Selective chemotherapy on Grapevine leafroll-associated virus-1 and -3

Different chemotherapeutic strategies on closely correlated phytoviruses, such as Grapevine leafroll-associated virus-1 (GLRaV-1) and -3(GLRaV-3), were tested in the same host in order to investigate selective chemotherapy of virus infections in plants. To eradicate these viruses from grapevine in vitro explants, antiviral treatments using heat or chemical drugs such as inosine monophosphate dehydrogenase (IMPDH) inhibitors (ribavirin, tiazofurin), purine biosynthesis inhibitors (6-thioguanine) and neuraminidase inhibitors (oseltamivir) were conducted. Phytotoxicity assay and thermal stress tests were performed before treatments; viruses were detected using ELISA and reverse transcriptase–polymerase chain reaction (RT-PCR). All chemicals were able to produce virus-free explants, but showed significantly different sanitation rates considering virus type. For GLRaV-1, higher sanitation rates were obtained using IMPDH inhibitors: 72.0% eradication was obtained upon administration of an exclusive inhibitor such as tiazofurin and 40.0% when using ribavirin. The most effective drugs against GLRaV-3 did not belong to IMPDH inhibitors: 78.0% virus-free explants were obtained using a neuraminidase inhibitor and 75.1% explants were sanitized using a purine biosynthesis inhibitor. Conversely, heat treatments showed similar efficacy against both viruses, achieving more than 55.0% virus-free explants, with a nonselective effect between GLRaV-1 and GLRaV-3. These findings suggest how highly correlated viruses could be differentiated in virus-specific events that are linked to selective chemotherapy of virus infections. However, virus-specific events that can influence chemical treatment generating selectivity did not seem to interfere with physical treatment.