The First Genetic Map for a Psoraleeae Legume: GBS Mapping of Tedera (Bituminaria bituminosa var. albomarginata) Reveals Highly Conserved Synteny with Soybean

The legume tribe Psoraleeae comprise six genera and around 135 species, and is closely related to the sub-tribe Glycininae, which contains soybean (Glycine max (L.) Merr.). No genetic maps are available for any Psoraleeae species, including tedera (Bituminaria bituminosa C.H. Stirt. var. albomarginata), an emerging drought-tolerant forage legume from the Canary Islands. Here we used an improved GBS method based on size-selection of double-digested adapter-ligated DNA which increases sequencing yield and quality by producing high diversity libraries. We applied this technique for genotyping a subset of an F2 population comprising 45 progeny and parents in one lane of HiSeq. We obtained over 150 M 100bp SE reads which were analysed using Stacks pipeline resulting in 845 high-quality SNP markers scored in all samples. Linkage mapping identified 11 linkage groups, close to the haploid chromosome number of this species (n=10). Analysis of synteny via BLASTn between the genomes of tedera and its close relative soybean using tedera GBS sequence tags revealed the presence of 264 (31.2%) GBS marker tags with one or more significant (<1e^-10) matches in the soybean genome and that marker order was conserved in large chromosomal blocks between the two genomes. Typically, one region of tedera aligned well with two regions of the soybean genome, reflecting the diploid and allotetraploid nature of the respective genomes. This finding, along with application of the method to the remaining 142 F2 progeny, will facilitate the transfer of genomic information between the well-resourced model genome of soybean and the ‘orphan’ genome of tedera.