A Survey of Geographical Distribution of Pathogenic Groups of Xanthomonas campestris pv. oryzae from Japan in 1977 and 1979

Abstract

A survey of geographical distribution of pathogenic groups of Xanthomonas campestris pv. oryzae in Japan was conducted. The isolates collected from various localities of Japan in 1977 and 1979 were examined for the qualitative virulence to five differential rice varieties. Of the 453 isolates tested, 266 (58.7%) were classified as bacterial group I, 141 (31.1%) as group II, 41 (9.1%) as group III, and 5 (1.1%) as group IV. The isolates of predominant groups I and II were found to be distributed in almost all localities of Japan. The isolates of group III were found in central and western parts of Japan, particularly in Nagano, Shizuoka, Nagasaki, Kumamoto, and Kagoshima prefectures. Five isolates of group IV were found: 2 of them in Okinawa and 3 in Nagasaki prefectures. No isolate belonging to group V was found in this test. In most of prefectures in both Kyushu and Shikoku regions, group II was isolated most frequently. Such a high incidence of group II may be attributed to predominant cultivation of Kogyoku group varieties which can be attacked by group II. However, the results that groups II, III and IV which can attack Kogyoku group varieties were found in the regions where Kinmaze group varieties had been cultivated extensively, suggest that some other factors must be involved in determining distributions of bacterial groups. In Akita and Yamagata prefectures located in nothern part of Japan, group II has been found to be distributed for the first time in this test. It is conceivable that in Nagasaki and Okinawa prefectures, group IV as well as groups I, II and III was distributed predominantly with high frequency. Most of the isolates belonging to groups II, III and IV were obtained from Kinmaze group varieties. Since there are the diverse distributions of pathogenic groups, it was pointed out that genetic and pathological approach to use horizontal resistance should be considered for reducing damage from the breakdown of vertical resistance by the variation in pathogenecity of the causal bacterium.