Incidence, Severity, and Distribution of Cassava Bacteria Blight Disease in Sierra Leone

Abstract

Cassava Bacterial Blight Disease (CBBD) is a major constraint in cassava production, initially manifesting on the lower leaves as scattered, cigar-shaped, water-soaked lesions. This study aimed to evaluate cassava bacterial blight disease in Sierra Leone. A field trial was conducted at the School of Agriculture and Food Sciences research site to evaluate disease susceptibility of various cassava genotypes and identify elite genotypes for population improvement. The experiment followed an augmented randomized complete block design (ARCBD). Additionally, a farmer field survey was carried out across all districts to assess the distribution and prevalence of CBBD. The cassava genotypes were classified into three categories: resistant (17.6%), susceptible (80.9%), and mildly susceptible (1.5%). Resistant genotypes, such as TME419, SLE0201, and SLE0087, exhibited no disease progression (rAUDPC = 0.0, SSV = 0.0), while susceptible genotypes, including SLICASS 4 and SLE0109, demonstrated rAUDPC values between 1100 and 2999. Genotype SLE0092 was the most severely affected, displaying the highest disease incidence (50%) and severity (3.1) nine weeks post-planting. The highest root weight (14.2 kg) was recorded for genotype SLE0185, while most genotypes showed moderate yields. A survey of 276 cassava fields across Sierra Leone revealed a widespread occurrence of CBBD, with a national mean incidence of 60.4%, which was notably higher in the Eastern region (69.2%) and Kambia District (78.6%). These findings emphasize the urgent need for the widespread cultivation of CBBD-resistant genotypes.