Four bacterial blight resistance genes, Xa1+Xa3+xa5+Xa21, pyramid elite japonica rice lines were developed for enhancing the resistance of rice against Xanthomonas oryzae pv. oryzae in Korea. Seven doubled haploid (RDL1-7) and ten F 6 lines (RPL1-10) having Xa1+Xa3+xa5+Xa21 which were derived from the cross between Ilmi, high grain quality japonica rice cultivar carrying Xa1, and Iksan575, elite line carrying Xa3+xa5+Xa21, were developed using marker-assisted selection for resistance genes and

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... henotypic selection for bacterial blight resistance and agronomic traits. Among resistance genes combinations in F 2 population, four resistance genes combination, Xa1+Xa3+xa5+Xa21, showed the highest resistance and conferred the enhanced resistance than three genes combination, Xa3+xa5+Xa21. Four genes pyramid lines (RDL and RPL) showed broad-spectrum resistant against 16 Korean bacterial blight isolates and the yield and quality of the lines did not alter by the inoculation of K3a, the most virulent race in Korea. In addition, these lines had excellent plant type and exhibited more enhanced yield than previously developed resistant cultivars. Four bacterial blight resistance genes combination, Xa1+Xa3+xa5+Xa21, was efficient and promising combination and developed lines with four genes could be useful materials and will be applied to the breeding programs for enhancing the resistance of japonica rice against bacterial blight. 서 언 벼흰잎마름병은 Xanthomonas oryzae pv. oryzae에 의한 세균 성 병으로 벼를 재배하는 대부분의 국가에서 발생하여 많은 피해를 주는 병 중 하나이다(Mew 1987). 벼흰잎마름병 방제용 으로 몇 가지 화학약제가 개발되어 사용되고 있으나 방제효과가 낮아 저항성 품종 재배가 가장 경제적이고 효율적인 방제 수단으 로 알려져 있다(Khush et al. 1989, Shin et al. 2011) 지금까지 약 40여개의 벼흰잎마름병 저항성 유전자가 보고되 었는데 이중 우성유전자가 26개, 열성유전자가 14개이며 이들 저항성 유전자는 9번, 10번 염색체를 제외한 10개의 염색체에 위치하며, 특히 4번 염색체 장완에 8개(Xa1, Xa2, Xa12, Xa14, Xa25, Xa30(t)(Cheema et al. 2008), Xa31(t), Xa38), 11번 염색 체 장완에 12개(Xa3/Xa26, Xa4, Xa10, Xa21, Xa22, Xa23, Xa30(t)(Jin et al. 2007), Xa32(t), Xa35(t), Xa36(t), Xa39, Xa40)