Genetic diversity assessment of Bambara groundnut (Vigna subterranea (L.) Verdc.) along climatic gradients in Chad

Bambara groundnut [Vigna subterranea (L.) Verdc.] is a nutrient-dense, drought-resilient African legume cultivated largely by smallholders in semi-arid zones. While widely cultivated due to its ability to biologically fix nitrogen, enrich soil fertility, and hold cultural significance, most production relies on germplasm propagated within families with limited breeding efforts. Understanding the genetic diversity across pedoclimatic regions is essential for improving seed yields, quality, and physiological traits. To explore this, 212 diverse Bambara groundnut landraces were collected from four regions in Chad, involving over 80 farmers, from which 172 were used to assess genetic and phenotypic variations in nutritional and agronomic traits. Genotyping revealed significant genetic differentiation between regions (p = 0.1), with farm-level factors being the primary driver of variation (p < 0.001), highlighting the role of farmer selection practices, preferences, and abilities. Farmer surveys confirmed that most Bambara groundnut growers rely on self-propagated and selected seeds for cultivation. Genetic, seed composition, and physiological data all pointed to regional and farm-based origins as the main source of variation. The findings underscore the importance of including farmers in breeding processes, particularly through the distribution of pre-breeding materials tailored for high nutritional value and drought resistance. Additionally, the identification of quantitative trait loci (QTLs) associated with fat and phytate content suggests potential applications for marker-assisted selection to develop improved germplasm. These strategies could improve food security and sustainability and reduce malnutrition.