Effect of thermotherapy duration, virus type and cultivar interactions on elimination of potato viruses X and S in infected seed stocks
African Journal of Plant Science
Virus infection in potato reduces yield through seed degeneration. This can be reduced by use of virusfree seed tubers. However, novel approaches are required to ensure availability of virus-free stocks, especially in developing countries where the seed potato system are evolving. Consequently, a laboratory experiment was conducted at Kachwekano ZARDI in Uganda to evaluate and determine appropriate procedures for cleaning valuable potato cultivars infected with the most prevalent potato
... lent potato viruses; potato virus X (PVX) and potato virus S (PVS) which are frequent in the potato farming system. Thus, 20 in-vitro potato plantlets from cultivars Victoria, Kinigi and Rwangume each batch infected with either PVX or PVS in three replicates were grown in a thermotherapy chamber for two, three and four weeks at 37 to 40°C in 16 h of light and 30 to 34°C for 8 h of darkness per day. An equal number plantlets and replicates of the same cultivars and virus infection combinations were grown in a standard tissue culture (TC) growth room at 16 to 18°C with 16 h of light without thermotherapy as controls. Results indicated that plantlet survival after in-vitro thermotherapy decreased with increasing duration of heat treatment. Virus elimination efficiency significantly (P ≤ 0.05) differed between heattreated plantlets and the controls but not between the duration of thermotherapy treatment. However, the highest proportion of virus-free plantlets was obtained after three weeks of thermotherapy. Significant (P ≤ 0.05) interactions were observed between thermotherapy duration and virus type on virus elimination efficiency where significantly (P ≤ 0.05) more PVS-free than PVX-free plantlets were obtained at the same thermotherapy duration. Three weeks of thermotherapy of virus-infected in-vitro plantlets, particularly for PVS, offered an equilibrium duration for adequate plantlet survival and maximum meri-clone regeneration to obtain the highest proportion of virus-free plantlets. The use of thermotherapy to obtain a high proportion of PVX-free plantlets from infected potato seed stock showed no clear trend and needs further investigation.