DOYLE, JEFF J.1*, JANE L. DOYLE1, JASON T. RAUSCHER1, REID G. PALMER2, and TONY BROWN3. 1L. H. Bailey Hortorium, Department of Plant Biology, Cornell University, 466 Mann Library Building, Ithaca, NY 14853, USA; 2USDA-ARS CICGR, Ames, IA 50011, USA; 3Centre for Plant Biodiversity Research, CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia. - Dissecting an extensive polyploid complex in Glycine subgenus Glycine (Leguminosae) using low copy nuclear genes, nuclear ribosomal genes, and chloroplast sequences.
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