Japanese Journal of Phytopathology
Online ISSN : 1882-0484
Print ISSN : 0031-9473
ISSN-L : 0031-9473
Natural occurrences of streptomycin resistant Xanthomonas oryzae, the causal bacteria of leaf blight disease of rice
Satoshi WAKIMOTOHideo MUKOO
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1963 Volume 28 Issue 3 Pages 153-158

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Abstract

Fifty five isolates of Xanthomonas oryzae were collected from various localities of Japan. The isolates were obtained in mass condition from diseased leaf specimens put on the slants of potato semi-synthetic media.
Each isolate was inoculated to slants of potato semi-synthetic media containing 1, 000ppm and 100ppm of dihydrostreptomycin sulfate, and were incubated at 25°C for 10 days.
Twenty three of the isolates developed well on the media containing 10ppm of dihydrostreptomycin sulfate. 16 of them developed well even on the media containing 1, 000ppm of dihydrostreptomycin sulfate. It may be noticed that most of the places where the resistant isolates were collected had never been sprayed with dihydrostreptomycin sulfate for the protection of the bacterial leaf blight disease of rice.
Proportions of dihydrostreptomycin resistant cells in each isolate were assayed. For this purpose, EDTA-Fe media added with dihydrostreptomycin sulfate at concentrations of 1, 000, 100 and 10ppm, were used. EDTA-Fe medium is suitable for development of colonies starting from single cells. The prepared plates were kept at 25°C for 8 days, and then produced. colonies were counted.
The proportions of the resistant cells contained in the isolates were much different from one isolate to another. Usually, the higher the concentration of dihydrostreptomycin sulfate, the fewer were the colonies produced. Some isolates, however, contained almost 100 per cent of resistant cells against even 1, 000ppm of dihydrostreptomycin sulfate.
It was considered that the wide distribution of the dihydrostreptomycin resistant isolates of X. oryzae, from practical view, would be important, because it might limit the use of the antibiotic against the bacterial leaf blight disease of rice.
A little difference, not so significant as against dihydrostreptomycin sulfate, was found among the isolates in their resistance against l-chloramphenicol and cellocidin.
l-chloramphenicol is considered to be the most effective antibiotic for the protection of bacterial leaf blight disease of rice, but the action of this antibiotic on most of the isolates in vitro tests was not completely cidal after 15 days incubation at the concentration of 100ppm.

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© The Phytopathological Society of Japan
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