Analyses of The pathogenic race mutation In Magnaporthe grisea

为了了解日本稻瘟病菌的遗传背景，我们利用DNA指纹图谱和电泳法对日本稻瘟病菌进行了鉴定。利用MGR586和pMG60I5进行DNA指纹分析，将7株日本分离株和24株野生型菌株聚为5个克隆谱系。在JBLA-K04这一谱系中，包括了来自不同病原小种的所有田间分离物，在这些田间分离物中，对142个菌株的核型与致病小种的关系进行了进一步分析，发现JBLA-K04和JBLB-K33是两个主要的克隆谱系。这些结果表明，日本稻瘟病菌的致病力变异来自于包括染色体重排在内的突变。我们还分析了稻瘟病菌菌株Ina168的一个核型突变。这种核型突变在脉冲场分离的核型中产生了一条额外的染色体带。这种突变的特征是以12.5%的自发性…的高比率发生更巧妙的是，通过删除应用程序，单向生成额外的频段。野生型菌株中与IIIa带共迁移的一条染色体带IIIb的1MB DNA。从该菌株中克隆了编码rRNA的基因rDNA，并对其进行了分析。该基因位于带IIIb上，单位大小为APP。8KB。RDNA簇的大小为APP。400kb的突变型和野生型。我们的结论是，rDNA簇不是核型突变的原因。利用rDNA对JBLA-K04菌株的染色体大小变异进行了检测。我们没有检测到较大的大小变异，这表明该簇不会对田间分离物的染色体重排负责。利用日本菌株构建了一个交叉系统，用于无毒基因的遗传分析。对水稻品种K59进行了无毒遗传分析，结果表明无毒分离：致病力=21：8。

We characterized Japanese rice blast fungus by means of DNA fingerprinting and electrophoretic karyotyping in order to know their genetic backgrounds. Seven Japanese differential strains and 24 field isolates were clustered into 5 clonal lineages, in the DNA fingerprinting analyses using MGR586 and pMG60I5. In JBLA-K04, one of the lineages, all field isolates from various pathogenic races were included, In these field isolates, a relationship between karyotypes and pathogenic races Further analyses using 142 strains, revealed that two major clonal lineages, JBLA-K04 and JBLB-K33. These results suggested that the variation of pathogenicity among Japanese rice blast fungus were derived from mutations including chromosomal rearrangements.We also analyzed a karyotypic mutation in Magnaporthe grisea strain Ina168. This karyotypic mutation generates one additional chromosomal band in the pulsed field separated karyotype. This mutation was characterized to occur at a high rate of 12.5% sponta … More neously, in uni-direction to generate the extra band, by deleting app. 1Mb DNA from a chromosomal band IIIb which comigrates with band IIIa in the wild type strain. rDNA, the gene encodes rRNA which reported to be causes of chromosomal rearrangement in yeasts, were cloned from the strain and analyzed. The gene located on band IIIb, and unit size of the cluster was revealed to be app. 8kb. The size of the rDNA cluster was app. 400kb in both mutant and wild type. We concluded that rDNA cluster was not the cause of the karyotypic mutation. The rDNA was used for detecting chromosomal size variation among field isolates belong to JBLA-K04. We could not detect major size variation, indicating that the cluster would not be responsible for the chromosomal rearrangement in field isolates.A cross-system utilizing Japanese strain was constructed for genetic analyses of avirulrence genes. A genetic analysis of avirulence toward rice variety K59 was performed, and revealed segregation of avirulence : virulence =21 : 8. Less