A simple method for maintaining Xanthomonas campestris pv. citri.
A typical colony of each of strains XW17, XW45, XW47, XW82, XW86, XW118, and XW138 of Xanthomonas campestris pv. citri was streaked onto nutrient agar, GY agar, minimal agar, and semi-enriched minimal agar plates, respectively. The agar plates, after incubated at 30 degrees C for 2-4 days, were inverted and stored at 4 degrees C in darkness. All of the X. campestris pv. citri strains retained their viability for at least 26 weeks on the semi-enriched minimal agar plates; whereas, cultures of these bacterial strains survived for only 2-10 weeks on the nutrient agar, 2-5 weeks on the GY agar plates and 12-26 weeks on the minimal agar plates. The bacterial strains which survived after 22-26 weeks on the semi-enriched minimal agar and minimal agar plates, respectively, also retained their ability to produce typical colonies and virulence. Thus, this semi-enriched minimal agar plate method is a simple and efficient way for maintaining the X. campestris pv. citri strains for a relatively long period.