Molecular Mechanisms of Striga Resistance in Nigerian Sorghum and Development of Marker-Assisted Selection Protocols

This study investigates the molecular mechanisms underlying Striga hermonthica resistance in Nigerian sorghum germplasm and develops marker-assisted selection protocols for accelerating resistance breeding. Striga is the most economically damaging weed in Nigerian cereal production, causing losses exceeding 30 billion naira annually across the northern states. While genetic resistance to Striga exists in some sorghum accessions, the molecular basis of resistance mechanisms including low germination stimulant production, hypersensitive response, and post-attachment resistance is incompletely characterised in Nigerian germplasm. This study screens 120 Nigerian sorghum accessions from the IAR genebank against Striga under naturally infested field conditions and controlled rhizotron experiments. Resistance mechanisms are investigated through strigolactone profiling using UPLC-MS, histological analysis of root penetration zones, and transcriptomic profiling of resistant versus susceptible responses using RNA sequencing. QTL and GWAS approaches using 50K SNP arrays identify genomic regions associated with each resistance mechanism. Markers are validated for predictive accuracy in independent germplasm panels. Findings reveal that strigolactone profile diversity is the dominant resistance mechanism in northern Nigerian landraces, with low producer accessions harbouring allelic variants at two LGS genes novel to Nigerian germplasm. Post-attachment hypersensitive response is associated with two independent genomic regions on chromosomes 3 and 7. Validated SNP markers for both mechanisms show over 82 percent prediction accuracy. The study contributes original molecular resistance characterisation for Nigerian sorghum and recommends rapid integration of validated markers into IAR Striga resistance breeding pipelines.

Keywords: Striga resistance, sorghum, molecular mechanisms, marker-assisted selection, Nigeria.