In Vitro Regeneration of African Yam Bean (Sphenostylis stenocarpa (Hochst ex. A. Rich.) Harms by Direct Organogenesis

Abstract

Studies on in vitro organogenesis of African yam bean (Sphenostylis stenocarpa) were carried out with the aim of developing a rapid regeneration system for this crop. Embryo and leaf explants were cultured on Murashige and Skoog (MS) containing varying concentrations and combinations of 6-benzyl aminopurine (BAP), kinetin and α-naphthalene acetic acid (NAA). The maximum number of shoots per explant (4.5) and percentage multiple shoot induction (100%) were obtained in MS supplemented with 0.05 mg.L-1 NAA and 0.5 mg.L-1 BAP. The maximum shoot length (135 mm) was obtained on a medium with 1.0 mg.L-1 kinetin and 0.1 mg.L-1 NAA. When cotyledonary node explants and shoot tip explants were cultured on media with BAP and kinetin singly, each at 1.0, 1.5 and 2.0 mg.L-1, both explants produced the maximum number of shoots (4.75) and shoot length (25 mm) on 2.0 mg.L-1 BAP while the least responses were obtained on 1.0 mg.L-1 kinetin. There was no organ formation from leaves as they all produced calli. Multiple shoots from the embryo produced roots directly on shoot induction medium while shoot tip-derived multiple shoots rooted when tested on both 0.25 and 0.5 mg.L-1 NAA. Shoots from cotyledonary nodes did not produce roots. Successfully rooted plantlets obtained from this study is the fi rst report of in vitro plant regeneration in African yam bean. This procedure for direct organ differentiation would facilitate micropropagation and improvement of this species through genetic transformation.