宁夏稻瘟病菌群体遗传结构研究

Genetic structure of Magnaporthe grisea population from rice in Ningxia Hui Autonomous Region,China

采用Pot2-rep-PCR指纹识别技术对宁夏稻瘟病菌的群体结构进行分析。根据每个菌株的指纹型将2002至2005年在9个地区采集的406个稻瘟病菌单孢菌株鉴定为65个单元型,其中,单元型NXH7包含176个菌株,占总菌株数的43.3%,在所有年份、地区和大多数水稻品种上出现,是宁夏稻瘟病菌中最广泛适应的单元型。对稻瘟病菌群体的时空变化分析发现,不同年份、不同地区的稻瘟病菌亚群体间遗传分化不明显(地区间Gst=0.0832,年份间Gst=0.0509),遗传结构相似;不同水稻品种上的亚群体遗传分化明显(Gst=0.2823)。提示寄主的选择作用是宁夏稻瘟病菌群体演化的主要力量。宁夏稻瘟病菌菌株间有较高的相似性,总体相似性大于62%,DNA指纹没有任何清晰的系谱结构,没有任何聚类组被大于60%的bootstrap值支持。提示宁夏稻瘟病菌群体可能是单一的无性系谱占绝对优势。总体而言,宁夏稻瘟病菌群体遗传多样性水平较低(H=0.0963,I=0.1806)。

The population structure of the rice blast fungus,Magnaporthe grisea,in Ningxia Hui Autonomous Region,China,was analyzed using Pot2-based rep-PCR DNA fingerprinting.A total of 406 monoconidial isolates of the fungus collected in nine districts during 2002 to 2005 were classified into 65 different haplotypes.Of the 65 haplotypes identified,the haplotype NXH7,the most common haplotype,contained 176 isolates,and was recovered from all districts,all years and most rice cultivars sampled,suggesting this haplotype is the most broadly adapted haplotype in Ningxia.Analysis of spatio-temporal change of the fungus showed that the populations differing in geographical location（Gst=0.083 2）or year（Gst=0.050 9）were not different significantly.The genetic divergence among the populations differing in cultivar was significant（Gst=0.282 3）,suggesting that selection by the host population was a major force in the evolution of M.grisea in Ningxia.High similarities were observed among isolates,and overall similarities were greater than 62%.DNA fingerprints showed no clear lineage structure.No groups were supported by bootstrap values greater than 60%.These data suggested that M.grisea populations in Ningxia were mostly dominated by a single clonal lineage.Overall,genetic diversity in the Ningxia＇s M.grisea population is low（H=0.096 3,I=0.180 6）.