Molecular And Cytogenetic Studies On Derivatives Of Wheat-thinopyrum Ponticum

Thinopyrum ponticum(2n = 10 x = 70), a wild relative of common wheat, has been frequently used in wheat breeding program because of the strong regeneration capacity and tillering ability, long spike, disease resistance, high protein levels and adaptive capacity. In order toget some intermediate tools materials, morphology, cytological analysis, disease resistance identification, molecular marker technique, and genomic in situ hybridization(GISH) were used to determine the homoeologous group of the substituted and added chromosomes and then agronomic traits evaluation were combined. The main results are as follows:1. In this study, 111 pairs of specific primer with clear bands and repeatability were selected from 712 SSR markers of wheat for Th. ponticum. Result showed that the selected 111 pairs of primer could be effectively applied to molecular marker analysis of the germplasm resources of Th. ponticum.2. A addition line A1-2-1-1, obtained from the BC1F4 between common wheat cultivar 7182 and Th. ponticum, whose chromosome configuration in PMC MⅠ was 2n = 22Ⅱ, but few was 2n = 21Ⅱ+2Ⅰ. Among the 124 specific primers, 6 markers could amplify specific bands of Th. ponticum in A1-2-1-1(Xwmc233-5D, Xwmc97-5D, Xcfd29-5D, Xwmc256-6A, Xwmc93-1A, 1D, TNAC1663-St). It was speculated that the pair of alien chromosomes were closest to 5 homoeologous groups of wheat, then 6 and 1 homoeologous groups. GISH analysis showed that the alien chromosomes came from Th. ponticum, but whether from Pseudoroegneria spicata or Thinopyrum bessarabicum should be in further investigation. Furthermore, the two chromosomes with greenish-yellow hybridization signals were homoeologous chromosomes, which might suppresses wheat homoeologous chromosome pairing.3. A substitution line A1-2-2-2(2n = 21Ⅱ), obtained from the BC1F4 between common wheat cultivar 7182 and Th. ponticum, was immune to powdery mildew. Cytological observation showed that the line had 21 pairs of chromosomes. Partial bands of three SSR markers Xwmc256, Xwmc580 and Xgpw7592 from chromosomes 6A were missing, which indicated chromosomes 6A of common wheat were lost. Genomic in situ hybridization(GISH) suggested that there may have a pair of chromosomes St in A1-2-2-2. A1-2-2-2 was suggested to be an alien disomic substitution of St(6A). Furthermore, 7182 and Th. ponticum had glabrous glume without pubescence, but A1-2-2-2 with short and dense glume pubescences, which suggested that the glume glabrous of 7182 might be dominant and was controlled by gene(s) on chromosomes 6A. High level of powdery mildew resistance, high tillering ability and genetic stability made A1-2-2-2 a potential germplasm for wheat improvement.Although several studies were carried out on Th. ponticum, it’s still not been clearly clarified. The production of alien substitution lines and addition lines is an important step for succesfully transferring favourable genes to wheat.