Abstract: A total of 37.89 Mb of publicly available DNA sequence in rice blast fungus, Magnaporthe grisea was studied for mono- to hexa-nucleotide simple sequence repeat (SSR or microsatellite) to determine the type, size and frequency. A total of 16 398 SSRs were observed in the whole genomic DNA sequence with criteria of SSR length >15 bp and 80% matches. Considering all six classes of SSR, they occurred on an average about once every 2.31 kb for mono- to hexa-nucleotide in genomic DNA. The most abundant microsatellite was mononucleotide repeat, with the SSR number being 4 392, followed by trinucleotide and pentanucleotide repeats, being 3 586 and 3 442, respectively. These three classes of SSR occupied 69.7% of total microsatellite repeats. The least abundance was dinucleotide repeat, only 680 tracts were found. Repeats of A,AG,AC,ACG,AGC,AAG,GGC,ACCT,ATCC,AAAG,AAAAG,AAAAT,AAAAC,AAAAAG, AAAAAT and AACTAG were predominant, whereas some motifs absent in whole genomic sequence. Comparison of distribution and abundance between different superlinkage groups showed that there was little difference among supperlinkage groups at this level. Availability of these data should facilitate the utilities of SSR on molecular marker developing, population, structural and functional study of non-coding DNA sequence of the phytopathogenic fungus.

Key words: Magnaporthe grisea, genome, simple sequence repeat, frequency, distribution, genetic marker

摘要： 利用已经公布的稻瘟病菌基因组测序结果，对该植物病原真菌基因组中的微卫星（SSR）的类型、大小及分布进行了系统分析。在已经公布的37.89 Mb的基因组序列中，共有16 398个由1~6个核苷酸为基序的SSR序列（匹配值为80％），其总长度占整个基因组碱基数的0.87％，平均2.31 kb碱基中就分布有1个大于15 bp的SSR。其中数量最多的是单碱基重复，达到4 392个，其次为三碱基重复序列 （3 586个），五碱基重复序列（3 442个），这3种SSR总数达11 420个，占SSR的 69.7%。数量最少的是二碱基重复序列，只有680个。在整个基因组中的主要基序有A，AG，AC，ACG，AGC，AAG，GGC，ACCT，ATCC，AAAG，AAAAG，AAAAT，AAAAC，AAAAAG， AAAAAT和AACTAG。有的基序类型则完全没有出现。对不同超级连锁群的分析结果表明，各连锁群之间的SSR分布有一定差异，但总体上仍是较为均衡的。这些结果为稻瘟病菌的基因标记、群体结构研究、非编码区DNA序列的结构及功能研究提供了一个较好的基础。

关键词: 稻瘟病菌, 基因组, 微卫星序列, 频率, 分布, 遗传标记