| Popis: |
The distribution and Caracterization of constitutive heterochromatin in A-Am genomes of diploid wheat (progenitor), polyploid wheat (hybrids) and triticales (primary and secondary) are analyzed and compared by C-bands. The Comparison of zones rich in highly repeated DNA sequences marked by C bands on the all chromosomes of Am - A genomes revealed an important structural heterogeneity. Four chromosomes of Triticum monococcum (1Am-3Am-4Am-5Am) are almost similar to their homologues in wheat (Triticum durum , Triticum aestivum ) and triticale, by the presence or absence of C bands. Contrary to the chromosomes 2Am (rich in heterochromatin), 6Am-7Am (absence of C bands) show a great differentiation compared to their homologues of Triticum durum and Triticum aestivum and x-Triticosecale Wittmack. In the triticales, A genome chromosomes are richer in heterochromatin compared to theirs homologous of polyploid wheats. This is explained by a "genome shock The confrontation of C- bands genome (Triticum monococcum) with a C+ bands genome (durum wheat / or common wheat) produces an interspecific hybrid which at the sixth generation reveals C+ bands (triticales). The variations observed in our vegetal material indicated the existence of an intervarietal and interspecific heterochromatic polymorphism. The presence of B chromosomes in triticales, could be explained as a manifestation of their adaptation. |
