EN
Tomato torrado virus, ToTV, is a serious pathogen of tomato causing strong necrosis on leaves and fruits, and of whole plants, leading to permanent wilting, being a cause of crops reduction. In Poland, three isolates of the ToTV were identified so far: Wal’03, Kra and Ros differing in their pathogenicity, showing that Kra and Wal’03 are the most extreme. The aim of our work was to determine whether a degree of the aggressiveness of the pathogen correlates with virus accumulation in host’s cells. Using real-time PCR approach we analyzed the relative and absolute expression of ToTV in Nicotiana benthamiana and Solanum lycopersicum plants. Analysis based on the standard curve method showed that the copy number of Kra is almost 10 000-fold higher than Wal’03 isolate in tomato tissue, whereas in tobacco, the results were normalized to reference gene: ß-actin, indicating 4-fold higher concentration of Kra in relation to Wal’03. The obtained results showed that Kra isolate was present in plants at a higher concentration that suggests its elevated replication rate responsible for higher aggressiveness.