DNA Polymorphism Changes in Bacopa monnieri (L.) Wettst Polyploids Affect Phytochemical and Antioxidant Profiles

This study aimed to evaluate the morphological, genetic, and phytochemical variations between diploid and colchicine-induced tetraploid Bacopa monnieri plants to explore the effects of polyploidy on plant traits and metabolite synthesis. Tetraploid lines were regenerated and acclimatized for four weeks in ½ HS medium. Morphological traits were measured, and cluster analysis was performed to assess phenotypic divergence. Genetic diversity was examined using RAPD markers, with data analyzed by UPGMA clustering. Phytochemical profiles, including bacosides, phenolics, flavonoids, triterpenoids, and antioxidant activity, were quantified by HPLC and spectrophotometric assays. Correlation analysis further revealed that bacoside accumulation is strongly linked to leaf and node morphological traits rather than overall plant size, suggesting genetic or metabolic regulation beyond simple vegetative growth. In contrast, phenolics, flavonoids, and triterpenoids showed positive correlations with growth traits and antioxidant activity, with triterpenoids exhibiting the strongest free radical scavenging effect. The average polymorphism rate correlated positively with bacoside content but not with other phytochemicals, indicating that genetic diversity plays a major role in bacoside biosynthesis. Results showed that most tetraploids had reduced length and biomass compared to diploids, except line 4-9, which exhibited increased growth and fresh weight. Morphological and genetic cluster analyses consistently identified three distinct groups, with lines 4-9 forming a unique cluster. Tetraploids, especially lines 4-1, 4-5, 4-7, and 4-9, accumulated significantly higher levels of bacosides and secondary metabolites, with line 4-9 yielding the highest bacoside compound (6.10 ± 1.11 mg/plant). Interestingly, some tetraploid lines showed reduced antioxidant activity despite increased phytochemical levels, possibly due to shifts in compound proportions or metabolic regulation. This study demonstrates that colchicine-induced tetraploidy enhances secondary metabolite production and genetic variability in B. monnieri, highlighting polyploid induction as a novel and promising approach to improving medicinal plant quality and diversity.