Evaluation of the Storage Root‐Forming Legume Yam Bean (Pachyrhizus spp.) under West African Conditions

Abstract

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. tuberosus, 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.

Heritability, combining ability and inheritance of storage root dry matter in yam beans

“…Nonetheless, the crop has attracted scientific and nutritional interest because its storage roots contain vitamins and micronutrients, such as iron and zinc (Noman et al, 2007;Dini et al, 2013), 56 to 58% starch (Forsyth et al, 2002) and 8 to 18% proteins Zanklan et al, 2007) on dry weight basis. Yam bean may offer nutritional benefits to local populations, where micro-nutrient deficiencies are rampant such as communities in the new introduction areas of East and Central Africa.…”

“…Yam bean may offer nutritional benefits to local populations, where micro-nutrient deficiencies are rampant such as communities in the new introduction areas of East and Central Africa. The crop is suitable for low-input agriculture on small farm holdings (Zanklan et al, 2007;Rodríguez-Navarro et al, 2009) because of its capability to improve soil fertility through Rhizobium-Bradyrhizobium-facilitated nitrogen-fixation (Castellanos et al, 1997), minimal pest incidences due to insecticidal rotenone in seeds and shoot Lautié et al, 2013), relatively short growth cycles, and wide geographic adaptation even in semi-arid conditions (Diouf et al, 1998;Belford et al, 2001). Yam bean gives high and stable yields of up to 80 t ha -1 of edible storage roots (Sørensen, 1996;Karuniawan, 2004); making its yield potential comparable to other root and tuber crops, such as cassava (Manihot esculenta Crantz) and sweetpotato (Ipomoea batatas) (Zanklan et al, 2007).…”

“…Storage root dry matter content in root crops is important for consumption and industrial processing , yet most yam bean varieties have low RDM which limits adoption (Zanklan et al, 2007;Agaba et al, 2016). Potential for improvement of RDM lies in hybridisation with the high RDM cultivar of Pachyrhizus tuberosus called the chuin (Ørting et al, 1996;Grüneberg et al, 2003;Zanklan et al, 2007).…”

“…Potential for improvement of RDM lies in hybridisation with the high RDM cultivar of Pachyrhizus tuberosus called the chuin (Ørting et al, 1996;Grüneberg et al, 2003;Zanklan et al, 2007). The chuin is known for high RDM (26 to 36%) and can be cooked or processed like cassava to "gari", a food staple for millions of people in West Africa (Zanklan et al, 2007;Padonou et al, 2013).…”

“…Through hybridisation and selection, the chuin may improve dry matter content of P. erosus accessions with high yields, wide adaptation, and drought tolerance (Belford et al ., 2001) and the P. ahipa accessions, with early maturity and erect or semi-erect growth habit (Zanklan et al, 2007). While studying the possibility of incorporating high dry matter from the chuin into the broader yam bean gene pool, Grüneberg et al (2003) observed fertile and vigorous interspecific hybrids between P. tuberosus-chuin and P. erosus and P. ahipa accessions.…”