Of the two major polyploid complexes in Glycine subgenus Glycine, the G. tomentella complex is the largest. G. tomentella is polymorphic--and polyphyletic--at the diploid level, with several clades well-defined in gene trees using 18S-26S nuclear ribosomal gene (nrDNA) ITS and histone H3-D sequences. Polyploids also called G. tomentella combine genomes of these and other Glycine taxa. The diversity of the G. tomentella complex includes one diploid genome that is also a donor for an allotetraploid race of the G. tabacina complex, the other major polyploid complex of the subgenus. This means that, in effect, a single large complex accounts for most neopolyploidy in Glycine. Some of the combinations hypothesized from DNA sequence data were predicted based on other data, such as isozymes and 5S rRNA gene repeat sizes, but other polyploid genome constitutions were unexpected, and indicate that there is more complexity in the group than was suspected. In most polyploid races, both of the predicted homoeologous nrDNA repeat classes are present but often in very unequal amounts. Polymorphism for chloroplast sequences in accessions from some G. tomentella allopolyploids suggests that in some cases both diploid progenitors may have served as maternal parents in the original cross that led to a given allopolyploid. This is in marked contrast to the G. tabacina complex, where crosses appear always to have involved the same taxa as chloroplast genome donors even when those crosses occurred several times.

Key words: Glycine, histone H3-D, Leguminosae, polyploidy, ribosomal genes