Field evaluation of the effectiveness of thermotherapy against cassava mosaic disease in Central African Republic.

Aim: The effectiveness of thermotherapy in managing cassava mosaic disease (CMD) was studied on a susceptible local cultivar in the field in the epidemiological conditions. Study Design: The field was laid out in randomized complete block design Place and Duration: Field experiment was conducted in forest zone at Kapou located in south west of Central African Republic according to University of Bangui during August 2010 and July 2011. Methodology: Diseased cassava cuttings were treated in a heated water bath at temperatures ranging from 43oC to 51oC for 30 min before being grown for 12 months in the field. Results: Temperatures from 43oC to 49oC were found to have no deleterious effect on either the survival of cuttings or on plant regeneration. One month after planting (MAP), up to 40% of the cuttings treated at 47oC to 49oC had regenerated a plant with no CMD symptoms compared to 7% of untreated cuttings. Between two and five MAP, cassava cuttings treated at 49oC produced plants with a significantly lower incidence of CMD than plants produced from untreated cuttings. All plants grown from treated cuttings developed significantly less severe CMD symptoms than untreated cuttings between 8 and 12 months after planting. The highest tuberous root yield was obtained with diseased cuttings treated at 49oC (4.7kg/plant), equivalent to the yield from untreated symptomless cuttings (4.6kg/plant). Conclusion: Our data clearly demonstrate the value of thermotherapy to maintain a high level of production using local cultivars under severe CMD epidemic conditions.(Resume d'auteur)