An in vitro procedure to eradicate potato viruses X, Y, and S from Russet Norkotah and two of its strains

Summary: A tissue culture method was developed for the eradication of three important potato viruses, PVX, PVY, and PVS, from the Russet Norkotah variety and two of its strains (TXNS 112 and TXNS 278). The method combined the use of liquid medium, thermotherapy, and chemotherapy. Initially, virus-free plants were inoculated with PVX, PVY, and PVS and, after 10 d, tested quantitatively for virus titer by ELISA to determine the initial virus concentration. The apical tip and the roots were removed from the inoculated plants, and only stem sections from inoculated plants were cultured in liquid medium containing MS inorganic salts, vitamins, and ribavirin (40 M or 80 M). After 5 d, half of the plants were subjected to thermotherapy and half were kept at room temperature. At 6 wk, the uppermost node (5–7 mm) was removed and recultured, and plants were tested then and again after 6 wk using ELISA to identify the virus-free plants. Ribavirin alone eradicated the viruses from some plants; however, more virus-free plants were obtained when the treatments included heat. Additionally, thein vitro culture technique using liquid medium promoted rapid lateral shoot elongation and resulted in significantly faster plant production. Also this approach, which required less skilled labor, produced more plants than the meristem culture method for virus eradication. A detailed procedure for elimination of multiple viruses is described. This procedure resulted in production of more than 10% virus-free plants.