Toxicity And Resistance Induction Of Fusarium Head Blight To Two Fungicides In Yangtze River Basin

Fusarium head blight?FHB?of wheat,caused by Fusarium graminearum Schwade,is a worldwide disease.FHB always popular in wheatarea of the middle and lower reaches of Yangtze River in China,it not only declines the production of wheat,and also produces fungi mycotoxin by the main deoxynivalenol,which are larger harmful to animals and people.At present,chemical control is still the main control measures for management of FHB in the production,but the long-term use of a single class of fungicides may result in resistant occurrence of resistant strains to fungicides and low control efficacy.Difenoconazole and tebuconazole are high activity,low toxicity,and broad-spectrum DMIs fungicides,which has specific mode of action to FHB.Therefore,in this study,the susceptibility of FHB to fungi difenoconazole and tebuconazole in the Yangtze River Basin was analyzed,the genetic stability of FHB to two fungicides was determined and the resistance was induced.It wants to clear that the resistance level and genetic regularity of the two kinds of fungicides of FHB in Yangtze River Basin.which provide an important advices for the production of rational pesticides use.The main research results are as follows:1.In May 2015,more than 100 samples of FHB and 176 strains were collected from 3provinces and 1 municipality?Hubei,Zhejiang,Jiangsu and Shanghai?in the Yangtze River Basin.According to the gathering place and morphological differences,we selected 30 strains as representative strains for population identification.The results showed that all strains belong to Fusarium graminearum,which are divided into F.asiaticum and F.graminearum.F.asiaticum is the dominant population.2.According to the gathering place,we selected 60 strains as representative strains,and measure its sensibility to difenoconazole and tebuconazole by the mycelial growth rate method.The results showed that 60 strains'average value of EC₅₀0 to difenoconazole was0.870±0.066?g/mL and the difference between maximum and minimum are 17.78 times.According to the city division,the average EC₅₀0 values of the strains collected in different cities were from high to low,respectively:Ezhou is 1.169±0.154?g/mL,Jiaxing is 0.999±0.107?g/mL,Nanjing is 0.875±0.216?g/mL,Yangzhou is 0.729±0.135?g/m L,Songjiang is0.628±0.131?g/mL.On the other hand,60 strains'average value of EC₅₀0 to tebuconazole was0.667±0.058?g/mL and the difference between maximum and minimum are 17.44 times.According to the city division,the average EC₅₀0 values of the strains collected in different cities were from high to low,respectively:Ezhou is 0.810±0.177?g/mL,Jiaxing is 0.763±0.128?g/mL,Nanjing is 0.638±0.099?g/m L,Songjiang is 0.629±0.101?g/mL,Yangzhou is0.554±0.126?g/mL.3.In this study the genetic regularity of two kinds of fungicides about FHB was determined.Five tested strains were screened for further subculture,and the strains of 1,5 and10 were determined for the two fungicides respectively,and compare the differences of EC₅₀between different generations of the same strain.The results showed that the resistance times of the strains to difenoconazole and tebuconazole was fluctuated within0.4-1.6,the floating range is small,which could explain that the toxicity level of two fungicides against the FHB can be inherited by asexual growth.4.Five strains were induced through two fungicide training methods on the plate.The sensitivity to fungicides(EC₅₀)was determined by the mycelial growth rate method,and the resistance rate was calculated.The results showed that the resistance level of strains to difenoconazole and tebuconazole are increased with the increase of generations comparing with the parent strain and there was no correlation between the increase range and the average resistance level.Compared with the parent strain,most strains appeared resistant strains,thus to a certain extent that there are some risk of resistance.Therefore,attention should be paied to reduce times of the use of difenoconazole and tebuconazole,and it was suggested that different fungicides should be mixed or wheeled to reduce the risk of drug resistance.5.The growth diameter of the induced by fungicides and parental strains were compared.The results showed that the diameter of colony growth of the induced strain was lower than that of the parent strain,indicating that the growth rate of the strain was decreased obviously.