西南地区稻瘟病菌群体遗传多样性分析

为明确西南地区稻瘟病菌Magnaporthe grisea(Hebert)Barr群体遗传结构及其多样性水平,选用13对SSR引物对来自18个县(市)的221个稻瘟病菌单孢菌株进行PCR扩增,利用最长距离法和生物学软件进行聚类分析和群体遗传多样性分析。结果显示,13对SSR引物均能扩增出一条大小相同且清晰的条带,多态位点百分率高达100%。221个菌株在0.16相异水平上可划分为13个遗传宗谱,宗谱SCL01含205个菌株,占总菌株数的92.76%,为优势宗谱;宗谱SCL02~SCL013为劣势宗谱,差异极大。在群体水平上,菌源丰富的8个区域稻瘟病菌群体的Nei’s基因多样性指数为0.2133,Shannon信息指数为0.3588,具有丰富的遗传多样性,且群体间差异较大;这8个种群基于UPGMA法大都聚为一类,种群遗传谱系与地理区域分布呈一定相关性,群体遗传多样性均值为0.2518,存在一定的遗传分化,且群体内多样性大于群体间,总遗传变异的59.37%存在于群体内。总体上,西南地区稻瘟病菌群体结构既有明显的优势宗谱,又存在许多复杂多变的特异性小宗谱,具有丰富的遗传多样性,与地理分布关系较为密切。

Analysis of genetic diversity among populations for the rice blast fungus Magnaporthe grisea in southwest China

In order to determine the genetic structure and levels of diversity among populations of the rice blast fungus Magnaporthe grisea in the region of southwest China, 221 single spore isolates from 18 counties (cities) in this region were amplified with 13 pairs of SSR primers. The results showed that specific products could be amplified clearly with all primer pairs, and the percentage of polymorphic loci was 100%. At 0.16 dissimilar levels, 221 isolates were classified into 13 genetic lineages by cluster analysis. SCL01, the most common lineage including 205 isolates, was the dominant lineage, whereas SCL02-SCL13 were disadvantaged lineages with significant genetic diversity. The Nei''s genetic diversity index and Shannon''s information index of M.grisea populations from eight regions were 0.2133 and 0.3588, respectively, indicating the existence of rich genetic diversity in fungal populations from different geographic regions. Most populations from the above eight regions were clustered into one group, which meant that the genetic lineages of the populations from different areas were related to their geographic distributions. Meanwhile, certain levels of genetic differentiation existed in the fungal populations among these regions, and the genetic diversity within-population was higher than that among-population, of which the former accounted for 59.37% of total genetic variation. Overall, populations of rice blast fungus in southwest China were rich in genetic diversity, and included one predominant lineage and multiple lineages that were distinctively diversified and closely associated with their geographic distributions.