Effect of Thermotherapy in the Elimination of Viruses on Four (4) Mosaic Diseased Cassava Cultivars

Abstract

In Ghana, cassava is the most favoured among all the root crops and indeed all food crops by consumers. Its per capita consumption (PCC) index is as high as 148kg/year followed by that of plantain (83kg/year: Annor-Frempong, 1991). Cassava mosaic disease (CMD) is considered the most important biotic constraint as it greatly reduces yields (Calvert and Thresh, 2002) significantly. Application of meristem culture combined with thermotherapy is reported to increase the survival rate of in vitro explants (Manganaris et al., 2003). It is against this background that this study was undertaken to ascertain the effectiveness of thermotherapy to generate large numbers of virus-free plants. The study assessed the effect of thermotherapy in the regeneration rate and eradication of cassava mosaic virus disease in four (4) local cassava cultivars. The cuttings of the four cassava accessions showed varying degrees of foliar symptom severity typical of the cassava mosaic disease. Shoots that were subjected to pre-culture thermotherapy at 35-37°C appeared to be disease-free of the cassava mosaic symptoms after three to four weeks of treatment. Thermotherapy treated meristem showed better survival rate in larger explant size than smaller ones in the cassava accessions studied indicating that virus-free planting materials could be produced using thermotherapy.

Keywords: Thermotherapy, cassava mosaic, meristem tip, tissue culture.