Micropropagation of the therapeutic-honey plants Leptospermum polygalifolium and L. scoparium (Myrtaceae)

Abstract

Demand for therapeutic honey is driving establishment of Leptospermum plantations. This study developed micropropagation methods for two species – Leptospermum polygalifolium Salisb. and L. scoparium J.R.Forst. & G.Forst. The study determined how shoot proliferation and adventitious rooting were influenced by the original explant position on the seedling and the concentration of benzyladenine (BA) in the proliferation medium. Hormone-free node culture was highly effective for both species. Nodal explants often formed roots in the absence of BA and developed elongated axillary shoots. Median shoot numbers of 584 and 659 were formed in 31–32 weeks from a single L. polygalifolium or L. scoparium seed, respectively. A low BA dose was effective for callogenesis and shoot proliferation of L. polygalifolium, but not L. scoparium. The median number of shoots produced from a single L. polygalifolium seed was 630 using 2.22-μM BA. This dose induced extremely high shoot numbers in some clones because explants often produced extensive callus and multiple short shoots. Shoots formed adventitious roots without indole-3-butyric acid and plantlets were acclimatised to nursery conditions. The original explant position did not influence shoot proliferation or adventitious rooting. Leptospermum polygalifolium and L. scoparium proved amenable to micropropagation, facilitating rapid establishment of nectar plantations.