Abstract
The comparative ability of three phage-types of Xanthomonas citri (Hasse) Dowson, A, B, and C, to survive in diseased tissues was examined by inoculating the mixture of an equal amount of each on leaves of adult Natsudaidai (Citrus natsudaidai) and Unshu (C. unshu, variety Sugiyama) trees. The population of phage-type C was overcome by those of the phage-types A and B, and quickly decreased to an undetectable level by conventional plating methods of isolation. When inoculated singly, however, the population level of C was maintained like that of types A and B. The selective reduction of C was accelerated by serial passages through host plants. No difference was observed in the processes of phage-type selection by Natsudaidai or Unshu. Unlike the assumed host specificity of phage-type A and B to Natsudaidai and Unshu, respectively, based on the isolation frequencies in field surveys, no particular relationship was revealed between them from the view point of growth and survival in the diseased tissues. The same results were obtained when two phage-types were inoculated in combination on citrus leaves.
