Abstract：Mitochondrial DNA(mtDNA) was extracted by tender root tissue and leaf tissue from seedlings of four materials such as PolA and its maintainer line PolB, Shaan 2A and its maintainer line Shaan 2B in Brassica napus L., and the extracted mtDNA was examined. The results showed that the mean content of mtDNA extracted from tender root tissue was about 3250ng/g.FW, significantly higher than that from leaf tissue in the same conditions. That is, the mean content of mtDNA extracted from tender root tissue was about 6.5 times of leaf tissue, and the mtDNA extracted from tender root tissue had a high purity. The agrose gel electrophoresis also showed that mtDNA extracted from tender root tissue had clearer bands than that from leaf tissue in Brassica napus L.. Moreover, the PCR result of mitochondrial genes showed that the repetition and stability of bands expanding from mtDNA extracted by tender roots were much better than that by leaves. Therefore, mtDNA extracted from tender root tissue have good quality and high concentration. Tender root tissue not only can easily be acquired, but also had no interference with chloroplast and its cpDNA. Tender root tissue is an ideal material for extracting mtDNA. It is a better method that mtDNA is extracted by tender root tissue in Brassica napus L..
