THERAPY CYCLING TO ELIMINATE HIGH-TITERED, MULTIPLE VIRUS INFECTION IN VITRO POT A TO PLANTLETS
A protocol for treatment of in vitro potato plantlets to eliminate systemic viruses was established. Efficiency decreased, however, for selected genotypes when a virus was high-titered and/or multiple viruses existed Modified nodal cutting (Mncs = < 0.5 mm) of the speciality potatoes 'Purple Fingers' infected with PVS, PVY, and PLRV and 'All Red" infected with PVS, PVx, and PLRV were established on a medium containing antiviral Ribavirin (20 mg/l) and subjected to 4-6 weeks thermotherapy. This cycle was repeated for clones testing positive by ELISA for more than one virus. After one therapy cycle, 14% of 'Purple Fingers' and 8% of 'All Red' plantlets tested were free from PVS, PVX, PVY, and PLRV. System inefficiency was primarily due to low elimination of PLRV which were 14% from 'Purple Fingers' and 13%from 'All Red'. Following the second cycle, 95% of 'Purple Fingers' and 64% of 'All Red' plantlets were virus free with 100% and 69% freedom for PLRV, respectively. A second therapy cycle was recommended to enchance system efficiency to eliminate recalcitrant viruses.