Design and application of a FA-based molecularly imprinted sensor for screening anti-Fusariumoxysporum substances...

Bulb rot caused by Fusarium oxysporum (F. oxysporum) is a major disease limiting the development of the Lanzhou lily industry. Fusaric acid (FA), a key virulence factor secreted by the pathogen, induces programmed cell death and accelerates bulb decay. Trace amounts of FA therefore serve as a critical biomarker for early disease warning and for screening eco-friendly biocontrol agents. To address the lack of rapid monitoring tools and reduce reliance on chemical pesticides, this study developed a molecularly imprinted electrochemical sensor for FA detection. The sensor was constructed on a chitosan-functionalized nitrogen-doped graphene-modified electrode to enhance conductivity, using FA as the template molecule and methacrylic acid as the functional monomer. Under the optimized conditions, the sensor exhibited a detection limit of 8.9 × 10^-4 μg mL^-1 and a linear range from 10^-3 to 10³ μg mL^-1. The sensor was further applied to screen 42 secondary metabolite samples (21 ethyl acetate extracts and 21 methanol mycelial extracts) derived from 21 endophytic fungal strains isolated from Lanzhou lily. Among the tested samples, the ethyl acetate extract of Penicillium crustosum ST12 showed the strongest inhibitory activity against F. oxysporum, with an inhibition rate of 69.33% in the FA-based screening assay.