The Difference Between Tebuconazole And Myclobutanil Enantiomers On Fumonisin Productions By Fusarium Verticillioides

Trizole fungicides are widely used in the control of Fusarium,comprising two or more enantiomers with different fungicidal activity,toxicity and environmental behavior.When toxigenic Fusarium infects crops,it will not only reduce the yield of crops due to diseases,but also further affect the quality of agricultural products through the production of mycotoxins,and even seriously endanger human and animal health.For example,fumonisins released by Fusarium verticillioides can cause equine leukoencephalomalacia,porcine pulmonary edema and liver cancer in rats,and it is also related to the occurrence of human esophageal cancer,which is a serious problem facing the safety of agricultural products at present.At present,the study of chiral pesticides focuses on the difference of enantiomer bioactivity,toxicity and environmental behavior.However,the effects of different enantiomers on mycotoxin production of Fusarium have not been reported.Therefore,the objectives of the present study were to make it clear that the enantioselectivity of myclobutanil and tebuconazole on fumonisins accumulation by F.verticillioides under different environment condition.Our results can provide useful preliminary information for predicting the possible risk of fumonisin contamination for applying chiral fungicides in field and provide the theory basis for decreased fungicide application.Main results for this study are as follows:1.Evaluate environmental conditions on the growth of F.verticillioides and fumonisin production.The growth rate of F.verticillioides accelerates with the increase of water activity,which the highest growing rate at 30?.The fumonisin-capability of F.verticillioides was significantly influenced by temperature,water activity,and fungicides dose.Fumonisins produced by F.verticillioides was significantly affected by temperature,water activity and dose of the tested agent.The optimum condition for F.verticillioides to produce fumonisin was 0.99 a_w,25?.2.To determine the concentrations of rac-myclobutanil,rac-tebuconazole and its enantiomers needed to inhibit the growth rate of F.verticillioides by 10,50,and 90%(EC₁₀,EC₅₀,and EC₉₀,respectively)under different culture conditions.The results showed that the rac-tebuconazole and its enantiomers show different effects,and the order of fungicidal activity is:?-?-tebuconazole>rac-tebuconazole>?+?-tebuconazole.?-?-Tebuconazole exhibits the maximal selective toxicity against F.verticillioides,it is 242 times more toxic than?+?-tebuconazole in 0.95 a_w,35?.The minimal selective toxicity against F.verticillioides 25.9 times more toxic than?+?-tebuconazole in 0.97 a_w,25?.While the rac-myclobutanil and its enantiomers no effect on the fungicidal activity to F.verticillioides.3.Evaluate the effects of different concentrations(EC₁₀,EC₅₀,and EC₉₀)of rac-myclobutanil,rac-tebuconazole and its enantiomers on fumonisins production.Under most conditions,?-?-tebuconazole was a stronger inhibitor of FB₁ and FB₂ production than?+?-tebuconazole,by 1.87 to 2.85 times,furthermore,?-?-tebuconazole inhibited FB₁ and FB₂ production than rac-tebuconazole.?+?-Tebuconazole can induce FB₂,but?-?-tebuconazole and rac-tebuconazole showd decrease FB₂.We also found that the level of EC₅₀ and EC₁₀ of myclobutanil and tebuconazole induced the accumulation of FB₁ and not detected FB₂ in 0.97 a_w and 0.95 a_w.Under different experimental conditions,rac-myclobutanil and enantiomers had no selective different effects on production of fumonisins to F.verticillioides.4.Evaluate the enantioselectivity of myclobutanil and tebuconazole on FUM1 and FUM6 expression.With water activity and fumonisin production decreasing,the results showed that the expression of FUM1 and FUM6 gradually declined,it had positive correlation as to what the overall trend of fumonisin production was going to be,and the expression level of FUM1 and FUM6 managed by myclobutanil enantiomers seemed no correlation on fumonisin production.The expression level of FUM1 and FUM6 managed by tebuconazole enantiomers increased,which had negative correlation as to what fumonisin production was going to be.Furthermore,the expression level of FUM1 and FUM6 had positive correlation,regardless of water activity.