Incidence and severity of African cassava mosaic disease (ACMD) and cassava bacterial blight (CBB) on some local and exotic cassava varieties in different ecological zones of Ghana

Abstract

Seven exotic varieties of cassava, namely TMS 30001, TMS 91934, TMS 4(2)1425, TMS 30555, TMS 50395, TMS 63397, and TMS 30572 developed in IITA, Ibadan, Nigeria, and three local varieties, namely 'Ankra', 'Bosomensia' and 'Katawia' were evaluated for African cassava mosaic disease (ACMD) and cassava bacterial blight (CBB) resistance in five ecological zones of Ghana. The trials were conducted in experimental fields of Crops Research Institute at Fumesua (Forest zone) in 1988, 1989, 1990; Aiyinase (High Rain Forest zone), Pokuase and Ohawu (Coastal Savanna zone), and Ejura (Forest-Savanna Transition zone) in 1989 and 1990; Techiman (Forest-Savanna Transition zone); and Nyankpala and Damongo (Guinea Savanna zone) in 1990. ACMD and CBB damage at 3 and 6 months after planting were scored on a 1-5 scale based on the severity of the diseases. The exotic varieties were significantly more tolerant to ACMD across the 3 years at Fumesua as well as in 1989 and 1990 across all locations. For CBB in 1990, the exotic varieties were significantly more tolerant than the local varieties in the Coastal Savanna zone where CBB incidence and severity was relatively high. Ghana Jnl agric. Sci. Vol.31(1) 1998: 35-43