Abstract
Fifty one isolates of Pseudomonas eriobotryae phages were obtained from the cankerinfected loquat plant (Eriobotrya japonica Lind.) which were collected from various localities of loquat cultivation areas in Japan. These phages originated from the blightinfected bud, from the halo lesions of the leaf, and from the canker twigs were designated as EP1, EP2, and EP3 respectively.
The phage particles of both EP1 and EP2 are tadpole-shaped, and consist of a polyhedral head attached with long tail. EP1 phage has a head of 105nm in diameter with a tail of 170nm in length and 31nm in width, while EP2 phage consists of a head of 92nm in diameter with a tail of 118nm in length and 27nm in width. On the other hand, the shape of EP3 phage is much different from that of above two phages, and consists of a polyhedral head of 92nm in diameter with an extremely short tail of 17nm in length and 22nm in width.
Forty nine species (55 isolates) of pathogenic bacteria including 41 species of pseudomonads were tested on the susceptibility to each phages by means of the drop method. The host range of EP1 phage was strictly specific for P. eriobotryae, while others were non-specific. EP2 phage attacked P. ovalis and EP3 phage attacked P. striafaciens, P. mori, and P. flura, besides P. eriobotryae. Most of the isolates of P. mori were susceptible to EP3, but any kinds of P. mori phage did not attack P. eriobotryae isolates.
All the 123 isolates of P. eriobotryae were classified on the bases of their susceptibility to EP1, EP2, and EP3 phages as follows:
strain I; isolates which are susceptible to only EP1 but not to EP2 and EP3
strain II; isolates which are susceptible to only EP2 but not to EP1 and EP3
strain III; isolates which are susceptible to only EP3 but not to EP1 and EP2
strain IV; isolates which are susceptible to both EP2 and EP3 but not to EP1
strain V; isolates which are resistant to all of three phages
These strains seem to be different in their distribution patterns: the isolates belonging to strain I and III were widely distributed in Japan, and those belonging to strain II and IV were found to be distributed only in the intensivly cultivated area in Nagasaki Prefecture.
