Evaluation of allelopathic potentialities of an invasive taxon, Mesosphaerum suaveolens (L.) Kuntze, and bio-assay-guided identification of the involved allelochemicals

Weeds in crop fields pose a serious threat and devastate the overall agro-economy. Popular weed management techniques include manual and mechanical tillage, as well as the application of synthetic herbicides. These are used worldwide but have tremendous harmful side effects on both human health and environmental sustainability. So, alternative techniques are in great demand. The use of invasive alien species, with allelopathic potentialities against obnoxious weeds, has emerged as an alternative strategy for the formulation of environmentally safe bioherbicides. In the present investigation, extracts of an invasive species, Mesosphaerum suaveolens (L.) Kuntze was evaluated for their allelopathic effects on three test species Vigna radiata (L.) Wilczek., Sorghum bicolor (L.) Moench, and Parthenium hysterophorus L. Hexane-ethyl acetate fraction (1:1 and 1:2) of the methanolic leaf extract of M. suaveolens exhibits maximum inhibition. Allelochemicals affected the T₅₀ (time required for 50% germination of the total seeds) value of the bioassay materials in reference to the control. Biochemical analysis of the seeds treated with allelochemicals elucidated the reduction in insoluble carbohydrates, nucleic acids, protein-amino acid contents, and amylase action. The standard physical parameters also get affected. An increase in the stress-related antioxidant defence enzymes- catalase (166.81%), superoxide dismutase (242.02%), peroxidase (80.19%), as well as soluble carbohydrate (131.53%) was observed in both the treated seeds and seedlings. The pigment profiles, i.e., chlorophyll a, b, and carotenoids, changed. Proline contents get altered (102.43%). There was a significant change in the levels of indole acetic acid (47.77%), gibberellin (52.23%), and nitrites (182.62%) in the allelochemical-treated seedlings. Bioassay-guided fractionation with GC-MS analysis identified the major allelochemicals as 3, 4, 5-trihydroxybenzoic acid, transferulic acid, chlorogenic acid, sabinene monohydrate, and p-coumaric acid. In-silico analysis showed that the reported allelochemicals exhibit strong binding affinities. Chlorogenic acid (- 6.24 and - 6.32 kcal/mol) interacted prominently with tryptophan synthase β-subunit (PDB: 5DW3) and auxin-binding protein 1 (PDB: 1LRH), while caryophyllene oxide (-6.91 kcal/mol) modulated the activity of 4-hydroxyphenylpyruvate dioxygenase (PDB: 6J63). The present findings firmly establish the allelopathic potential of the invasive herb M. suaveolens as a robust, eco-friendly bioherbicide and provide clear direction for the sustainable management of the alien species.