Melia volkensii Gurke is a drought-tolerant tree native to East Africa’s arid and semiarid lands (ASALs), with vast but underutilized potential for agroforestry and sustainable livelihoods in the ASALs. Its cultivation is limited by difficulties in propagation via conventional means. Full exploitation of the ability of thidiazuron (TDZ) to elicit regeneration in plant tissue cultures, as sole plant growth regulator (PGR), is hampered by high costs. This study tested the effectiveness of a low-cost agrochemical TDZ for in vitro propagation of M. volkensii. Zygotic embryos from mature seeds were cultured on Gamborg’s B5 medium containing 0 to 4？mg/L of agrochemical TDZ from Kingtai Chemicals Co.,Ltd., China. Callus induction frequency was 96.67 to 100%. Significantly large callus fresh mass was produced at 0.05？mg/L TDZ concentration (ANOVA, ). The effect of TDZ on embryogenicity was significant over certain ranges of concentrations (Anova, ). Multiple somatic embryos developed within 14 days of subculture to hormone-free B5 medium. Somatic embryos developed into microshoots which elongated when transferred to MS medium supplemented with 0.1？mg/L 6-benzylaminopurine plus 10% coconut water. The Kingtai-TDZ showed a high potency and suitability for use in M. volkensii tissue culture. 1. Introduction Melia volkensii Gurke (Meliaceae: mahogany family) is a drought-tolerant, fast-growing multipurpose tree indigenous to the arid and semiarid lands (ASALs) of East Africa [1, 2]. Its other desirable properties include coppicing ability, termite-resistant wood, and suitability for dry land agro-forestry and bee-keeping [3]. It can be cultivated commercially for valuable mahogany timber, insect repellants, and larvicidal and medicinal compounds [4, 5]. Muok et al. [6] estimated the timber related income from a 10 to 15 year plantation of M. volkensii to be Ksh 3 million (~US$ 35,294) per hectare. The species has been overexploited for its valuable timber [6–8], and there is an urgent need for conservation interventions. Among the suggested conservation strategies is the domestication of the species in agroforestry systems [9, 10]. However, propagation of the species via seed is constrained by difficulties in seed extraction, poor germination, and high post-germination mortality [6, 11, 12]. Propagation by stem cuttings is also reported to be difficult [2, 12]. In view of these difficulties, there is need for tissue culture protocols for mass propagation and wider dissemination of the species. There are limited reports on tissue culture of M. volkensii. Indieka et
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