The interspecific rice hybrid of the Asian Oryza sativa and the African Oryza glaberrima, New Rice for Africa (NERICA-4) development was initiated due to threatening global food insecurities in part due to its desirable agronomical features compared to other NERICA cultivars. It is fairly tolerant to drought, has quicker growth rate and high yields. However, production is still faced by numerous challenges, leading to fluctuations in its availability and losses to farmers. Improvement via genetic transformation has become integral in solving key production challenges including effects of climate change, insect pests and diseases. Success of any transformation relies on an efficient callus induction and regeneration process to recover whole plants from the transformed cells. Therefore, this study explored NERICA-4 in vitro regeneration via indirect somatic embryogenesis by optimizing plant growth regulators particularly auxins; 2, 4-Dichlorophenoxyacetic acid (2, 4-D) and 1-Naphthaleneacetic Acid (NAA) and the cytokinin 6-Benzylaminopurine (BAP). All phytohormone regimes above-zero concentration of the auxins tested had a positive effect on calli induction. Comparison of 2,4-D and NAA showed the former is a better calli-inducing hormone, either used independently or in combination with cytokinins. In all combinations tested, both compact and friable calli were produced. However, the latter were more efficient sources of somatic embryos. Regeneration of whole plants from generated calli was done with a frequency of up to 66.67%. The reported regeneration protocol provides an efficient route for recovery of transformed cells in NERICA 4 rice genetic improvement processes.

Keywords: NERICA-4, Auxin, Cytokinin, Oryza sativa, in vitro regeneration