A Potential Legume Crop, Apios americana: Insights from the Characterization of an Apios Collection.

Apios americana (Apios) is a nitrogen-fixing legume, adapted to the diverse climatic conditions of central and eastern North America. It produces tubers (modified stem-tubers) that are rich in protein, have a long shelf life under refrigeration (>1 year), and contain isoflavones with potential health benefits. Apios was part of staple diet of Native American Indians, but following European colonization, consumption declined and it has not been widely grown. This may be due to lack of awareness, absence of dedicated breeding programs, and lack of markets. Blackmon and Reynolds, in the 1980s, made the only significant effort toward domestication. Their breeding efforts (1985-1994) resulted in several promising lines, of which 53 remain. The goals of this study are: 1. Perform phenotypic evaluation of the Blackmon collection in multiple years, and in multiple environments (Iowa, Virginia and Pennsylvania); 2. Develop genomic resources, including a high-quality reference de novo transcriptome assembly, an expression catalog, and a large set of RNA-Seq-derived SNPs for marker-assisted selection and association analysis; 3. Perform genomics-assisted characterization of the collection; and 4. Develop the first linkage map, using a pseudo-testcross strategy. We have identified several promising genotypes – yielding up to 1.5 kg of tuber yield/plant. Re-sequencing the leaf transcriptomes from all the genotypes provided 58,154 SNPs and 39,609 gene expression markers (GEMs). Interestingly, both SNPs and GEMs revealed similar population structure and pedigree relationships. Association analysis conducted using SNPs and GEMs identified marker-trait associations for at least 11 traits. The linkage map developed has 13 linkage groups, with 880 recombinationally distinct loci and covers ~1137 cM. In summary, this study demonstrates accelerated characterization of an underutilized plant by combining phenotyping and high-throughput sequencing. Procedures and methods developed can be leveraged for both staple and minor crops.