Cryptic introgression of Dasypyrum villosum parental DNA in wheat lines derived from intergeneric hybridization.

Cytogenetic and DNA molecular analyses have been carried out in 3 wheat introgression lines (ILs; CS×V58, CS×V59, and CS×V60) derived from Triticum aestivum cv. 'Chinese Spring' (CS) × Dasypyrum villosum(Dv) intergeneric hybridization. All lines, which showed several phenotypic differences compared to CS, had the same chromosome number (2n = 42) and structure as CS, and neither chromosomes nor chromatin from Dv were apparently added to their complement. However, Feulgen/DNA cytophotometry showed that there was more nuclear DNA in the lines than in the parental wheat (by 1.85%, 2.76%, and 1.26% in CS×V58, CS×V59, and CS×V60, respectively). Molecular investigation indicated the presence of Dv DNA in the ILs. AFLP analysis of genomic DNA from the ILs, CS, and Dv detected a total of 120 polymorphic bands, of which 7 (5.8%) were present in some or all the ILs and Dv but were absent in CS. PCR amplification, sequence analysis of amplicons, and Southern blot hybridization confirmed the presence of Dv-specific sequences in each of the ILs. These results indicate cryptic introgression of Dv DNA sequences into the genome of the ILs. Some implications of this finding are discussed.

Quantification of genetic relationships among A genomes of wheats.

The genetic relationships of A genomes of Triticum urartu (Au) and Triticum monococcum (Am) in polyploid wheats are explored and quantified by AFLP fingerprinting. Forty-one accessions of A-genome diploid wheats, 3 of AG-genome wheats, 19 of AB-genome wheats, 15 of ABD-genome wheats, and 1 of the D-genome donor Ae. tauschii have been analysed. Based on 7 AFLP primer combinations, 423 bands were identified as potentially A genome specific. The bands were reduced to 239 by eliminating those present in autoradiograms of Ae. tauschii, bands interpreted as common to all wheat genomes. Neighbour-joining analysis separates T. urartu from T. monococcum. Triticum urartu has the closest relationship to polyploid wheats. Triticum turgidum subsp. dicoccum and T. turgidum subsp. durum lines are included in tightly linked clusters. The hexaploid spelts occupy positions in the phylogenetic tree intermediate between bread wheats and T. turgidum. The AG-genome accessions cluster in a position quite distant from both diploid and other polyploid wheats. The estimates of similarity between A genomes of diploid and polyploid wheats indicate that, compared with Am, Au has around 20% higher similarity to the genomes of polyploid wheats. Triticum timo pheevii AG genome is molecularly equidistant from those of Au and Am wheats.

Identification of novel low M(r) glutenin subunits in the high quality bread wheat cv Salmone and their effects on gluten quality.

Southern-blot hybridization with a probe specific for genes encoding for low M(r) glutenin subunits showed that the high quality bread wheat cv Salmone contains two DNA fragments designated as SF720 and SF750. These fragments were found to occur on the chromosome-1B satellite, and to be associated with the presence of two strongly staining low M(r) glutenin subunits in the two-dimensional A-PAGE x SDS-PAGE pattern of cv Salmone. Comparison of 65 F(6) random lines derived from the cross between cv Salmone and the medium quality line FAP74809 revealed that the presence of fragments SF720 and SF750 had significant positive effects on several quality related parameters such as SDS sedimentation volume, Farinograph stability and Alveograph strength (W), tenacity (P) and elasticity (L). Additive effects of high M(r) glutenin subunits 1 and 7+9 on gluten quality were found as well. Fragments SF720 and SF750 were suggested to occur at a locus other than Glu-B3, as indicated by their relatively high frequency of recombination with the Gli-B1 locus.

Molecular linkage map of Einkorn wheat: mapping of storage-protein and soft-glume genes and bread-making quality QTLs.

