Incidence and molecular characterization of potato leaf roll virus in seed potato production in Serbia

The distribution and frequency of potato leaf roll virus in the four most important potato growing regions in Serbia were studied during the seven years (2012–18). One hundred randomly collected potato tubers were sampled from each seed lot. The young leaves that developed in three weeks were sampled and tested to record infection rate. The presence of potato leaf roll virus was detected by double-antibody sandwich enzyme-linked immunosorbent assay and disease incidence was calculated using standard formula. The obtained result showed that the highest prevalence of potato leaf roll virus was detected from seed potato samples originated from the Raški region during 2018 (20.7%), while in the Moravički region, only 2.3–11.1% of the potato leaf roll virus was detected every year. The average annual potato leaf roll virus infection was the highest in 2012 (8.4%) and 2018 (8.0%). For further confirmation of potato leaf roll virus infection, reverse transcription (RT)-PCR was performed using specific primers PLRVCPvEcoRI /PLRVCPcNcoI, designed to amplify a 650 bp fragment of the full-length coat protein gene. The PCR products derived from 26 isolates were directly sequenced using the same primer pair as in RT-PCR. The coat protein sequence analysis revealed that the Serbian potato leaf roll virus isolates showed very low nucleotide diversity (95.9–100%). They shared the highest nt identities of 98.08–99.36% with the sequences of potato leaf roll virus isolates deposited in the GenBank from other parts of the world. Phylogenetic analysis and the haplotype network of the coat protein gene sequences showed that the Serbian potato leaf roll virus isolates could be classified in two different groups indicating two possible introductions of the virus to Serbia. The results of this study confirmed the importance of potato leaf roll virus in seed potato production in Serbia. Additionally, this research highlights the need for a continuous monitoring of the potato seeds produced in Serbia as well as imported seeds for the presence of potato leaf roll virus