Citrus Canker And Identification Of Strains Of Antagonistic

Citrus canker (Citrus bacterial canker disease) is one of the important bacterial diseases on citrus, caused by Xanthomonas axonopodis pv.citri. It is easy to spread and difficult to prevent. Citrus canker is not only popular in China, but also occurred in foreign countries. So it has been classified as a quarantine disease by domestic and broad. How to control citrus canker has been a worldwide problem, there are not yet a way to cure currently over the world, and chemical control is the main methods at present. Due to its enormous effects on human and environmental, to search a safe and efficient control methods is very necessary. Biocontrol depending on its safety, efficiency, less pollution and low cost is accepted by the general public, in recent years, more and more scholars studied the biological control metheds all the way, using biological control methods to deal with citrus canker has great potential.In this study, using Xanthomonas axonopodis pv.citri as the target, to screen the effective ingredients against the Xanthomonas axonopodis pv.citri as the purpose, the research of the bacteria isolated and purified, the screen of the activestrains against Xanthomonas axonopodis pv.citri, classification and identification of the antagonistic strains, the best optimization of fermentation conditions of the strains against Xanthomonas axonopodis pv.citri.The results are as follows:(1) After dilution the bacterial suspension, bacteria using mixing method, fungi and actinomycetes were isolated by using smear method,247 strains were obtained, of which 126 were bacteria.(2) Through flat confrontation experiments and the use of acupuncture inoculation tested on Citrus Tree, screened many bacteria strains that has antagonistic activity of citrus canker, two of this strains of antagonistic effect is very significant, named strain 24 and 861. Flat confrontation trials shows strain 24’s diameter is about 44mm, strain 861’s is 55mm. Test on Citrus Tree indicate the control effects of strain 24 is about 89.47%, and the efficiency of strain 861 even reached 94.74%.(3) According to observation of morphological characteristics, physiological and biochemical characteristics test,16S rDNA fragments amplified by sequencing and phylogenetic analysis, Biolog automated microbial analysis method, Screening of the strain 24 and 861 were classified. The results showed that, strain 24 was identified as Vibrio, and the NCBI accession number is FN997623.1 recently Vibrio diazotrophicus relationship,99% homology detection, Biolog the detect of 24 with Vibrio diazotrophicus have the similarity of 0.548. Based on the test results, the strain 24 was identified as Vibrio diazotrophicus. Strain 861 was identified as Serratia marcescens, Biolog result is similar to Serratia marcescens, and have the similarity of 0.535, the NCBI accession number is CP0039591 recently Serratia marcescens relationship,99% homology detection.(1) Culture from the different culture medium, temperature, pH, fermentation time, bottling capacity five factors on the fermentation conditions of strain 24 and 861 optimization. Results showed that the most suitable medium, the strain of anti Xanthomonas axonopodis pv.citri active substances produced by the LB; the optimum culture temperature was 30℃; it had the best antiviral effect as its pH is about 7.0; culture time 24 h; group training for 60 mL/100 mL bottling quantity. For the strain 861, the best medium is LB; the optimum temperature is about 36℃, the optimum pH is about 7.0 and culture time of 24h; the best bottling quantity is 60 mL/100 mL.