Abstract:

The wheat-rye 1RS/1BL translocation has made a great contribution to the wheat production in the world since the Green Revolution. The 1RS/1BL translocations, for the existence of the short arm of rye(Secale cereale L．) chromosome 1R, often have many good traits such as high yield potential, multi-resistance to diseases and good adaptation to acid soil. Many studies also illustrated that 1RS carries a lot of rust resistance genes (Sr31, Lr26, Yr9) and powdery mildew resistance gene (Pm8). As a result, the short arm of 1R is frequently used as alien chromatin in wheat (Triticum aestivum L．) improvement.
But one major concern about this translocation recently is its single origin, with the consequence being loss of resistances to new races of stripe rust and powdery mildew. The other concern is that most of wheat cultivars carrying this chromosome arm were shown a defective grain quality, in particular, sticky dough and a reduction in dough strength. The reduction in dough strength was thought to be due to the presence of monomeric secalins from rye (Sec-1) and the substitution of glutenins and gliadins (Glu-3 and Gli-1).
In order to develop new potentially usable disease resistant alien germplasm and improve the quality of 1RS/1BL translocations, cross was carried out between the Triticum aestivum L．cv．“Xiaoyan 6” and Secale cereale L．cv．“German White”. “German White” is a winter rye cultivar which is immune from stripe rust and powdery mildew. “Xiaoyan 6” is an elite winter wheat cultivar derived from the cross common wheat × Thinopyrum ponticum (2n=70). It possesses the characteristics of good processing quality, high yield potential, earliness, good stress tolerance and wide adaptation.
Wheat-rye hybrids between “Xiaoyan 6” and “German White” were obtained in 1994. The F₁ were treated with colchicines. The F₂ and the subsequent generations were self-crossed and planted in the field. Each individual plant was selected with the qualities of seed set, wheat-like plant type and good resistance to rust and powdery mildew. A set of wheat-rye germplasm with resistances to rust and powdery mildew were bred. In order to identify genetic basis of these resistant lines, sequential C-banding–GISH (genomic in situ hybridization) was employed to analyze the chromosome compositions in somatic cells. As a result, two 1RS/1BL homozygous translocation lines BC152-1-1 and BC01-89-1 were selected. One of them, BC152-1-1 had a chromosome number of 2n=42 in somatic cell and its chromosome composition were 40 normal wheat chromosomes and one pair of 1RS/1BL Robertsonian translocation chromosomes (PlateⅠ-A,B). The other one, BC01-89-1 (2n=43) was a 1RS/1BL Robertsonian translocation line added one 3R chromosome with both terminal deletions (PlateⅠ-C,D). In addition, the high-molecular-weight glutenin subunits (HMW-GS) in endosperm and major quality characteristics of “Xiaoyan 6”, BC152-1-1 and BC01-89-1 were analyzed. The results showed that BC152-1-1 and BC01-89-1 carried HMW-GS 14+15 derived from “Xiaoyan 6” (Fig.1), and their grain protein content, wet gluten content and SDS sedimentation value were greatly improved.

Key words: Triticum aestivum, Secale cereale, 1RS/1BL translocation line, Sequent C-banding-GISH, HMW-GS