VARIATION IN THE DNA CONTENT OF GLYCINE SPECIES

Nuclei were isolated from cotyledons of a range of accessions from 14 species of Glycine. These were stained with ethidium bromide and the relative fluorescence for each genotype was measured by flow cytometry. The DNA content was estimated by comparison of relative fluorescence with that from nuclei from seedling leaves of Allium cepa, whose DNA content has been calculated previously by chemical assay. The 4C amounts for diploid Glycine ranged from 3.80 to 6.59 pg. Two groups of diploid species appeared from the analysis. The first consisted of species with amounts ranging from 3.80 to 5.16 pg and included G. canescens (AA), G. argyrea (A1A1), G. clandestina (A2A2), G. microphylla (BB), G. latifolia (B1B1), G. tabacina 2n = 40 (B2B2), G. tomentella 2n = 38 (EE) and 2n = 40 (DD), G. max and G. soja (GG), G. arenaria and G. latrobeana. A second group had higher DNA contents ranging from 5.27 to 6.59 pg, and consisted of G. curvata, G. cyrtoloba (CC), and G. falcata (FF). The polyploid species, G. tabacina 2n = 80 (AABB, BBB1B1), G. tomentella 2n = 78 and 2n = 80 (AAEE and DDEE, respectively) contained amounts approximating to the sums of the respective parental diploid species thought to have given rise to these allotetraploids. Intraspecific variation was detected in the DNA content of G. canescens. Within the overall distribution of DNA amounts found in A genome species, each genome contained a range of DNA contents specific to that species. This phenomenon was also detected amongst B genome species.