Origin and evolution of the forage allotetraploid species Stylosanthes scabra

The genus Stylosanthes includes nitrogen-fixing and drought-tolerant species of considerable economic importance for perennial pasture, green manure and land recovery. Stylosanthes scabra is adapted to variable soil conditions, being cultivated to improve pastures and soils worldwide. Previous studies have proposed S. scabra as an allotetraploid species (2n = 40) with a putative diploid A genome progenitor S. hamata or S. seabrana (2n = 20) and the B genome progenitor S. viscosa (2n = 20). Cost et al. aimed to provide conclusive evidence for the origin of S. scabra.

The authors performed fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH) experiments and Illumina paired-end sequencing of S. scabra, S. hamata and S. viscosa genomic DNA, to assemble and compare complete ribosomal DNA (rDNA) units and chloroplast genomes.

Cost et al. report the first time the whole plastomes for S. scabra, S. hamata and S. viscosa. The results obtained are helpful to develop molecular markers to assist breeding efforts in S. scabra. The approach used might be also extendable for studying the origin of other Stylosanthes allopolyploids