The Sensitivity Difference Of Rhizoctonia Solani To Three Fungicides In Liaoning Province

Rice sheath blight is one of the three major diseases of rice in the world.The disease can occur in all stages of rice growth and development and has a great impact on rice yield.At present,chemical agents is still important the control of Rhizoctonia solani（R.solani）.Therefore,this thesis tested the sensitivity of R.solani in Liaoning Province to three chemical agents with different mechanisms of action:hexaconazole,thifluzamide and azoxystrobin.And screened strains with large differences in sensitivity to the same agent and strains domesticated against hexaconazole,and compared the biological characteristics and physiological and biochemical differences between the strains with different sensitivity to the same agent.We hope to find the most sensitivest biological characteristics to the agent.The traits provide a basis for the study of the susceptibility of pathogens to drugs and provide a reference for the rational use of drugs.The specific results are as follows:1.Sensitivity detection of R.solani to three fungicidesThe growth rate method was used to determine the susceptibility of R.solani from different areas in Liaoning Province to three different types of fungicides,hexaconazole,thiafluzamide,and azoxystrobin.Their sensitivity baselines were0.0225μg/m L,0.0659μg/m L and 0.0269μg/m L,respectively;Taking 5 times greater than the sensitive baseline as the criteria for the classification of resistant bacteria,two hexaconazole resistant strains were detected,from Dandong and Xinmin,with the frequency of resistance being 6.67%and 14.29%respectively;2 resistant strains to azoxystrobin were all from Dalian,with a resistance frequency of 13.33%;no resistant strains to thiafluzamide were found.R.solani had no cross-resistance to hexaconazole,thiafluzamide and azoxystrobin.2.Research on the biological characteristics of different sensitive strainsAmong the three agents,thiafluzamide and azoxystrobin selected strains with a large difference in sensitivity to study their biological characteristics.In addition to selecting strains with large differences in sensitivity,hexaconazole also selected several domesticated strains for comparison.Most of the strains with low sensitivity to fungicide have thicker hyphae,shorter branches,and different branch angles;The hyphae grow slowly,the dry weight of hyphae and sclerotia is smaller,and the sclerotia formation and production time is late;The sensitive strains have thinner hyphae,longer branches,and most of the branch angles are at right angles;the hyphae grow faster,the dry weight of hyphae and sclerotia is larger,and the sclerotia formation and production time is earlier.Most rice leaves inoculated with drug-sensitive strains have a high incidence and disease index,while those inoculated with domesticated resistant strains have relatively low incidence and disease index.3.Physiological and biochemical research on different sensitive strainsSince the selected three fungicides are different types and different mechanisms of action,the substances affected by them will be tested separately to determine the differences between different strains under the action of the reagents.The comparison of the ergosterol content of the different sensitive strains treated with medicines and the control strains showed that the ergosterol reduction ratios of the two domesticated resistant strains DL₂1XH and DL₂6XH and the two wild resistant strains XM2 and DD₂10 after the treatments were 21.25%,20.85%,17.65%and 16.90%respectively,which are significantly lower than the ergosterol reduction of sensitive strains;The ergosterol synthesis ability of the two untreated drug domestication resistant strains was stronger than that of the original strain,which indicates that the less sensitive strains and the drug resistant strains have stronger ergosterol synthesis ability than the sensitive strains after being interfered by hexaconazole.It may be the cause of strain insensitivity.The insensitivity of the less sensitive strain to thiafluzamide may be due to its higher SDH activity.The SDH activities of the less sensitive strains LY₁5 and DL₁1were 891.3653 and 572.3335 U/g,respectively,while the SDH activities of the sensitive strains BX₂14 and PJ₁6 were respectively 469.7303,440.8310 U/g;Under the action of thiafluzamide,the SDH activity of the less sensitive strains was139.4762,107.4127 U/g,which was still higher than the SDH activity of the more sensitive strains 60.9207 U/g and 48.0953 U/g.Without drug treatment,the mitochondrial respiratory chain complex Ⅲ activities of azoxystrobin-resistant strains DL₁1 and DL₂4 were 3.925 and 5.460 U/g,respectively,which were significantly lower than the enzyme activities of sensitive strains LY₁4 and XM4 at 9.984 and 6.552 U/g After the treatment,the enzyme activities of sensitive strains LY₁4 and XM4 decreased by 7.332 U/g and 4.576 U/g,while the enzyme activities of resistant strains DL₁1 and DL₂4 decreased by 1.221U/g and 2.236 U/g,respectively,indicating that azoxystrobin It has a stronger effect on the activity of respiratory chain complex Ⅲ of sensitive strains.