Cytological and molecular characterization of a Triticum aestivum × Lophopyrum ponticum backcross derivative resistant to barley yellow dwarf

Barley yellow dwarf is the most damaging virus-caused disease in bread wheat (Triticum aestivum L.). A resistant line, SW335.1.2-13-11-1-5 (2n = 47), derived from a cross of T. aestivum × Lophopyrum ponticum was characterized by meiotic chromosome pairing, by in situ DNA hybridization and by expression of molecular markers to determine its chromosome constitution. All progeny of this line had three pairs of L. ponticum chromosomes from homoeologous chromosome groups 3, 5, and 6 and the 2n = 47 progeny had an additional L. ponticum monosome. The pairs from groups 3 and 6 were in the added state, while the group 5 pair was substituted for wheat chromosome 5D. Several wheat–wheat translocations with respect to the parental wheat genotype occurred in this line, presumably owing to the promotion of homoeologous chromosome pairing by L. ponticum chromosomes. It was hypothesized that homoeologous recombination results in homoeologous duplication–deletions in wheat chromosomes. An aberrant 3:1 disjunction creates the potential at each meiosis for replacement of these wheat chromosomes by homoeologous L. ponticum chromosomes. Wheat chromosomes 3A and 6A appeared to be in intermediate stages of this substitution process.Key words: wheat, wheatgrass, Lophopyrum, barley yellow dwarf virus, disease resistance, homoeologous chromosome recombination, homoeologous pairing, alien chromosome substitution.

Identification of a Triticum–Lophopyrum noncompensating translocation line and detection of Lophopyrum DNA using a wheatgrass specific molecular probe

A Triticum–Lophopyrum translocation line was produced by a series of backcrosses between F1 hybrids derived from the cross Triticum aestivum × Lophopyrum ponticum (Podp.) Love and their progenies and bread wheat. Cytogenetic studies of progeny of crosses between the wheat-alien translocation line and doubled ditelosomics of the group 5 homoeologues of 'Chinese Spring' indicated that the translocated chromosome consisted of the long arm of chromosome 5B of wheat and short (S) arm of chromosome 6 (6AgS) of decaploid L. ponticum (2n = 70), which carries the gene(s) for resistance to colonization by wheat curl mite (Eriophyes tulipae Keifer). The frequencies of resistance to mite colonization were similar (p = 0.64) for F1 progenies from crosses between the noncompensating translocation line and double ditelosomics for 5A, 5B, and 5D and averaged 61.4%, but the frequency of F2 seeds per head (11.8) was lowest (p > 0.05) for hybrids involving 5B double ditelosomics. A repetitive DNA probe found abundantly in wheatgrass was also used to detect the Lophopyrum chromatin in this wheat-alien translocation plant. Although this probe hybridized faintly to wheat DNA in Southern hybridization, the probe's diagnostic hybridization to DNA from the wheat-Lophopyrum translocation plant clearly showed the presence of Lophopyrum DNA.Key words: wheat, Lophopyrum, wheatgrass, Eriophyes tulipae, translocation, hybrids, repetitive DNA sequence.