Abstract: 【Objective】A new inoculation method was used to discuss the difference of the influence of ‘Bingtang’ sweet orange and C-05 on the growth characteristics of Xanthomonas axonopodis pv. citri (Xac)by comparing different influences of leaves on Xac.【Method】The fully expanded leaves with light green of ‘Bingtang’ sweet orange and citron C-05 were sterilized by 75% ethyl alcohol and 1% NaClO, cut and cultured with Xac in the same petri dish to determine the influence of ‘Bingtang’ sweet orange or citron C-05 on the growth of Xac in MT medium or the NYGA medium replaced the middle place of the MT medium (MA). And the leaves’ solution of ‘Bingtang’ sweet orange or citron C-05 were extracted and added with 25%, 50%, and 75% to MT medium to determine the influence on the growth of Xac; also these were added with different ratios to NYGB medium to determine the content of extracellular polysaccharide (EPS) of Xac,respectively. 【Result】The leaves of ‘Bingtang’ sweet orange promoted the growth of Xac on MT medium. The proliferation of the strain could be viewed after 1 week, the average diameter of Xac was 0.5 mm larger than CK. After 2 weeks, the average diameter of Xac was 5.27 mm, which was the 3 times of that of CK. From 2 to 3 weeks was the rapid growth stage of Xac, the average diameter of Xac was from 5.27 mm to 13.41 mm, which was more than 5 times of that of CK. After 3 weeks, the Xac cultured with the leaves of ‘Bingtang’ sweet orange in MT medium grew smoothly and steadily. Compared with that of CK, the diameter of Xac cultured with the ‘Bingtang’ sweet orange was very significantly different. The Xac cultured with the leaves of ‘Bingtang’ sweet orange in MA medium was 4.58 mm after 1 day, and that of CK was 6.19 mm. After 3 days of inoculation, the average diameter of Xac cultured with ‘Bingtang’ sweet orange was the same as CK, and there were no significant differences with each other. After 5 days, the Xac cultured with the leaves of ‘Bingtang’ sweet orange grew rapidly and the average diameter was 21.31 mm, which was very significantly different with CK. Also, the leaves’ extracted solution of ‘Bingtang’ sweet orange was able to increase the growth speed and the content of EPSof Xac. Compared with CK, they all reached very significant level. The leaves of citron C-05 could control the growth of Xac in MT medium. After 1 week, there were no significant differences with CK. After 2 weeks, the average diameter of Xac cultured with the leaves of citron C-05 was the half of that in MT medium. After 3 weeks, the average diameter of Xac in MT medium containing the leaves of citron C-05 was 2.06 mm, which was smaller than CK (2.62 mm), and the diameter of Xac cultured for 2 and 3 weeks all reached very significant differences when they compared with CK, respectively. The Xac cultured in MA medium containing the leaves of citron C-05 were growing slowly and the average diameter of Xac was all lower than CK in different point times and they all reached very significant level comparing with CK, respectively. There were no significant differences in the influence of the leaves’ extracted solution of citron C-05 on the growth and the content of EPS of Xac compared with CK, respectively. 【Conclusion】Some substance in the leaves of ‘Bingtang’ sweet orange could promote the growth and the content of EPS of Xac. The substance in the leaves of citron C-05, which was able to control the growth of Xac, might be induced by defensive reaction, when the leaves of citron C-05 and Xac were contracted with signals. ‘Bingtang’ sweet orange might be break this kind of reaction by some substance promoted the growth of Xac.

Key words: ‘Bingtang&rsquo, sweet orange, citron C-05, Xac, the leaves&rsquo, extracted solution, exopolysaccharides (EPS)