Developing an Original Theory of Spatial Genetic Structure of Rust Pathogen Populations and Its Implications for Durable Resistance Deployment in Nigerian Wheat

Durable resistance to wheat rusts requires understanding the spatial population structure and dispersal dynamics of pathogen populations, as well as the selective pressure imposed by different resistance gene deployment strategies, and developing an original theory of these dynamics for Nigerian pathogen populations provides both basic scientific contribution and applied breeding implications. This study developed an original theory of spatial genetic structure of wheat rust (Puccinia striiformis f. sp. tritici) populations and resistance gene deployment strategy in Nigeria, combining population genomics, landscape epidemiology, and evolutionary modelling. Pathogen samples were collected from 72 sentinel plots in wheat-growing zones of Borno, Gombe, and Plateau States across three seasons (2021 to 2023). Genotyping using DArTseq genotyping-by-sequencing generated 8,423 genome-wide SNP markers across 180 isolates. Landscape genetics analysis, including isolation by distance, gradient forest analysis, and barrier detection, was applied to characterise the factors structuring pathogen genetic diversity across the three-zone study area. Results showed that pathogen genetic structure followed climate gradients more strongly than geographic distance (R2 = 0.71 versus 0.43). Two genetically distinct populations were identified, corresponding to the Sahel margin (Borno-Gombe corridor) and the Plateau highland, with limited directional gene flow from south to north. The original Spatially Informed Resistance Gene Deployment Theory proposes that durability is maximised by deploying distinct resistance gene combinations in the two identified pathogen sub-populations rather than national uniform deployment. Expert review by 18 plant pathology and breeding scientists confirmed the framework's original contribution.

Keywords: wheat rust, population genetics, resistance gene deployment, Nigeria, landscape genetics