Abstract:In order to study the changes of physiological fitness between the tebuconazole-resistant strains and tebuconazole-sensitive strains of Rhizoctonia 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 carbon source included dextrose, sucrose, fructose, galactose, xylose, glycerin respectively, and the nitrogen source included ammonium sulfate, sodium nitrate, sub-sodium nitrate, urea, alanine, leucine, serine, proline, arginine, histidine, cysteine, lysine respectively. The results showed that, in the different carbon source all the strains grew fastest in dextrose, glycerin and sucrose after cultured 7 days, the colony diameter and dry weight were 3.1750-7.5667 cm and 0.0334-0.0554 g respectively, but 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), but no any obvious difference among WW, WW1 and WW2. In the different nitrogen sources, all the strains could utilize nitrites, sub-nitrates, arginine and ammonia more effectively, the colony diameter and dry weight were 6.2-8.8 cm and 0.0336-0.0543 g respectively, but could not utilize cysteine, the colony diameter and dry weight were only 1.4217-3.4750 cm and 0.0178-0.0297 g respectively. In the same nitrogen source, WWL grew slower than WW, WW1 and WW2, however, the difference of growth speeds of WW, WW1 and WW2 was not marked.