Using Thermotherapy And Meristem Tip Culture For Producing Virus-Free Cassava Planting Material From Six Varieties Cultivated In Côte d’Ivoire

Abstract

Cassava cultivation in Côte d’Ivoire is constrained by cassava mosaic disease (CMD) caused by African cassava mosaic virus (ACMV) and East African cassava mosaic Cameroon virus (EACMV-CM). The disease is transmitted principally through infected cuttings. This study combined thermotherapy and meristem culture to produce virus -free in vitro plantlets. These sanitation techniques were applied to six highly valued cassava varieties. Cuttings taken from plants showing CMD symptoms were grown in greenhouses as mother plants. At 2 weeks old, PCR of these plants showed presence of ACMV and EACMV-CM in single and double inf ections respectively. Heat treatment was then applied of day/night with 40/36°C and a photoperiod of 16/8 h. Meristem tips were used to produce in vitro plantlets, which were re-checked f or viruses using PCR, and virus-free plantlets were multiplied through several sub-cultures. Using 60 isolated meristematic explants, we regenerated 44 in vitro plantlets. We achieved a sanitation success rate of 100 % for f our varieties (Agba blé 3, IM89, Koko Soclo 5 and Bayéré), 80 % for Yacé and 62.5 % f or Yacé 2. A second indexing of viruses showed that 88.33 % of regenerated in vitro plantlets were free from both ACMV and EACMV -CM. After three consecutive sub-cultures of the virus-free plantlets from all six varieties, we obtained 800 in vitro plantlets. This study showed that the thermotherapy technique combined with meristem culture was eff ective in eliminating these viruses. The use of virus -free planting material will reduce the impact of CMD and boost cassava production in Côte d’Ivoire.