Wheat Powdery Mildew Triadimefon Resistance Monitoring Technology Standardization

The paper studied and compared the methods of collection , transport and keeping of Blumeria graminis f.sp. tritici which cause wheat powdery mildew and fungicide resistance monitoring. These results create the standard method to monitor B. graminis fsp. tritici resistance to triadimefon. The isolates of B. gram mis f.sp. tritici should be collected at random and at least 100 isolates in one location. Several methods can be used to transport isolates to Lab, such as leaf segments in water agar( 1 %),seedlings cultivated in tube, wheat bud in test tube. The strains can be kept on wheat seedlings for two weeks or kept on wheat bud under low temperature for I month. The later is better for keeping strains for long time. Sensitivity of B.graminis f.sp. tritici to triadimefon should be tested in viva, e.g. on wheat seedlings or wheat leaf segments. The seedlings should cultivated under standardized condition. The study show that 15 pieces of wheat buds were cultivated in a plastic cup , 6cm diameter and 8cm high , with lOg and lOOml hogland nutrition . The leaves of 15d old seedlings were the best to be used for monitor the resistance of the pathogen to fungicides. if leaf segments are to be used, the top and the basic segments should not to be used. When monitoring resistance, different fungicide treatment methods will lead to different results. Comparison studying of all methods of treatment shows that the monitoring result was more stable and higher sensitive with leaf segment treatment than treat whole seedlings treatment. What more, complex method, floating leaf segment-toxin culture, was better than sole treat method, So, floating leaf segment-toxin culture and spraying leaf segment are the two best methods to used in monitoring resistance with leaf segment, fungicide cultivating cultivars or spraying cultivars are the two best methods to used in monitoring resistance with cultivars. The EC50 triadimefon to of the same isolates varies along with the number of inoculating conidia. Take isolates yc88 for example, when the inoculating ascend from 215 conidialcm2 to 765 conidia/cm2, the EC50 varies from 0.0467 i g/ml to 0.3911 i g/ml. The later is about 10 times of the former. When the inoculating conidia varies among in 350?50 conidialcm2, the EC50 shows stable and consistent to the result in field. The resistant isolates of B. graminis f.sp. tritici to triadimefon have been found in field. The average resistant index is 3.2245 times and the highest is 6.7430 times. The resistant level of the powdery mildew in yixinjiangsu province is highest and the resistant frequency up to 40%. In B.graminis f.sp. tritici there is the cross-resistance between to triadimefon, diniconazole, and myclobutanil but not in diisothicyanatomethane and mancozeb.