Assessment of the Severity and the Incidence of African Cassava Mosaic Disease in Western Democratic Republic of Congo

This study focuses on the assessment of the severity and incidence of African Cassava Mosaic Disease (CMD) in the western Democratic Republic of the Congo (DRC) to assess the status of CMD and determine viral strains responsible for the disease. Epidemiological surveys were conducted in western DRC (former provincial configuration) from 2016 to 2017 following the standard protocol adopted Central and West African Virus Epidemiology (WAVE) programme. A total of 292 cassava leaf samples, exhibiting CMD symptoms and asymptomatic characteristics, were collected from 146 fields distributed across five provinces (Equateur, Kasaï-Oriental, Kinshasa, Bas-Congo and Bandundu). The mean rate incidence and mean severity in the field were 31.4% and 3, respectively; indicating that the Province was highly infected with CMD. In all provinces, infections transmitted by cuttings were more frequent.common. Molecular PCR analyses revealed an overall infection rate of 89.73%, with the detection of ACMV, EACMV, as well as other unidentified Begomoviruses. Mixed infections (ACMV+EACMV) and virus detected and not identified, were also observed. Results indicate a significant predominance of ACMV with a variable distribution across different areas. The detection of unidentified viruses in several samples suggests the presence of variants that are still poorly characterised; requiring further sequencing studies. These results highlight the importance of large scale distribution and promotion programs for CMD resistant plant materiel in these provinces.