Phytotoxic and Antifungal Effects of Plantago major and Sambucus nigra Bioextracts on Key Agricultural Pathogens: Corynespora cassiicola, Fusarium oxysporum, and Penicillium oxalicum

Sustainable agricultural practices increasingly focus on natural bioactive agents for managing phytopathogens. This study investigates the antifungal and phytotoxic properties of methanolic bioextracts derived from <i>Plantago major</i> leaves (MBPm) and <i>Sambucus nigra</i> roots (MBSn) to explore their potential applications. Bioextracts were prepared through methanolic maceration, with yields of 6.02% (<i>P. major</i>) and 6.42% (<i>S. nigra</i>). Antifungal assays evaluated inhibitory effects on <i>Fusarium oxysporum</i>, <i>Corynespora cassiicola</i>, and <i>Penicillium oxalicum</i>, while phytotoxicity assays assessed concentration-dependent impacts on <i>Solanum lycopersicum</i> seed germination. A qualitative evaluation of major polyphenolic compounds was conducted using Ultra-Performance Liquid Chromatography coupled with a Photodiode Array Detector and Electrospray Ionization Mass Spectrometry (UPLC-PDA-ESI-MS) to identify bioactive compounds known for their significant biological activity. <i>P. major</i> bioextracts demonstrated significant inhibition of <i>F. oxysporum</i> (90.06%) and <i>C. cassiicola</i> (83.19%), while <i>S. nigra</i> bioextracts achieved 89.65% and 92.16% inhibition, respectively. Both bioextracts showed minimal impact on <i>P. oxalicum</i>, with effects observed only at 50 mg/mL. Low concentrations of <i>S. nigra</i> bioextract enhanced seed germination, whereas higher doses inhibited it. Identified bioactive compounds included acteoside, isoacteoside, chlorogenic acid, and dicaffeoylquinic acid isomers. The findings highlight the potential of these bioextracts as biocontrol agents and modulators of seed germination processes, contributing to sustainable agricultural strategies. While this study was conducted under controlled laboratory conditions, these results provide a strong foundation for future evaluations in field settings to explore their broader agricultural applications.