Studies On The Resistance Mechanism Of Rhizoctonia Cerealis To Tebuconazole

The three tebuconazole-resitant strains (WX1, WX2, and WWL was middling resistant strains and high resistant strain respectively) of wild-type(WW) of Rhizoctonia cerealis were generated in the laboratory by ultra-violet (UV) and selection on PDA medium amended with the tebuconazole. The EC50 values was increased from 0.0120μg/ml of WW strain to 0.1226μg/mL, 0.2585μg/mL, 0.4004μg/mL for WX1, WX2, WWL respectively. The resistance ratios of WX1, WX2, WWL were 10.2-, 21.5- and 33.4-fold, respectively.In order to study the changes of physiological fitness between the tebuconazole-resistant strains and tebuconazole-sensitive strain of R. cerealis, different carbon source and nitrogen source were selected to prepare Czapak medium and to study their effect on the colony diameter and dry weight. The effect of different pH values and temperature values to tebuconazole-resistant strains and tebuconazole-sensitive strain of R. cerealis was also studied. The results showed that, in the different carbon source, all the strains grew fastest in dextrose, glycerin and sucrose after cultured 7 days, grew slowest in xylose and fructose. In the same carbon source, high tebuconazole-resistant strain (WWL) grew slower than tebuconazole-sensitive strain (WW) and middling tebuconazole-resistant strains(WW1 and WW2) , however the difference of growth speed was not evidence among WW, WW1 and WW2. In the different nitrogen source, all the strains could utilize nitrites, sub-nitrates, arginine and ammonia more effectively, but could not utilize cysteine. In the same nitrogen source, WWL grew slower than WW, WW1 and WW2. However, the difference of growth speed was not evidence among WW, WW1 and WW2. All the strains grew fastest in 6, 7, 11, 12 of pH values, but grew slowest in 4 and 10 of pH values. The diameters of the mycelial colonies for WWL were clearly bigger than that for WX1, WX2 and WW when the pH values was 4, but the diameters of the mycelial colonies for WWL was smaller than that for other strains when the pH values was 5, 11and12, respectively. However, the difference of diameters of the cycelial colonies was not evidence among all the strains when the pH values was 6, 7, 8, 9, and 10 respectively. All the strains grew fastest at 20 and 25℃, grew slowest at...