Theor Appl Genet (1992) 83:305-312 9Springer-Verlag 1992 Nonhomoeologous translocafions between group 4, 5 and 7 chromosomes within wheat and rye C.J. Liu, M.D. Atkinson, C.N. Chinoy, K.M. Devos, and M.D. Gale * Cambridge Laboratory, Colney Lane, Norwich NR4 7UJ, UK Received March 5, 1991; Accepted May 16, 1991 Communicated by J.W. Snape Summary. Genetic maps of wheat chromosome 4A and rye chromosome arm 5RL, and the chromosomal loca- tions of 70 sets of isozyme and molecular homoeoloci have been used to further define the structure of wheat chromosomes 4A, 5A and 7B, and rye chromosomes 4R, 5R and 7R. We provide evidence, for the first time, which is consistent with the presence of an interstitial segment on 4AL originating from 5AL, and of a segment original- ly from 5RL on 7RS. The evolutionary origins of the present chromosomes are discussed. Key words: Wheat - Rye - RFLP - Isozymes - Evolu- tionary translocations Introduction Wheat (Triticum aestivum; 2n = 6x = 42, genomes AABB- DD), barley (Hordeum vulgare, 2n=2x=14, genome HH) and rye (Secale cereale, 2n=2x=14, genome RR) are all part of the tribe Triticeae and, presumably, these now distinct genomes were all derived from a single com- mon ancestor. Over the past two decades it has become increasingly clear that there remains much similarity be- tween the various Triticeae genomes, even though they have long been isolated. Evidence for homoeology was first demonstrated by the ability of chromosomes to compensate for one another in nullisomic-tetrasomic combinations (Sears 1954, 1966). Later more evidence was assembled from both induced intergenomic pairing and recombination within hexaploid wheat (Riley and Chapman 1958) and between the wheat genomes and those of related species (Naranjo 1982; Koebner and * To whom correspondence should be addressed Shepherd 1986), and from the concurrence of chromoso- mal and intrachromosomal locations of marker genes, particularly biochemical and molecular loci. These are often observed to be triplicated in wheat and have ho- moeoloci in one or more related species (see McIntosh et al. 1990). The most recent evidence derives from the detailed genetic maps that are beginning to emerge, such as for the homoeologous group 7 chromosomes of wheat (Chao etal. 1989), where the chromosomal location, order and genetic distances between markers is remark- ably conserved over the A, B and D genomes. The main disturbance to co-linearity of maps between genomes arises from intra- and interchromosomal trans- locations. Many intervarietal translocations have arisen since speciation, and an extensive, although probably not exhaustive list for wheat has been prepared by Schlegel and Schlegel (1989). Other evolutionary translocations (Gale et al. 1990) arose before the formation of species barriers and characterise the various Triticeae genomes. In hexaploid wheat, evolutionary translocations in- volving chromosome arms 4AL (formerly 4BL), 5AL and 7BS were proposed by Naranjo et al. (1987) follow- ing a study of induced homoeologous chromosome pair- ing with the aid of differential chromosome staining. Some confirmatory evidence for the 4AL to 5AL translo- cation is also available from the nonhomoeologous loca- tions of marker gene sets, e.g. ~-Amy-1 (Ainsworth et al. 1983) and for the 7BS to 4AL translocation from various isozyme and RFLP loci (Chao et al. 1989). In rye a sim- ilar situation exists involving chromosomes 4R, 5R and 7R. The translocation between chromosome arms 4RL and 7RS has long been recognised (K611er and Zeller 1976). It has also been speculated that, while largely homoeologous with group 5, chromosome 5R has a small amount of homoeology with group 4. Supporting evidence is summarized by Naranjo et al. (1987).