The leaf rust resistance gene Lr47 confers resistance to a wide spectrum of leaf rust strains. This gene was recently transferred from chromosome 7S of Triticum speltoides to chromosome 7A of hexaploid wheat Triticum aestivum. To facilitate the transfer of Lr47 to commercial varieties, the completely linked restriction fragment length polymorphism (RFLP) locus Xabc465 was converted into a PCR-based marker. Barley clone ABC465 is orthologous to the type-I wheat sucrose synthase gene and primers were designed for the conserved regions between the two sequences. These conserved primers were used to amplify, clone and sequence different alleles from T. speltoides and T. aestivum. This sequence information was used to identify the T. speltoides sequence, detect allele-specific mutations, and design specific primers. Cosegregation of the PCR product of these primers and the T. speltoides chromosome segment was confirmed in four backcross-populations. To complement this dominant marker, a cleavage amplified polymorphic sequence (CAPS) was developed for the 7A allele of Xabc465. This CAPS marker is useful to select homozygous Lr47 plants from F2 or backcross-F2 segregating populations, and in combination with the T- speltoides specific primers is expected to facilitate the deployment of Lr47 in new bread wheat varieties.

Telosomic stocks have been extensively used to map genes to chromosome arms and to determine gene-to-centromere genetic distances. It has been suggested that if a chromosome arm is present as a telosome, recombination frequencies will be drastically reduced in the centromeric region. However, previous studies have not considered the bias in recombination estimates due to selection against aneuploid gametes produced by failure of pairing at the first meiotic division. Formulas are derived here for adjusting recombination estimates for this bias. Adjusted recombination frequencies between markers located on both sides of the centromeres are analyzed in three different pairs of wheat (Triticum aestivum) isogenic segregating populations involving bibrachial and telocentric chromosomes. Recombination frequencies estimated from crosses involving telocentric chromosomes were not significantly different from recombination frequencies estimated from isogenic crosses involving bibrachial chromosomes. The implications of the present findings for karyotype evolution, and specifically for Robertsonian fissions and fusions, are discussed.

Rust resistance genes Lr37, Sr38, and Yr17 are located within a segment of Triticum ventricosum (Tausch) Cess. chromosome 2NS translocated to the short arm of bread wheat chromosome 2AS. Characterization of this chromosome segment by 13 restriction fragment length polymorphism (RFLP) markers indicated that the 2NS translocation replaced approximately half of the short arm of chromosome 2A (distal 25-38 centimorgans, cM). The objective of this study was to develop polymerase chain reaction (PCR) assays based on RFLP marker cMWG682 to facilitate the transfer of this cluster of rust resistance genes into commercial wheat (Triticum aestivum L.) cultivats. DNA sequence was obtained from the A-, B-, D-, and N-alleles of cMWG682 and was used to design N-allele specific primers. The 2NS fragment amplified by PCR primers cosegregated with the presence of the RFLP-2NS band in all backcross populations. A cleaved amplified polymorphic sequence (CAPS) was used to develop a marker for the 2A-allele. This marker can be used to differentiate homozygous and heterozygous plants carrying the 2NS translocation in the final cycle of backcross introgression or in screenings for homozygous plants in segregating populations. Finally, a third PCR assay was developed by means of TaqMan technology as a high-throughput alternative for selection of the 2NS/2AS translocation in large segregating populations in breeding programs that have access to real time PCR equipment. These molecular markers were used to develop four hard red spring isogenic lines homozygous for the 2NS chromosome segment. One of the isogenic lines, derived from 'Anza,' did not show the expected resistance in spite of the presence of all the RFLP markers for the 2NS chromosome segment. Analysis of F1 hybrids suggested that a suppressor of the Lr37 gene is present in Anza. These isogenic lines will provide a valuable tool to test the effects of the large 2NS translocation on quality and agronomic performance.

Grain Protein Content (GPC) of wheat (Triticum aestivum L. and T. turgidum L.) is important for improved nutritional value and is also one of the major factors affecting breadmaking and pasta quality. A quantitative trait locus (QTL) for high GPC was detected a few years ago in the short arm of chromosome 6B from accession FA15-3 of Triticum turgidum L. var. dicoccoides. New molecular markers are presented here to facilitate the transfer of this high GPC gene into tetraploid and hexaploid wheat cultivars. Two sets of PCR (polymerase chain reaction) primers were designed to amplify regions of the non-transcribed spacer of the XNor-B2 locus. This locus was selected because it mapped on the peak of the QTL for GPC. The first pair of allele-specific primers produced an amplification product only when the T. turgidum var. dicoccoides XNor-B2 allele was present. The second pair of primers amplified fragment(s) of similar length in the different genotypes that after digestion with the restriction enzyme BamHI allowed differentiation of the T. turgidum var. dicoccoides allele. Four microsatellites markers were mapped on the short arm of chromosome 6B at both sides of the QTL peak and two on the long arm. Five additional amplified fragment length polymorphism (AFLP) markers were mapped into the QTL region on 6BS. These PCR markers together with 10 restriction fragment length polymorphism (RFLP) markers showed that the hexaploid cultivar Glupro, selected for high GPC, carries a distal segment of chromosome 6BL and a proximal segment of 6BS from dicoccoides accession FA15-3 encompassing the segment with highest LOD score for the GPC QTL.