| The development of oak silkworm industry was seriously affected by the empty-gut disease of oak silkworm infected by Enterococcus pernyi.Fusarium wilt of melon infected by Fusarium oxysporum results in decreasing on the yield and quality of melon,which seriously restricts the sustainable development of melon industry.At present,chemical pesticides are mostly used in production to prevent and control the occurrence of these two diseases,but frequent use of pesticides is easy to cause the increase of pathogen resistance and impact on the ecological environment,and even endanger human health.Therefore,the development of new biocontrol agents is an urgent measure to solve the green prevention and control of insect and plant diseases.Silver Nanoparticles?Ag NPs?,due to their strong bactericidal properties and not easy to cause pathogen resistance,are increasingly be concerned in control of agricultural pests and diseases,and have a good development prospects.In this study,two methods?CL: Mycelium fermentation broth synthesis,CW: Synthetic method of mycelium soaking solution?were used to synthesize Ag NPs with Ag NO3 by using fermentation broth of different Trichoderma strains,such as Trichoderma atroviride,T.crassum,T.longbranchiatum,T.spirale,T.virens,T.afroharzianum,T.koningiopsis,T.hamatum,T.citrinoviride and T.velutinum,to analyze and screen Ag NPs with inhibitory effects on Enterococcus pernyi and Fusarium oxysporum and therir characteristics.The effects of Ag NPs on the growth and development and disease control of oak silkworm and melon were also discussed.The results are as follows:1.Ag NPs could be synthesized with CL and CW methods for 10 kinds of Trichoderma strains.The amount of Ag NPs synthesized with CL method was higher than that of CW method.The synthesis amount of Ag NPs-T.virens-CL was the highest?217.9 mg?,followed by Ag NPsT.longbranchiatum-CL?155.2 mg?.However,T.longbranchiatum-CL had the strongest bacteriostatic effect on E.pernyi and F.oxysporum.After comprehensive consideration,Ag NPs-T.longbranchiatum was selected as the Ag NPs for further study.2.Ag NPs-T.longbranchiatum with strong inhibitory effect on pathogen and Ag NPs-T.atroviride with low inhibitory effect on pathogen were selected for characterization analysis.The results showed that Ag NPs-T.longbranchiatum-CL had a face-centered cube structure with abundant surface functional groups,good monodispersity and small particle size,the reason of it's strong antibacterial effect was explained.3.The study on the growth and development of oak silkworm and the prevention and control of empty-gut disease of oak silkworm was carried out by using Ag NPs-T.longbranchiatum-CL.The results showed that low concentration(25 mg·m L-1,100 mg·m L-1)of Ag NPs had no fatal toxicity to oak silkworm,and prolonged the development time of 2nd instar(about prolonging 10 hours at 25 mg·m L-1and 19 hours at 100 mg·m L-1),and increased the weight of three-molting instars.After Ag NPs treatment,the activity of SOD,POD and CAT in haemolymph of oak silkworm and the activity of protease and amylase in intestinal fluid were significantly increased.Ag NPs could significantly increase the body weight of tussah and improve the survival rate of susceptible tussah.The survival rates of two treatments were 64.36%(25 mg·L-1)and 84.28%(100 mg·L-1),respectively.4.The effects of Ag NPs-T.longbranchiatum-CL on the germination and growth of melon seeds and control of melon blight were studied.The results showed that low concentration(25 mg·L-1)of Ag NPs could promote the germination and growth of melon seeds,while high mass concentration(>25 mg·L-1)showed negative effects.After Ag NPs treatment,CAT and POD activity in melon increased first,then decreased,while SOD decreased first,then increased.Ag NPs can reduce the incidence and disease index of melon blight. |
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