Development of an in vitro propagation protocol for ex situ conservation of two critically endangered species of Commersonia (Malvaceae) from Western Australia
Protocols for in vitro propagation of two critically endangered species, Commersonia adenothalia C.F.Wilkins ms and Commersonia sp. Mt Groper (R. Cranfield & D. Kabay 9157), from south-western Western Australia were established utilising both shoot and in vitro leaf explants. Regeneration from leaf explants was highest, with an average of four shoots per leaf explant per a 4-week incubation period on ½-strength Murashige and Skoog (MS) medium with 2.5 µM thidiazuron (TDZ) + 2.5 µM 3-indoleacetic acid (IAA) for C. adenothalia and 13 shoots per leaf explant on ½-strength MS medium + 4.5 µM 6-benzylaminopurine (BAP) and 2.5 µM 1-naphthaleneacetic acid (NAA) for C. sp. Mt Groper. Shoot proliferation using single shoot explants of C. adenothalia resulted in a maximum average of 3.5 shoots per shoot explant per a 5-week incubation period on ½-strength MS medium + 5 µM kinetin and 0.5 µM BAP, whereas maximum mean shoot multiplication with C. sp. Mt Groper (×30 shoots per shoot explant per a 5-week incubation period) was recorded with ½-strength MS medium + 2.5 µM kinetin and 1 µM BAP. In general, C. sp. Mt Groper was much more reactive to cytokinins than was C. adenothalia, with prolific regeneration of shoots from leaf explants or shoot explants. Both species produced roots readily on ½-strength MS medium without added hormones or with 5 µM indole-3-butyric acid (IBA) (100% rooting in 3–4 weeks) and rooted plantlets survived the transition to soil (~70% survival).