Performance of cassava brown streak disease-tolerant varieties in Zanzibar, Tanzania

Abstract

Cassava is an important staple food in subtropical regions; however, its production is adversely affectedby cassava brown streak disease and poor soil fertility. Five improved and two local cassava varieties wereevaluated for three seasons across two sites in Kizimbani, Zanzibar. Highly significant differences were detectedamong varieties, sites and years for fresh shoot yield, and fresh root yield. For cassava brown streak diseaseassociated root necrosis, highly significant differences were detected only between varieties but not sites oryears. On average, the site that had a slightly higher soil nitrogen level recorded ∼126% higher fresh root yield. Two improved varieties, ‘Kizimbani’ and ‘Machui’, produced significantly higher fresh root yields than the bestlocal variety, ‘Mwari’. However, the local variety ‘Boma’ is preferred by farmers in Zanzibar because it has betterfresh consumption qualities than ‘Mwari’. ‘Boma’ is highly susceptible to cassava brown streak disease andproduces a poor yield. The four released varieties, ‘Kama’, ‘Kizimbani’, ‘Mahonda’ and ‘Machui’ were superior to‘Boma’ in cassava brown streak disease resistance and yield. Further, soil fertility improvement and productionsystem intensification are needed to enhance productivity.