Introduction

China Taigu wheat is one kind of nuclear male sterility germplasm. The fertility d of Taigu wheat is controlled by a single dominant nuclear male sterility gene Ms2 (Deng and Gao 1980). All of the male sterile plants are heterozygous (Ms2ms2). So, hybrid seeds from male sterile plants always produced 50% fertile and 50% male sterile plants. (Deng and Gao 1980; Liu et al. 1986). After many efforts, the combination of the dominant dwarf gene Rht10and the male sterility gene Ms2 was established, which makes it possible to discriminate fertile plants from male sterile lines during heading stage (Liu and Yang 1991). At the same time, the dwarf male sterile line still could not be widely used for hybrid seed production because the fertile plants have to be removed before flowering, which increased seed production cost. If hybrid seeds of fertile plants could be discriminated from those of male sterile plants, the dominant male sterile line could be used for multiplying male sterile seeds by making crosses between male sterile and fertile plants with the same genetic background and to produce hybrid seeds by crossing male sterile plants with normal varieties or elite lines. After screening out the sterile seeds, the hybrid seeds left could be used for yield testing or for production.

It has been proved that the blue aleurone layer of wheat seed is controlled by a dominant gene located on the chromosome 4E of Elytrigia elongatum (Li et al. 1982). The chromosome 4E of Elytrigia elongatum has been successfully added to common wheat and a 4E addition line (2n=42W+4E') with blue seeds has been developed (Sun and Li 1985; Shen et al. 1991). Based on this strategy, we are planning to breed for male sterile wheat lines using blue seed color as selection makers to distinguish fertile seeds from male sterile seeds. It has been established that the dominant gene Ms2 controls the nuclear male sterility of Taigu w dheat located on chromosome 4D (Liu et al. 1986). Therefore, the possibility exists to combine these two genes by pairing and segmental exchange between partially homologous chromosomes (Sear 1972; Kaul 1987). In this way, a male sterile durum wheat line with a blue seed marker has been bred, whose chromosome constitution is AABB+4D(Ms2)/4E (Tian 1991; Zhang 2001). In this paper, we report the breeding of wheat combination lines of Rht10, Ms2 and a blue seed marker. The chromosome structures of male fertile plants and sterile plants, as well as the inheritance ratio of male sterile plants to fertile plants, have been investigated.

Materials and methods

A nuclear male sterile durum wheat line 89-2343 (2n=4x=AABB+4D(Ms2)/4E) with a dominant nuclear male sterile gene Ms2, was crossed with a wheat line 7739-3 of Triticum aestivum L. (2n=6x=42, AABBDD) to produce progenies. Then, another common wheat 4325 of Tritium aestivum L. (2n=6x=42, AABBDD (Ms2ms2Rht10rht10)) with dwarf male sterile and white seed, was crossed with the fertile plants having blue seed marker from progenies of 89-2343/7739-3 to screen out the common wheat combinations of dominant nuclear male sterile gene Ms2,Rht10 and a blue seed marker.

The segregation ratios for blue seed male sterile plants and white seed male fertile plants were tested on 13 new male sterile lines, which were derived from the combinations of dominant nuclear dwarf male sterile wheat line with blue seed marker. Cytological check by investigating the root tips and pollen mother cells was made between dwarf male sterile plants with blue seeds and fertile plants with white color.

Hybrid seeds in the same spike generally displayed two colors, i.e. blue and white. In the next season, blue and white seeds harvested from the same spike were planted separately in the field.