The Sensitivity Test And Resistance Risk Assessment Of Ustilaginoidea Virens To Propiconazole Fungicides

Propiconazole with safety,low toxicity,little dosage,less residual,wide bacteriocidal spectrum is one of the triazole fungicide.Propiconazole is extensive used to preventing and treating rice heading stage disease,such as Rice False Smut and Rice Sheath Blight.In this experiment,Ustilaginoidea virens are regarded as the research object and detected sensitivity to propiconazole and evaluated the risk of resistance to propiconazole,which has some guidences to prevent and treat Rice False Smut in production.Primary research as follows:1.Two hundred and thirty samples of infection Rice False Smut were collected from Nanjing,Yangzhou,Xuzhou,Yancheng,Huaian,Ganyu,Jintan in Jiangsu province and from Changsha in Hunan province.After these samples were separated and purified,111 strains of Ustilaginoidea virens were obtained.Sensitivity of 111 strains to propiconazole was measured by hypha growth rate method.It turned out that,the EC50 values of propiconazole to 111 strains ranged from 0.0022 to 0.1069μg/mL,and the mean value was(0.0485±0.0183)μg/mL.The sensitivity frequency distribution of these 111 strains displayed a successional unimodal curve,which was an approximately normal distribution and there was no subpopulation of sensitivity decline.Hence the mean EC50 value could be used as the sensitivity baseline of Ustilaginoidea virens to fungicides propiconazole.In these 111 strains,EC50 value of strain NJ013 which was the high sensitive strain to propiconazole fungicides was 0.0022 μg/mL.However,the value of EC50 was 0.1069 μg/mL in strain CS067,which was the least sensitive strain to propiconazole fungicides.The value of EC50 was 0.0486 μg/mL in strain HA225,which approached the mean value of EC50in 111 strains.Firstly,measurement some biological characteristics(growth velocity of hypha and sporulation quantity)of these 3 strains,The results are that hypha growth rate of strain CS067 is less than that of strain NJ013 and strain HA225 and spore output of strain CS067 is more than that of strain NJ013 and strain HA225.Secondly,CYP51 gene which is associated with these 3 strains resistant propiconazole was cloned and aligned sequences.We found that compared with strain CS067 and strain HA225,the CYP51 gene of strain NJ013 was mutative.The 477th basic group in the CYP51 gene of strain NJ013 mutated from A to T,which results the 131th amino acids of gene encoding was changed from Val(V for short)to Asp(D for short);and the 1269th basic group changed from T to C,but amino acids of gene encoding was invariant.V113D may led to sensitivity rising of strain NJ013 to propiconazole.2.The sensitivity to propiconazole and the part of biological characteristics(growth velocity of hypha and sporulation quantity)were measured about mutant UV34-3,UV34-11 and wild strain 34-1.We can find that the resistance level to propiconazole of mutant UV34-3 and UV34-11 strain was 8.7times and 10.5times of wild strain 34-1 respectively.The growth velocity of hypha and sporulation quantity of mutant UV34-3 and UV34-11 are lower than or weight against wild strain 34-1.CYP51 gene which is associated with these 3 strains resistant propiconazole was cloned and aligned sequences.The result is that gene sequences of mutant UV34-3 and UV34-11 are same to strain 34-1.Compared with strain 34-1,the resistance level to propiconazole of mutant UV34-3 and UV34-11 rises 8.7times and 10.5times.That may results from expression quantity of gene CYP51 of mutant strain UV34-3 and UV34-11 rising or ABC and MFS transport protein gene changing.3.The sensitivity to propiconazole and a part of biological characteristics(growth velocity of hypha and sporulation quantity)were measured about mutant strain with T-DNA insertion B857 and wild strain P1.We found that the resistance level to propiconazole of mutant B857 was 41.2times of wild strain PI.CYP51 gene which is associated with these 2 strains resistant propiconazole was cloned and aligned sequences.The result is that compared with strain P1,the 173th basic group changed from A to G,but amino acids of gene encoding was invariant;and the 175th basic group changed from T to A,amino acids of gene encoding was changed from Thr to Ser;and the 780th basic group changed from T to C,but amino acids of gene encoding was invariant.The 3 basic groups of CYP51 gene of T-DNA insertion mutant B857 changing that possibility is very little.Compared with strain P1,the resistance level to propiconazole of mutant B857 rises 41.2times.That may results from expression quantity of gene CYP51 of mutant strain UV34-3 and UV34-11 rising or ABC and MFS transport protein gene changing.4.In the paper,the sensitivity assay of wild strains to propiconazole was studied,as well as a part of biological characteristics of 3 strains with different sensitivity to propiconazole were compared of 3 strains with different sensitivity to propiconazole.The sensitivity to propiconazole and a part of biological characteristics of mutant strain which we obtaind from test conditions and wild strain were compared.The molecular mechanism of Ustilaginoidea virens to propiconazole effectting resistance(CYP51 protein gene appearring point mutation or expression quantity rising or ABC and MFS transport protein gene changing)was diversity.On the basis of the experiment,we concluded that Ustilaginoidea virens have a low or moderate resistance risk to propiconazole.