Two molecular maps of Triticum monococcum L were produced and integrated. The integrated map includes a total of 477 markers, 32 RFLPs, 438 AFLPs, one morphological (soft glume (Sog)) and six storage-protein markers, and covers 856 cM. The trait Sog with the recessive allele sog maps to linkage group 2S. Probably, this is the T. monococcum homologue of Tg and Tg2 in hexaploid and tetraploid wheats, respectively. Loci coding for seed storage proteins were allocated to chromosomes 1L (HMW GLU1,2 and Glu1), 1S (LMW GLU6,7, LMW GLU1-4, omega GLI1-4, gamma GLI5 and Gli-1) and 6L (alpha/beta GLI7-14). Parameters related to bread-making quality (SDS sedimentation volume, specific sedimentation volume (SSV) and total protein content) were studied in one of the two populations. A QTL that is consistently present across environments was detected for SDS sedimentation volume and for SSV. The position of the QTL on chromosome 1S was in close agreement with the map positions of storage-protein loci. A second QTL was mapped on chromosome 5. For protein content, two significant QTLs were mapped to linkage groups 1 and 5.

RFLP patterns of gliadin alleles in Triticum aestivum L.: implications for analysis of the organization and evolution of complex loci.

A correspondence between RFLP patterns and gliadin alleles at the Gli-1 and Gli-2 loci was established in a set of 70 common wheat (T.aestivum L.) cultivars using γ-gliadin (K32) and α-gliadin (pTU1) specific probes. All Gli-B1 and Gli-D1 alleles which differed in encoded γ-gliadins showed definite RFLP patterns after hybridization with the K32 probe. Two groups of Gli-B1 alleles, Gli-B1b-like and Gli-B1e-like, were identified, and these could originate from distinct genotypes of the presumptive donor of the B-genome. Intralocus recombination and/or gene conversion as well as small deletions, gene silencing and gene amplification were assumed to be responsible for the origin of new gliadin alleles. Silent γ-gliadin sequences were shown to exist in all of the genotypes studied. K32 also differentiated Gli-A1a from all other Gli-A1 alleles as well as the Gli-B11 allele in cultivars carrying the 1B/1R (wheat/rye) translocation. PTU1 was shown to recognize several Gli-A2 alleles, but not the Gli-B2 or Gli-D2 alleles. Moreover, this probe hybridized to chromosome 1R sequences suggesting the existence of rye gene(s), probably silent, for α-gliadin-like proteins on chromosome 1R.

Production and genetic characterization of near-isogenic lines in the bread-wheat cultivar Alpe.

Two biotypes of the bread-wheat cultivar Alpe were shown to possess contrasting alleles at each of the glutenin (Glu-B1, Glu-D1, Glu-B3 and Glu-D3) and gliadin (Gli-B1 and Gli-D1) loci on chromosomes 1B and 1D. Fourteen near-isogenic lines (NILs) were produced by crossing these biotypes and used to determine the genetic control of both low-molecular-weight (LMW) glutenin subunits and gliadins by means of one-dimensional or two-dimensional electrophoresis. Genes coding for the B, C and D groups of EMW subunits were found to be inherited in clusters tightly linked with those controlling gliadins. Southern-blot analysis of total genomic DNAs hybridized to a γ-gliadin-specific cDNA clone revealed that seven NILs lack both the Gli-D1 and Glu-D3 loci on chromosome 1D. Segregation data indicated that these "null" alleles are normally inherited. Comparison of the "null" NILs with those possessing allele b at the Glu-D3 locus showed one B subunit, seven C subunits and two D subunits, as fractionated by two-dimensional A-PAGExSDS-PAGE, to be encoded by this allele. Alleles b and k at Glu-B3 were found to code for two C subunits plus eight and six B subunits respectively, whereas alleles b and k at Gli-B1 each controlled the synthesis of two ß-gliadins, one γ and two ω-gliadins. The novel Gli-B5 locus coding for two ω-gliadins was shown to recombine with the Gli-B1 locus on chromosome 1B. The two-dimensional map of glutenin subunits showed α-gliadins encoded at the Gli-A2 locus on chromosome 6A. The use of Alpe NILs in the study of the individual and combined effects of glutenin subunits on dough properties is discussed.

Cultivar identification in T. aestivum using highly polymorphic RFLP probes.

Two probes, specific for HMW-glutenins and γ-gliadins have been used to identify 50 common wheat Italian cultivars, most of which are closely related, and four common wheat cultivars originating outside Italy. The probes revealed complex polymorphic patterns; three probe/enzyme combinations had the necessary sensitivity for the identification of all 54 cultivars. As already shown for potato and barley, the use of four-cutter restriction enzymes and polyacrylamide gels proved particularly useful for detecting polymorphism.