Horizontal transferred T-DNA and haplotype-based phylogenetic analysis uncovers the origin of sweetpotato

The hexaploid sweetpotato is one of the most important root crops worldwide. However, its genetic origins are controversial. In this study, we identified two progenitors of sweetpotato by horizontal gene transferred Ib T-DNA and haplotype-based phylogenetic analysis. The diploid progenitor is the diploid form of I. aequatoriensis , contributed the B1 subgenome, Ib T-DNA2 and lineage 2 type of chloroplast genome to sweetpotato. The tetraploid progenitor of sweetpotato is I. batatas 4x, donating the B2 subgenome, Ib T-DNA1 and lineage 1 type of chloroplast genome. Sweetpotato derived from the reciprocal cross between the diploid and tetraploid progenitors and a subsequent whole genome duplication. We also detected biased gene exchanges between subgenomes. The B1 to B2 subgenome conversions were almost 3-fold higher than the B2 to B1 subgenome conversions. This study sheds lights on the evolution of sweetpotato and paves a way for the improvement of sweetpotato. ### Competing Interest Statement The authors have declared no competing interest.