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A survey of cassava mosaic disease (CMD) was carried out in Ghana from 2007-2008 to assess CMD incidence, infection type, severity and adult whitefly population. A total of 136 famers' fields across major cassava producing areas in the Brong Ahafo, Western, Northern, Ashanti and Volta regions were assessed. CMD was prevalent in most of the 136 fields surveyed. Frequently encountered local landraces were susceptible to the disease. CMD incidence reached 100% in farmers' fields. Mean disease incidence ranged from 46% in the Ashanti region to 90% in the Western region of the country. CMD incidence averaged 66.0%, with cutting-borne infection and Whitefly-borne infections being 54.0% and 12.0%, respectively. CMD shoot symptom severity ranged from 2.0 to 3.7 in the farmers' fields, with a mean of 2.9. Mean adult whitefly population was 0.47. The high prevalence of CMD requires a concerted effort in the management of CMD in the country. Original scientific paper.

Cassava mosaic disease (CMV), caused by one or a combination of cassava mosaic geminiviruses, is ranked among the most important constraints to profitable and efficient production of cassava. Effective control measures require in-depth knowledge of the viral causative agent. Using rolling-circle amplification and unique enzymes, the full genome of two species of cassava mosaic geminivirus isolated from infected cassava plants in Ghana were cloned into pCambia 1300 and pET-28b. The sequences of the genome were determined on an ABI sequencer and a pairwise comparison was performed with other cassava-infecting geminiviruses from different countries. It was revealed that cassava grown in Ghana is attacked by two species of geminivirus in either single or mixed infections. These are the African cassava mosaic virus (ACMV) and the East African cassava mosaic virus (EACMV)-like, with high sequence similarity of 94% and 80%, respectively, between the DNA-A and DNA-B components of each virus, and 66% and 41% similarity of the common region (CR) (for A and B accordingly). The DNA-A of ACMV and EACMV-like contained 2781 and 2800 nucleotides, respectively, while their DNA-B components had 2725 and 2734 nucleotides, respectively. ACMV DNA-A was over 97% similar to those of other ACMVs from the continent. In contrast, EACMV-like DNA-A was over 98% similar to the isolates from Cameroon and other West African countries, and less than 88% similar to other EACMV species. Thus ACMV and EACMV-like were named African cassava mosaic virus-Ghana and East African cassava mosaic Cameroon virus-Ghana. Computer analysis revealed that their genome arrangement follows the typical old world bipartite begomovirus genome. The association of these two species and their interaction might account for the severe symptoms observed on infected plants in the field and in the greenhouse.

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Cassava mosaic disease (CMD), arguably the most important viral disease of cassava, an important food security crop has in recent times, been reported to be associated with satellites in some parts of sub-Saharan Africa. We investigated the status of Cassava mosaic begomovirus and associated satellites in CMD-affected cassava plants in Ghana using polymerase chain reaction. In all, 110 CMD-affected cassava leaf samples collected from cassava fields in Southern Ghana. Africa cassava mosaic virus (ACMV) was detected in 107 (97%) cassava leaf samples, out of which 76 (69%) was in mixed infections with East Africa cassava mosaic virus-Cameroon (EACMV-CM). EACMV (CM) alone was detected in three (3%) cassava leaf samples. Out of the 110 cassava leaf samples affected by cassava mosaic begomoviruses, satIII and satII were detected in 66 (60%) and 47 (43%), respectively. To the best of our knowledge, detection of CMBassociated satellites in Ghana is the first in the country and possibly in West Africa, and has serious epidemiological implications on the management of CMD, thereby requiring further studies and concerted efforts to safeguard cassava production.