Evaluation of the storage root-forming legume yam bean (Pachyrhizus spp.) under west African conditions

The yam bean (Pachyrhizus spp.) contains three closely related cultivated species: P. tuberosus (Lam.) Sprengel, P. erosus (L.) Urban, and P. ahipa (Wedd.). Its storage root dry matter content (SRDM) is usually low, although genotypes with a high SRDM have been identified ('Chuin' accessions). Flowers are often removed through flower pruning (FP) to increase storage root fresh matter yield (SRFY). The main objectives of this study were to investigate the potential for use in Benin (West Africa), to estimate the effect of FP, and to test whether roots could be processed into gari. In total, 34 accessions were tested at one drought-stress and one irrigated location. Means and genetic variance components were estimated for 33 agronomic traits. Without FP, the SRFYs of P. tuberosus, P. erosus, and P. ahipa were 13.9, 23.4, and 12.4 t ha(-1), respectively, and the seed yields were 2.2, 5.2, and 2.1 t ha(-1), respectively. The FP caused SRFY to increase by 48, 91, and 61% in P. tuberosu, P. erosus, and P. ahipa, respectively. The storage root dry matter yield (SRDY) of P. erosus was only slightly higher (-8.5 t ha(-1)) than that of the Chuin accessions (-8.0 t ha(-1)). Under drought, the SRDY was least affected in P. erosus. Early-maturing P. ahipa accessions were identified. All species could be used to make gari, which contained, on average, 5.5% protein, 58.5% starch, and 23.8% total dietary fiber. The crop has the potential for use in West Africa and has a large genetic variation for genetic improvement.