Molecular profiling of 35 Phacelia species using SCoT molecular markers and genome size estimation

The genus Phacelia comprises numerous species with significant ecological, agricultural, and ornamental value. Despite its diversity, the genetic relationships and genome size variation within Phacelia have remained poorly characterized. In this study, the nuclear DNA content (genome size) of 40 accessions representing 35 Phacelia species was estimated using flow cytometry (FCM), and genetic diversity was assessed using Start Codon Targeted (SCoT) molecular markers. The 2C nuclear DNA content ranged from 1.00 pg ( P. ciliata ) to 3.61 pg ( P. egena ), with notable inter- and intra-specific variation observed. SCoT marker analysis generated clear and reproducible banding patterns, enabling the construction of a UPGMA dendrogram that resolved the accessions into distinct groups, largely consistent with morphological and taxonomic relationships. Some closely related taxa, such as P. capitata and P. brachyloba , exhibited both high genetic similarity and comparable genome sizes, while significant divergence was observed among others. Although several well-supported clades identified in the SCoT-based phylogeny corresponded closely to established sections and subsections, certain taxa traditionally classified together were found in separate branches, suggesting complex evolutionary histories and potential morphological convergence. The results demonstrate that combining SCoT markers and genome size estimation provides valuable insights into the genetic diversity and evolutionary relationships within Phacelia , underscoring the importance of integrative molecular approaches for taxonomic and conservation studies in this genus.