Science

New CMD-resistant cassava varieties released in Nigeria
A.G.O. Dixon, M. Akoroda, R.U. Okechukwu, P. Ilona, F. Ogbe, C. Egesi, G. Ssemakula, L. Sanni, J. Lemchi, C. Ezedinma, B. Maziya-Dixon, O. N. Eke-okoro, E. Okoro, A. A. Adeniji, G. Tarawali, and K. Nwosu.

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Newly released varieties in Nigeria
TME 419 TMS 98/0581 TMS 98/0510 TMS 98/0505 TMS 97/2205

INTRODUCTION

A severe form of cassava mosaic disease (CMD), started in Uganda in the mid1990s, and spread to neighboring countries and beyond. The severe CMD is caused by a highly virulent Ugandan strain of East African cassava mosaic virus (EACMV-Ug2), an interspecific hybrid of African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV). When EACMV-Ug2 co-infects cassava with ACMV, the symptoms are very severe. The CMD pandemic in Uganda led to cassava being almost totally abandoned, resulting in food insecurity there in the late 1990s. ACMV and EACMV, which recombined in Uganda to produce EACMV-Ug2, both exist in Nigeria and when they co-infect cassava, the plants also suffer very severe damage. Even if EACMV-Ug2 does not spread to Nigeria, varieties with a diverse genetic make up for resistance to CMD are needed to forestall any eventual evolution of a new, severe strain. A strategy was adopted using a large pool of human resources. NARS, universities, industry, government, farmers, and processors were to engage in activities to lead to cultivar-substitution. The susceptible varieties on farmers’ fields would be replaced by superior genotypes that are not only CMD resistant or tolerant but also high yielding with a high dry matter content.

a
TMS 96/1632

b
TMS 92/0057

c
TMS 92/0326

d
TMS 98/0002

e
NR 87184

METHODS

During the 2003/2004 and 2004/2005 seasons, on-farm trials (OFTs) and demonstration trials (DEMOs) were conducted using a fast track participatory selection...