Characterisation of the Virome of Wild Grasses Bordering Wheat and Sorghum Farms in North East Nigeria: Implications for Virus Spillover and Emerging Disease Risk

Wild grass species bordering cereal farms in North East Nigeria serve as hosts for a diverse and largely uncharacterised community of plant viruses, constituting potential reservoirs for virus spillover into wheat, sorghum, and pearl millet production systems. The risk of emerging virus diseases originating from wild grass-cereal interface zones has not been evaluated in Nigeria, representing a critical gap in national crop biosecurity knowledge. This doctoral research characterises the virome of wild grasses growing within 50 metres of wheat and sorghum farms across Gombe, Borno, Yobe, and Adamawa States using high-throughput sequencing and bioinformatic metagenomics. A total of 300 composite wild grass samples representing 24 species are collected across two seasons, subjected to total RNA extraction and ribosomal depletion, and sequenced on the Illumina NovaSeq platform. Virome characterisation uses de novo assembly, taxonomic classification, and comparison against Viruses.EMBL reference database augmented with a custom African grass virus sequence repository assembled as part of this research. Novel virus discovery pipeline outputs are subjected to phylogenetic placement and host range testing through agro-inoculation on cereal and grass hosts. The research also assesses insect vector communities at the farm-wild grass interface to identify plausible transmission pathways for identified viruses. An original theoretical framework models spillover probability as a function of virus prevalence in wild grasses, vector abundance, and host genetic distance, providing a generalisable risk assessment tool. Keywords: virome, wild grasses, wheat, virus spillover, North East Nigeria.