Distribution and characteristics of groundnut rosette disease in Kenya

Groundnut rosette is a major virus disease of peanut in sub-Saharan Africa. The disease is caused by a complex of three agents: GRAV (groundnut rosett e assistor luteovirus), GRV (groundnut rosette umbravirus), and the associa ted satellite RNA (Sat-RNA). During the 1997 to 1998 crop season, the incid ence of rosette in farmers' fields was estimated at 24 to 40% in western Ke nya and 30% in the Rift Valley. Sequence analysis of Kenyan isolates reveal ed that GRAV-CP sequences shared 97 to 100% and 95 to 98% sequence homology at nucleotide and amino acid levels, respectively, amongst themselves and with the Malawian and Nigerian isolates. The ORFs 3 and 4 of GRV were simil ar, with a homology of 99% at the nucleotide and amino acid levels among Ke nyan isolates. The GRV sequences of Kenyan isolates were closer to the Mala wian (95 to 96%) than to the Nigerian (87 to 88%) isolates. Sat-RNA shared 89 to 94% nucleotide identity with those from Malawi and Nigeria. A closer sequence relationship was observed between Kenyan and Malawian isolates in all regions compared. This is the first report on the distribution and mole cular characterization of groundnut rosette disease complex in East Africa.