Study Of Fungicides On Virulence And Expression Of Related Regulatory Gene To Maize Ear Rot In Fengyang,Anhui Province

Maize ear rot is a worldwide fungal disease that not only reduces corn yield,but also causes fungal toxin contamination,which seriously affects the quality of corn and threatens human and animal health.Effective control of maize ear rot has become very urgent and important.The scarcity of resistant varieties and immaturity of biological control make chemical control the most basic and effective control measures.The special fungicide for maize ear rot has not been reported,so the screening of fungicides can provide a theoretical basis for chemical control.The biological characteristics of Fusarium graminearum,Fusarium oxysporum and Fusarium verticilliods,the main pathogens causing Maize Ear Rot in Fengyang,Anhui Province,were identified by the study of factors such as light,temperature,pH,carbon and nitrogen sources.The optimal temperature for the mycelial growth of Fusarium graminearum was 25?,the lethal temperature was 45?,10 min.The optimum carbon source was mannitol,and the optimum nitrogen source was yeast.The optimal temperature for spore germination of Fusarium graminearum was 28?,the lethal temperature was 45?,10 min.The optimal carbon source for sporulation was glucose,and the optimum nitrogen source was yeast.The optimal temperature for the mycelial growth of Fusarium oxysporum was 28?,the lethal temperature was 60?,10min.The optimum carbon source was maltose,and the optimum nitrogen source was beef extract.The optimal temperature for spore germination was 25?,and the lethal temperature was 55?,10 min.The optimal carbon source for sporulation is glucose,and the optimal nitrogen source is beef extract.The optimum temperature for mycelial growth and spore germination of Fusarium verticilliods was 28?,and the lethal temperature was 55?,10 min.The optimum carbon and nitrogen sources for mycelial growth were mannitol and peptone,and the optimum carbon and nitrogen sources for sporulation were glucose and beef extract,respectively.The optimum pH for mycelial growth and spore germination of three species of Fusarium was 7.0.Darkness is beneficial to mycelial growth and spore germination.Seven fungicides were selected to test the virulence to Fusarium graminearum,Fusarium oxysporum and Fusarium verticilliods indoor,single and combined fungicides with better efficacy were screened out.Difenoconazole has the strongest virulence effect on the mycelial growth of Fusarium graminearum,with the EC₅₀value 0.370?g/mL.Azoxystrobin has the strongest virulence effect on the spore germination of Fusarium graminearum,with EC₅₀0 value 0.097?g/mL.The combine of pyraclostrobin and difenoconazole displayed great synergistic effect at a ratio of 9:1and 7:3,with the SR values 5.338 and 4.413,respectively.The EC₅₀ value were 0.275?g/mL and 0.200?g/mL,respectively.Epoxiconazole has the strongest virulence effect on the mycelial growth and spore germination of Fusarium oxysporum,with EC₅₀ value 0.047?g/mL and 0.088?g/mL,respectively.The combine of pyraclostrobin and difenoconazole displayed great synergistic effect at a ratio of 9:1and 7:3,with the SR values 3.903 and 2.650,respectively,the EC₅₀ value were 0.173?g/mL and 0.094?g/mL,respectively.The virulence effect of epoxiconazole on the mycelial growth of Fusarium verticilliods was the strongest,with the EC₅₀ value0.035?g/mL.The carbendazim had the strongest virulence effect on the spore germination of Fusarium verticilliods,with the EC₅₀ value 1.802?g/mL.The combine of pyraclostrobin and difenoconazole displayed great synergistic effect at a ratio of 8:2?9:1 and 7:3,with the SR values 3.759?3.300 and 3.003,respectively,the EC₅₀ values were 0.193?g/mL?0.428?g/mL and 0.163?g/mL,respectively.The screening results showed that the combine of pyraclostrobin and difenoconazole displayed significant synergistic effect on the mycelial growth of three Fusariums at a ratio of 9:1 and 7:3.The relative expression of four related regulatory genes ChsV,FUBT,SOD and POD in Fusarium oxysporum showed that epoxiconazole and the combine of pyraclostrobin with difenoconazole could down-regulate ChsV,FUBT,POD genes and up-regulate SOD genes,which might affect the pathogenicity,the production of fusaric acid and self-defense ability of Fusarium oxysporum,and provide a way for the study of the mechanism of action.