Screening Of An Actinomycete Against Phytophthora Capsici And Studying Its Antagonism Activity

Pepper Phytophthora Blight caused by Phytophthora capsici is a kind of fungal disease which can seriously harm the quality and yield of pepper.In the past,the prevention and control of pepper blight is mainly based on chemical control.The long-term use of chemical agents,on the one hand,it is easy to cause pesticide residues and harm the environment.On the other hand,it is easy for the host plants to develop drug resistance.Nowadays,the advantages of biocontrol bacteria in the control of crop diseases have become increasingly prominent,and has also achieved obvious results.In this paper,a biocontrol actinomycete against Phytophthora capsici was obtained through screening and identification.Its fermentation conditions and extraction of antagonistic substances were conditionally screened.The specific results are as follows:(1)In order to obtain the actinomycetes with good biocontrol effect against Phytophthora capsici,an actinomycetes CY-1 with obvious antagonistic effect against Phytophthora capsici was isolated and screened from 48 soil samples collected from the rhizosphere of pepper by the method of plate-contrast.In order to clarify the species and genera of CY-1,molecular identification and physiological and biochemical characteristics observation were used to identify CY-1.Preliminary identification results showed that CY-1 was related to Streptomyces scabies.(2)In order to obtain more active substances for the fermentation of biocontrol actinomycetes CY-1,single factor method was used to screen the carbon and nitrogen sources of CY-1 fermentation broth,and the ratio of carbon and nitrogen sources was optimized.The results showed that the optimal carbon source of CY-1 was corn meal,the optimal nitrogen source was yeast powder,and the optimal C/N ratio was20:1.The optimal fermentation medium formula(1L)of biocontrol actinomycetes CY-1 was as follows: corn meal 40 g,yeast powder 2g,sodium chloride 0.5g,dipotassium hydrogen phosphate 0.5g,magnesium sulfate heptahydrate 0.5g,and ferrous sulfate heptahydrate 0.01 g.(3)In order to determine the antagonistic activity of biocontrol actinomycetes CY-1,the antibacterial effect of CY-1 against 14 plant pathogens was determined,and the antagonistic effect of CY-1 against Phytophthora capsici was determined by inoculation method in vitro.The results showed that the strain CY-1 had a good inhibitory effect on all the oomycetes in the tested pathogens,and the inhibitory effect on Phytophthora capsici was the best,with the inhibitory rate of 96.93%.The results of in vitro inoculation experiment showed that the use of CY-1 fermentation broth could play a good prevention and control effect on Phytophthora capsici.The actinomycete CY-1 has the potential to control Phytophthora capsici,and further studies are needed to identify the value of its antimicrobial activities.(4)In order to study the antibacterial active substances of CY-1,three extractants with different polarity were selected to extract the active substances of CY-1fermentation broth,and the antibacterial effects of the three extracts were tested by plate antibacterial test.The results showed that the crude fermentation extract with ethyl acetate as extraction agent had the best antibacterial activity against Phytophthora capsici.Since ethyl acetate is a moderately polar organic solvent,it is speculated that the antibacterial activity of CY-1 may have a certain polarity.