Near-isogenic lines (NILs) carrying bacterial blight resistance genes (Xa4, xa5 and Xa21) were developed in japonica rice using Suweon345 as genetic background. NILs were selected by gene specific DNA markers and inoculation of K1 or K3a race. NILs conferring Xa4 were resistant to K1, K2, K3, and moderately resistant to K3a. NILs conferring xa5 were resistant to K1, K2, K3, and K3a. NILs having Xa21 were susceptible to K1, while resistant to K2, K3 and K3a. Target genes of NILs with the genetic background of Suweon345 were also confirmed by using eleven Philippines races and International Rice Bacterial Blight (IRBB) NILs carrying Xa4, xa5 and Xa21. All NILs had no significant difference from their recurrent parents in the major agronomic traits except for panicle length and brown rice 1,000 grain weight. Heading date of NILs ranged from Aug. 10 to Aug. 11, which was similar to that of recurrent parent, Suweon345. Culm length, number of grains per panicle and ratio of ripened grain of NILs were similar to those of Suweon345. Milled rice of NILs was ranged from 4.82 to 4.93MT/ha. These NILs will be useful for improving resistance to K3a race of bacterial blight pathogens in Korean japonica cultivars.

Korean Japonica resistant rice cultivars mainly posses one of the genes, Xa1 or Xa3 for BB resistance. These resistance genes are becoming susceptible to K3a, resulting in the breakdown of resistance of Japonica cultivars. Especially, glutinous rice cultivars exhibit high susceptibility to bacterial blight(BB) in Korea. This study was carried out to develop glutinous Japonica near-isogenic lines(NILs) conferring useful single gene such as Xa2, Xa3, xa5, Xa21, etc. Six NILs conferring Xa2, Xa3, xa5, xa8, Xa14 and Xa21 genes were developed. Six NILs with Sangjuchalbyeo genetic background were selected by DNA markers and inoculation of K1, K2, K3 and K3a race. NILs having Xa14 was resistant to K1 and susceptible to K2, K3 and K3a. NILs with Xa2 and xa8 was resistant to K1, K2 and susceptible to K3 and K3a. NIL with Xa3 was resistant to K1, K2, K3, but susceptible to K3a. NIL with xa5 was resistant to K1, K2, K3, and K3a. NIL having Xa21 was susceptible to K1, while resistant to K2, K3 and K3a. Identification of xa5 and Xa21 genes were carried out by STS markers. Heading date of NILs ranged from Jul. 31 to Aug. 6. Culm length, No. of grains per panicle and ratio of ripened grain of NILs were a little different to those of Sangjuchalbyeo. Milled rice of NILs were ranged from 437kg/10a to 463. Agronomic traits of NILs containing Xa2, Xa3, xa5, xa8, Xa14 and Xa21 were similar or a little different to those of recurrent parent. These NILs would be useful to develop durable resistant glutinous varieties in Korea.