Abstract

Cassava mosaic disease (CMD) and Cassava brown streak disease (CBSD) are the major biotic constraints that destroy cassava tuberous production, reduce cassava productivity, and negatively impact food security of households in DRC. Epidemic status of those viral diseases was evaluated in 400 cassava fields in the North-Eastern DRC. Assessment was conducted along main roads at 10 km intervals, with 30 plants evaluated per field using an X-shaped transect. The epidemiological parameters evaluated included disease incidence, severity, source of infection, whitefly abundance, and molecular incidence. In addition, foliar and stems symptoms, root necrosis were considered for CBSD diagnostic. A total of 54 cassava varieties were identified in farmers’ fields, of which only six were improved varieties; notably, these improved varieties were the most affected by CBSD. Both diseases were widespread with heavy epidemic pressure in the prospected provinces. CMD field evaluation was as follows: Bas-Uele (I:77.9%, S:3), Tshopo (I:75%, S:3), Haut-Uele (I:50.4%, S:2) and Ituri (I:30.5%, S:3). However, CBSD was prevalent in Ituri (I:23.8%, S:2), Haut-Uele (I:1.4%, S:2) and in Tshopo (I:1.3%, S:2). The PCR analysis of 140 leaf samples revealed a lower molecular incidence than that observed during field assessments. This discrepancy may reflect limitations in diagnostic sensitivity, low viral titers, or the presence of genetically diverse viral populations. No CBSD was identified by PCR in Bas-Uele Province. Whitefly density per plant was relatively high in Ituri (18) followed by Bas-Uele (9), Tshopo (7) and Haut-Uele (6). The major factor of these viral pandemics spread is the use of infected cassava planting materials. To limit this trend, an urgent reliable healthy cassava system is needed in DRC.

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