M. C. Ramírez

Chromosome engineering in wheat to restore male fertility in the msH1 CMS system

Pollen fertility restoration of the CMS phenotype caused by H. chilense cytoplasm in wheat was associated with the addition of chromosome 6HchS from H. chilense accession H1. In order to develop an euploid restored line, different genomic combinations substituting the 6HchS arm for another homoeologous chromosome in wheat were evaluated, with the conclusion that the optimal combination was the translocation T6HchS·6DL. The double translocation T6HchS·6DL in H. chilense cytoplasm was obtained. This line is fertile and stable under different environmental conditions. However, a single dose of the T6HchS·6DL translocation is insufficient for fertility restoration when chromosome 6D is also present. Restoration in the msH1 system is promoted by interaction between two or more genes, and in addition to the restorer of fertility (Rf) located on chromosome 6HchS, one or more inhibitor of fertility (Fi) genes may be present in chromosome 6DL.

Exploitation of nuclear and cytoplasm variability in Hordeum chilense for wheat breeding.

Our work in this area is supported by grants (to S. G. A.) AGL2008-03720, and P09-AGR-4817 from Spanish Ministry of Science and Innovation, Junta de Andalucia and FEDER. C. R.-S. acknowledges financial support from CSIC (JAE-Doc program).

High-throughput genotyping of wheat-barley amphiploids utilising diversity array technology (DArT)

BackgroundHordeum chilense, a native South American diploid wild barley, is one of the species of the genus Hordeum with a high potential for cereal breeding purposes, given its high crossability with other members of the Triticeae tribe. Hexaploid tritordeum (×Tritordeum Ascherson et Graebner, 2n=6×=42, AABBHchHch) is the fertile amphiploid obtained after chromosome doubling of hybrids between Hordeum chilense and durum wheat. Approaches used in the improvement of this crop have included crosses with hexaploid wheat to promote D/Hch chromosome substitutions. While this approach has been successful as was the case with triticale, it has also complicated the genetic composition of the breeding materials. Until now tritordeum lines were analyzed based on molecular cytogenetic techniques and screening with a small set of DNA markers. However, the recent development of DArT markers in H. chilense offers new possibilities to screen large number of accessions more efficiently.ResultsHere, we have applied DArT markers to genotype composition in forty-six accessions of hexaploid tritordeum originating from different stages of tritordeum breeding program and to H. chilense-wheat chromosome addition lines to allow their physical mapping. Diversity analyses were conducted including dendrogram construction, principal component analysis and structure inference. Euploid and substituted tritordeums were clearly discriminated independently of the method used. However, dendrogram and Structure analyses allowed the clearest discrimination among substituted tritordeums. The physically mapped markers allowed identifying these groups as substituted tritordeums carrying the following disomic substitutions (DS): DS1D (1Hch), DS2D (2Hch), DS5D (5Hch), DS6D (6Hch) and the double substitution DS2D (2Hch), DS5D (5Hch). These results were validated using chromosome specific EST and SSR markers and GISH analysis.ConclusionIn conclusion, DArT markers have proved to be very useful to detect chromosome substitutions in the tritordeum breeding program and thus they are expected to be equally useful to detect translocations both in the tritordeum breeding program and in the transference of H. chilense genetic material in wheat breeding programs.

Selection and molecular characterization of imidazolinone resistant mutation-derived lines of Tritordeum HT621

Imidazolinone herbicides resistant varieties, induced by mutations at the AHAS gene (acetohydroxyacid synthase), have been developed in many crops. Hexaploid tritordeum (Tritordeum Asch. & Graebn.) is the amphiploid derived from the cross between Hordeum chilense (HchHch) and durum wheat Triticum turgidum L. (Thell) (AABB). Tritordeums have the potential to become a new crop with high added-value for food or feed. Mutagenesis with EMS was conducted to obtain imidazolinone resistant lines derived of the tritordeum HT621. Eleven M3 plants were selected after imidazolinone treatment and five descendants of two of these lines (HT621-M3R1-3 and HT621-M3R10-1) were analyzed at the molecular level. Partial sequences of the three homologous AHAS loci in genomes A, B, and Hch were obtained as well as those of HT621. A partial sequence of the AHAS gene in Hordeum chilense is first described in this work, and the designation ahasL-Hch1 is proposed. A single Ser-Asn627 substitution at the AHAS locus in the B genome is responsible of resistance in both lines. We propose the name AhasL-B2 for this resistance allele. This is the first report of the selection of imidazolinone resistant lines of tritordeum and the molecular characterization of the mutation conferring this resistance.

Applicability of chromosome-specific SSR wheat markers for the introgression of Triticum urartu in durum wheat breeding programmes

This work has been performed with the financial support of the Spanish Ministry of Science and Innovation (AGL2009-11359) and the Consejeria Economia, Innovacion y Ciencia of the Junta de Andalucia (P09-AGR-4817) and FEDER. C. R.-S. acknowledges financial support from CSIC (JAE-Doc program).

Introgression of 1Dx5+1Dy10 into tritordeum.

Abstract.The uses of hexaploid tritordeum as a crop for human consumption require improvement of its bread-making quality. For this purpose chromosome 1D of bread wheat with the Glu-D1 allele encoding for high-molecular-weight glutenin subunits Dx5+Dy10 was introgressed into tritordeum. Different primary tritordeums were crossed with wheats carrying subunits Dx5+Dy10. The hybrids were backcrossed to tritordeum and seeds for the next backcross (or selfing) were selected for the presence of chromosome 1D using SDS-PAGE. Forty two chromosome plants carrying subunits Dx5+Dy10 were obtained after two backcrosses and selfing. Chromosome characterization of these plants using fluorescence in situ hybridisation (FISH) proved that either chromosome substitution 1Hch/1D or 1A/1D had been obtained. A homozygous plant with a translocation of the entire 1DL arm to 1HchS was also obtained. The complete chromosome substitution lines have better agronomic characteristics than the lines with translocations.