Molecular identification of viruses infecting cassava in selected Local Government Areas of Oyo State

Abstract

Cassava is one of the most important food crops in Nigeria in terms of production and utilization. However, low productivity of the crop is associated with major virus diseases. A survey was conducted to identify the viruses infesting cassava in five Local Government Areas (LGAs) of Oyo State Nigeria. Twenty five cassava fields were surveyed in February 2018 during which 75 symptomatic cassava leaves were collected. Total nucleic acid extraction of the samples was done using Cetyl Trimethyl Ammonium Bromide (CTAB) extraction protocol followed by multiplex Polymerase Chain Reaction (PCR) for African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV) identification. Symptoms observed included leaf curling, mosaic and “candle-like” sticks. Both ACMV and EACMV were detected in single infections at Akinyele LGA, whereas only ACMV was found in Atiba, Egbeda and Ikereku LGAs. Conversely, none of the samples from Afijio LGA tested positive for both viruses. Of the total leaf samples, 22.7 % were positive for ACMV, whereas 2.7 % tested positive for EACMV. The highest ACMV disease incidence was encountered in Akinyele (6.7 %), Egbeda (6.7 %) and Ikereku (6.7 %) LGAs while 2.7 % of the total samples were positive for ACMV in Atiba LGA. The low incidences of ACMV and EACMV implied that cassava production is not threatened by these viruses in the surveyed areas. However, adoption of resistant cassava cultivars should be intensified as a precautionary measure.