Activity Of A Novel DMI Fungicide Mefentrifluconazole Against Fusarium Fujikuroi And Magnaporthe Oryzae

Rice bakanae disease（RBDF）and rice blast disease（RBDM）,caused primarily by Fusarium fujikuroi and Magnaporthe oryzae,respectively,are destructive fungal diseases that lead to substantial reductions in both the yield and quality of rice crops.Fungicide application is the primary strategy for managing RBDF and RBDM.Mefentrifluconazole（MFZ）is a novel demethylation inhibitor（DMI）fungicide produced by BASF with high anti-fungal activity and minimal adverse side effects.However,its biological activity against Fusarium fujikuroi and Magnaporthe oryzae is not well studied.This study aimed to determine their baseline sensitivity to MFZ and its effect on their biochemical and morphological characteristics.The main results are as follows:For F.fujikuroi1.Baseline sensitivity to MFZ was established using mycelial growth and spore germination methods.The EC₅₀ values ranged from 0.0305 to 0.7579μg/m L and 0.1091 to1.6870μg/m L,with average EC₅₀ values of 0.2469±0.01669μg/m L and 0.6397±0.0324μg/m L,respectively.Both baseline sensitivity curves were unimodal in a sensitive range,indicating that MFZ exhibits excellent inhibitory activity against F.fujikuroi.2.Based on the observation of light microscopy and scanning electron microscopy,the mycelia branches of F.fujikuroi increased and contorted under the treatment of MFZ.In addition,the morphology of the spores was altered,accompanied by wrinkling and flattening.3.Treatment with MFZ significantly reduced the ergosterol content,increased the relative conductivity of the cell membrane,disrupted its integrity,and decreased chitin content of F.fujikuroi.4.Pot experiments demonstrated that MFZ exhibited excellent protective and curative activities against F.fujikuroi compared to phenamacril and prochloraz fungicides.In addition,the curative effect was up to 87.99%,while the protective effect was 76.48%,suggesting that the curative effect is more efficient than the protective effect.5.The treatment with MFZ at a concentration of 0.05μg/m L significantly reduced the production of Fumonisins（FB1,FB2,and FB3）in F.verticillioides and F.proliferatum,respectively.In F.proliferatum,FB1,FB2,and FB3 were reduced from 49349.29 to35317.71μg/kg,10937.13 to 7977.43μg/kg,and 4710 to 2270μg/kg,respectively.In addition,the content of Gibberellic acid（GA3）in F.fujikuroi had no significant difference compared to the control,and was slightly reduced from 9228.32 to 8615.32μg/kg.For M.oryzae1.The mycelial growth method was used to establish the baseline sensitivity to MFZ.EC₅₀ values ranged from 0.4131 to 1.5761μg/m L,with an average EC₅₀ value of 1.0189±0.3595μg/m L.The baseline sensitivity curve was unimodal in a sensitive range,and no resistant isolate was found,suggesting that MFZ exhibits excellent inhibitory activity on M.oryzae.2.After treatment with MFZ,the mycelia showed increased branching with visible contortion,shrinkage,and rupture.3.Treatment with MFZ significantly reduced the ergosterol content,increased the relative conductivity of the cell membrane,disrupted its integrity,and decreased chitin content of M.oryzae.Overall,these results demonstrate excellent inhibitory activity of MFZ against F.fujikuroi and M.oryzae,indicating that it could be an excellent alternative fungicide for controlling rice bakanae and blast diseases in China.