Development of an in vitro procedure to eradicate potato viruses X, Y, and S from the potato (Solanum tuberosum L.) variety Russet Norko two of its strains

Abstract

A tissue culture method was developed for the eradication of three of the most important potato viruses': PVX, PVY, and PVS from the Russet Norkotah variety and two of its strains (TXNS 278 and TXNS 112). 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 days, tested quantitatively for virus titer by ELISA, to determine the initial concentration of the viruses. The apical tip and the roots were removed from the inoculated plants, and only the stem was planted without any support in liquid medium containing MS inorganic salts, vitamins, and ribavirin (40 pM or 80 pM). Plants were maintained under standard growing conditions for 5 days. Half of the plants were then subjected to heat treatment (16 h day length at 35'C and 8 h night at 33'C) , while the remaining plants were kept at room temperature (16 h day length and 8 hours night at 25'C) . After six weeks, the uppermost node (5-7 mm) was removed and transplanted onto a solid medium containing MS and vitamins. Plants were tested using ELISA to identify the virus free plants. Six later a second ELISA test conf irmed that the plants still free. weeks were Ribavirin alone eradicated the viruses from some plants; however, more virus f ree plants were obtained when the treatments included heat. The use of liquid medium enhanced plant growth and also allowed production of more than 5 plants per treated stem, rather than the single plant that is normally obtained by the use of meristems or the nodal cutting method. This procedure is also less time consuming, and required little expertise, compared to the meristem culture method to obtain virus-free plants. A detailed procedure for elimination of multiple viruses is described which resulted in production of more than 10% virus-free plants.