Effect of thermotherapy duration, virus type and cultivar interactions on elimination of potato viruses X and S in infected seed stocks

Abstract

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 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.

Phytotoxicity and Other Adverse Effects on the In Vitro Shoot Cultures Caused by Virus Elimination Treatments: Reasons and Solutions

“…Potato (S. tubeosum L., 'Baraka') plantlets treated by 37 ± 2 • C for 40 days under continuous light survived in a rate of 61.5% [122]. Different sensitivity of potato cultivars was also reported by Waswa et al [133]. In their experiments 'Kinigi', 'Rwangume', and 'Victoria' cultivars regenerated in 54.3%, 65.3%, and 39.3%, respectively, in the average of the whole experiment.…”

“…However, the survival rate of potato (S. tubeosum L.) varieties depended also on the virus infection of them: PVS infected plants of 'Rwangume' and 'Victoria' survived the thermotherapy to a greater extent (75.4% and 67.1%) compared to PVX infected plants (61.7% and 67.1%). Responses of 'Kinigi' variety were contrary: the survival rate of PVS infected plants was 54.6%, while PVX infected ones survived at a rate of 64.6% [133]. Artichoke (Cynara cardunculus L. var.…”

Major In Vitro Techniques for Potato Virus Elimination and Post Eradication Detection Methods. A Review

“…So the combined meristem culture with thermotherapy is better than the use of these two techniques alone. The use of thermotherapy combined with cryotherapy is also another possible complex method of thermotherapy and other therapy, and it has been used for other plants Moses et al 2017).…”

Plant protection from virus: a review of different approaches

“…The peculiarities of the apical meristem method consist of the complexity of the regeneration of meristems that are 0.1 mm in size. Their engraftment and regenerative ability increase when the size of the meristems increases, but the risk of viruses being present also increases ( Moses et al., 2017 ). It is necessary at this stage to increase the method’s effectiveness and suppress the viral pathogenesis in a larger area of the meristem.…”

“…These methods essentially represent a single biotechnological complex method of plant virus recovery. This method is widely used worldwide, and different plant species have been revitalized with its help ( Alam et al., 2013 ; Moses et al., 2017 ; Wang et al., 2021 ). Significant disadvantages of the tissue culture-based rehabilitation method include the possibility of self-clonal variations.…”