Enhanced Inhibition of Fusarium graminearum Growth and Deoxynivalenol Production by Quinolizidine Alkaloids Combined with Berberine: In Laboratory Culture Media and Pig Feed

Phytochemicals with antifungal activity against Fusarium graminearum (F. graminearum) are considered potential in-feed anti-mycotoxigenic agents that may complement conventional post-harvest control strategies. Therefore, we screened fourteen phytochemicals, including seven quinolizidine alkaloids (QAs), for anti-F. graminearum activity, evaluated their individual and combined efficacy in inhibiting mycelial growth, spore germination, and deoxynivalenol (DON) production, and explored the underlying mechanisms via transcriptomic analysis. Matrine (MT), sophoridine (SR), and sophocarpine (SC) exhibited antifungal activity against F. graminearum, with minimum inhibitory concentrations (MICs) of 5, 4, and 4 mg/mL, respectively. The three QAs at their MICs completely inhibited mycelial growth and DON production in liquid cultures, but were less effective on potato dextrose agar plates and in pig feed. Particularly pronounced antifungal activity and inhibitory effects on DON production were observed when the three QAs were applied in combination with berberine hydrochloride (BBR). The observed inhibition appears to be attributed to dysregulated expression of the TRI cluster genes and ERG biosynthesis genes, coupled with significant modulation of steroid biosynthesis (ko00100) and central carbon/lipid metabolism pathways. These findings provide preliminary experimental evidence supporting the further exploration of QA–BBR combinations to control fungal proliferation and DON accumulation in pig feed.