Study On Identification,Biological Characteristics And Bactericide Screening Of Fructus Aurantii Canker Pathogens

Fructus aurantii（FA or zhiqiao）consists of the dry,unripe fruits of Citrus aurantium L.and its cultivated varieties.It is one of the authentic medicinal materials in Jiangxi Province.It has high medicinal value.The development of FA industry plays an important role in promoting the development of local economy and increasing farmers’income.However,with the continuous expansion of the planting scale of FA in Jiangxi Province,the types of diseases and insect pests continue to increase,and the degree of harm continues to aggravate.In this paper,we studied the isolation,pathogenicity detection,morphological observation and 16Sr DNA sequence analysis of the canker occurring in Jiangxi FA during its growing period in recent years to determine its pathogenic bacteria,and the biological characteristics of its pathogenic bacteria were studied and indoor screening of fungicides.Understanding the occurrence rule of pathogen and clarifying the characteristics of pathogen that causing disease will lay a foundation for further research on field control of the pathogen.The research results are reported as follows:1.Through the separation of pathogen from leaves of FA canker from 7 different bases,a total of 31 strains were obtained.The pathogenicity of these strains was detected,and 9 strains of pathogen that could cause FA canker were obtained.Morphological observation and 16Sr DNA sequence analysis were carried out and then the causative pathogen of FA canker was determined to be xanthomonas axonopodis pv.citr.2.In the study of biological characteristics,the pathogen of FA canker can grow well in SOC,SOB and LB medium,and the optimum medium is SOC.It can grow in the range of temperature 16～40℃,and 32℃is the optimum temperature for its growth.It can grow normally in the p H range of 5.0 to 10.0,and 8.0 is the suitable p H value.It can grow very well under a Na Cl concentration of 1%to 3%,and it has a strong ability of salt tolerance.It can make use of disaccharides and monoses in varying degrees,while the utilization degree of xylose,galactose,fructose is much more higher.Strain Xg7 made the strongest utilization degree of lactose（OD600=0.6194）,while the other strains made strongest utilization degree of fructose,and the OD600 values are respectively:0.7998,0.7139,0.7609 and 0.7466.The isolated strains did not utilize nitrate and ammonium nitrogen to a high degree,and had no significant effect on the growth of the strains.The pathogen could grow well in the medium containing ampicillin,and showed a certain resistance to it with the weakest sensitivity,and displayed almost no resistance to other antibiotics tested with a stronger sensitivity.3.In the indoor toxicity test of 41 fungicides to Xcc,there were 9 kinds of fungicides,including 50%Chlorobromoisocy-anurate,53%Zhongshengmycin,4%kasugamycin et,which showed certain inhibitory effect on FA canker.The value of EC₅₀ is an important index to measure the fungicide toxicity.The lower the EC₅₀ value,the more toxic the fungicide is.It can be seen that the bacteriostatic effects of 9fungicides on the pathogenic bacteria of FA canker from the largest to the smallest are as follows:4%kasugamycin(EC₅₀=0.0222),53%Zhongshengmycin(EC₅₀=45.8775),8%difenoconazole Zhong Shengmycin(EC₅₀=64.5654),50%thiram(EC₅₀=232.1133),50%Chlorobromoisocy-anurate(EC₅₀=402.9953),80%ethylicin(EC₅₀=527.1085),triadimefon·ethylicin 32%EC(EC₅₀=1438.7986),70%mancozeb(EC₅₀=1489.7041),64%oxadixyl mancozed(EC₅₀=2224.3340).As can be seen from the EC50 value,the antibacterial effect of 4%kasugamycin WP is particularly outstanding,followed by 53%Zhongshengmycin and 8%difenoconazole Zhong Shengmycin,while 70%mancozeb and 64%oxadixyl mancozed have certain antibacterial effect at various dilution ratios,but the effect is poor.4.The results of the field efficacy test showed that the 4 kinds of medicaments have a certain control efficiency on FA Canker,and their preventive effects are as follows:70%mancozeb（67.81%）>>8%benzyl·Zhongsheng（56.12%）>45%Chunlei·Cuquinoline（41.78%）,6%Kasugamycin and 80%Ethylicin have no obvious inhibitory effect on ulcer disease.