A survey of cassava plants in the coastal region of Tanzania showing severe symptoms of cassava mosaic disease

Abstract: Cassava (Manihot esculenta Crantz) is a root crop that plays an important role in many households in Africa. It is sometimes called “Africa´s food insurance”. The advantages with the crop are that cassava is drought-resistant and it can grow in a semi-dry land. It is a perennial crop and does not require much labor. Moreover, it can grow on low soil fertility and the roots can remain in the ground until needed. The cassava production has some constraints, however. Several diseases and pests can limit the production. The major diseases causing the largest losses in cassava production are cassava mosaic disease (CMD), cassava brown streak disease (CBSV) and bacterial blight disease. CMD is caused by begomovirus infection and the symptoms are overall dwarfing of the plants with curled leaves. Today, there are some varieties of cassava, which are resistant to CMD and a lot of work has been performed to achieve a crop that farmers can rely on. However, there are still a lot of diseased plants in the fields. In this report, a small survey of 33 fields in the coastal region was carried out with plants that had severe symptoms of CMD. The aim with this project is to test if recently appearing severe disease symptoms in cassava are associated with any new genotypes of cassava mosaic begomoviruses (CMBs). Among the 33 samples, there were differences in the Restriction Fragment Length Polymorphism (RFLP) pattern for the begomovirus amplification products. Five of the amplification products were selected and sent for sequencing of the DNA-B genomic component. The sequence results showed that two of the cassava samples with very severe symptoms of CMD were infected with virus isolates of East African cassava mosaic Zanzibar virus (EACMZV) and the other samples with East African cassava mosaic virus (EACMV).