|MUNOZ-RODRIGUEZ, PABLO - University Of Oxford
|WELLS, TOM - University Of Oxford
|WOOD, JOHN - University Of Oxford
|CARRUTHERS, TOM - Royal Botanic Gardens, Kew
|Jarret, Robert - Bob
|SCOTLAND, ROBERT - University Of Oxford
Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2022
Publication Date: 1/22/2022
Citation: Munoz-Rodriguez, P., Wells, T., Wood, J., Carruthers, T., Anglin, N.L., Jarret, R.L., Scotland, R. 2022. Discovery and characterisation of sweetpotato’s closest tetraploid relative. New Phytologist. 234:1185-1194. https://doi.org/10.1111/nph.17991.
Interpretive Summary: Crops tend to evolve from more primitive forms. Those primitive forms of the crop are in turn often derived from species that are related to the crop, but are are distinct from it. Various programs have studied the plant species related to the sweetpotato. In the past, a unique form of sweetpotato was collected in Ecuador. This was known as 4X sweetpotato. It was proposed to be a form that contributed to the development of the modern day sweetpotato. This study shows that this unique form is indeed closely related to the modern sweetpotato and that it contributed to the development oif the sweetpotato, but that it is not a form of the sweetpotato, but is an entirely new and unique species.
Technical Abstract: Despite the status of sweet potato (Ipomoea batatas (L.) Lam.) as a globally significant food crop, its origin is poorly understood1–4. Cultivated sweet potato is hexaploid (2n=6x=90), possessing three subgenomes, and its evolution from the common ancestor with its closest diploid relative, Ipomoea trifida (Kunth) G.Don (2n=2x=30), implies the existence of a tetraploid intermediate (2n=4x=60)5–7. However, the identity of the tetraploid intermediate plants that are the closest relatives of domesticated sweet potato remains unknown, impeding research and breeding programmes2,8. Although a number of tetraploid plants resembling I. batatas exist in germplasm collections and herbaria9–15, it is not clear whether they share a common origin or had a role in the evolution of the hexaploid sweet potato. Here we characterise the phenotypic and genomic variation in tetraploid plant collections closely related to hexaploid sweet potato. We use an integrated approach16 to distinguish modern hybrid tetraploids from ancient auto-tetraploids that existed prior to the origin of hexaploid sweet potato. In the process, we identify wild auto-tetraploid plants from Ecuador and Colombia that are morphologically distinct and most closely related to the cultivated crop in phylogenetic analyses. We therefore designate a new species, and name it Ipomoea aequatoriensis T.Wells & P.Muñoz. This represents the closest crop wild relative (CWR) of sweet potato, and its most likely tetraploid progenitor. The discovery of this new species will better facilitate research into the process of polyploidization in the origin of hexaploid sweet potato, and could also allow the incorporation of adaptive traits from CWR.