Geographical Distribution of Pathogenic Races of Xanthomonas oryzae pv. oryzae in Japan in 1991 and 1993

Abstract

A survey of geographical distribution of pathogenic races of Xanthomonas oryzae pv. oryzae in Japan was conducted. The isolates collected from various localities of Japan in 1991 and 1993 were tested for their virulence to rice cultivars with each resistance gene including the near-isogenic lines. Of the 213 isolates collected in 1991, 133 were classified as race I, 79 as race II and 1 as race III. Only one isolate of race I was identified as race I A, while others as race I B, on the basis of the virulence to IR BB11 with resistance gene Xa-11. Race II isolates were divided into two subgroups based on the virulence to rice cultivar Asominori with resistance gene Xa-17. Of the 164 isolates collected in 1993, 92 were classified as race I, 55 as race II, and 16 as race III. All the isolates of race I belonged to race I B. Races II and III isolates were divided into two and four subgroups, respectively. One isolate H9396 collected from Kagoshima Prefecture showed a new virulence pattern which was different from those of the known races. This isolate was virulent to Kinmaze, Toyonishiki and Asominori but avirulent to other differential cultivars including IR24.