Study On Agricultural Antifungal Activity Of Uvaria Grandiflora Extracts

Botanical pesticide is an important part of the development of new green pesticides,which is in line with the development direction of modern agriculture.Forty kinds of tropical plants in Hainan province were selected in this study,and the plants with high agricultural biological activity（antifungal,insecticidal and nematicidal activities）were screened by bioassay-guided method.The experimental results showed that the extract of Uvaria grandiflora had high agricultural biological activity,and the most obvious one was its high inhibitory activity against phytopathogen.The EC₅₀ values of Uvaria grandiflora extract against Colletotrichum musae,Rhizoctonia solani,Phytophthora capsici and Gilbertella persicaria were only59.31μg/m L,100.84μg/m L,171.39μg/m L and 118.12μg/m L.Furthermore,based on the antifungal activity,the compound with high antifungal activity in the extract of Uvaria grandiflora was isolated and purified.By comparing its ¹HNMR,¹³CNMR and HRMS with known data,it was proved that this compound was zeylenone.The in vitro antifungal test results showed that zeylenone exhibited antifungal activities against ten kinds of plant pathogenic fungi at 50μg/m L.For example,the inhibitory rates of zeylenone against Colletotrichum musae and Phytophthora capsici were 84.3%and 88.1%,respectively.The inhibitory rates of zeylenone against Rhizoctonia solani,Pyricularia oryzae,Fusarium graminearum,colletotrichum siamense,Colletotrichum gloeosporioiles,Colletotrichum capsici,Gilbertella persicaria and Neoscytalidium dimidiatum were 40%～70%.Furthermore,the EC₅₀values of zeylenone against Rhizoctonia solani,Pyricularia oryzae,Pyricularia oryzae,Colletotrichum musae,Phytophthora capsici and Gilbertella persicaria were4.91μg/m L、21.38μg/m L、22.94μg/m L、3.37μg/m L、6.98μg/m L and 17.27μg/m L.The antifungal activity of zeylenone was comparable to that of commercial fungicides azoxystrobin and osthole.The potted experiment results showed that the protective effect of 5%microemulsion of Uvaria grandiflora extract against Phytophthora capsici was 100%at 1000μg/m L,which was comparable to the commercial fungicide dimethorphine.The control effect on Colletotrichum musae was 62.3%at 1000μg/m L,which was higher than the commercial fungicide azoxystrobin.The control effect on Podosphaera xanthii was 98.4%at 1000μg/m L,which was similar to the commercial fungicide propiconazole.The control effects against Pseudoperonospora cubensis and Phytophthora infestans were 100%and 98%at 250μg/m L,which were better than commercial fungicide cyazofamid.In the protective effect test of Uvaria grandiflora extract against Pseudoperonospora cubensis,it was found that different concentrations of the 5%microemulsion of Uvaria grandiflora extract had obvious promoting effects on cucumber roots,stems and leaves.The field efficacy test showed that the control effect on cucumber powdery mildew was 80.63%when the dosage of 5%microemulsion of Uvaria grandiflora extract was175 g/ha applied at the early stages of the disease,which was better than that of commercial fungicide Lunasen^?.At the same time,when the dosage of 5%microemulsion of Uvaria grandiflora extract was 375 g/ha applied at the middle and late stages of the disease,the control effect on Pseudoperonospora cubensis was40.64%,which was similar to that of commercial fungicide Yinfali^?.