Genetic Characterization of Cassava Brown Streak Virus in Cassava Farms Across Ondo and Ekiti States

Cassava brown streak disease (CBSD), caused by Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), poses a devastating threat to cassava production in East and Central Africa, and its potential spread into West Africa has alarmed agricultural stakeholders. Surveillance data from Southwest Nigeria remain limited. This study investigated the presence and genetic diversity of CBSV and UCBSV in cassava farms across Ondo and Ekiti States, Southwest Nigeria. A total of 200 cassava leaf samples showing foliar mosaic, chlorotic streaking, and root necrosis symptoms were collected from 20 farms. Total RNA was extracted and RT-PCR performed using CBSV and UCBSV coat protein-specific primers. Amplicons from positive samples were sequenced and phylogenetically analyzed. CBSV was confirmed in 12% of sampled farms, with distribution suggesting possible introduction via planting material exchange. UCBSV was not detected. Phylogenetic clustering with East African CBSV isolates implies recent introduction rather than endemic circulation. These findings represent the first molecular confirmation of CBSV presence in Southwest Nigeria and underscore the need for stringent planting material certification across state boundaries. Keywords: Cassava brown streak virus, RT-PCR, cassava, Southwest Nigeria, Ekiti State.