Production and cytogenetic analysis of BC1, BC 2, and BC 3 progenies of an intergeneric hybrid between Triticum aestivum (L.) Thell. and tetraploid Agropyron cristatum (L.) Gaertn.

Intergeneric hybrids between Triticum aestivum cv 'Chinese Spring' and Agropyron cristatum 4x (2n= 5x=35, ABDPP genomes) with a high level of homoeologous meiotic pairing between the wheat chromosomes were backcrossed 3 times to wheat. Pollination of the F1 hybrid with 'Chinese Spring' resulted in 22 BC1 seeds with an average seed set of 1.52%. Five BC1 plants with 39-41 chromosomes were raised using embryo rescue techniques. Chromosome pairing in the BC1 was characterized by a high frequency of multivalent associations, but in spite of this there was no evidence of homoeologous pairing between chromosomes of wheat and those of Agropyron. All of the plants were self sterile. The embryo rescue technique was again essential to produce 39 BC2 plants with chromosome numbers ranging from 37 to 67. The phenomenon of meiotic non-reduction was also observed in the BC3 progenies. In this generation male and female fertility greatly increased, and meiotic pairing was fairly regular. Some monosomic (2n=43) and double monosomic (2n=44) lines were produced. Analysis of these progenies should permit the extraction of the seven possible wheat-Agropyron disomic addition lines including those with the added chromosomes carrying the genes involved in meiotic non-reduction and in suppression of Ph activity.

C-banding and in-situ hybridization analyses of Agropyron intermedium, a partial wheat x Ag. intermedium amphiploid, and six derived chromosome addition lines.

C-banded karyotypes of Agropyron intermedium (2n=6x=42, E1E2X), a partial amphiploid Triticum aestivum -Ag. intermedium (2n=8x=56, TAF46), and six derived chromosome addition lines, were analyzed. In Ag. intermedium, diagnostic C-bands were present on 14 pairs of chromosomes, designated from A to N, while the remaining seven pairs, designated O to U, either lacked, or had only faint, C-bands and were not always identified unambiguously. All seven Ag. intermedium chromosome pairs of the partial amphiploid TAF46, and the added Ag. intermedium chromosomes present in the six derived addition lines, were identified by their characteristic C-banding patterns. Chromosome morphology and banding patterns were similar to those of the corresponding chromosomes present in the parent Ag. intermedium accession, suggesting that these chromosomes were not structurally rearranged. In-situ hybridization, using a 18s.265s rDNA probe, showed that the Ag. intermedium chromosomes 1Ai-1 and 5Ai-l present in the addition lines L3 and L5 were carrying actively transcribed nucleolus organizer regions. The results are discussed with respect to the genomic relationships of these chromosomes.

Nitrate reductases in hexaploid and tetraploid wheats and Aegilops.

Nitrate reductase activity (NR activity), protein content (NR protein) and polypeptides were compared in shoots of Triticum aestivum ssp. vulgare (L.) cv Fidel (bread wheat, AABBDD genome), Triticum dicoccum cv Vernal (AABB genome), Aegilops squarrosa var. strangulata (DD genome) and the amphiploid 365 (AABBDD genome), produced by crossing T. dicoccum cv Vernal and Ae. squarrosa var. strangulata. Constitutive NR protein and activity were found in shoots of all seedlings grown without nitrate, with the highest activity in the bread wheat. The inducible NR protein and activity developed upon the addition of nitrate. A 116-K polypeptide was identified as the main component of the NR from the bread wheat, while a faint, sometimes discernable 94-K band appeared on Western blots. Only one NR polypeptide could be identified in Ae. squarrosa -the 94 K. An intermediary situation was observed with the tetraploid T. dicoccum and the amphiploid: The 94-K polypeptide was the only one separated from NR of seedlings grown in the absence of nitrate. The 116-K polypeptide appeared after the addition of nitrate. The intensity of its band on the gel increased with the duration of the nitrate treatment. When comparing Ae. squarrosa and T. dicoccum, the constitutive isozyme (94-K polypeptide) was found in the D as well as in the AB genomes, while the inducible NR (116-K polypeptide) was absent from the D genome. Addition of the D genome into the AB genome slightly reinforced the expression of the inducible form (AB genome expression) in the amphiploid wheat. We postulate that the inducible form of NR in the bread wheat resulted from an evolutionary selection pressure favoured by cultivation.

Studies on maternal inheritance in polyploid wheats with cytoplasmic DNAs as genetic markers.

Restriction fragment patterns of DNA fragments obtained after EcoRI cleavage of chloroplastic (cp) and mitochondrial (mt) DNAs isolated from different wheat species were compared. T. aestivum, T. timopheevi, Ae. speltoides, Ae. sharonensis and T. urartu gave species specific mt DNA patterns. Consequently, the cytoplasmic genomes of wheat cannot have originated from contemporary Ae. speltoides, Ae. sharonensis and T. urartu species. It is shown that cp and mt DNAs of Ae. ventricosa, a tetraploid used to transfer eyespot resistance into T. aestivum, contains cp and mt DNAs differing from DNAs isolated from T. aestivum and other wheats. In contrast, the cytoplasmic DNAs of Ae. ventricosa and Ae. squarrosa reveal an important homology, suggesting that Ae. squarrosa was the female parent of Ae. ventricosa. Disomic addition lines (T. aestivum - Ae. ventricosa) in both Ae. ventricosa cytoplasm and T. aestivum cytoplasm contained cytoplasmic DNAs identical to those of the maternal parent. Restriction patterns of the cp and mt DNAs isolated from eight lines of Triticale differing in their cytoplasm have been compared to those of the maternal parent. A strict maternal inheritance has been observed in each case.