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

Abstract

During 1991-93, a survey of the geographical distribution of pathogenic races of X. oryzae pv. oryzae was conducted in Japan. Isolates were collected from various locations and were tested for virulence to rice cultivars carrying resistance genes, including 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. On the basis of the virulence to IRBB11 (with resistance gene Xa-11), 1 isolate of race I was identified as race I A, while the others were race I B. Race II isolates were divided into 2 subgroups based on the virulence to rice cv. 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. Isolates of races II and III were divided into 2 and 4 subgroups, respectively. One isolate, H9396, collected from Kagoshima Prefecture showed a new virulence pattern which was different from patterns of the known races. This isolate was virulent to cv. Kinmaze, Toyonishiki and Asominori but was avirulent to other cultivars, including IR24.