OCCURRENCE OF STONE FRUIT VIRUSES IN PLUM ORCHARDS IN LATVIA

To evaluate the occurrence of nine viruses infecting Prunus a large-scale survey and sampling in Latvian plum orchards was carried out. Occurrence of Apple mosaic virus (ApMV), Prune dwarf virus (PDV), Prunus necrotic ringspot virus (PNRSV), Apple chlorotic leaf spot virus (ACLSV), and Plum pox virus (PPV) was investigated by RT-PCR and DAS ELISA detection methods. The detection rates of both methods were compared. Screening of occurrence of Strawberry latent ringspot virus (SLRSV), Arabis mosaic virus (ArMV), Tomato ringspot virus (ToRSV) and Petunia asteroid mosaic virus (PeAMV) was performed by DAS-ELISA. In total, 38% of the tested trees by RT-PCR were infected at least with one of the analysed viruses. Among those 30.7% were infected with PNRSV and 16.4% with PDV, while ApMV, ACLSV and PPV were detected in few samples. The most widespread mixed infection was the combination of PDV+PNRSV. Observed symptoms characteristic for PPV were confirmed with RT-PCR and D strain was detected. Comparative analyses showed that detection rates by RT-PCR and DAS ELISA in plums depended on the particular virus tested. The results obtained in this study revealed that commonly grown plum cultivars in Latvia are infected with economically important stone fruit viruses and highlight the need to implement a programme to produce and propagate virus-free planting material.