The crop wild relatives of the sweetpotato are members of the Batatas complex, a syngameon of morphologically challenging species. There are fourteen named species in the complex, but careful consideration of the available taxonomy suggests it is wanting. The members of this complex are very common throughout the Americas, especially in disturbed habitats. For example, they can often been seen carpeting roadsides throughout their range.
The sepals of these species are distinct and even a dried vine remaining on a chain link fence can easily be assigned to this group. In contrast, distinguishing between the named species is very difficult and as our thoughts evolve it may be because there are difficult species delineation problems yet to be resolved. We also are uncertain about the pattern of interfertility among the populations of the Batatas complex. Recent studies show morphologically distinct populations may hybridize readily, while essentially indistinguishable populations are not interfertile. It is likely this complicated pattern found among a sample of populations from the Carolinas, may be repeated in various configurations across the Americas.
There are many calls for a major reworking of the taxonomy of the Batatas complex. The emerging consensus is that there will be certain groups of populations that will be recognized as distinct species, while other groups of populations will represent species complexes with varying degrees of differentiation among various populations. However, it is very clear that an extremely large sample of populations and excellent systematic data will be needed to thoroughly untangle the Batatas complex.
We are applying the tools of molecular systematics and Next Generation sequencing techniques to unravel this complex collection of morning glories. We are very curious to see what these data suggest with respect to the relationship between morphology, evolutionary relationships, and population genetic structure.
These systematic questions are important. We plan to harness the genetic variation among the wild relatives of sweetpotato for crop improvement. The systematic and population genetic results will allow us to identify the relevant gene pool for contributing to sweetpotato breeding. For example, wild relatives from arid regions may be a source of traits important for drought resistance. Wild relatives have been very critical sources of improvement for resistance to pathogens, improving adaptability to various environmental conditions and general vigor for many important crop species. The use of wild relatives for sweetpotato improvement is in its beginning stages and deserves tremendous research attention.