Correlation of potato virus S and virus M contents of potato meristem tips with the percentage of virus-free plantlets produced in vitro

Using sensitive Dot-ELISA, potato virus 8 (PVS) and potato virus M (PVM) contents per single potato meristem tip of 4-leaf primordia were determined, and were correlated with the percentage of virus-free plantlets obtained by meristem-tip culture preceded by chemo- and thermotherapy of the plants. Treatment of PVS-infected cv. Majestic plants for 26 days at 35 degrees C resulted in 85% of the meristems having less than 10 pg of virus, and 89% of the derived progenies were similarly virus-free. When stem cuttings were dipped for 15 days in various chemicals, the mixture of 5 mg/l ribavirin + 5 mg/l DHT was the most effective. For cvs Majestic and Primura, 90 and 72% of the meristems had less than 10 pg of virus, and resulted in 74 and 67% virus-free progenies respectively. In PVM infection of the two cultivars, the same mixture yielded 70 and 66% meristems with less than 10 pg of virus, and 69 and 68% virus-free progenies.