Wheat - Rye Africa Amphidiploid Allopolyploid Process Variation And Molecular Markers

As an endangered wild rye species, Secale africanum was found only in southern Africa. It is essential to conserve the species and to study its potential value for wheat improvement. The S. africanum was recently considered as an excellent wild species re- sistant to wheat stripe rust and powdery mildew. Following the success of distant crosse -s between S. africanum and common wheat, several S. africanum–wheat amphiploids were produced. They provided a potential bridge for gene transfer from S. africanum to vast number of wheat varieties. Moreover, the genome in situ hybridization (GISH) of wheat- S. africanum amphiploids revealed that the S. africanum genome displayed sign- ificant divergence to the Secale cereale genome. It is thus valuable to study the genetics of the newly artificial wheat-S. africanum amphiploids and develop the molecular mark- ers for the future gene transfer from S. africanum to wheat.1. We performed the PCR analysis on S. africanum, wheat-S. africanum amphiploids, T.eastivum cv.Anyuepaideng and other materials by 100 ISSR primers. 100 ISSR primers were used for the PCR amplification of wheat-S. africanum amphiploids genomic DNA, and 26 primers could produce clear and polymorphic bands. A total of 401 bands were amplified form 26 primers, of which 330 bands (about 78%) were polymorphic. These results suggested that higher genetic diversity existed in Secale genetic resources, and the ISSR markers could be used as effective molecular techniques to evaluate the genetic diversity of Secale.2. A specific segment of 561 bp, named pSaUBC815561, was obtained from S. africanum by using primer UBC815, while this segment was not amplified from control wheat lines. Primer UBC815 also amplified from wild species of genus Secale, including Secale vavilovii, Secale sylvestre and other cultivated ryes. Based on sequence of pSaUBC815561, a pair of special primers U815-F and U815-R was designed, and it was used to amplify the DNA of wheat related species in Triticeae, to validated the specificity of pSaUBC815561. In addition , PCR analysis was performed on a set of Chinese Spring-Imperial addition lines and wheat-rye introgression lines the result showed that all the seven pairs of Secale chromosomes and the tested wheat-Secale offsprings contained this specific DNA segment. Therefore, pSaUBC815561 could be used as a specific marker for detection of chromosomes of Secale genome in wheat.3. We used improved methylation-sensitive amplification polymorphism(MSAP) method to analyze the levels of DNA methylation in S. africanum–wheat amphiploids and their parents. We found that the levels of DNA methylation of S. africanum was 29.14%, the four wheat parents were averaged at 37.95%, 35.61%, 39.03%, 38.67%, while the levels of DNA methylation in four S. africanum–wheat amphiploids were 43.53%, 39.75%, 42.09%,41.73%, repespectively. The above results suggest that DNA methylation at the majority of genomic loci exhibited faithful transmition from parents to intra-specific hybrids, and the obvious diversity existed in all studied amphiploids and parental lines. These alterations might play a role in regulating differential gene expression in amphiploids, which may be related to the amphiploid evolution.