The Mycoparasite Coniothyrium Minitans Dimethachlon Fungicide Resistance And Resistance Mechanisms Of Mutation Analysis

Sclerotinia sclerotiorum (Lib.) de Bary is an important parthogen, responsible for leaf blight, stem rot and pod rot of oil seed rape (Brassica napus L.), resulting in great losses to this crop, especially in the canola-growing areas along the Yangtze River in China. In recent years, biocontrol of sclerotinia diseases using the mycoparasite Coniothyrium minitans has attracted attention of many researchers. We hypothesized that maintaining high level of C. minitans population and integration of fungicides with C. minitans may improve the control efficacy of C. minitans.A study was initiated to mutate C. minitans to be resistant to the fungicide dimethachlon and to evaluate the resistance mechanisms of the selected mutants. Four mutants resistant to dimethachlon were isolated by incubation of the parent type strain SV-5-2 (conidia or mycelia) on potato dextrose agar (PDA) amended with the fungicide. The trait of the fungicide resistance was proved to be genetically stable as the 10th-generation progenies of these isolates were still resistant to dimethachlon. The mutated strains of C. minitans were slightly lower than parental strain in the mycelial growth, and production of amylase and protease .The wild-type strain Chy-1 and mutants of C. minitans were compared for sensitivity to osmotic pressure produced by glucose, sucrose, sodium chloride, potassium chloride, magnesium sulfate, sorbitol, mannitol or glycerol. Result showed that Chy-1 was greatly different from the fungicide-tolerant strains of C. minitans in sensitivity to osmotic pressure. In this study, we have successfully amplified a genomic fragment encoding a two-component histidine kinase gene from C. minitans with high homology to previously identified genes from other fungal species.