Allelopathic suppression of seed germination and carbohydrate metabolism: Integrated physiological and gene expression analysis of Raphanus raphanistrum L. aqueous extract on Cuscuta chinensis L. and Solanum lycopersicum L.

Allelopathy offers a sustainable approach to weed management through naturally derived plant compounds. This study evaluated the effects of water-based extracts of Raphanus raphanistrum L. on the germination of seeds, initial seedling growth, and starch-metabolism-related gene expression in Cuscuta chinesis and Solanum lycopersicum. Seeds were treated with 0, 1, 2, 4, 6, 8, or 10% (w/v) extract. Germination percentage and germination speed, mean germination time, mean daily germination, water imbibition, and seedling growth were measured. Relative expression of BAM and CUSAMY2 was assessed by quantitative reverse transcription PCR. The extract caused concentration-dependent inhibition in both species C. chinensis germination was completely suppressed at concentration of 4% and above, whereas tomato germination declined progressively and was fully inhibited at 10 % radicle, plumule, and total seedling lengths also decreased, significantly with increasing extract concentration, with a minimum length of 0.1 mm recorded at 8%, molecular analysis showed marked treatment-dependent changes in BAM and CUSAMY2 expression, including strong repression to 0.01- 0.04-fold relative to the control under several treatments. These molecular responses were associated with reduced germination and seedling growth. Overall, R. raphanistrum aqueous extract exhibited strong allelopathic activity, particularly against C. chinensis, and interfered with physiological and molecular processes involved in early germination. The plant is a potential source of natural bioherbicidal compounds, although chemical characterization and soil- and field-based validation are required before practical application.