No abstract

A previous RFLP analysis showed that the Aegilops ventricosa chromosome 6M^ which compensates for the absence of 6D in 6M^ (6D) wheat substitution lines was a 2/6 translocated chromosome, either 2S-6S.6L or 2S-6L.6S. The distal part of its long arm consists of a translocated segment belonging to homoeologous group 2. Chromosome 6M^ carries a gene(s) for resistance to cereal cyst nematode. In order to define the part of 6M^ (2S or 6S or 6L) involved in this resistance, addition lines with a 6M^ deleted either for its short arm or for the distal part of its long arm were evaluated. It was shown that the gene(s) is carried by the group 2 translocated segment. The hypothesis that the gene(s) could be allelic to Cre2, another gene conferring resistance to the nematode introduced into the wheat complement from Ae. ventricosa is discussed.

Les lignées d'addition blé-Aegilops ventricosa Tausch. VI. — Etude de la localisation chromosomique de la résistance à l'égard d'Heterodera avenae Woll.

An Aegilops ventricosa Tausch (2n = 28, DvDvNvNv) subtelocentric chromosome added to wheat (Triticum aestivum L.) in a disomic addition line was found to carry the genes for resistance Yr17, Lr37, Sr38, and Cre5 already transferred onto chromosome 2AS of the wheat line VPM1. Previous works demonstrated that this Ae. ventricosa chromosome is translocated with respect to the standard wheat genome. The present investigations showed that this chromosome pre-existed in Ae. ventricosa and contains only chromatin specific to the N genome. Using biochemical markers and suitable cytogenetic materials including the monoisosomic addition line for the translocated long arm (6NvL-2NvS), its structure was defined as being 6NvSdel.6NvL-2NvS. It consists of a segment of the short arm 2Nv, containing the resistance genes, attached to a group 6 chromosome lacking a distal part of its short arm. The 2 re arrangements could already be present in Aegilops uniaristata Vis. (2n = 14, NN), the source of the Nv genome of Ae. ventricosa.

The chromosome 7Dv of Aegilops ventricosa (syn. Triticum ventricosum, 2n = 4x = 28, genome DvDvMvMv) carries the gene Pch1 for resistance to eyespot. This gene has previously been transferred to chromosome 7D of bread wheat, T. aestivum (2n = 6x = 42, genome AABBDD). To (1) enhance the level of resistance of bread wheat by increasing the copy number of Pch1, and (2) create eyespot-resistant triticales, meiotically stable Pch1-carrying durum lines were selected from the backcross progenies of a cross between Ae. ventricosa and T. durum cv. Creso ph1c (2n = 4x = 28, genome AABB). The Pch1 transfer, likely resulting from homoeologous recombination, was located at the distal position on the long arm of chromosome 7A. The 7A microsatellite marker Xgwm 698 was found closely linked in repulsion to the introgression in the resistant recombination lines, and the endopeptidase allele located on chromosome 7A of cv. Creso ph1c was lost.

Agropyron cristatum (2n = 4x = 28, PPPP) possesses potentially valuable traits that could be used in wheat (Triticum aestivum) improvement through interspecific hybridization. Homoeologous pairing between wheat chromosomes and P chromosomes added to wheat in a set of wheat - A. cristatum addition lines was assessed. First, the Ph-suppressing effect of P chromosomes (except 7P) was analyzed. It was concluded that this system is polygenic with no major gene, and consequently, has no prospect in the transfer of alien genes from wild relatives. In a second step, the potential of the deletion ph1b of the Ph1 gene for inducing P-ABD pairing was evaluated. Allosyndetic associations between P and ABD genomes are very rare. This very low level of pairing is likely due to divergence in the repeated sequences between Agropyron and wheat genomes. Development of translocation lines using ionizing radiation seems to be a more suitable technique than homoeologous recombination to exploit the A. cristatum genome in wheat improvement.

The chromosome 7Dv of Aegilops ventricosa (syn. Triticum ventricosum, 2n = 4x = 28, genome DvDvMvMv) carries the gene Pch1 for resistance to eyespot. This gene has previously been transferred to chromosome 7D of bread wheat, T. aestivum (2n = 6x = 42, genome AABBDD). To (1) enhance the level of resistance of bread wheat by increasing the copy number of Pch1, and (2) create eyespot-resistant triticales, meiotically stable Pch1-carrying durum lines were selected from the backcross progenies of a cross between Ae. ventricosa and T. durum cv. Creso ph1c (2n = 4x = 28, genome AABB). The Pch1 transfer, likely resulting from homoeologous recombination, was located at the distal position on the long arm of chromosome 7A. The 7A microsatellite marker Xgwm 698 was found closely linked in repulsion to the introgression in the resistant recombination lines, and the endopeptidase allele located on chromosome 7A of cv. Creso ph1c was lost.