Sexual and asexual propagation of Syzygium maire, a critically endangered Myrtaceae species of New Zealand

ABSTRACT

Syzygium maire (swamp maire) is an endemic New Zealand Myrtaceae tree species. Current threats to this species include habitat destruction, myrtle rust, declining remnant populations and low capacity for natural regeneration. Large-scale replanting for conservation/restoration initiatives would mitigate against these threats. However, there is limited information available on propagation of this species. In this study, we looked at sexual propagation using seed germination and asexual propagation using softwood cuttings. For seed germination, we examined the effect of seed pretreatments (intact fruit or de-pulped seed) and temperature settings (15/25°C or 20/30°C) to optimise germination. For softwood cutting propagation, we investigated the diameter of the cuttings (1–2 mm or 3–5 mm) and application of exogenous indole-3-butyric acid (IBA) (0, 1.5, 3.0, or 4.5 g L⁻¹) on their efficacy of producing adventitious rooting. The most critical factor for seed germination was the removal of seed pulp. De-pulping the seeds shortened the mean time to germination and positively affected the germination percentage, regardless of the incubation temperature. Germination percentage of ≥94.5% was achieved in seeds sown without pulp. Propagation by softwood cutting of 1–2 mm in diameter was possible without IBA treatment (63.3% of cuttings rooted), but the application of 1.5 g L⁻¹ IBA increased the rooting percentage (to 75%), thereby inducing the production of a higher number of roots. Seed germination and softwood cutting were effective strategies to propagate S. maire. The findings of this research contribute to the knowledge of propagation and restoration of S. maire populations.

Te whakawhänui me te whakawhanaungātanga o te Syzygium maire, he momo Myrtaceae kua tata te mate o Aotearoa

Ko te Syzygium maire (maire tawake) he momo rākau Myrtaceae o Aotearoa. Ko nga whakatumatuma o tēnei momo ko te whakangaro kainga, te waikura ramarama, te heke haere o ngā toenga taupori, me te iti te kaha ki te whakahounga maori. Ko te whakatō tauine nui mo nga kaupapa tiaki/whakaora ka whakaiti i ēnei whakatuma. Hēoi, he iti noa ngā kōrero mo te whakatipuranga o tēnei momo. I roto i tēnei rangahau, i tiro mātou ki te whakawhanaungatanga mā te whakamahi i te whakatipu kākano me te whakawhanaungatanga mā te tapahi rakau ngawari. Mo te whakatipu kakano, i tirohia e mātou te pānga o nga maimoatanga o mua o te kākano (te hua tōtika, te kākano kua whakakorehia rānei) me nga tautuhinga pāmahana (15/25°C, 20/30°C) kia pai ake te whakatipu. Mo te whakatipu rākau ngāwari, i tirohia mātou ki te whitianga o ngā haea (1–2 mm, 3–5 mm ranei) me te tono o te waikawa indole-3-butyric (IBA) (0, 1.5, 3.0, 4.5 g L⁻¹) rānei. i runga i to rātou kaha ki te whakaputa i nga huanga pūtake. Ko te take tino nui mo te whakatipu kākano ko te tango i te penupenu purapura. Ko te whakakore i nga kākano ka whakapotohia te wā ki te whakatipu, ka pā te pai ki te pāheketanga o te whakatipu, ahakoa te pāmahana hēki. Ko te ōrau germination o ≥94.5% i tutuki i roto i nga kākano i ruia me te kore penupenu. Ka taea te whakatipu ma te tapahi rākau ngāwari o te 1–2 mm te whānui me te kore he maimoatanga IBA (63.3% o nga haea i pakiaka), engari ko te tono 1.5 g L⁻¹ IBA ka nui ake te pāheketanga o te huaranga (ki te 75%), nā reira ka whakangao hanga kia whakawhānui ake te nama o nga pakiaka. He rautaki whai hua te whakatipu kākano me te tapahi rākau ngāwari ki te whakatipu Maire tawake. Ko ngā kitenga o tēnei rangahau ka whai wāhi ki te mōhio ki te whakatipu me te whakahoki mai i ngā taupori maire tawake.

KEYWORDS:

• Austropuccinia psidii
• auxins
• cuttings
• germination
• seeds
• swamp maire
• threatened
• endemic species

Acknowledgements

We thank the New Zealand Department of Conservation (DOC) for granting permission to collect fruit from the Taranaki region under DOC Permit number 69441-FLO. The authors wish to thank Cliff John for supplying seeds, Julie Ryan and Ian King for technical assistance in the greenhouse, and Alby Marsh for editing the abstract in Te Reo Māori. Special thanks to the Te Rūnanga o Ngāti Ruanui, Te Kotahitanga o Te Atiawa and Te Korowai o Ngā Ruahine Iwi Authorities. The work was undertaken at the Palmerston North location of Plant & Food Research and Ōtari Native Botanic Garden (Wellington City Council) with the findings of this work being communicated with representatives of Rangitāne o Manawatu and Port Nicholson Trust of Wellington.

Author contribution

Conceptualisation: J.C.B, K.v.d.W., J.N.; methodology: J.C.B., K.v.d.W.; investigation, data collection: J.C.B., K.v.d.W., J.A.S.; supervision: J.C.B., K.v.d.W.; formal analysis: A.M.; funding acquisition J.N.; preparation of tables and figures: J.C.B., A.M.; manuscript writing and revisions: J.C.B.; manuscript editing: J.C.B., K.v.d.W., J.A.S., A.M., J.N. All authors have read and agreed to the published version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data presented in this study are included in the paper; further inquiries can be directed to the corresponding author.

Additional information

Funding

This research received funding from New Zealand’s Biological Heritage (“NZBH”) National Science Challenge Ngā Rākau Taketake (“Challenge”), authorised work under Manaaki Whenua Landcare Research Concession Number CA-31615-OTH.