Molecular detection of two cassava Begomoviruses in some parts of Southern Nigeria

Cassava mosaic disease (CMD), caused by an array of is the most economically important viral disease of cassava in sub-Saharan Africa. The most frequently reported in West Africa are African cassava mosaic virus (ACMV) and East African cassava mosaic Cameroon virus (EACMCV). In this study, 42 cassava leaves and 30 symptomatic weeds belonging to the Asteraceae, Cucurbitaceae and Leguminosae families were collected from backyard gardens in Edo, Ondo, Anambra, and Delta States in 2009. Deoxyribonucleic acid (DNA) extracts from these leaves were tested for ACMV and EACMCV in a multiplex polymerase chain reaction (PCR) assay. The PCR primers used were designed to amplify the replicase regions of DNA-A components of both viruses. Most of the cassava plants within the survey area were either symptomless or showed mild symptoms. ACMV was detected in 16% of cassava leaves from Edo State but not in any of the cassava leaves from the other three states. One weed sample each from Edo State (5.56%) and Ondo State (10%) were also positive for ACMV. EACMCV was not detected in any of the samples tested. The low virus occurrence observed from PCR results and the observed low incidence of the CMD characteristic mosaic symptoms on cassava leaves in the states sampled may be attributed to the use of CMD resistant or tolerant cassava varieties, and may be a result of the massive distribution of virus resistant cassava cuttings to these States by the International Institute of Tropical Agriculture (IITA).