Activity and mechanism of metconazole against Fusarium verticillioides

Maize ear rot is a serious fungal disease that occurs worldwide and Fusarium verticillioides is the predominant causal pathogen of maize ear rot in China. In order to determine the potential application of metconazole against maize ear rot, the effects of metconazole on the mycelial growth, conidium production and germination, and germ tube elongation of 35 F. verticillioides strains collected from Shandong, Henan and Jiangsu provinces in China from 2019 to 2021 were determined by mycelial growth rate and spore germination method, respectively. Its effects on type B fumonisins (FBs) production and the expression levels of FBs biosynthesis genes of F. verticillioides were determined. The mechanism of action was explored by measuring the production of ergosterol, glycerol and malondialdehyde (MDA), and mycelial conductivity of F. verticillioides after metconazole treatment. Meanwhile, the control effect of metconazole on maize ear rot in the field was evaluated. The results showed that metconazole had strong antifungal activity against 35 strains of F. verticillioides, and had a dose-dependent inhibitory effect on mycelial growth, conidium formation and germination, and germ tube elongation of F.verticillioides. The EC₅₀ values of metconazole inhibiting mycelial growth of F.verticillioides ranged from 0.005 to 0.029 μg/mL, with an average EC₅₀ value of (0.012 ± 0.006) μg/mL. The average inhibition rates of EC₅₀ concentration of metconazole on conidial formation, germination and germ tube elongation of F. verticillioides were (20.59 ± 5.75) %, (24.88 ± 5.15) % and (59.98 ± 9.11) %, respectively. Metconazole significantly reduced the production of FBs and the expression level of FBs biosynthetic genes, and the inhibition rate on FBs production was 29.04%. The production of ergosterol in mycelia of F. verticillioides was significantly reduced, and the inhibition rate was 39.10%. At the same time, the production of glycerol and MDA, and relative conductivity were increased, and the induction rates of glycerol and MDA were 66.39% and 33.74%, respectively. Field experiments showed that the control effects of 90, 135 and 180 a.i. g/hm² metconazole against maize ear rot were (20.93 ± 4.65) %, (27.75 ± 5.71) % and (46.05 ± 9.90) %, and the yield increase rates were (8.86 ± 8.84) %, (17.28 ± 11.91) % and (33.20 ± 12.07) %, respectively, which were better than the control fungicide prothioconazole + tebuconazole. This study evaluated the potential of metconazole against maize ear rot and provided a theoretical basis for uncovering its activity and mechanism against F. verticillioides.