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It is of interest to know that ZELLER and BAIER (1973) recently described
a wheat-rye chromosome substitution line in which wheat chromosome 4A
was replaced by rye chromosome 5R. This substitution (Blaukorn) also is
characterized by blue aleurone and additionally by pubescent peduncle.
It is, however, not yet certain whether the segnent with the gene for
blue aleurone is carried by the hairy neck chromosome or attached to a
wheat chromosome by a translocation. We intend to locate the blue-kernel-colour
gene after backcrossing 'Blaukorn' to Chinese Spring for several generations.
Linkage of pubescent peduncle and blue aleurone, however, would support
the assumption that both loci are carried by the 5R rye chromosome. The cytological analysis of the somatic chromosomes of the Hungarian strain 205 - 70 revealed that the genome is comprised of 40 complete chromosomes and two long telocentric chromosomes. In crosses of the strain with disomic Chinese Spring and Kolibri, resp. 20 bivalents and two univalents occurred in the PMC's. Furthermore the strain 205 - 70 was crossed with each of the six monosomic Chinese Spring lines of the homoeologous groups 4 and 5. Table 2 demonstrates that in the F1 hybrids of monosomic lines 4A, 4B, 4D, 5B and 5D, 19 bivalents and three univalents usually were formed. In the monosomic plants of the cross between Chinese Spring monotelocentric 5A and the Hungarian strain, 20 bivalents and one univalent most frequently occurred (Figure 1). The unpaired chromosome of the critical cross most probably is the long arm of rye chromosome 5R. This arm is characterized by a large constriction visible in most of the PMC's. This phenomenon has also been reported by BIELIG and DRISCOLL (1970a, b) and is typical for the complete chromosome 5R, too, if present as a univalent (KATTERMANN 1937, O'MARA 1951, ZELLER and BAIER 1973). Different authors reported several instances of substitutions and translocations of wheat chromosomes belonging to homoeologous groups 4 and 5 by rye chromosome 5R (see ZELLER and FISCHBECK 1974). Spontaneous chromosome substitutions and translocations may serve as evidence for the homoeology of rye chromosome 5R. The present case of a substitution of the wheat chromosome pair 5A by a telo-5RL pair supports the assumption that at least this arm of the hairy neck chromosome is homoeologous to wheat group 5. Recently we reported in numerous spontaneous chromosome substitutions and translocations of different origin the preferred tendency of a specific rye chromosome (1R) to replace the complete wheat chromosome 1B or a part of it. We proposed to designate this behaviour of chromosomes of the sub-tribe Triticinae preferential substituting ability (ZELLER 1973). It appears likely that strain 205 - 70 is a further example of this phenomenon. More instances of identified 5R substitution and translcoation lines, however, must be known to be able to state that rye chromosome 5R is homoeologous to group 4, 5 or both groups. Possibly chromosome 5R is one of the three interchanged chromosomes which differentiate Secale cereale L. from Secale montanum GUSS., the presumptive ancestor of cultivated rye (see RILEY 1955). Literature Cited O'MARA, J.G. 1951. Cytogenetic studies on Triticale. II. The kinds of intergeneric chromosome addition. Cytologia 16 : 225-232 QUINN, C.J. and C.J. DRISCOLL 1967. Relationships of the chromosomes of common wheat and related genera. Crop Sci. 7 : 74-75 RILEY, R. 1955. The cytogenetics of the differences between some Secale species. J. Agric. Sci. 46 : 377-383 SEARS, E.R. 1967. Induced transfer of hairy neck from rye to wheat. Z. Pflanzenzuchtg. 57 : 4-25 ZELLER, F.J. 1973. 1B/1R wheat-rye chromosome substitutions and translocations. Proc. 4th Int. Wheat Genet. Symp., Mo. Agr. Exp. Sta., Columbia, Mo., U.S.A. 209-222 ZELLER, F.J. and A.C. BAIER 1973. Substitution des Weizenchromosomenpaares 4A durch das Roggenchromosomenpaar 5R in dem Weihenstephaner Weizenstamm W 70 a 86 (Blaukorn).Z. Pflazenzuchtg. 70 : 1-10 ZELLER, F.J. and G.W. FISCHBECK 1974. Chromosomenadditionen,-substitutionen und-translokationen als Grundlagen fur die Ubertragung artfremden Ermbaterials in den Saatwiezen (Triticum aestivum L.). Advances in Plant Breeding, Suppl. 4, 55pp. Verlag Paul Parey, Berlin and Hamburg (Received Sept. 1, 1974) |
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