Saez-Vasquez, J.; Theoduloz, C.; Poblete, F. Contreras, A.; Hubert, E.; Meza-Basso, L. Programa de Biología Vegetal, Facultad de Recursos Naturales, Universidad de Talca, Casilla 747 Talca, Chile.Four clones of the Chilota Potato Collection from the germplasm bank of the Universidad Austral de Chile, with potential combined resistance to PVX, PVY and PVS, were mechanically inoculated with these viruses in order to demonstrate wether they were truly resistant or not. Virus coat protein in the inoculated clones was determined by means of NCM-ELISA, DAS-ELISA, Western Blot and NASH. Two of the four inoculated clones were resistant to both PVY and PVS. This information will allow the utilization of these two clones in plant breeding programs.