Variation in DNA content of 21 individual chromosomes among six subspecies in common wheat.

In order to consider at chromosomal level the phylogeny of wheat, DNA content of 21 individual chromosomes was measured cytophotometrically at M1 or A1 of meiosis in monosomic plants and compared among seven strains belonging to six subspecies of common wheat, Triticum aestivum.1) Nuclear DNA content at pollen tetrad did not differ at all among seven strains.2) DNA content of individual chromosomes varied from chromosome to chromosome in any strain.3) Significant difference was found among three genomes, A, B and D, the ratio being 1.14:1.21:1.00. This ratio apparently differed from those of two earlier reports based on nuclear DNA content of putative diploid ancestors (T. monococcum: Aegilops speltoides: Ae. squarrosa). The authors suggested diploid species of section Sitopsis, with a little higher DNA content than Ae. speltoides as B genome donor to polyploid wheat.4) There was not significant difference among seven homoeologous groups, but homologous chromosomes.5) Total DNA content of seven strains calculated from DNA content of individual chromosomes was very similar to one another, being clearly compatible with the results of nuclear DNA content at pollen tetrad.