Isodon lophanthoides var. graciliflorus (Benth.) H. Hara, serves as one of the botanical sources for the traditional Chinese medicine “Xihuangcao”. Mixed germplasm resources and insufficient high-quality cultivars hinder its sustainable and high-quality development. In this study, we generated a multi-branched mutant B88, induced by ethyl methanesulfonate (EMS). It exhibits a 36.78% increase in branching, and a 39.64% increase in plant height at maturity compared to the wild-type (WT) plants, implied high-yield potential. Although Simple Sequence Repeat (SSR) molecular markers revealed genetic variations, it retained the same chromosome number as the WT, indicating genetic stability and continuity. Transcriptomics revealed differentially expressed genes (DEGs) enriched in phytohormone biosynthesis and signal transduction pathways, and metabolomic identified 54 differentially accumulated metabolites (DAMs), mainly flavonoids and terpenoids. DEGs and DAMs were significant enriched in diterpenoid biosynthesis, particularly the gibberellin (GA) pathway, with 4.79-fold higher GA content compared to the WT and three key genes (ent-Copalyl Diphosphate Synthase, CPS; Gibberellin 20-oxidase, GA20ox; Gibberellin 2-oxidase, GA2ox) showing significant difference, suggesting that GA may have a comprehensive regulatory effect on plant height, branching, and accumulation of bioactive compounds in I. lophanthoides var. graciliflorus. This study strongly supported the value of the breeding material-B88 mutant, enriched the genetic diversity of I. lophanthoides var. graciliflorus, and revealed the potential of EMS mutagenesis in the improvement of medicinal plants, offering new insights for elucidating the effects of EMS mutagenesis on the growth regulation, quality improvement, and germplasm innovation of I. lophanthoides var. graciliflorus.
Zou et al. (Thu,) studied this question.