Molecular Mechanism Of Sclerotinia Sclerotiorum To The DCF Fungicide Dimethachlon

Sclerotinia stem rot of rapeseed is an important fungal disease which can severely reduce the yield and quality of rapeseed. Dicarboximide fungicides are widely used for controlling the disease. Its mode of action is not very clear, either the resistance mechanism to it.In this study, one field resistant isolate HN456-1-JBJ(EC5056.55μg/ml), and three resistant mutants FD47R(EC509.24μg/ml), HT84R(EC5095.51μg/ml) and LA50R(EC5094.87μg/ml) were obtained and studied in details. Sensitivity assay confirmed that these resistant isolates had much higher EC50values, even the resistance levels of them were different.All resistant isolate/mutants were sensitive to hyperosmosis,hydrogen peroxide, less virulence or aggressiveness than the wild isolates on detached leaves without fungicide treatment. Much electrolyte was leaked out of the mycelium in resistant isolate/mutants.From the mutant FD47R, a V238A point mutation was determined in the HK gene, a kind of Histidine kinase-group Ⅲ gene from HOG (high osmolarity glycerol) signaling pathway. No expression of the HK gene was observed in another resistant mutant HN456-1-JNJ. These result indicated that the resistance was associated with the functions of the corresponding genes in HOG (high osmolarity glycerol) pathway.