Production And Molecular Cytogenetic Analysis Of Wheat-agropyron Cristatum 6P Deletion/Translocation Lines

The narrow genetic background of common wheat(Triticum aestivum L., 2n =6x = 42) restricts its yield and quality improvement. Chromosome 6P of Agropyron cristatum(2n =4x =28, PPPP) confers several desirable agronomic traits to wheat, such as high grain number per spike and enhanced resistance to certain diseases. Transferring these elite genes to common wheat is an effective method to increase the genetic diversity, disease resistance and yield. In this study, wheat-A. cristatum 6P disomic addition line 4844-12 was used as bridge material to produce A. cristatum 6P deletion lines and wheat-A. cristatum 6P translocation lines by an efficient induction method and molecular cytogenetic identification.1. An efficient method to induce wheat-A. cristatum chromosomal translocation: The plants at the flowering stage of the addition line 4844-12 were irradiated with 60 Co gamma rays at a dose of 20 Gray(Gy) and a dose rate of 0.5 Gy/min. A series of wheat-A. cristatum 6P translocation lines were identif ied by genomic in situ hybridization(GISH) and the translocation frequency was more than 10%.2. The physical map of A. cristatum 6P chromosome: A. cristatum 6P deletion lines and wheat-A. cristatum 6P translocation lines were used to map 6P-specific markers. In this study, 255 novel 6P-specific sequence-tagged-site(STS) markers were physically mapped to 31 regions of chromosome 6P. One-hundred nineteen and 136 STS markers were mapped to 14 bins in 6PS arm and 17 bins in 6PL arm, respectively. In addition, three and 10 chromosome 6P specific-locus amplif ied fragment(SLAF) markers were physically located to 6PS and 6PL arm, respectively.3. Production and category of A. cristatum 6P deletion lines: Thirty-one A. cristatum 6P deletion lines were induced by gametocidal chromosome and irradiation. Based on the results from GISH and 6P-specific STS markers, these deletion lines were categorized into 18 types: eight 6PS telosomics, five 6PL terminal deletions with 6PS arm, one 6PL internal deletion with 6PS arm, three 6PL terminal deletions without 6PS arm, two 6PL internal deletion without 6PS arm; six 6PL telosomics, five 6PS terminal deletions with 6PL arm and one 6PS terminal deletions without 6PL arm. The BC3F1 and BC2F2 progeny of the deletion lines have been obtained.4. Molecular cytogenetic analysis of wheat-A. cristatum 6P translocation lines: Many wheat-A. cristatum 6P translocation lines were induced by irradiation and backcrossed with Fukuhomugi. Sixty-six lines were identif ied in BC3F1 and BC2F2 progeny. Thirty-one lines were characterized by FISH and molecular markers. The results showed that 12 wheat chromosomes from 6 wheat homoeologous groups were translocated with A. cristatum 6P chromosome. Seventeen, 5 and 9 lines were translocated to wheat A, B and D genome, respectively, including 1A, 4A, 5A, 6A, 7A, 1B, 5B, 7B, 1D, 3D, 5D and 6D. These lines carried 6P different or overlapping segments: 15 lines carried the whole or partial 6PS chromosomal segments, 9 lines carried the whole or partial 6PL chromosomal segments and 7 lines carried both 6PS and 6PL chromosomal segments. The centromeric analysis showed that 4 wheat-A. cristatum 6P whole-arm translocation lines carried A. cristatum centromere, 3 whole-arm translocation lines carried wheat centromere, 1 small fragmental translocation line carried both A. cristatum and wheat centromeres.5. Agronomic traits of the deletion and translocation lines: The spike traits of A. cristatum 6P deletion lines showed that 6PL telosomics were better than 6PS telos omics, suggestting that 6PL arm might carry a main loci of multikernel gene. Four wheat-A. cristatum 6P translocation lines exhibited high grain number per spike, 1 line exhibited high thousand kernel weight, 3 lines exhibited both high grain number per spike and thousand kernel weight. In addition, A.cristatum chromosome 6P-originated leaf rust resistance gene(s) was located on the region 6PS-0.81-1.00. Fifteen translocation lines were high resistant to lesf rust.In this study, the efficient method of inducing wheat-A. cristatum translocation can offer a reference for the production of wheat-relative species translocation. The physical map of A. cristatum 6P chromosome supplied many molecular markers in quick and accurate detection of 6P chromatins in wheat background. A. cristatum 6P deletion lines are very helpful for gene discovery as well as 6P chromosome structural and functional analysis. Various types of wheat-A. cristatum 6P translocation lines provides a widely genetic basis for effective utilization of 6P-derived useful genes.