Epidemiology and Molecular Dynamics of Cassava Mosaic Viruses in Côte d’Ivoire: Current Agronomic Challenges in Côte d’Ivoire

Abstract

Aims: This study aimed to characterize cassava mosaic viruses and assess the factors influencing the dynamics of this disease in central and central-western Côte d'Ivoire in order to support effective management strategies. Study Design:  Descriptive transversal epidemiological survey. Place and Duration of Study: Conducted from November 2019 to August 2020 in the departments of Bouake, Yamoussoukro, and Daloa, the main cassava-producing areas, the study combined in-depth field surveys and molecular diagnostics. Methodology: A total of 183 cassava plantations in 15 villages were randomly sampled. In each selected field, one sample was collected per variety and per case, depending on whether it was symptomatic or asymptomatic to mosaic disease. CMD symptoms were assessed on 5,896 plants using a severity scale of 1 to 5. Agronomic data were recorded. Approximately 200 symptomatic and asymptomatic leaf samples were subjected to DNA extraction and PCR testing targeting African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV). Results: The results showed a relatively high phenotypic prevalence of CMD. Informal exchange of planting cuttings was a major factor in infection compared to cuttings from official sources. Crop age and season influenced vulnerability. Symptom severity was generally moderate, although hot spots with severe symptoms were identified. Molecular analyses confirmed the predominance of ACMV followed by ACMV-EACMV co-infections. Of the 200 plants analyzed, 35% of asymptomatic cassava mosaic plants (18 plants) and 77% of symptomatic plants (115 plants) were infected by the virus. It is significant that many asymptomatic plants tested positive for CMD viruses, highlighting the challenge of latent infections in disease management. Conclusion: The study highlights the complex epidemiology of a serious cassava disease in Côte d'Ivoire. In addition, viruses are uniformly distributed across the different cassava production areas. It recommends integrated control strategies such as certification of cuttings, vector control and molecular surveillance. Together, these measures are essential to reduce the impact of the disease, maintain cassava yields, and ensure food security for vulnerable populations that depend on this staple crop.