| Rice and wheat are widely cultivated around the world and are the main food sources of the current world population.However,rice and wheat are affected by rice blast and wheat head blight during the growth of rice and wheat,resulting in a significant decline in yield and quality,posing a certain threat to the food security of the world’s population.The use of fungicides has played an important role in the chemical prevention and control of two plant diseases,but there are many shortcomings in the use of conventional dosage forms:emulsifiable concentrates and microemulsions use a large amount of organic solvents and emulsifiers,which areflammable and explosive,high control costs,and poor environmental compatibility;during the processing of wettable powders,the dust pollution is serious,the suspension rate is low,and the control effect is poor;the suspensions and water emulsions are prone to instability such as delamination,water separation,and Austenitic maturation,and the shelf life is short.In addition,the conventional dosage form does not have the ability of slow and controlled release,and the effective ingredients are easily degraded and lost in the environment,resulting in a decrease in the prevention effect.It requires multiple applications to achieve the desired prevention and control effect.Mesoporous silica nanoparticles(MSNs)are common slow and controlled drug release carriers,which can not only avoid the photolysis of active ingredients,prolong the duration of pesticides,but also reduce the toxicity to non-target organisms and reduce environmental pressure.MSNs loaded with fungicides will provide new solutions for the green,efficient and safe prevention and control of rice blast and wheat head blight.In this paper,pyraclostrobin,prothioconazole and prochloraz are selected as fungicides commonly used in the prevention and control of rice blast and wheat head blight,and the drug-loaded mesoporous silica sustained-release agent has prepared by the sol-gel method.To characterize its physical and chemical properties,test its biological activity against pathogens(Magnaporthe oryzae;Fusarium graminearum),and investigate its safety to non-target organisms.The specific research results include:(1)Pyraclostrobin-loaded mesoporous silica nanoparticles(Pyraclostrobin@MSNs)were prepared by the sol-gel method,with an average particle size of about 200 nm,and the observation of the microscopic morphology showed that the Pyraclostrobin@MSNs had round shape,uniform size,rough surface,the pyraclostrobin entered the worm-like pore channels of MSNs;FTIR,BET and XRD measurement results showed that pyraclostrobin was successfully loaded by MSNs;TGA analysis showed that the drug loading was 38.9%.The release behavior study showed that the conditions of pH=5 and pH=9 were beneficial to the release of pyraclostrobin,and high temperature(45 and 35℃)were beneficial to the release of pyraclostrobin.The fitting results of the release models showed that the pyraclostrobin was released from MSNs by means of simple diffusion.The bioassay results showed that under the same concentration(10 mg/L),the commercial capsule suspension and Pyraclostrobin@MSNs had good control effect against M.and F.graminearum,as well as longer duration.The control effect of commercial capsule suspension against M.oryzae was slightly better than that of Pyraclostrobin@MSNs,and the control effect of Pyraclostrobin@MSNs against F.graminearum is slightly better than that of the commercial capsule suspension.Simultaneously,the test results of the inhibitory rate of the mycelial growth and the EC50 of the commercial capsule suspension and Pyraclostrobin@MSNs at different incubation times also confirmed this conclusion.The safety test results showed that Pyraclostrobin@MSNs had an LC50 of 15.58 mg/L for zebrafish for 96 h and an LC50 of 92.68 mg/kg for earthworms for 14 days.The acute toxicity of Pyraclostrobin@MSNs was low,indicating it was relatively friendly to water and soil environments.(2)Prothioconazole-loaded mesoporous silica nanoparticles(Prothioconazole@MSNs)were prepared by the sol-gel method,with an average particle size of about 200 nm,and the observation of the microscopic morphology showed that the Prothioconazole@MSNs had round shape,uniform size,rough surface,the prothioconazole entered the worm-like pore channels of MSNs;FTIR,BET and XRD measurement results showed that prothioconazole was successfully loaded by MSNs;TGA analysis showed that the drug loading was 38.8%.The release behavior study showed that the conditions of pH=5 and pH=9 were beneficial to the release of prothioconazole,and high temperature(45 and 35℃)were beneficial to the release of prothioconazole.The fitting results of the release models showed that the prothioconazole was released from MSNs by means of simple diffusion.The bioassay results showed that under the same concentration(10 mg/L),the commercial oil-based suspension concentrate and Prothioconazole@MSNs had good control effect against M.oryzae and F.graminearum,as well as longer duration.The control effect of Prothioconazole@MSNs against M.oryzae was significantly better than that of the commercial oil-based suspension concentrate,while control effect against F.graminearum was slightly better than that of the commercial oil-based suspension concentrate.Simultaneously,the test results of the inhibitory rate of the mycelial growth and the EC50 of the commercial oil-based suspension concentrate and Prothioconazole@MSNs at different incubation times also confirmed this conclusion.The safety test results showed that Prothioconazole@MSNs had an LC50 of 13.98 mg/L for zebrafish for 96 h and an LC50 of 139.05 mg/kg for earthworms for 14 days.The acute toxicity of Prothioconazole@MSNs was low,indicating it was relatively friendly to water and soil environments.(3)Prochloraz-loaded mesoporous silica nanoparticles(Prochloraz@MSNs)were prepared by the sol-gel method,with an average particle size of about 240 nm,and the observation of the microscopic morphology showed that the Prochloraz@MSNs had round shape,uniform size,rough surface,the prochloraz entered the worm-like pore channels of MSNs;FTIR,BET and XRD measurement results showed that prochloraz was successfully loaded by MSNs;TGA analysis showed that the drug loading was 40.6%.The release behavior study showed that the conditions of pH=5 and pH=9 were beneficial to the release of prochloraz,and high temperature(45 and 35℃)were beneficial to the release of prochloraz.The fitting results of the release models showed that the prochloraz was released from MSNs by means of simple diffusion.The bioassay results showed that under the same concentration(10 mg/L),the commercial emulsifiable concentrate and Prochloraz@MSNs had good control effect against M oryzae and F.graminearum,as well as longer duration.The control effect of Prochloraz@MSNs were significantly better than that of the commercial emulsifiable concentrate against both M.oryzae and F.graminearum.Simultaneously,the test results of the inhibitory rate of the mycelial growth and the EC50 of the commercial emulsifiable concentrate and Prochloraz@MSNs at different incubation times also confirmed this conclusion.The safety test results showed that Prochloraz@MSNs had an LC50 of 15.98 mg/L for zebrafish for 96 h and an LC50 of 130.25 mg/kg for earthworms for 14 days.The acute toxicity of Prochloraz@MSNs was low,indicating it was relatively friendly to water and soil environments. |
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