Genome-Wide Resequencing Reveals the Distribution Status and Genetic Diversity of Brasenia schreberi Germplasm Resources

Brasenia schreberi J. F. Gmel. (Cabombaceae) is a perennial aquatic herb of significant ecological and economic value in China. In recent years, wild populations have declined drastically due to water pollution, habitat loss, and over-harvesting, making germplasm conservation imperative. During 2023–2025, we conducted systematic field surveys across suspected distribution areas nationwide and identified 16 extant populations spanning 11 provinces, including five newly discovered localities that have not been reported for nearly three decades. The study performed population genetic analyses on 16 B. schreberi accessions to systematically elucidate their genetic diversity levels and population genetic structure. The results demonstrated that extremely high genetic differentiation existed among populations (FST = 0.845), with 84.48% of total genetic variation attributable to inter-population divergence. Population genetic structure analysis partitioned the accessions into eight distinct genetic clusters. Overall genetic diversity was low across populations (observed heterozygosity Ho: 0.0383–0.2166; expected heterozygosity He: 0.0235–0.1620), with allelic richness (Na: 1.0368–1.3650) and effective number of alleles (Ne: 1.0250–1.2810) both at low levels, reflecting the narrow genetic base of wild B. schreberi resources. Among ex situ conserved accessions, most maintained genetic backgrounds highly consistent with their wild progenitors, demonstrating that current conservation strategies can effectively preserve genetic integrity in the short term. However, genetic admixture was detected in Y-CQLB (Chongqing Leibo) and Y-AHZY (Anhui Zongyang), indicating contamination risks during the ex situ conservation process. This study provides important theoretical foundations for the scientific conservation, precise management, and sustainable utilization of B. schreberi germplasm resources.