In Korea, Xanthomonas oryzae pv. oryzae is divided into K1, K2, K3, K3a, K4 and K5 race by using differential varieties of Milyang23, Cheongcheongbyeo, Pungsanbyeo, Hangangchalbyeo and Milyang42. There is a difference between theory and current situation. The reason is that this differential varieties are Tongil-type and discrimination system constructed from the 1970s to the 1980s. So this study was carried out for reclassification of race of Xanthomonas oryzae pv. oryzae.

Isolates collected from 2001 to 2018 are divided using differential varieties. also, pathogenicity precisely checked up using the IRBB series (IR24, IRBB1, IRBB2, IRBB3, IRBB4, IRBB5, IRBB7, IRBB8, IRBB10, IRBB11, IRBB13, IRBB14, IRBB21), which is a Near-isogenic lines. As a result of comparing the pathogenicity with the classified race, it was confirmed that some of the pathogens classified as K3a race were different pathogenicity from the previously reported pathogenicity of K3a race. In other words, although K3a has been reported to show a resistance response to Xa21, a group of K3a race showing certain susceptibility to Xa21 has been identified.

In this way, although the classification system can be classified into the same race, it can be divided into different groups by confirming the pathogenicity by monogenic near-isogenic lines. Based on this, it is necessary to establish a detailed and efficient classification system of korean race classification.