| Tobacco,which plays an important role in promoting the development of agricultural economy and increasing the income of farmers,is an important economic crop in China.Tobacco black shank disease(TBSD)is one of the main diseases of tobacco production.This disease damages both the yield and quality of tobacco and threatens the economic benefits of tobacco production.In order to control the occurrence and epidemic of TBSD effectively,to secure the tobacco production,this study was carried out.In this study,the growth rate of mycelia were used to determine the indoor virulence of Phytophora nicotiana Breda de Haan,and the inhibitory effects of 11 kinds of synthetic antimicrobial peptides against P.nicotiana were studied.Finally,the pot and field experiments were conducted using the laboratory-screened chemical and biological fungicides.The results were as follows:1.P.nicotiana,which isolated from infected tobacco plant,was identified accurately and the pathogenicity was tested.Based on that,eight fungicides' virulence against P.nicotiana was determined using the method of mycelial growth rate.In this research,the result show that Phenazino-1-carboxylic acid suspension concentrate being the best control effect,the minimum inhibition concentration,EC50 was 0.5276 ?g/m L,correlation coefficient r was 0.9571;the following were 58% Metalaxyl-mancozeb wettable powder,80% Mancozeb wettable powder and 72% Dimethomorph-propineb wettable powder with each EC50 was 2.6328 ?g/m L,3.0775 ?g/mL,5.8530 ?g/m L and correlation coefficient r being respectively 0.9906,0.9368,0.9553.Then the fungicide of relatively insignificant effect were 30% Metalaxyl-hymexazol acqueous solution,52.5% Famoxadone-cymoxanil water dispersible granule and 70% Hymexazd wettable powder,respectively EC50 24.9082 ?g/m L,107.8243 ?g/m L,293.0293 ?g/mL and correlation coefficient r 0.9983,0.9985,0.9853.The control effect of 50% Chloroisobromine cyanuric acid soluble power acid is relatively poor with EC50 was 9074.5566 ?g/mL,r was 0.5336.2.According to the results of laboratory toxicity test,4 kinds of fungicide with strong virulence against P.nicotiana were selected for pot experiment:58% Metalaxyl-mancozeb wettable powder,80% Mzncozeb wettable powder,72% Dimethomorph-propineb wettable powder controlled and Phenazino-1-carboxylic acid suspension concentrate,controlled by water.It turned out that the disease index of the 4 treatments were significantly declined,compared with the control,and all the 4 treatments achieved good control results against TBSD.The biological fungicides,Phenazino-1-carboxylic acid suspension concentrate solution 1200 times liquid had the best control effort on TBSD with the control effort reach 87.49%.This was followed by 80% Mancozeb wettable powder solution 400 times liquid with the control effort of 74.98%,and 72% Dimethomorph-propineb wettable powder was the least effective,only 37.49%.3.The field experiment was performed by using 58% Metalaxyl-mancozeb wettable powder,80% Mancozeb wettable powder,72% Dimethomorph-propineb wettable powder and phenazino-1-carboxylic acid suspension concentrate on the foundation of indoor and pot experiments.By pouring root experiments 3 times and investigating 4 times,the results showed that phenazino-1-carboxylic acid suspension concentrate had a positive trend on the control of TBSD among indoor,pot and field experiment.The control effort of 58% Metalaxyl-mancozeb wettable powder was 75.78%,less than phenazino-1-carboxylic acid suspension concentrate 66.96%,the 72% Dimethomorph-propineb wettable powder has least control effect on TBSD in addition.4.Among the 11 kinds of synthetic antimicrobial peptides,antimicrobial peptides numbered T12,T13 and T18 have significant antifungal effects against P.nicotiana.The higher concentration the antimicrobial peptides have,the wider inhibition zone they have,the better antifungal effects they have.The antifungal effects decreased with the time prolonged.But the degree of this decreasing is different during different antimicrobial peptides. |
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