Screening And Synergistic Effect Of Ustilaginoidea Virens Sustained-release Film Agent

Rice false smut?Ustilaginoidea virens?Cooke?Takahashi?is a fungal disease caused by the infection of rice spikelet.In recent years,the disease has became an important common disease of rice fields in China.At present,the propiconazole,tebuconazole,difenoconazole,prochloraz and other pesticides had been used to control rice false smut but the“3R1P”problems?pesticide resistance,pesticide residue,rampant and environmental pollution?had been occurred by using chemical pesticides for longer term.In the current,rice false smut had been selected as the research object to screen effective synergistic agents and sustained-release film agents of prevention and controlling of it and the indoor bioactivity and field efficacy had been studied for providing new ways for the disease prevention and control.The main conclusions had been displayed in follows:1.A rapid method of the isolation of the U.virens was invented.It was determined that the HP-7 strain randomly selected from the 8 strains of Huangping as U.virens.The U.virens separation success rate by spore knock off method showed that fresh yellow,green yellow and green chiamydospore separation rate are 98.33%,1.66%and 0%respectively.The U.virens separation success rate by flame burning method showed that fresh yellow,green yellow and green chiamydospore separation rate are 63.33%,31.66%and 5%respectively.The fresh yellow chiamydospore was the best material for the isolation of U.virens and the green yellow chiamydospore was not suitable as the separation material.Segregation of fresh yellow chiamydospore using spore knocking method had the highest success rate.The strain of HP-7 were identified as U.virens by koch's rule,colony morpHology and rDNA-ITs sequence analysis.2.The sensitivities of HP-7,MT-5 and CB-3 strains to conventional fungicides and natural product citral were clarified.The strains of HP-7,MT-5 and CB-3 were randomly selected from 7 strains of Huangping,8 strains of Meitan and 5 strains of Chibi.The sensitivity of HP-7 strain to 7 fungicides is:tebuconazole>azoxystrobin>difenoconazole>hexaconazole>carbendazim>thiopHanate-methyl>jingganmycin.The sensitivity of MT-5 strain to 6 fungicides is:tebuconazole>difenoconazole>carbendazim>azoxystrobin>hexaconazole>jingganmycin.The sensitivity of CB-3strain to 6 fungicides is:tebuconazole>hexaconazole>azoxystrobin>thiopHanate-methyl>carbendazim>jingganmycin.The toxicity test of citral to U.virens showed that the EC₅₀0 value of citral to HP-7 strain was 32.0081 mg.L^-1.3.A synergistic formulation was screened out for inhibiting U.virens.A mixture of carbendazim and hexaconazole,carbendazim and difenoconazole,azoxystrobin and difenoconazole were prepared with different mechanisms of action.The results show that there are three synergies in total:when carbendazim and hexaconazole were mixed by 3:1,the CTC value was 251.04,and azoxystrobin was mixed with difenoconazole 1:3,the CTC value was 126.66.When azoxystrobin was mixed with difenoconazole 1:1,the CTC value was 154.03,which is much greater than 120,and the synergistic effect is significant.4.The 5%natural product citral sustained-release pHarmaceutical film was developed with good biological activity against U.virens.The biological activity of the 5%citral sustained-release pHarmaceutical film on U.virens was determined.The results showed that the inhibitory rates of 5%citral sustained-release pHarmaceutical film diluted by 50 times and 1600 times were 73.19%and 24.92%,respectively.The pHysicochemical properties of the 5%citral sustained-release pHarmaceutical film were determined mensurated.As a result,it was found that the stability of citral was increased after inclusion of citral.After 15 days,the remaining percentage of citral essential oil at 30?was only 28.4%,while the remaining percentage of inclusion complex was 74.2%.The pH value of 5%citral slow-release film agent is between5.51-7.45,and the viscosity value is between 2-177 mpa·s.The absorbance value is the largest when the wavelength is between 225-245 nm.5.The field efficacy of 5%citral sustained-release film and 30%difenoconazole·azoxystrobin were clarified.The results of average disease control efficacy showed that the 30%difenoconazole·azoxystrobin of 3200 times solution in chemical pesticides had the best effect,reaching 87.88%,and 20%Jinggangmycin wettable powder was the best effect of 1600 times in biological pesticides,up to63.55%.The results of the control of the average disease index showed that the 30%difenoconazole·azoxystrobin was the best in chemical pesticides,reaching 87.21%,and 5%citral sustained release film agent 800 times had the best effect in biological pesticides,up to 65.39%.