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

Cassava is an important staple food in subtropical regions; however, its production is adversely affected by cassava brown streak disease and poor soil fertility. Five improved and two local cassava varieties were evaluated for three seasons across two sites in Kizimbani, Zanzibar. Highly significant differences were detected among varieties, sites and years for fresh shoot yield, and fresh root yield. For cassava brown streak disease associated root necrosis, highly significant differences were detected only between varieties but not sites or years. 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 best local variety, ‘Mwari’. However, the local variety ‘Boma’ is preferred by farmers in Zanzibar because it has better fresh consumption qualities than ‘Mwari’. ‘Boma’ is highly susceptible to cassava brown streak disease and produces 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 production system intensification are needed to enhance productivity.