First Report of the Green Rosette Variant of Groundnut Rosette Disease in Kenya.

Groundnut (Arachis hypogaea L.) is an important food crop in sub-Saharan Africa. One of the major production constraints is groundnut rosette disease, which is caused by a complex of two viruses, groundnut rosette assistor luteovirus (GRAV) and groundnut rosette umbravirus (GRV) together with the associated satellite RNA (satRNA) (1). Two main forms of the disease have been described: chlorotic and the green rosette. Variants of the satRNA have been shown to be largely responsible for the different forms of the disease (1). Chlorotic rosette has been the predominant form in all of sub-Saharan Africa while green rosette has been reported in the western and southern regions of Africa (2). During the 1997-1998 crop season, disease surveys conducted in Kenya showed the incidence of the rosette disease in farmers' fields to be 24 to 40% in a total of 23 fields surveyed in the western regions of the country (Homabay, Kendubay, Kisumu) and 30% in 8 fields sampled in the Rift Valley (Cheplamus, Marigat) regions. Representative peanut plants showing rosette symptoms were analyzed for the presence of GRV by reverse transcription polymerase chain reaction (RT-PCR). With primers specific to a portion of ORF4 of GRV RNA (3), RT-PCR gave a product of expected size (approximately 300 bp). The PCR product was cloned in pGEM-T vector and sequenced. The sequenced region showed 89% nucleotide sequence identity with published GRV sequences. Green rosette was observed on groundnut cultivars Nyaela Red and Homabay Local in the Kendu Bay region. The incidence of the green rosette was 5.3% of the plants with rosette symptoms. References: (1) A. F. Murant and I. K. Kumar. Ann. Appl. Biol. 117:85, 1990. (2) R. A. Naidu et al. Ann. Appl. Biol. 132:525, 1998. (3). M. E. Taliansky et al. J. Gen. Virol. 77:2335, 1996.