Estimation of genome size and characterization of Sphaerophysa salsula (Pall.) DC based on flow cytometry and genomic survey

Sphaerophysa salsula (Pall.) DC. is a perennial herbaceous subshrub in the genus Sphaerophysa, recognized for its ecological significance and medicinal potential. To characterize its genomic architecture, genome size, heterozygosity, repeat content, and GC content were examined through flow cytometry and high-throughput sequencing integrated with K-mer analysis. Simple sequence repeats (SSRs) were further identified from preliminary assemblies. Results showed that the estimated genome size was 682.20 Mb, whereas K-mer analysis indicated a size of 526.76 Mb, with a heterozygosity of 0.56% and repeat content of 50.14%, indicative of a complex genome with micro-heterozygosity and extensive repeat content. The preliminary genome assembly yielded 846 895 contigs (N50=1 457 bp) and 575 487 scaffolds (N50=4 357 bp). A total of 167 445 SSRs were predicted, with mononucleotide repeats being the most abundant (51.55%) and 8–11 repeat units accounting for the majority (82 119). These findings expand the genomic resources of Fabaceae, providing a valuable reference for whole-genome sequencing, chromosome-level assembly, and comparative analysis of S. salsula, as well as a foundation for studying adaptive evolution and functional genes in key metabolic pathways within Fabaceae.