The Optimization Of Fermentation Condition And Preliminary Evaluation Of Control Effect Of Actinomycetes LY26 Anti Phytophthora Capsici

Phytophthora blight of pepper is a kind of soil borne disease which caused serious damage in pepper production and had a great impact on the yield and quality of pepper.In recent years,great attention has been paid to the biological control of crop diseases.As an important part of biological control,the research of biological control bacteria has gradually developed.In this paper,Phytophthora capsici was used as the indicator pathogen to study the biological control of P.capsici from the aspects of screening,identification,optimization of fermentation conditions and control efficiency.The results are as follows:(1)Actinomycetes strain LY26,which has antagonistic effect on P.capsici,was isolated from the soil of pepper cultivated in Hunan Province by plate dilution method.The antagonistic actinomycete strain LY26 may belong to Streptomyces scabies or S.europaeiscabiei.By measuring the antibacterial spectrum of LY26 strain,found that it had a wide antibacterial spectrum and had a good inhibitory effect on a variety of pathogenic fungi.The inhibitory rate of LY26 strain on P.infestans was more than90%,which had a certain research and utilization value.(2)In order to improve the production of active substances in LY26 fermentation products,the fermentation conditions were optimized.Among the tested carbon and nitrogen source medium,the best carbon source was rice flour,the best nitrogen source was yeast powder,the ratio of carbon and nitrogen of rice flour to yeast powder was 30:1,the culture medium of actinomycete LY26 had the highest antagonistic activity,the best carbon and nitrogen formula was: rice flour 40g/L,yeast powder 1.35g/L,sodium chloride 0.5g/L,potassium dihydrogen phosphate 0.5g/L Magnesium sulfate heptahydrate 0.5g/L,ferrous sulfate heptahydrate 0.01g/L.(3)In order to study whether the antagonistic metabolites of LY26 are affected by cell wall.The results showed that the antibacterial activity of LY26 was not affected by different metabolites in and out of cells,which provided guidance for the follow-up study.(4)In order to further clarify the biocontrol effect of LY26 on,the control effect of LY26 on Phytophthora blight of pepper in vitro and in vivo was measured by preinoculation and root filling.After inoculation with actinomycetes LY26 fermentation broth,the incidence rate of pepper fruit was only 28.79%.When pepper inoculated with P.capsici 5d,the control effect of LY26 on Phytophthora blight of pepper reached 60.36%.After inoculation with 12 d,the control effect of LY26 on Phytophthora blight of pepper was still 41.99%.But on the whole,the active substances produced by LY26 fermentation have a good control effect on Phytophthora blight of pepper which means the fermentation broths of LY26 is a potential biological control product.