为了研究线粒体基因组在小麦族物种中的遗传变异与进化关系，选用小麦族的14个二倍体及7个多倍体物种，对其线粒体rrn18-trnfM 基因区域进行PCR扩增并对扩增所得的片段进行克隆测序。获得大小不同的2种片段类型，大片段为513或515 bp，小片段为447或449 bp。其主要差异在trnfM区，即大片段存在trnfM基因，小片段缺失trnfM基因，再次证明以前报道的大麦属和小麦属间的分歧。而中间偃麦草同时存在两扩增片段类型，表明多倍体物种mtDNA具有双亲遗传现象。中间偃麦草的RT-PCR分析发现小片段没有转录，大片段能转录，因而考虑高频重组和选择性表达作为中间偃麦草的线粒体基因组独特的进化系统，这与核基因组进化系统不同。
The tribe Triticeae provides a vast gene pool for improving the genetic variation of common wheat (Triticum aestivum L.). However, the inter-specific hybridization is commonly occurred under natural and artificial conditions, which increase the difficulty of the molecular polygenetic analysis of Triticeae based on data from nuclear genes. The mitochondrial DNA sequences provide a conserved system, which was confirmed to be useful for the study of the genomic inheritance and evolution. In mitochondrial genome, genes trfM and rrn18, encoding a mitochondrial initator tRNAMet and 18S rRNA, respectively, are tightly linked and the intergenic region exhibits polymorphism in cereal. To determine the variation of mitochondrial rrn18-trnfM region in tribe Triticeae, 21 species including 14 diploid and 7 polyploid species were screened by means of PCR, cloned and sequenced. The results showed that two types of the amplified fragments, with 513, 515 or 499 bp and 449 or 447 bp, respectively, were obtained in these species. The analysis of the sequences demonstrates that the main difference between the two types of the fragments was in the trnfM region, in which the longer fragments contained trnfM, while the smaller ones lost the part of the trnfM sequence. The facts supported that divergence history of these species is between the barley and wheat/rye lineage. However, the Thinopyrum intermedium presented two types of the fragment simultaneously, indicating the heritage of the paternal mtDNA during its polyploidization. RT-PCR of the Th. intermedium indicated that the smaller fragments were not expressed. It was, therefore, to deduce that the frequent recombination and the selective expression of mitochondrial genome are its unique evolutionary system, differing from the nucleus. Additionally, the relationship between the mitochondrial genome and the evolution among polyploids in tribe triticeae was also discussed.
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