In vitro regeneration of recalcitrant embryonic axes: Effects on the biomass characteristics of resulting plants

Abstract

In vitro regeneration of the embryonic axes of recalcitrant seeds is a necessary step in practices such as cryopreservation of zygotic germplasm, micropropagation, and the production of disease-free plants. As recalcitrant seeds usually harbour surface and tissue-borne microflora, axes used for in vitro culture are invariably subjected to decontamination treatments such as surface-sterilisation with antiseptic substances, treatment with surface- and systemic fungicides and antibiotics, and culturing on variously-modified media formulations. The effects of these treatments are usually evaluated only on the basis of the level of decontamination achieved, with little information available on how these decontamination treatments affect the establishment and/or biomass characteristics of the plants subsequently produced. This study investigated the effects of different in vitro culture media, surface-steriliants, phenolic-controlling compounds, systemic fungicides and antibiotics on biomass accumulation and partitioning of seedlings obtained from embryonic axes of Syzygium cordatum, a recalcitrant-seeded multipurpose tree species indigenous to eastern and southern Africa. Embryonic axes were found to be infected with tissue-borne fungi at harvest, and any development after in vitro culture depended on decontamination.