Combined ribavirin treatment and cryotherapy for efficient Potato virus M and Potato virus S eradication in potato (Solanum tuberosum L.) in vitro shoots

Abstract

Potato germplasm held as field collections accumulate virus infections, making them unsuitable for distribution as planting stock. Elimination of these viruses from in vitro cultures provides healthy materials for germplasm distribution. An in vitro collection of 33 potato cultivars and hybrids was evaluated for five viruses: Potato leafroll virus (PLRV), Potato virus M (PVM), Potato virus S (PVS), Potato virus X (PVX), and Potato virus Y (PVY) by ELISA and RT-PCR. PLRV was not detected in any accessions. Seven accessions were singly infected by PVM, 15 were mix-infected by PVM and PVS, and four by PVM and PVY. One accession had both PVS and PVX, and one was mix-infected by PVM, PVS, and PVY. Two accessions were singly infected by PVY, and three were virus-free. Cryotherapy, chemotherapy, and a combination of both methods were tested on several potato accessions. For cryotherapy of shoot tips, the PVS2-vitrification protocol was used. Chemotherapy using prolonged culture with 100 mg L−1 ribavirin on PVM and PVS eradication was investigated both alone and combined with cryotherapy. Cryotherapy alone eliminated single PVM infection in 38.6% of shoot cultures, but totally virus-free shoots were not found in mix-infected accessions. Treatment with ribavirin alone was only effective for eliminating both PVM and PVS after three subcultures on ribavirin, or ribavirin followed by cryotherapy. Three subcultures on ribavirin followed by cryotherapy resulted in 100% virus-free potato shoots. Future studies will include cultivars infected with PVX and PVY. This is the first report of combined chemo- and cryotherapy for virus elimination in potato.