Baseline Of Blumeria Graminis F.sp.tritici To Two Fungicides And Analysis Of Genetic Diversity Of SDH Genes

Wheat powdery mildew disease is a typical air-borne polycyclic disease caused by obligate parasitic fungus Blumeria graminis f.sp.tritici.It is now listed by the International Fungicide Resistance Action Committee（FRAC）as a pathogen with a high inherent risk of resistance.Succinate dehydrogenase inhibitor（SDHIs）fungicides,as a new type of fungicides,have been developed more broad-spectrum types,such as fluazole hydroxylamine,etc.Fungicides are now classified by FRAC as having a medium to high risk of inherent resistance.Triazole fungicides are the main fungicides used to control wheat powdery mildew in China.At present,some scholars have proposed to mix,mix or alternate application of triazole agents with other fungicides with different mechanisms of action,so as to strengthen the cross-resistance relationship research of new inhaled fungicides,drug resistance risk prediction and field resistance monitoring,For example,Syngenta Company will use pydiflumetofen and propiconazole as a combination of companion agents to prevent and control wheat diseases.In this study,the susceptibility of Blumeria graminis f.sp.tritici to pydiflumetofen and propiconazole was determined by leaf segment leaching method in vitro,and the sensitivity baseline was established respectively,so as to provide the basis for prolonging the market life of pydiflumetofen and propiconazole,and provide the theoretical basis for rational drug use of wheat disease control and reducing the use of chemical agents.The results are as follows:In this study,the sensitivity of Blumeria graminis f.sp.tritici to pydiflumetofen was determined to be within the EC₅₀range of0.0061～1.6354μg·m L^-1.The Shapiro-Wilk normal distribution test was carried out on the measured EC₅₀data,and the P-value was obtained as0.23599.The P value>0.05 was consistent with the hypothesis of normal distribution test,and the sensitivity baseline was determined to be（0.2664±0.2701）μg·m L^-1.In this study,the sensitivity of Blumeria graminis f.sp.tritici to propiconazole was determined to be within the EC₅₀range of0.0068～2.3672μg·m L^-1.The Shapiro-Wilk normal distribution test was carried out on the measured EC₅₀data,and the P-value was obtained as2.301e-06.P<0.05 did not conform to the hypothesis of normal distribution test,and the average value of EC₅₀was determined to be（0.5764±0.5282）μg·m L^-1.SDHB,SDHC and SDHD genes of 60 strains of Blumeria graminis f.sp.tritici were amplified and sequenced.SDHB gene of Blumeria graminis f.sp.tritici is 789bp in length,contains an intron with a length of 51bp（268bp-318bp）and encodes 245 amino acids.SDHC gene of Blumeria graminis f.sp.tritici is 540bp in length,containing an intron with a length of 87bp（11bp-97bp）and encodes 150 amino acids.SDHD gene of Blumeria graminis f.sp.tritici is 610bp in length and contains an intron with a length of 97bp（145bp-241bp）,encodes 170 amino acids.After comparison,there was no change in the gene sequence or amino acid sequence of SDHB and SDHC,Three SNPs were found to change in SDHD gene,at the 75th,244th and 523rd sites,respectively.The genetic diversity analysis of SDHD gene showed that the haplotype polymorphism Hd was0.387,the nucleotide polymorphismπwas 0.00128,the genetic differentiation coefficient Kst value was 0.09325,and the Snn value was0.13174.The results showed that the three sites where SDHD gene mutated were synonymous mutants without changing amino acids.