Molecular Cytogenetics Identification And Characterization Of Wheat-Thinopyrum Ponticum Additions,substitutions And Translocations

Wheat, one of the most important crops in the world, has been cultivated even longer than the civilization history of human. This domestication may have contributed to limited genetic variability in this species because of artificial selection. The introduction of genetic traits from alien species has been necessary in order to enrich the genetic diversity available for wheat improvement, and many useful traits have been introduced into wheat from alien species. Thinopyrum panticum (Host) Liu & Wang [Agropyrum elan gatum (Host) Beauv; Elytriga elan gatum (Host) Nevski], a decaploid species (2n10x70, StStEEbEX) in the tribe Triticeae, is an important source for improving the genetic variability of cultivated wheat. We aimed to gain some novel germplasms which contain the genetic materials of Th. ponticum and possess some elite agronomic traits by genetic analysis derivatives of two wheat-Thinopyrum panticum hybrid combinations [(CS/ 87W032 II Xiaoyan 6/3/40765) and (Jin2148XBC1-1-5?2- 2)]. Firstly, the undesirable individuals were eliminated through the morphological traits selection. Then, twelve relatively stable novel germplasms were selected through root-tip cells chromosome counting and the chromosome paring analysis in 1999 and 2000. The result of acid polyacrylamide gel electrophoresis (A-PAGE) of gliadin showed that 9 of the 12 and one of their parents 揃eiJing 837?have the identical IRS chromosome-specific gliadin marker GIdB3. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis ectrophoresis (SDS-PAGE) analysis of HMW glutenin subunits showed that there are 6 new lines had the specific band of Th. ponticum. In order to get more steady materials for future breeding, offspring of the 12 lines continued to be analysed cytogenetically. Ten seeds were randomly chosen in each line. Genomic in situ hybridization (GISH) was employed to identify the chromosomal constitution one by one. With digoxigenin-labelled 揅hinese Spring? (Triticum aestivum L) genomic?DNA as probe and 20-fold genomic DNA of Pseudoroegneria stipifolia (St genome) as block, GISH revealed there are 2 substitution indivaduals, 4 addition individuals, 14 transtocation individuals, 6 substition-translocation individuals and 6 addtion-translocation individuals. Using iii pTa7l as probe, locus of 18S-5.8S-26S rDNA (Nor-RI) was detected on the Robertsonian translocated chromosome found in all individuals conveyed it. Further analysis indicated that the Robertsonia translocation was concerning with B-genome chromosomes. Using genomic DNA of rye (Secale cereale L. R) as probe and wheat genomic DNA as block, GISH proved that the translocation chromosomes are 1 BU1 RS, which was inherited from one of their parents, Beijing 837. GISH is a powerful technique for identifying the genomic constitution of hybrids and initial characterization of recombination lines that contain alien segments. It is rapid, sensitive, accurate, effective and gives unique information about alien chromatin in wheat.background. But it has some limitation, false conclusion of GISH caused by cross-hybridization between genomes was discussed in this paper. The results of this study suggest us that we must be prudent in identification of alien chromosomes. It is easy to draw a false conclusion if only a single technique is adopted. Multiple methods should be used to check with each other and confirm the results.