| Strobilurin fungicide is a one of the most important class of fungicides used the natural antibiotics strobilurin A as lead compounds.It is a new type of bactericide as the energy resistance inhibiter.Strobilurin fungicide is a kind of efficient,broad-spectrum and systemic bactericide which has good activity for almost all of the fungi diseases(Oomycetes classes,Algae phylum,Ascomycetes phylum and Deuteromycetes)such as powdery mildew,rust,clever blight,mesh spot,downy mildew,blast,etc.It has good activity and can effectively control the other series of fungicide resistant pathogens.It also can improve the vegetative growth and production of crops.Strobilurin fungicide has become the world's largest fungicide category due to the high biological activity and unique mechanism.On the fungicide development history,it has set a new milestone after benzimidazole and triazole fungicides.At present,we have more then ten kinds of the commercialization of Strobilurin fungicides.Strobilurin fungicide accounted for 5.5% of the world pesticide market and accounted for 21.2% of the total global level of fungicide market in 2013.It is estimated that the world market of predicts will reachto $3.688 billion in 2018.As two varieties of them,pyraclostrobin and fluoxastrobin are widely used in recent years and broad prospects for application.However,because people use pesticidies not science which Lead a lower utilization rate in the process of application and most of the pesticides residues in soil ecosystems or the water ecosystem and bring potential damage to ecological environment security.In order to evaluate influence on aquatic ecological environment security,the present study sected zebrafish(Dania rerio)as the model organism.Zebrafish is kind of model organism internationally recognized in developmental biology.They have been widely applied in application,life science and water quality analysis,because of their small size,low cost breeding,strong vitality.Firstly,the acute toxicities of pyraclostrobin and fluoxastrobin in zabrafish were determined.Then,according to the 96 h LC50 values,the concentrations of subchronic toxicity experiment were set up.In this study,the zebrafish was exposed to a control and three concentrations of pyraclostrobin(0,0.001,0.01 and 0.1mg?L-1)and fluoxastrobin(0,0.001,0.01 and 0.1mg?L-1)respectively and were measured on days of 7,14,21 and 28.The present study was conducted to investigate the influence of Reactive Oxygen Species(ROS)content,Superoxide Dismutase(SOD),Catalase(CAT),Peroxidase(POD),Glutathione S-transferases(GST)activity,Malondialdehyde(MDA)content,the DNA damage of the zebrafish livers and the determination of pesticide residues.The results will be useful to evaluate the effects of pyraclostrobin and fluoxastrobin on the oxidative damage and genetic toxicity of zebrafish.which is also important to comprehensive understanding and evaluation of pyraclostrobin and fluoxastrobin potential toxic harm on the soil ecosystem to provide basic data.Main results were summarized as follows:(1)The pyraclostrobin was highly toxic to zabrafish with an LC50(96h)value of 0.056mg?L-1.The fluoxastrobin was very toxic to zabrafish with an LC50(96h)value of 0.514mg?L-1.The results showed that toxicity of the pyraclostrobin was higher than the fluoxastrobin.(2)Pyraclostrobin and fluoxastrobin can produce obvious effects of oxidative stress on zebrafish.In each group,the ROS levels were higher than the control.A significant difference could be observed between the treatments and control groups during the whole experiment.In addition,the ROS levels significantly increased with increasing concentrations of pyraclostrobin and fluoxastrobin.(3)Under the exposure of pyraclostrobin(0.001,0.01 and 0.02mg?L-1),the SOD and CAT activities in zebrafish were in suppressed phenomenon.The SOD and CAT activities exposed to fluoxastrobin(0.001,0.01 and 0.1mg?L-1)in zebrafish were activated at first and then in a suppressed state.Enzyme activity anomalies showed that the zebrafish liverd suffered some degree of damage.(4)The GST activity was influenced during the exposure of pyraclostrobin and fluoxastrobin.A significant difference could be observed between the treatments and control groups during the whole experiment.The GST activity of the concentration(0.001 and 0.01mg?L-1)group exposured to pyraclostrobin was inhibited on days 7,14 and 21.Nonetheless,the GST activity was activated on day 28 of exposure.And the GST activity of the concentration(0.02mg?L-1)was activated all the time.During the exposure period of fluoxastrobin,GST activity of the treatment group were received a degree of activation.In addition,the GST activity of the concentration(0.02mg/L)group was similar with the control on day 21.(5)A significant difference could be observed between the treatments and control groups during the whole experiment exposed to the pyraclostrobin and fluoxastrobin.The MDA content exposured to pyraclostrobin increased.Under the exposure of pyraclostrobin,the MDA content increased on days 7,14,21 and returned to control levels on day 28.Under the exposure of pyraclostrobin,the MDA content increased after exposed by 14 days,and a slight decreased on day 28.The MDA content exposured to fluoxastrobin decreased on days 7,28 and increased on days 14 and 21.(6)Under the exposure of two fungicides,the DNA damage increased greatly with the increase of the concentration and exposured time.In the present study,there was an obvious dose-effect relationship.Meanwhile,the comet assay was the most sensitive indicators in the present study.(7)At the same time,there should always be a specific method to detect the residues of pyraclostrobin and fluoxastrobin.The recovery rate of each treatment exposed to pyraclostrobin and fluoxastrobin ranged from 90.3%-100.4%.The residual concentration changed no more than 10%,which indicated that the concentrations of pyraclostrobin and fluoxastrobin were stable during the entire exposure. |
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