Identification of chromosome translocations in the Bulgarian wheat variety Gladiator 113

G. Ganeva* and S. Landjeva

Institute of Genetics, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria

The Bulgarian variety Gladiator 113 is of breeding interest owing to its long multispikelet spike, complex disease resistance and high grain protein content. It has been isolated through crosses (Skorospelka 35 x Mexipac) x Siete Ceros, combined with radiation treatments of parents and hybrids (Savov 1987). The variety was expected to carry translocations from its close or more distantly related ancestors: a 1BL.1RS translocation from Skorospelka 35 (Mettin et al. 1973), and a 2A.2D translocation from the Brazilian variety Fronteira (Berzonsky 1996) through Mexipac or Siete Cerros. Additional structural rearrangements were likely to have been induced by the radiation treatments.

To identify the chromosome interchanges in Gladiator 113, chromosome N-banding technique (Gill et al. 1991) was applied on mitotic chromosomes in Gladiator 113 and on meiotic chromosomes in F1 hybrids of Gladiator 113 with varieties Chinese Spring, Rusalka and Rannaya 12.

In all hybrids, multivalents were recorded in the majority of cells (Table 1). The most frequently observed polyvalent configurations were 1"" or 2"",1''' ,1'''+1"". This indicates that at least four chromosomes in the hybrids participate in translocations. Penta- and hexavalents were also observed, but with lower frequency.

A 5A.6B translocation was identified in all hybrids (Fig.1a, b, c). The translocated chromosomes formed ring or chain quadrivalents (in 40 % of the examined cells), heterologous rod bivalents (47 %), a trivalent plus univalent (6 %), or four univalents (7 %). The aberration, however, does not alter the N-banding pattern of the two chromosomes (Fig. 2). To our knowledge, a 5A.6B translocation has not been reported earlier, although both chromosomes were known to be involved in exchanges with other chromosomes (Schlegel 1996). This translocation is supposed to be a newly induced structural aberration as a result of radiation treatments.

A 2A.2D translocation was not identified with certainty. Chromosome 2D rarely formed polyvalent associations with 2A, and paired more frequently with other A or D genome chromosomes (Fig.1c). in hybrids Rannaya 12 x Gladiator 113 more complex chromosome associations, involving chromosome 1B, were expected to be formed, as variety Rannaya 12 was reported to carry a 1B.2D translocation (Schlegel 1996). Chromosome 2D, however, was not observed in configurations with 1B.

The wheat-rye translocation 1BL.1RS was observed in meiosis in all F1-hybrids forming rod bivalents with chromosome 1B (Fig.1a, b), and in mitosis in Gladiator 113 (Fig. 2). This translocation is supposed to have been transmitted to Gladiator 113 from Skorospelka 35, thus contributing important genes.

The present study shows that variety Gladiator 113 carries translocations, involving chromosomes, which control plant morphogenesis and development, adaptability, yield quantity and quality. This knowledge is of importance when utilizing this variety and its hybrids in wheat breeding.

Acknowledgments

References

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Gill BS, Friebe B and Endo TR (1991) Standard karyotype and nomenclature system for description of chromosome bands and structural aberrations in wheat (Triticum aestivum L). Genome 34: 830-839.

Mettin D, Bluthner WD and Schlegel R (1973) Additional evidence on spontaneous 1B/1R wheat-rye substitutions and translocations. Proc 4th Int Wheat Genet Symp: 179-184.

Savov P (1987) A contribution to the gene pool of wheat. Genetics and Breeding (Sofia) 20 (5): 375-380. (in Bulgarian, with English summary).

Schlegel R (1996) A compendium of reciprocal translocations in wheat. 2nd Edition. Wheat Inf Serv 83: 35-46.