PeerJ (Nov 2024)
Tilianin content and morphological characterization of colchicine-induced autotetraploids in Agastache mexicana
Abstract
Background Agastache mexicana Linton & Epling subsp. mexicana (Lamiaceae) is an aromatic medicinal plant, characterized by a high concentration of tilianin, a flavonoid with therapeutic potential in cardiovascular diseases. In this study, we have explored the use of colchicine to obtain autotetraploid lines of A. mexicana and analyze their morphological characteristics. In addition, we aimed to identify polyploid plants with a high content of tilianin. Methods In vitro seedlings at the stage of cotyledon emergence were dipped in colchicine solution at 0.0%, 0.1%, 0.3%, and 0.5% (w/v) for 6, 12, and 24 h. Seedlings were cultured on half-strength basal Murashige and Skoog medium supplemented with 20 g/L sucrose. After 2 months, the shoots from surviving seedlings were excised and grown individually in the same medium to obtain plantlets. The ploidy level of all materials was verified through flow cytometry and chromosome counting before acclimatization and transfer to the greenhouse. The investigated characteristics included length, density and stomatal index, leaf area, chlorophyll content, flower size and color, and tilianin content measured by high-performance liquid chromatography. Results The most efficient production of tetraploid in terms of percentage was achieved with 0.1% colchicine for 6 h resulting in no generation of mixoploids. Tetraploid plants had twice the number of chromosomes (2n = 4x = 36) and nearly twice the total DNA content (2.660 ± 0.236 pg) of diploids. Most tetraploid A. mexicana plants showed variations in flower and leaf characteristics compared to the diploid controls. High-performance liquid chromatography analysis showed that tetraploid plants with small leaves produced the greatest amount of tilianin; up to 32.964 ± 0.004 mg/g dry weight (DW), compared to diploid plants with 6.388 ± 0.005 mg/g DW. Conclusion In vitro polyploidization using colchicine demonstrates potential for enhancing bioactive constituents of A. mexicana. This approach has proven effective in generating elite tetraploid lines with increased tilianin production.
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