Molecular epidemiology of cassava mosaic geminiviruses in Zambia
R. M. MULENGA (1), J. Ndunguru (2), P. C. Chikoti (1), D. W. Miano (3), J. P. Legg (4), O. J. Alabi (5). (1) Zambia Agriculture Research Institute, Mount Makulu Central Research Station, Chilanga, Lusaka, Zambia; (2) Mikocheni Agricultural Research Institute, Dar-Es-Salaam, Tanzania; (3) University of Nairobi, College of Agriculture and Veterinary Sciences,
A diagnostic survey was conducted between April and May 2014 to determine the status of cassava mosaic geminiviruses in Zambia. Cassava mosaic disease (CMD) symptoms were mostly mild to moderately severe across farmers’ fields in Western, Northwestern, Northern, Luapula, Lusaka and Eastern provinces of Zambia although plants with very severe symptoms were also observed in Eastern, Lusaka and Luapula provinces. Sixty percent of the 226 survey samples were positive in PCR using primers amplifying a 550 bp product specific to the core coat protein (CCP) region of most geminiviruses. Sequence analysis of the cloned 550 bp products revealed the presence of <i>African cassava mosaic virus</i> (ACMV), <i>East African cassava mosaic virus</i> (EACMV) and <i>East African cassava mosaic Malawi virus</i> (EACMMV) as single or mixed infections of different proportions in the CCP-positive samples. Further analysis showed that 59.6% of these samples had single infection of ACMV, 7.4% had EACMMV alone, 1.5% had EACMV alone, 27.5% had ACMV+EACMMV and 3.8% had ACMV+EACMV. Rolling circle amplification and sequence analysis of the complete DNA A genome of three EACMMV isolates showed that they shared 98.2-99.9% identity among themselves, 97.9-98.4% with DNA A of EACMMV isolate MK (AJ006460), and 98.2-98.7% with EACMMV isolate MH (AJ006459). The results provide the first molecular evidence for the presence of ACMV, EACMV and EACMMV in Zambia and represent the first report of EACMMV in Zambia.
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