Effect of Explant Physiology and Media Composition on Callogenesis of Vitellaria paradoxa Leaf Explants

Vitellaria paradoxa (shea tree) is an economically and medicinally important species indigenous to sub-Saharan Africa. Although the species holds substantial value, domestication efforts have been constrained, primarily due to the absence of efficient propagation alternatives, especially for the East African subspecies (V. paradoxa subsp. nilotica) which remains understudied in tissue culture research. This study investigated the influence of leaf explant developmental stage and media composition on callogenesis and embryogenic potential in V. paradoxa subsp. nilotica. Thus, leaf explants from six distinct growth stages were cultured on Murashige and Skoog (MS) media supplemented with various concentrations of 2,4-D, TDZ, NAA, and BAP. Callogenesis was significantly influenced by explant age, media strength, and specific PGR combinations. Results revealed that explants from Stage III (11–15 days) and Stage IV (16–20 days) exhibited the highest callus induction rates (up to 100%), particularly on half-strength MS media containing 2.0 mg/L 2,4-D and 0.5–1.0 mg/L TDZ. Histological analysis suggests that varying responses at the different stages relate to chloroplast distribution, trichome density/orientation, and vascular tissue maturity. Pro-embryogenic structures were successfully induced, representing a developmental milestone with strong prospects for advanced stages of differentiation. The findings also emphasize the importance of explant physiology and media formulation in developing regeneration protocols for V. paradoxa from leaf explants.