Screening Of Gaeumannomyces Graminis Resistant Strains To Fungicide Carabrone

Carabrone, a kind of sesquiterpene lactone compound extracted from a compositae plant called Carpesium macrocephalum, is a broad-spectrum antifugual activity substance with high efficiency, which is tend to be developed into a new type of fungicide. This research, aiming at the further study of the mechanism of carabrone, conducted induction of drug-resistant mutant when Gaeumannomyces graminis was viewed as the target fungy, obtained resistant mutants with genetic stability through resistance selection and method combining UV with fungicide Screening, thus laying the foundation for further research and rational use of carabrone and its analogues and providing materials for conducting research on the acting mechanism of carabrone.1. The sensitivity of four strains of Gaeumannomyces graminis which was isolated from four cities of Agricultural Microbiology Culture Collection,Shaanxi,Henan and Hebei（named JK、SX、HN and HB）was tested by the method of mycelial growth rate. The EC50 values is 53.06μg/mL, 49.90μg/mL, 45.36 μg/mL and 108.11 μg/mL respectively.All the tested strains were inhibited seriously by carabrone.Besides, high differential of EC50 values was among the different strains.2. Five resistance mutants was obtained by selection for resistance to fungicide and UV irradiation and fungicide selection. Four resistant mutants which named SX31-5、HN32-6、HN32-7 and HN32-9 were obtained by selection for resistance to fungicide,the EC50 values were 239.98³35.92 μg/mL,the resistance level was 4.85⁶.79, the mutation frequency was 0.01.One resistant mutant was induced by UV irradiation and fungicide selection,which named SX-ZWYJ,the EC50 values were 199.62 μg/mL,the resistance level was 4.04, the mutation frequency was 1.04×10^-4.3. Determination of the resistant stability of the resistant mutant strains shows that after nine generations were subcultured on the PDA without drug,The EC50 values of these four resistant strains such as SX-ZWYJ, HN32-6, HN32-7 and HN32-9 decreased slowly and had no significant differences as well as relatively high genetic stability. Among them, the EC50 value of the resistant strain SX31-5 enjoyed the maximum decrease and the low genetic stability.4. The determination results of biological characteristics of the resistant mutants indicate that: The growth rate of all the low-resistant strains significantly reduces when compared with initial strains, and as resistance level increases, the diameter of fungi colony gradually becomes smaller;The pathogenicity of other resistant strains, however, were significantly worse than the initial strain, while the pathogenicity significantly reduced as the level of resistance increased;the carabrone resistance appeared in resistant strains did not affect the biological characteristic of the optimum growth temperature, the optimal growth temperature for all resistant mutants was 26℃, which was the same as that of the initial strain;the generation of resistance will influence the optimum pH value for resistant strains growth and make the optimum growth pH value higher,the optimum growth pH value for resistant strains with higher level of resistance such as HN32-7 and HN32-9 is 7.0,for resistant mutant strains except HN32-7 and HN32-9, the optimal pH value for growth is 6.0 as the same as susceptible strains...