The Sensitivity Of Population Of Blumeria Graminis F. Sp Tritici Isolates To Tradimefon And Quinoxyfen In China

Isolates of Blumeria graminis f. sp tritici were sampled from 6 provinces or cities, and the sensitivity of 108 isolates to triadimefon and 104 isolates to quinoxyfen was tested with seed treatment and detached leaf segment methods. The results showed that mean EC50 of isolates to triadimefon was 94.34 mg/L, and the mean resistance factor (RF) was 45.14. The frequency of resistant isolates to triadimefon reached to 97.25%.The resistance of Blumeria graminis f.sp.tritici from Hebei to triadimefon was higher than that of other five provinces.The average of the baseline to quinoxyfen was 5.9×10-3 mg/L. Results of the correlation analysis demonstrsted that there was no cross-resistance between triadimefon and quinoxyfen in Blumeria graminis f. sp. tritici.The resistance of isolates to triadimefon was caused not only by the single site mutation in the gene, which was found by detecting the resistant site 136 in the CYP51 gene of powdery mildew population in China with the technology of Allele-specific Polymerase Chain Reaction (AS-PCR), as well as cloning and sequencing them. Comparing the sequence of the resistant and the sensitive one, we found there were another five mutation sites in the gene 175,185,398,419 and 430. By constructing the protein′structure, as well as comparing the sequence to the one of high homology and known three-dimensional structure, we testified that these five sites seats in the important location which can decide the structure oh the protein. According to the theory of the structure decides the property, we analysed initially and determined that these sites have something to do with the resistance. Additionally, according to the relationship between the resistance base-line and the mutation site, we found the isolates mutated both in the 175 and 185 site, these isolates′resistance base-line are more than5; The sites 398, 419 and 439 belong to chain fixed mutation, the isolates with the resistance base-line be more 65 mutated respectively at the there sites. So we divided the resistance base-line in to three gradients: the sensitive, the moderate resistance and the high resistance (the sensitive EC50≤5,the moderate resistance 5﹤EC50≤65)and the high resistance EC50﹥65)...