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.