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SITE-SPECIFIC ANALYSIS & MANAGEMENT

Performance of Improved Cassava Genotypes for Early Bulking, Disease Resistance, and Culinary Qualities in an Inland Valley Ecosystem

International Institute of Tropical Agriculture, Ibadan, PMB 5320, Oyo Rd., Ibadan, Nigeria; A.G.O. Dixon also at Sierra Leone Agricultural Research Institute, Freetown

^* Corresponding author (r.okechukwu{at}cgiar.org).

Cassava (Manihot esculenta Crantz) is commonly grown on residual moisture after rice (Oryza sativa L.) in inland valley swamps (IVS), but not much work has been done to select genotypes that could bulk early, and have high storage root yield in the IVS. Earlier improvement work focused on development of varieties adapted to upland conditions (12-mo cycle), but recently farmers are requesting varieties that can mature early (6-mo cycle) and are adapted to the IVS. The choice of the IVS is to be able to grow the crop during the dry season and in areas with marginal land that have streams passing through. Growing cassava during the dry seasons in the IVS with residual moisture as a second crop after rice has the potential to generate extra income from sale of both root and foliage for humans and livestock. Twenty-one improved cassava genotypes and four popularly grown landraces were evaluated during the dry season in an inland valley slope at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. Results showed that all genotypes sprouted well and were vigorous in growth. While cassava bacterial blight severity (CBBS) was low and not significant, 11 of the genotypes (including two landraces) showed moderate to resistant expression of cassava mosaic disease (CMD) symptoms. Though the genotypes showed moderate damage due to cassava green mite (CGM), fresh root yields obtained from the top performers (92/0427, 91/02327, 91/02322, 91/02324, and 94/0239) were as high as 25 to 28 t ha^–1, with 36% dry matter content in 6 mo. Most of the improved cassava genotypes bulked early, had a low cyanogenic potential, acceptable culinary quality, and few storage root rots.

Abbreviations: CBB, cassava bacterial blight • CBBS, cassava bacterial blight severity • CGM, cassava green mite • CMD, cassava mosaic disease • CNP, cyanogenic potential • HI_r, root harvest index • HI_s, shoot harvest index • IITA, International Institute of Tropical Agriculture • ISU, African landrace Isunikankiyan • IVS, inland valley swamps • MAP, month(s) after planting

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Received for publication March 15, 2008.