CBN-V Video Archives - S7-12
Developing Viral Challenging Systems for Assessing Geminivirus Replication and Symptom Production in Cassava
(Manihot esculenta)

Fofana I.B.F.^1,2., N.J. Taylor¹, J.S. Pita^1,2, A. Sangare² and C.M. Fauquet¹

1. International Laboratory for Tropical Agricultural Biotechnology (ILTAB), Danforth Plant Science Center, 975 Warson Road, St Louis, MO 63132 iltab@danforthcenter.org
2. Centre National de Recherche Agronomique, 01 BP 1740 Abidjan 01, Côte d’Ivoire

        Cassava (Manihot esculenta Crantz) is a Euphorbaceous shrub cultivated throughout the tropics for its starchy roots. Viral diseases are the single largest constraint for cassava production in Africa, causing significant yield reduction throughout the continent. Cultivars with varying degrees of resistance have been obtained through conventional breeding. More recently a landrace (TME 3), resistant to African cassava mosaic disease (ACMD) was discovered in a field in Nigeria. In order to investigate levels and mechanisms of resistance within these cultivars in the laboratory, we have developed two systems to study viral replication, movement and symptom apparition. Microparticle bombardment procedures have been optimized for successful inoculation of plantlets with infectious viral clones and applied to study symptomology and pathogen interaction of four major ACMD-causing geminiviruses in three African cultivars. A cassava protoplast protocol is also being developed to enable investigations on viral replication in single cells of susceptible and resistant cultivars. The latter utilizes the production of suspension cultures from non-embryogenic calli. Viable protoplasts have been isolated from these suspension cultures and procedures for transfection with viral DNA are under development. Among other applications these challenging systems will allow us to study interaction of geminivirus species and strains in infected plants and to determine whether resistance is based on suppression of viral replication and/or movement.

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