Ae. variabilis accession 13E was provided by Dr. MuJeeb-Kazi, CIMMYT, Mexico. Wheat line J-11ph^1b was developed by Yang et al. (1998). An amphiploid between J-11ph^1b and 13E was obtained from the colchicine treatment of hybrid F₁.

For somatic chromosome counts, root tips of seedling were pretreated with water at 0C for 24h and fixed in ethanol-acetic acid (3:1) for at least 1 week, and stained by the conventional Feulgen method. Giemsa C-banding procedure was carried out according to Ren and Zhang (1995). Identifications of C-banded Ae. variabilis chromosomes mainly followed Friebe et al. (1996).

Endosperm gliadin protein and glutenin subunits were separated by acid polyacrylamide gel electrophoresis (APAGE) and sodium dodecyl sulphate -polyacrylamide gel electrophoresis (SDS-PAGE), respectively. Powdery mildew resistance in seedling and stripe rust resistance in adult-plant were assessed. The methods were identical to those described by Yang et al. (2000).


Results and discussion

Morphologic observation: The amphiploid and its selfed progenies showed upright growth habit with the plant height of 65-70cm. This was identical to that of Ae. variabilis parent but lower than wheat parent J-11ph^1b with the plant height of 120-130cm. It is likely that the plant height of amphiploid was strongly influenced by Aegilops genome. On the other hand, the amphiploid had a mean of six spikes per plant indicating that the tillering ability was affected by its wheat parent, because its Aegilops parent always produced more than 20 spikes per plant. The spike characteristics of the amphiploid were intermediate between the parents but showed rachis brittleness and black tenacious glume at maturity (Fig. 1). The fertility of the amphiploid was considerably lower than those of parents and the seed-set rate was less than 30 per cent.

When the wheat and alien genomes are brought together, genomic interaction would affect genetic expression of qualitative and quantitative traits in the new background. The black glume of the amphiploid shows that the genes controlling the color pigmentation located on Ae. variabilis chromosomes (Spetsov et al. 1997) was expressed in amphiploid background. The quantitative traits such as plant height were frequently controlled by multigenes. Therefore, such quantitative traits are expected to show intermediate values between the two parents. We developed hybrid plants between wheat lines with other 12 Ae. variabilis and Ae. kotschyi accessions and found the plant height of the hybrids close to those of taller parents (Yang and Liu unpub.). But the height of the present amphiploid resembled Aegilops, a Shorter parent. This indicates that Ae. variabilis accession 13E may carry a novel dwarfing gene(s) which easily expressed in the wheat background. Pichl (1996) reported that a number of selections from the progenies from crosses between wheat and alien species including Aegilops possessed new types of dwarfness. It is likely that the dwarfing system in 13E of Ae. variabilis in present study is different from those in common wheat and can be exploited in wheat improvement to enrich the dwarfing resources. Cytological identification: Ae. variabilis has 28 chromosomes. Two pairs of these are satellited chromosomes, one pair is bigger than the other (Fig. 2). This agrees with the chromosomes 1U^v and 5U^v carrying satellites in Ae. variabilis revealed by Friebe et al. (1996). A complete amphiploid containing 70 .chromosomes was identified by somatic chromosome counting (Fig. 3.), and eight satellited chromosomes were observed. Wheat parent J-11ph^1b possessed four satellited chromosomes of 1B and 6B. Therefore, the satellite from both J-11ph^1b and Aegilops chromosomes were totally expressed in its complete amphiploid. This differs from the finding that nucleolar competition existed in many other artificial amphiploids such as primary hexaploid triticale (Lukazaweski and Gustafson 1987).