Enhancing agronomic traits and bioactive compound accumulation in Thai Andrographis paniculata via EMS-induced variation

Andrographis paniculata is a self-pollinating medicinal plant with limited natural genetic diversity, which restricts the development of improved cultivars with desirable agronomic traits and stable accumulation of key bioactive compounds, particularly andrographolide (AP1). To overcome this limitation, ethyl methanesulfonate (EMS) mutagenesis was applied to native Thai germplasm to induce phenotypic and phytochemical variation and to generate novel genetic resources for breeding improvement and gene function analysis. Optimal EMS treatment conditions (1.0% and 1.5% EMS for 5 and 8 h) were used to generate mutant populations. Screening of the M1 and M2 generations revealed extensive phenotypic variation, including alterations in plant architecture (e.g., dwarfism, multiple stems, variable bush size), flowering time, and leaf morphology. High-throughput phenotyping of M2 plants classified the population into four distinct morphological clusters, with some lines exhibiting significantly increased biomass, reaching up to 3.67-fold higher digital volume than the wild type. High-performance liquid chromatography (HPLC) analysis revealed substantial variation in secondary metabolite accumulation, with several M2 lines showing markedly elevated AP1 (up to 8.18% dry weight) and neoandrographolide (up to 2.21% dry weight) contents. Correlation analysis demonstrated a positive association between AP1 content and yield-related traits, including plant volume, area, and height, whereas flowering time showed no significant effect on compound accumulation. This study demonstrates that EMS mutagenesis is an effective approach for expanding morphological and phytochemical diversity in A. paniculata. The identified mutant lines with diverse agronomic performance and enhanced bioactive compound content represent valuable pre-breeding materials for the development of high-yielding and phytochemically superior cultivars, and also provide a promising platform for future studies on gene function and trait regulation in A. paniculata.