Distributions, ex situ conservation priorities, and genetic resource potential of crop wild relatives of sweetpotato [Ipomoea batatas (L.) Lam., I. series Batatas]

Crop wild relatives of sweetpotato [Ipomoea batatas (L.) Lam., I. series Batatas] have the potential to contribute to breeding objectives for this important root crop. Uncertainty in regard to species boundaries and their phylogenetic relationships, the limited availability of germplasm with which to perform crosses, and the difficulty of introgression of genes from wild species has constrained their utilization. Here, we compile geographic occurrence data on relevant sweetpotato wild relatives and produce potential distribution models for the species. We then assess the comprehensiveness of ex situ germplasm collections, contextualize these results with research and breeding priorities, and use ecogeographic information to identify species with the potential to contribute desirable agronomic traits. The fourteen species that are considered the closest wild relatives of sweetpotato generally occur from the central United States to Argentina, with richness concentrated in Mesoamerica and in the extreme Southeastern United States. Currently designated species differ among themselves and in comparison to the crop in their adaptations to temperature, precipitation, and edaphic characteristics and most species also show considerable intraspecific variation. With 79% of species identified as high priority for further collecting, we find that these crop genetic resources are highly under-represented in ex situ conservation systems and thus their availability to breeders and researchers is inadequate. We prioritize taxa and specific geographic locations for further collecting in order to improve the completeness of germplasm collections. In concert with enhanced conservation of sweetpotato wild relatives, further taxonomic research, characterization and evaluation of germplasm, and improving the techniques to overcome barriers to introgression with wild species are needed in order to mobilize these genetic resources for crop breeding

Proposal to change the conserved type of Ipomoea, nom. cons. (Convolvulaceae)

Ipomoea L. is the largest (650–900 species, depending on the concept adopted) and most iconic genus in Convolvulaceae, a family of c. 1880 species (data from Staples, Convolvulaceae Unlimited, 2012 at: http//convolvulaceae.myspecies.info), including the important crop sweetpotato, Ipomoea batatas (L.) Lam. (Tabl. Encycl. 1: 465. 1793), and several ornamental species commonly known as “bindweeds” or “morning glories” (Wilkin in Kew Bull. 54: 853–876. 1999; Mabberley, Mabberley's Plant‐book. 2008). The genus has a long history of taxonomic and nomenclatural problems, mainly for the lack of a clear morphological circumscription and overlap with other genera. In his Species plantarum (1753), Linnaeus distinguished two genera, Convolvulus L. and Ipomoea, whose species suffered numerous re‐arrangements, between Ipomoea and Convolvulus, but especially into numerous more recently described genera, which amount today to a total of 60 (Staples in World Checklist of Vascular Plants, v.2.0. 2020, http://wcvp.science.kew.org/ retrieved 2 Apr 2020)