Somatic karyotype, heterochromatin distribution, and nature of chromosome differentiation in common wheat, Triticum aestivum L. em Thell

Abstract

Heterochromatin distribution and structural differentiation of somatic chromosomes of five common wheat cultivars — Chinese Spring, Wichita, Cheyenne, Timstein, and Hope — were studied by an acetocarmine/N-banding technique. Detailed morphological observations on acetocarmine stained somatic chromosomes of Chinese Spring were made on all A genome chromosomes (except 1A), all B genome chromosomes, and chromosomes 1D, 2D, and 7D. N-banding patterns of chromosomes 2A, 3A, 5A, 6A, 1D, 2D, and 7D were described for the first time. Substitution lines of 21 individual chromosomes each of Cheyenne, Timstein, and Hope in Chinese Spring were analyzed by N-banding. A high frequency of N-band polymorphism was observed, especially for most of the B genome chromosomes. Chromosomes 3A, 5A, 2D, and 7D showed a constant banding pattern. Three cases of doubtful substitutions, Hope 2A, 2B, and Timstein 7A, and several cases of incomplete and chromosomally modified substitutions were observed. The reduced level of chromosome pairing that is often observed in intercultivar hybrids of wheat may be due to heterochromatic differentiation, genic and structural heterozygosity, or hybrid dysgenesis.