Abstract
Forty one isolates of Xanthomonas citri and forty two isolates of the related phage were obtained from the diseased citrus leaves collected from various citrus areas in Japan.
The phage isolates were classified into 2 groups according to their characteristics. One is a virulent phage named CP1, and the other could be a temperate one named CP2. CP1 phage is the typical one which is widely distributed in Japan. The electronmicroscopic study revealed that CP1 phage has a spherical head of 68mμ in diameter, with a tail of 160×15mμ in length and width. At 55°C after 10min., the phages are almost completely inactivated.
CP1a phage could be a mutant from CP1 and they are distinguishable from one another in the progressive effect of serum albumin and some other proteins on the efficiency of plating. The host range, morphological and serological characteristics, and thermal inactivation point of CP1a are the same as that of CP1.
CP2 phage originally isolated from the culture of the bacterial isolate N6006 produces turbid plaques on the plates seeded with the bacteria presenting a strictly reverse host range from CP1. The particle of CP2 phage consist of a polyhedral head with no visible tail, the diameter of which is 70mμ. The thermal inactivation point of this phage is equal to that of CP1.
The bacterial isolates collected from various localities of Japan were classified accord-ing to phage sensitivity as follows:
1. Sensitive to CP1 but not to CP2…………Lysotype A
2. Sensitive to CP2 but not to CP1…………B
3. Resistant to both CP1 and CP2…………C
Lysotype A and B are widely distributed in Japan. Most of the isolates belonging to A decompose mannit to produce acid. Those belonging to B usually do not, but there are some exceptions.
In the needle inoculation test, not any differentiation in pathogenicity was observed among the isolates according to their localities or source hosts.
