Quantification of two Potato virus Y strains in single and mixed infections by RT-qPCR highlights its epidemiological landscape in Brazil

ABSTRACT Potato virus Y (PVY) is recognized as one of the most common and destructive pathogens seriously affecting potato producing areas worldwide. More recently PVYNTN and PVYN:O/N-Wi, have emerged as the main strains present in the PVY infected plants detected in Brazilian potato fields. In this study, samples of potato collected in south part of Minas Gerais - Brazil were first tested by DAS-ELISA and then by RT-PCR multiplex in order to discriminate the PVY strains. Afterward, part of them was tested by RT-qPCR to confirm and quantify the viruses in infected tissues. The sensitivity of the techniques for detecting PVY isolates present in the sampled locations was investigated, as well as the occurrence of mixed infections, aiming to understand the general epidemiological picture of this pathogen in potato producing fields. In the multiplex RT-PCR test, the samples with O and N serotypes were identified as infected with PVYNTN and PVYN:O/N-Wi strains. When tested by RT-PCR for amplification of PVYE, 41 samples (67,2%) were positive, having a characteristic electrophoretic profile for this recombinant strain, and 9 isolates were also observed with atypical patterns for recombinant PVYE. The best technique to detect mixed infection was RT-qPCR, with the concentration of PVYNTN being much higher than that of PVYN:O/N-Wi. These results show the importance of using the most suitable method for the diagnosis and surveying of PVY strains in crop fields and reveal, for the first time, the dissemination of PVYE recombinants to several Brazilian potato fields. RESUMO O Potato vírus Y (PVY) é reconhecido como um dos patógenos mais comuns e destrutivos que ocorre nas áreas produtoras de batata em todo o mundo. Recentemente a PVYNTN e a PVYN:O/N-Wi emergiram como as principais estirpes presentes nos campos de batata brasileiros. Neste estudo, amostras de batata provenientes do Sul de Minas Gerais foram testadas inicialmente por DAS-ELISA e RT-PCR multiplex para discriminar as estirpes de PVY. Posteriormente, parte deste material foi testada por RT-qPCR para confirmar e quantificar os vírus nos tecidos infectados. Foi investigada a sensibilidade das técnicas para detecção de isolados de PVY presentes nos locais amostrados, bem como a ocorrência de infecções mistas, visando entender o quadro epidemiológico geral deste patógeno nos campos produtores de batata. No teste RT-PCR multiplex, as amostras com sorotipos O e N foram identificadas como infectadas pelas estirpe