An analysis of viruses associated with cassava mosaic disease in three Angolan provinces

Seventeen cassava plants showing strong cassava mosaic disease symptoms were sampled from three Angolan provinces. The DNA-A component of two isolates was amplified by rolling circle amplification (RCA) and characterized. The complete DNA-A of 2,778 nucleotides from sample AOS showed very high similarity to African cassava mosaic virus (ACMV), and that of 2,799 nucleotides from sample A07 showed high identity to East African cassava mosaic virus (EACMV), particularly to EACMV-Uganda2 Severe strain. This represents the first report of complete ACMV and EACMV DNA-A sequences from Angola. PCR followed by direct sequencing of PCR products of a portion of DNA-A and DNA-B detected ACMV or EACMV in all 17 cassava plants. None of the five other cassava mosaic virus species were found. The presence of a mixed infection of ACMV and EACMV-Uganda2 Severe strain, associated with cassava mosaic disease pandemic, highlights the need for stricter controls on the importation of infected cassava stem cuttings from neighbouring countries and further investigations on the sanitary status of cassava plants in the presently unsurveyed provinces of Angola.