At present, bacterial leaf blight of rice caused by Xanthomonas oryzae pv. oryzae is highly damaging to rice production in Indonesia as most of the existing commercial rice varieties are susceptible to the existing  pathotypes of the bacteria. To solve  such problems, varietal rotation should be based on information on the existence and dominance of local pathotypes in a particular rice ecosystem. To obtain this information, a total of 117 isolates of X. oryzae pv. oryzae, collected from West Java, Central Java, and Yogyakarta, were evaluated for their pathotype variation on five differential rice varieties during the dry season of 2000. When disease severity was < 10%, the reaction was classified as resistant (R) and when > 11%, was susceptible (S). The data indicated that 3.42% of the isolates were pathotype III, 12.82% were pathotype IV, and 83.76% were pathotype VIII. In West Java, the bacterial pathotypes III, IV, and VIII were 4.94%, 14.81%, and 80.25%, respectively. In low elevation areas, 4.94%, 9.88%, and 45.68% were pathotypes III, IV, and VIII, respectively and in medium areas, 4.94% were pathotypes IV and 34.57% were pathotype VIII. In Central Java, no pathotype III was found, while pathotypes IV and VIII were as much as 4.52% and 90.48%, respectively. In low elevation areas, no pathotypes III was recovered, and a total of 9.53% and 76.19% were identified as pathotypes IV and VIII, respectively, and in medium areas only pathotype VIII (14.29%) was identified. In Yogyakarta, pathotypes IV and VIII were found. In low elevation areas, 6.67% and 93.33% were pathotypes IV and VIII, respectively and in medium areas, 14.29% and 85.71% were pathotypes IV and VIII, respectively. The data indicated that variation in pathotype composition over different locations was obvious and locally specific resistant varieties to the disease are needed in the management of this important bacterial disease in rice.

Bacterial leaf blight (BLB) is a major disease of rice in Indonesia. Cilacap District of Central Java Province and Kuningan District of West Java Province are two endemic areas of BLB. The field trial was carried out in Cilacap and Kuningan in planting season of 2017 to evaluate resistance to BLB of 20 rice genotypes including 10 new improved varieties, one differential variety, nine isogenic lines. The trial was arranged in a completed block design with three replications. Data collected were: 1) Incidences and severities of BLB; 2) Resistances of the rice genotypes to BLB; and 3) Pathotypes of Xanthomonas oryzae pv. oryzae (Xoo). The results showed the incidence of BLB disease in Cilacap of 0-100% and disease severity of 0 to 85.18%. In Kuningan, the disease incidence was 0-100% and the disease severity from 0 to 79.26%. The varieties of Inpari-32, Java-14, and the lines of IRBB-5, IRBB-7, IRBB-21, and IRBB-57 were resistant to BLB in Cilacap and Kuningan. Those varieties/lines were expected to be used as a source of resistance to BLB in Cilacap and Kuningan. Xoo pathotype test showed that 14 Xoo isolates from Cilacap classified as pathotype VIII, while nine Xoo isolates from Kuningan were classified as pathotype III. The planting of resistant varieties based on the existence of the dominant of Xoo pathotypes which specific in the field can reduce the incidence and the severity of BLB disease effectively and efficiently, while the assembly of BLB resistant varieties can use the resistant genes of xa5, Xa7, and Xa21 as they were still effective to control the dominant pathotypes of BLB in Indonesia.