Cassava mosaic disease and associated viruses in Zambia: occurrence and distribution

Abstract

Cassava mosaic disease (CMD) is caused by cassava mosaic begomoviruses (CMBs), which are transmitted by the whitefly (Bemisia tabaci) in sub-Saharan Africa. CMD and the pathogenic viruses associated with cassava were assessed in a country-wide survey in seven provinces of Zambia between April and May 2009. CMD incidence was highest in Northwestern (71.2%) and lowest in Western (34.3%) provinces. Disease symptoms were severe in Eastern (3.94) and Lusaka (3.88), moderate in Central (3.54), Luapula (3.48) and Northern (3.31) and mild in Northwestern (3.01) and Western (2.50) provinces. In addition, the numbers of adult whitefly were assessed on cassava fields, and found to be highest in Lusaka (2.12) and lowest in Central (0.02) province. Polymerase chain reaction detected two virus species: African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV), that occurred as single and dual infections in 65.4% (ACMV), 25% (EACMV) and 9.6% (ACMV + EACMV) of the positive reactions. None of the samples were positive for EACMV-Ug. This is the first comprehensive report of CMD and the pathogenic viruses infecting cassava in Zambia.