Linear differentiation of cereal chromosomes : I. Common wheat and its supposed ancestors.

Using the Giemsa technique of differential staining (the BSG test), we have studies the karyotypes and constructed the idiograms of T. aestivum L. var. 'Diamant' and 'Chinese Spring', T. Monococcum L. v. 'hornemannii' ssp. roles occidentali georgicum Dek., Aegilops squarrosa L. v. 'Meeyeri', T. aestivum. The karyotypes of 'Chinese Spring' and 'Diamant' differ drastically both in total structural heterochromatin content and its localization on the nine morphologically homeologous chromosomes. The rest of the twelve pairs of chromosomes showed no morphological similarity. This indicates considerable differences in the phylogeny of the varieties, and also an absence of unique karyotype in T. aestivum.Three chromosomes of Ae. Squarrosa are similar to those of 'Chinese Spring', yet, on the whole, the chromosomal structural specificity of the diploids studied is so high that we fail to understand the nature of the homology between common wheat and its supposed diploid ancestors.The role of introgression in the evolution of the genomes of Triticum and Aegilops, and also the meaning of the conjugation and BSG tests in resolving the phylogeny, is discussed.

Linear differentiation of cereal chromosomes : II. Polyploid wheats.

The BSG test was used in a comparative study of the linear chromosome differentiation and the idiograms of T. Macha ssp. tubalicum v. 'letschchumicum ' Dek. et Men., T. georgicum Dek., T. timopheevi. Zhuk., T. carthlicum Nevski, T. dicoccum Schrank, v. 'rufum', T. durum Desf. v. 'Arnautka' were compiled.The karyotype of each polyploid wheat species consists of two groups of chromosomes. The first is formed by ten pairs of "constant" chromosomes occurring almost in all species and the second by all the rest of the "variable" chromosomes that are either fully specific for the species in question or occur only in a few species. T. timopheevi largely differs from other species of polyploid wheats in the high level and specific localization of structural heterochromatin on chromosomes. The rols of introgression in wheat evolution and the necessity of establishing a General Cytological Nomenclature of Cereal Chromosomes are discussed.

Linear differentation of cereal chromosomes : III. Rye, triticale and 'Aurora' variety.

The BSG test was used in an investigation of the linear differentiation in rye variety 'Zhitkinskaya', common wheat variety 'Aurora' and two secondary Triticale namely AD-196 and F-1239.Chromosomes of 'Aurora' variety and wheat chromosomes within Triticale may be easily divided into "constant" and 'variable' chromosomes as described previously (lordansky et al. 1977; Zurabishvili et al 1977).It is necessary to emphasize that the diversity of "variable" chromosomes underlies karyotypical polymorphism within wheat and Triticale species. The polymorphism observed exists in parallel with strict homomorphism of homologous chromosomes.In IB chromosomes of 'Aurora' variety, the short arm is substituted by the rye chromosome arm. The karyotype of Triticale AD-196 consists of six pairs of rye chromosomes and fifteen pairs of wheat chromosomes.