High-quality genome and variation map reveal valuable loci and the genetic basis of trait divergence driven by geographic dispersal in Crotalaria pallida

Abstract Crotalaria is a genus of the Fabaceae family with agricultural and medicinal value, but to date the genome has not been fully sequenced. Although Crotalaria pallida is widely distributed in tropical and subtropical regions, the degree of genetic diversity and the specific traits influenced by geographic dispersal remain unknown. We here report a high-quality genome assembly of C. pallida with 98.52% coverage which is assembled into 8 chromosomes. C. pallida is closely related to Lupinus angustifolius, with genetic divergence occurring ~42.5–57.4 million years ago (MYA). Re-sequencing of 236 C. pallida accessions revealed a genetic diversity decrease as C. pallida spread from Africa to America and Asia, and from Asia to China and finally to Hainan. Significant divergence was observed in seven traits between non-Hainan and Hainan accessions. Genome-wide association studies identified 73 loci for 18 agronomic traits, 25 of which overlapped with divergent sweeps between non-Hainan accessions and Hainan accessions. Furthermore, the dispersal of C. pallida in Hainan reduced genetic diversity, leading to a divergence in allelic frequencies at four candidate genes (CpPTR, CpMYB, CpRLPK, and CpNADK) associated with plant height. This study reveals the genetic basis of trait divergence driven by geographic dispersal and offers valuable resources for the strategic development of C. pallida breeding.