Phytopathology. 1999 Oct;89(10):928-33. doi: 10.1094/PHYTO.1999.89.10.928.
ABSTRACT Strains of Xanthomonas oryzae pv. oryzae that are virulent to rice lines carrying the Xa21 resistance gene were widely distributed in Korea. A total of 105 strains collected during 1987 to 1996 in Korea was characterized by pathogenicity tests and restriction fragment length polymorphism analysis of the XorII methyltransferase (xorIIM) and avrXa10 genes. Although the lesion lengths on rice line IRBB21, which carries Xa21, decreased as plant age increased, resistance and susceptibility of the plants to 31 strains were clearly differentiated at the seedling (14, 21, and 28 days old), maximum tillering, and flag leaf stages. The resistance or susceptibility of seedlings was correlated with bacterial populations within an inoculated leaf. There was a significant change in the population structure of X. oryzae pv. oryzae with regard to virulence to Xa21 over the last 10 years; this change in population was confirmed by genome analysis. Lineage I, which is avirulent to Xa21 and does not have a genomic xorIIM homolog, was the predominant lineage found between 1987 and 1989, while lineage II, which is virulent to Xa21 and contains the xorIIM homolog, was predominant in strains collected between 1994 and 1995. Our results demonstrate that introduction of Xa21 into commercial rice should be based on the regional structure of X. oryzae pv. oryzae populations and suggest that Xa21 will not be useful in Korea.
对携带 Xa21 抗性基因的水稻品种具有毒性的稻黄单胞菌菌株在韩国广泛分布。1987 年至 1996 年期间共采集了 105 株菌株，通过致病性测试和 XorII 甲基转移酶（xorIIM）和 avrXa10 基因的限制性片段长度多态性分析对其进行了表征。尽管携带 Xa21 的 IRBB21 水稻品种上的病斑长度随植株年龄的增加而减小，但在幼苗（14、21 和 28 天龄）、最大分蘖和旗叶期对 31 株菌株的抗性和敏感性仍能明显区分。幼苗的抗性或敏感性与接种叶片内的细菌种群有关。过去 10 年来，X. oryzae pv. oryzae 对 Xa21 的毒性的种群结构发生了显著变化；通过基因组分析证实了这种种群变化。无毒性且基因组中没有 xorIIM 同源物的 I 系是 1987 年至 1989 年期间发现的主要谱系，而对 Xa21 具有毒性且含有 xorIIM 同源物的 II 系则是 1994 年至 1995 年期间采集的菌株中主要的谱系。我们的结果表明，将 Xa21 引入商业水稻应基于 X. oryzae pv. oryzae 种群的区域结构，并表明 Xa21 在韩国将不会有用。
