Elimination of a new ampelovirus (GLRaV-Pr) and Grapevine rupestris stem pitting associated virus (GRSPaV) from two Vitis vinifera cultivars combining in vitro thermotherapy with shoot tip culture

A new virus species designated as Grapevine leafroll associated virus-Pr (GLRaV-Pr), which is classified in a distinct phylogenetic group of the genus Ampelovirus (Closteroviridae), was recently characterized from Greek grapevine cultivars. Elimination studies of GLRaV-Pr were carried out in two grapevine cultivars, ‘Mantilaria’ and ‘Prevezaniko’, co-infected with Grapevine rupestris stem pitting associated virus (GRSPaV, Flexiviridae). Both viruses were detected by nested RT-PCR assays. Virus elimination was achieved by combining in vitro thermotherapy with meristem (≤0.2 mm) or shoot tip culture (≤0.5 cm). The survival and regeneration rate of meristems was very low. On the other hand, high survival rates were observed in the cultured shoot tips accompanied with high elimination rates for both viruses. Data obtained in this study indicate that virus elimination depends on the genotype of grapevine. The results confirmed that sanitation is easier for species of the Closteroviridae family than for GRSPaV, whereas it seems that eradication of GLRaV-Pr and GRSPaV is feasible even with larger plant tissue parts if combined with an appropriate thermotherapy profile in vitro.