Molecular Cytogenetic Characteristics Of Line 08-723 Between Common Wheat And Thinopyrum Intermedium With Resistance To Powdery Mildew

Wheat powdery mildew, caused by Blumeria graminis f.sp. tritici, is a serious fungal disease in the wheat growing areas around the world. The loss of resistance caused by virulent races happens frequently in wheat breeding and production. Development of resistant cultivars provides an effective approach for disease control, eliminating the use of fungicides and minimizing crop losses. Therefore, it is urgent to search for new powdery mildew resistance genes. Transfer of alien genes from related species into common wheat through wide hybridization plays an important role in wheat resistance improvement. Thinopyrum intermedium (2n=42, JJJSJS StSt) has long been known to have superior resistance to various diseases, and they can be easily crossed with wheat, making them a potential source of gene pool for wheat improvement.A stable wheat line 08-723, derived from the progenies of common wheat CM 107 and Th. intermedium, exhibiting similar agronomic traits to CM 107, is immune to powdery mildew in field. In this study, the chromosome constitution of line 08-723 was identified by ISH(in situ hybridization) and Sequential C-banding-GISH. Combining with disease resistance observation, the relationship between the alien chromosomal fragment and powdery mildew resistance was studied. The main results are as follows:1. The resistance investigation showed that CM 107 and MY26 were highly susceptible, while line 08-723 and the F1 population of 08-723×MY26 were immune to powdery mildew. The segregation ratio for resistant and susceptible plants of F2 population and F2:3 families respectively showed good fit into a ratio of 3:land 1:2:1, which suggested that there is a single dominant resistance gene responsible for the powdery mildew resistance in line 08-723 and that the gene segregates normally.2. The somatic chromosome number per cell of 08-723 was 2n=42. It was observed to produce 21 bivalents and no univalent or multivalent in meiotic metaphase I of pollen mother cells (PMCs), suggesting that 08-723 was cytological stable.3. GISH (Genomic in situ hybridization) with Th. intermedium and Thinopyrum bessarabicum genomic DNA respectively as probes displayed that a St genome chromosomal fragment of Th. intermedium was found to be transferred into one pair of wheat chromosome’s short arms with a interstitial translocation. GISH analyses of different F2 individual demonstrated that the powdery mildew resistance came from the alien translocation fragment.4. Double-FISH (Double fluorescence in situ hybridization) with pAsl and pSc119.2 showed that a pair of A genome chromosomes were involved in the translocation. Double-FISH with pTa-535 and Triticum urartu genomic DNA as probes, the mixed Aegilops speltoides and Aegilops tauschii genomic DNAs as blocks suggested that the translocation chromosome might be 6A chromosome. A short terminal segment in the translocated arm from an unidentified B genome chromosome was detected with total genomic DNA of A. speltoides as a probe and a mixture of T. urartu and A. tauschii genomic DNAs as the block.5. Sequential Giemsa C-banding and GISH analyses further revealed that the translocation occurred in the wheat chromosome 6AS and the alien St chromosomal fragment with ca.90% of the arms’ length, and a unidentified B-genome chromosomal fragment on telomere was about ca.10% in length. Based on all the results, the translocation chromosome in line 08-723 can be denoted as?B·?St-T6AL.