Abstract
Cassava mosaic disease (CMD) caused by the whitefly-transmitted begomoviruses (family Geminiviridae) is a major threat to Cassava limiting the production potential of the crop in North eastern Nigeria. This study aims at evaluating the current status of Cassava mosaic disease severity, whitefly abundance in the farmers’ field as well as the Gemini viruses causing the disease in the six (6) States: Bauchi, Yobe, Gombe, Borno, Adamawa and Taraba States. A total of forty nine (49) farmers’ fields were surveyed and in each field, thirty plants were assessed along the two diagonals, leaf samples were collected from the fields surveyed and the techniques based on polymerase chain reaction (PCR) were used for the detection of Cassava mosaic begomoviruses (CMBs) in the sampled leaves. The results of the study revealed that Cassava mosaic disease symptom severity was generally mild. It was highest in Gombe (2.70) and lowest in Yobe (1.15). Adult whitefly (Bemisiatabaci) population was highest in Gombe (105.07) and lowest in Taraba (18.09). Differential PCR results using specific primers for African Cassava mosaic virus (ACMV), East African Cassava mosaic virus (EACMV) and East African Cassava mosaic virus Uganda (EACMV-Ug) detected single infections of ACMV and EACMV in 48.1% and 18.5% of the positive samples respectively. None of the samples was tested positive to the East African Cassava mosaic virus-Uganda (EACMV-Ug). Co-infections of ACMV and EACMV were detected in 11.9% of the tested samples. Twenty one point five percent (21.5%) of the samples analyzed were negative to all the viruses tested. Further studies on the characterization of Cassava mosaic virus diversity by sequencing for thorough understanding of the existing types of virus strains in the study area is recommended.

Key words: Cassava, Severity, Incidence, EACMV-Ug and Bemisiatabaci