Figure 4

Tetraploidy of Miscanthus relative to sorghum, with extensive colinearity and a single chromosome fusion. Panel A. Horizontal axis shows genetic map position of markers on the 19 Miscanthus linkage groups, in centiMorgans; vertical axis shows physical map position of markers aligned to the 10 sorghum chromosomes in megabases. Each dot corresponds to a single marker. Markers that could not be uniquely mapped to sorghum are shown along the horizontal axis as black dots. Duplication and colinearity of nearly all chromosomes is evident (markers in magenta). A copy of sorghum chromosome 7 (markers in sky blue) has been inserted into a copy of sorghum chromosome 4 (markers in green) to produce Miscanthus linkage group 7. Markers on Miscanthus linkage group 13, which are also syntenic with sorghum chromosome 7, are shown in a darker blue. Panel B. Circos plot showing centromeric insertion of sorghum chromosome 7 into sorghum chromosome 4 to form Miscanthus linkage group 7 (approximate boundaries indicated by arrows). Each line represents an orthologous relationship between a mapped Miscanthus marker and its unique counterpart on the Sorghum bicolor genome. Both Miscanthus linkage groups 7 and 8 have a region corresponding to sorghum chromosome 4, which is inverted with respect to the other markers (dark green arrow and lines). As also shown, Miscanthus linkage group 8 is an intact copy of sorghum chromosome 4, and Miscanthus linkage group 13 is an intact copy of sorghum chromosome 7.