Study On Biology Of Fungicide-resistance Of Rhizoctonia Solani

Rice sheath blight caused by fungus Rhizoctonia solani Kiihn was considered to be the most destructive disease in China. The loss of rice grain caused by the disease was more than6.8billion kilograms every year. In this paper, biological characteristics of fungicide-resistance of the fungus to3fungicide, Jinggamgmycin, Propiconazole and Carbendazim, was detected using the fungus isolates collected in Guangxi. The purpose was to provide a scientific basis for the risk assessment of fungicide-resistance of the fungus, and offer a scientific basis for sustainable management of the diease effectively in Guangxi.480isolates of the fungus ware got from disease samples collected from the main rice growing areas in Guangxi. The population feature of fungicide-resistance was detected using these isolates. Correlation between fungicide-resistance and other biological characters was detected using representative isolates. Stability of fungicide-resistance was detected using representative isolates. The results were as follows.1. The fungicide-resistance of the fungus population to the3fungicides, repectively, belonged to characteristics of quantitative trait with continuous variation, and submitted to normal distribution.fungicide-resistance (in the way of inhibition rate to mycelium) of the fungal population to Jinggangmycin was from13.02%to82.31%. Isolates with the maximum fungicide-resistance was11-339-1, and isolates with the minimum fungicide-resistance was11-15-1, and average of inhibition rate was46.34%, and standard deviation of inhibition rate was12.32. EC50of the isolate with most sensitive to Jinggangmycin was369.4μg/mL, and that with most resistance to Jinggangmycin was2059μg/mL, and average EC50was1178.3μg/mLo fungicide-resistance (in the way of inhibition rate to mycelium) of the fungal population to Propiconazole was from23.01%to80.22%. Isolates with the maximum fungicide-resistance was11-437-1, and isolates with the minimum fungicide-resistance was11-33-1, and average of inhibition rate was53.61%, and standard deviation of inhibition rate was10.96. EC50of the isolate with most sensitive to Propiconazole was0.0042μg/mL, and that with most resistance to Propiconazole was0.0347μg/mL, and average EC50was0.0182μg/mL。fungicide-resistance (in the way of inhibition rate to mycelium) of the fungal population to Carbendazim was from16.61%to82.45%. Isolates with the maximum fungicide-resistance was11-458-1, and isolates with the minimum fungicide-resistance was11-78-1. and average of inhibition rate was56.00%, and standard deviation of inhibition rate was11.87. EC50of the isolate with most sensitive to Carbendazim was0.1374μg/mL, and that with most resistance to Carbendazim was0.5632μg/mL, and average EC50was0.3152μg/mL.2. There was significant correlation between fungicide-resistance of the fungal population to Jinggangmycin and that to Propiconazole, and also there was significant correlation between fungicide-resistance of the fungal population to Jinggangmycin and that to Carbendazim, and also there was significant correlation between fungicide-resistance of the fungal population to Propiconazole and that to Carbendazim,3. There was no significant correlation between fungicide-resistance of the fungal population to3fungicides, Jinggangmycin, Propiconazole, and Carbendazim, respectively, and3geographic parameters of location from where the fungus got, latitude, longitude, and altitude.4. There was no significant correlation between fungicide-resistance of representative isolates to3fungicides, Jinggangmycin, Propiconazole, and Carbendazim, respectively, and4biological characters of the isolates, sclerotia production, mycelium growth rate, pathogenicity, and crude toxin production.5. The fungicide-resistance of representative isolates remained about the same in8months after storage at room temperature. No obvious change was found in the fungicide-resistance of the representative isolates that were inoculated to host rice in succession for4times. Also, no obvious change was found in the fungicide-resistance of the representative isolates that were transferred and grown successively at slant medium of PSA for12times.