Cytogenetic identification of Triticum peregrinum chromosomes added to common wheat.

C-banded karyotypes of a complete set of 14 Triticum peregrinum whole chromosome addition lines and 25 telosomic addition lines are reported. The added T. peregrinum chromosomes were not structurally rearranged compared with the corresponding chromosomes of the donor accession. Comprehensive karyotypic analysis confirmed Triticum umbellulatum as the donor species of the Uv genome and identified Triticum longissimum as the donor species of the Sv genome of T. peregrinum. Neither the Uv nor Sv genome chromosomes of the T. peregrinum accession showed large modifications when compared with the ancestral U and S1 genomes. Key words : Triticum aestivum, Triticum peregrinum, Triticum umbellulatum, Triticum longissimum, chromosome addition lines, C-banding.

Molecular genetic maps of the group 6 chromosomes of hexaploid wheat (Triticum aestivum L. em. Thell.).

Restriction fragment length polymorphism (RFLP) maps of chromosomes 6A, 6B, and 6D of hexaploid wheat (Triticum aestivum L. em. Thell.) have been produced. They were constructed using a population of F7-8 recombinant inbred lines derived from a synthetic wheat x bread wheat cross. The maps consist of 74 markers assigned to map positions at a LOD >= 3 (29 markers assigned to 6A, 24 to 6B, and 21 to 6D) and 2 markers assigned to 6D ordered at a LOD of 2.7. Another 78 markers were assigned to intervals on the maps. The maps of 6A, 6B, and 6D span 178, 132, and 206 cM, respectively. Twenty-one clones detected orthologous loci in two homoeologues and 3 detected an orthologous locus in each chromosome. Orthologous loci are located at intervals of from 1.5 to 26 cM throughout 70% of the length of the linkage maps. Within this portion of the maps, colinearity (homosequentiality) among the three homoeologues is strongly indicated. The remainder of the linkage maps consists of three segments ranging in length from 47 to 60 cM. Colinearity among these chromosomes and other Triticeae homoeologous group 6 chromosomes is indicated and a consensus RFLP map derived from maps of the homoeologous group 6 chromosomes of hexaploid wheat, tetraploid wheat, Triticum tauschii, and barley is presented. Key words : RFLP, wheat, linkage maps, molecular markers.

Isolation and identification of Triticum aestivum L. em. Thell. cv Chinese Spring-T. peregrinum Hackel disomic chromosome addition lines.

Analyses of RFLPs, isozymes, morphological markers and chromosome pairing were used to isolate 12 Triticum aestivum cv Chinese Spring (genomes A, B, and D)-T. peregrinum (genomes S(v) and U(v)) disomic chromosome addition lines. The evidence obtained indicates that each of the 12 lines contains an intact pair of T. peregrinum chromosomes. One monosomic addition line, believed to contain an intact 6S(v) chromosome, was also isolated. A CS-7U(v) chromosome addition line was not obtained. Syntenic relationships in common with the standard Triticeae arrangement were found for five of the seven S(v) genome chromosomes. The exceptions were 4S(v) and 7S(v). A reciprocal translocation exists between 4S(1) and 7S(1) in T. longissimum and evidence was obtained that the same translocation exists in T. peregrinum. In contrast, evidence for syntenic relationships in common with the standard Triticeae arrangements were found for only one U(v) chromosome of T. peregrinum.; namely, chromosome 2U(v). All other U(v) genome chromosomes are involved in at least one translocation, and the same translocations were found in the U genome of T. umbellulatum. Evidence was also obtained indicating that the centromeric regions of 4U and 4U(v) are homoeologous to the centromeric regions of Triticeae homoeologous group-6 chromosomes, that the centromeric regions of 6U and 6U(v) are homoeologous to the centromeric regions of group-4 chromosomes, and that 4U and 4U(v) are more closely related overall to Triticeae homoeologous group-6 chromosomes than they are to group-4 chromosomes.

Standard karyotype of Triticum searsii and its relationship with other S-genome species and common wheat.

C-banding polymorphism was analyzed in 14 accessions of Triticum searsii from Israel, and a generalized idiogram of the species was established. One accession was homozygous for whole arm translocations T1S(s)S·4S(s)S and T1S(s)L·4S(s)L. C-banding analysis was also used to identify 7 T. aestivum cv 'Chinese Spring'-T. searsii disomic chromosome addition lines, 14 ditelosomic chromosome addition lines, 21 disomic whole chromosome, and 31 ditelosomic chromosome substitution lines. The identity of these lines was further confirmed by meiotic pairing analysis. Sporophytic and gametophytic compensation tests were used to determine the homoeologous relationships of the T. searsii chromosomes. The results show that the T. searsii chromosomes do not compensate well for their wheat homoeologues. The C-banding patterns of T. searsii chromosomes are distinct from those of other S-genome species and from the B-genome chromosomes of wheat, indicating that T. searsii is not a direct B-genome donor species of T. turgidum and T. aestivum.

Use of recombinant substitution lines in the construction of RFLP-based genetic maps of chromosomes 6A and 6B of tetraploid wheat (Triticum turgidum L.).

RFLP-based genetic maps of chromosomes 6A and 6B of Triticum turgidum have been constructed using data obtained by the study of Triticum turgidum var 'durum' cv 'Langdon'-T. t. var 'dicoccoides' recombinant substitution lines (RSLs) supplemented with data obtained from F3 families derived from 'Langdon' dicoccoides 6A and 6B disomic substitution lines. The average RFLP frequencies detected for the two chromosomes in a test of 45 DNA clones with six restriction enzymes were 56% and 53%, respectively, and a subset of 32 clones gave frequencies of 75% and 72%, respectively. Seventeen loci were mapped in 6A and 18 in 6B. With the possible exception of 5 loci in the centromeric region of 6A, all of the mapped 6A and 6B loci are located in the same arm as are homologous loci in hexaploid wheat, and the linear order of the loci is the same in the two chromosomes, except possibly close to the centromere. Major differences in genetic distances exist between homologous loci located in the proximal regions of the 6AL and 6BL linkage groups, however, the distances being much larger in the former than in the latter. The 6B maps that were constructed using data from both the RSL and the F2 populations and using data from the RSL population alone closely resemble one another, indicating that the 6B RSL population, composed of 85 lines, can be reliably used for genetic mapping. Additional studies must be conducted before the utility of the 6A RSL population, composed of 66 lines, can be adequately assessed.

Evidence that Aco-B2 and Aco-D2 of Triticum aestivum are located in chromosomes 4B and 4D.

Studies designed to determine the chromosomal locations of variant Aconitase-2 alleles of Triticum aestivum disclosed that Aco-B2 and Aco-D2 are not located in chromosomes 5B and 5D, as formerly reported. Reinvestigation of the chromosomal locations of the genes provided strong evidence they are instead located in chromosomes 4B and 4D. Also, four Aco-B2 alleles were identified but no variant Aco-D2 alleles were detected.