ABSTRACT

The current threat of myrtle rust (Austropuccinia psidii) to New Zealand Myrtaceae, including a number of indigenous and socio-economically important species, requires that ex situ conservation is used to complement in situ populations. New Zealand’s Myrtaceae have received little attention in terms of ex situ conservation. In this study, we assessed the integrated ex situ conservation strategies for selected New Zealand Myrtaceae. We particularly investigated seed banking options by assessing seed desiccation tolerance, in vitro culture, pollen cryopreservation and zygotic embryo cryopreservation of the recalcitrant Syzygium maire. A desiccation trial was conducted on six Myrtaceae species: Lophomyrtus bullata, L. obcordata, Metrosideros diffusa, M. umbellata, M. bartlettii and Syzygium maire. S. maire seeds and embryos showed extreme sensitivity to desiccation confirming its recalcitrant behaviour. The seeds of the other species were desiccation tolerant i.e. orthodox. Zygotic embryos of S. maire were successfully cryopreserved using an encapsulation-dehydration technique. Pollen cryopreservation was successful for M. excelsa following desiccation to about 5% moisture content, rapid freezing and rapid thawing. For M. bartlettii, one of the most endangered and a nationally critical Myrtaceae species in New Zealand, we tested the efficacy of hand pollination in producing viable seeds. Our assessment confirmed that one of the M. bartlettii trees at Otari is self-incompatible, and successful hand pollination using pollen obtained from different genotypes growing in the gardens at the University of Auckland resulted in seed production with c. 20% germination. Tissue culture protocols were successfully developed for selected Myrtaceae. In addition, photoautotrophic micropropagation techniques were developed for the first time for L. scoparium. This paper highlights the importance of holistic conservation strategies to ensure future access to New Zealand’s unique Myrtaceae germplasm as a key component of long-term management response to the threat posed by A. psidii.

摘要

桃金娘锈病（Austropuccinia psidii）目前对新西兰桃金娘科的威胁，包括许多土著和社会经济上重要的物种，要求利用非原生境保护来补充原生境种群。在异地保护方面，新西兰的桃金娘科很少受到关注。在这项研究中，我们评估了选定的新西兰桃金娘科的综合非原生境保护策略。我们通过评估顽固的S虫的种子脱水耐性，体外培养，花粉冷冻保存和合子胚胎冷冻保存，特别研究了种子库选择。对桃金娘科的六个物种进行了干燥试验：黑麦草（Lophomyrtus bullata），暗纹L. obcordata，白花大都市Metrosideros，伞形分枝杆菌（M. umbellata），巴尔特提分枝杆菌（M. bartlettii）和梅勒（Syzygium maire）。梅尔链霉菌的种子和胚胎对干燥表现出极大的敏感性，证实了其顽强的行为。其他物种的种子耐干燥，即是正统的。使用封装-脱水技术成功冷冻保存了沙门氏菌的合子胚。花粉冷冻保存成功为M.棕竹下干燥约5％的水分含量，快速冷冻和解冻迅速。对于M. bartlettii新西兰桃金娘科是新西兰最濒危且对国家至关重要的桃金娘科物种之一，我们测试了人工授粉在产生可行种子方面的功效。我们的评估证实，Otari的一棵M. bartlettii树是自交不亲和的，并且使用从奥克兰大学花园中生长的不同基因型获得的花粉成功进行的手授粉导致了c。的种子生产。发芽20％。针对所选桃金娘科成功开发了组织培养方案。此外，首次为光头乳酸杆菌开发了光合自养微繁殖技术。本文强调了整体保护策略的重要性，以确保将来获得新西兰独特的桃金娘科种质资源，作为长期管理应对psidii造成的威胁的关键组成部分。