| Citrus canker disease caused by Xanthomonas axonopodis pv.citri.(Xac.) is a worldwide quarantine disease. So far, no effective method can be used to eradicate this disease. In this research, the isolation of canker disease has been performed firstly and then this isolated disease was used to conduct the inoculation assay. The results are following:Three different isolating methods were used, including dilution method, streaking method and tissue isolating method. The results showed that 4 to 5 fresh disease spots with 5mm diameter, sterilized by 75% alcohol for 30s and then 2% sodium hypochlorite for 12 to 15min, washed by sterile water 3 to 5 times were proper treatment for obtaining pure colony and streaking method is the best way to isolate the canker disease with its sample process and pure colony.With the needle-prick inoculation method, all the 6 species in citron have been found presenting typical disease spots on all the needle prick holes and the other tissue of the leaves without needle pricking were also found have being infected. The typical canker spot on all the 6 citron species were smaller then those in susceptible 'Bingtang' sweet orange with shallower crateriform heave.Compared with susceptible' Bingtang' sweet orange,6 species in citron showed different disease time. There was yellow halo on the third day and water soak heave on the sixth day after inoculation on the needle prick holes of' Bingtang' sweet orange. But the early typical disease symptom appeared on citron were in the seventh day after inoculation with yellow halo on the Java lemon and the water soak appeared at the 12th day after inoculation. There were largest amount of disease spots of leaf tissue without pricking by needle on the Java lemon, and smallest on the' yunnan xiaoxiangyuan'(C. medica L. var. yunnanensis S. Q. Ding)The another wild citrus genotypes, daoxianhuapiju and daoxianhuapigan, belong to moderately resistant varieties.
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