Micropropagation of marula, Sclerocarya birrea subsp. caffra (Anarcadiaceae) by axillary bud proliferation and random amplified polymorphic DNA (RAPD) analysis of plantlets

Abstract

The availability of a rapid vegetative amplification procedure of mass-selected superior trees greatly accelerates the development of a new tree species as a crop. This study outlined the protocol for in vitro propagation of marula nodal explants from marula seedlings. Surface sterilized explants were cultured on Murashige and Skoog media (MS) supplemented with 26 combinations of N⁶-benzyladenine (BA) and kinetin (KN). Shoots were elongated on MS media supplemented with low BA and KN or BA and Gibberellin A3 (GA₃) concentrations. Elongated shoots were rooted on half strength MS media supplemented with indolebutyric acid (IBA) at differing concentrations. MS media supplemented with 4.8 µM BA and 2.4 ìM KN resulted in average 2.5 shoots per responding explant. Moderate shoot elongation was achieved on MS media supplemented with 1.2 µM BA plus 1.0 µM KN. Maximum rooting was observed on half- strength MS media supplemented with 10 µM IBA. Marula plants were acclimatized and established in soil in the growth room at an average micropropagation rate of 0.56 per responding nodal explant. The developed protocol has potential for routine micropropagation of elite Sclerocarya birrea subsp. caffra. Randomly amplified polymorphic DNA (RAPD) analysis scoring 1845 markers showed intraclonal genetic stability between explant parent and micropropagated plants.

Key words: Anacardiaceae, axillary bud proliferation, marula, randomly amplified polymorphic DNA (RAPD), somaclonal variation.