNRSV infection on test plants was also investigated. Cucumis sativus cv. Wisconsin, Cucurbita maxima cv. Buttercup and Cucurbita pepo cv. Melonowa _ Zółta appeared to be the most useful test plants for the differentiation of isolate-specific pathogenicity.

Prune dwarf virus (PDV), a worldwide pathogen of stone fruit trees, has many isolates with different biological, serological and molecular properties. Monoclonal antibodies (MAbs) to the Prunus mahaleb isolate of PDV were used to investigate the serological variability of virus isolates, by TAS-ELISA (triple antibody sandwich enzyme-linked immunosorbent assay). The twenty-two PDV isolates from Germany (1), Italy (7), Poland (13) and the USA (1) were characterised against eight single MAbs. The virus showed high serological variability. Analysis of the MAbs reaction allowed for the identification of 13 serogroups.