In vitro morphogenesis of somatic embryo-like structures derived from Sclerocarya birrea subsp. caffra leaf explants

Abstract

Sclerocarya birrea is an indigenous tree that is highly valued for its medicinal and nutritional properties by local communities. Marula products are also in high demand in the pharmaceutical, cosmetic and food industries. With the increasing demand of marula products, micropropagation can become a viable option in the conservation, propagation and breeding of this plant. Themost commonly used micropropagation techniques include direct and indirect shoot organogenesis, and somatic embryogenesis. Recently, several reports described shoot organogenesis through somatic embryo-like structures from different explants, mainly leaves and hypocotyls. The induction of embryo-like structures from leaf explants of Sclerocarya birrea subsp. caffra was compared on Murashige and Skoog (MS) and woody plant medium (WPM) with different concentrations of benzylaminopurine (BA) in combination with naphthalenacetic acid (NAA), indole-3-butryric acid (IBA) and indole-3-acetic acid (IAA). Induction of embryo-like structures from88.8%of the leaf explant cultures was achieved on MS medium with a concentration of 4.0 μM BA and 1.0 μMNAA. Similar high levels (78 100%) of regeneration were achieved on WPM with different concentrations in the range of 1.0 4.0 μM BA and 1.0 4.0 μM IBA. However, induction of embryo-like structures was lower on MS medium with similar concentrations of BA and IBA. For all the culture conditions the rate of conversion of embryo-like structures into fully differentiated shoots was low. The highest conversion of embryo-like structures into shoots was 22% for 4.0 μM BA and 1.0 μM NAA on MS medium. Histological studies revealed that the globular stage embryo-like structures consist of vacuolized parenchymatous cells. This protocol has potential for application in micropropagation and plant breeding research.