ABSTRACT

Santalum yasi is a high-value hemiparasitic tree endemic to Fiji, Niue and Tonga. It has been overexploited for its oil-yielding heartwood and is now threatened. Remaining stands lack genetic diversity and are likely to be suffering from inbreeding depression, although the species still has significant genetic diversity overall. We argue that the best way to conserve this species is through an active domestication program that will adequately sample and conserve the genetic base in ex situ and circa situm plantings. The approach to S. yasi tree-breeding can be characterised as a low-input strategy involving the early use of molecular markers for population parameter determination. Long-term success will have strong interdependent links with the conservation of the remaining genetic resources. A strategy based on recurrent selection and breeding for key traits—including heartwood volume and oil yield per year, oil quality and environmental adaptability related to cyclone resistance and the tolerance of pests and diseases—is recommended. The establishment of genetic conservation stands based on collections of the species throughout its natural range in Fiji and Tonga has commenced. Challenges associated with the conservation and domestication of S. yasi are discussed. These include the advanced age required before oil characterisation can be undertaken; the need to assess genotype–host-plant interactions; and the need for comparatively sophisticated equipment and destructive harvesting to carry out oil assessments. Capacity development of professional staff in the Pacific Islands is an additional prerequisite for implementing an effective strategy. Research into the variation and heritability of heartwood formation and oil characteristics, and a better understanding of the breeding biology of S. yasi and geneflow between it and exotic Indian sandalwood (S. album), are high priorities. It will be more than a decade—probably around 20 years—before S. yasi individuals in planned, well-designed trial plantings have sufficient heartwood development to enable oil-trait assessment. Establishment of such trials is an immediate priority. In addition to this long-term activity, we recommend a simple interim strategy that promotes high genetic diversity of seedling-based planting stock. This can be implemented using a combination of gene conservation stands, progeny trials that can be culled to seedling seed orchards, and genetically diverse community-based seed stands. The strategy will both provide a safeguard against the further loss of diversity and promote wide outcrossing. Releasing fragmented populations from inbreeding depression is expected to increase general vigour.

摘要

Santalum yasi是斐济，纽埃和汤加特有的高价值半寄生树。它的采油心材已经被过度开采，现在正受到威胁。剩下的林分缺乏遗传多样性，并且可能遭受近交衰退的困扰，尽管该物种总体上仍具有显着的遗传多样性。我们认为，保护该物种的最佳方法是通过积极的驯化计划，该计划将适当地采样和保护异地和大约种植地的遗传基础。雅氏葡萄球菌的方法树木育种可以被描述为一种低投入的策略，涉及早期使用分子标记来确定种群参数。长期的成功将与其余遗传资源的保存有着紧密的相互依存的联系。建议采取一项基于轮回选择和育种的关键性状的策略，这些关键性状包括每年的心材量和产油量，与旋风抗性有关的油质和环境适应性以及对病虫害的耐受性。已经开始根据斐济和汤加整个自然范围内物种的采集建立遗传保护林。与亚述链球菌的保护和驯化有关的挑战讨论。其中包括在进行油特性分析之前所需的高龄；需要评估基因型与寄主植物的相互作用；以及需要相对先进的设备和破坏性收割来进行石油评估。太平洋岛屿专业人员的能力建设是实施有效战略的另一个先决条件。研究心材形成和油性的变异性和遗传性，以及更好地了解柳树的育种生物学及其与外来印度檀香（S. album）之间的基因流，是当务之急。在亚述葡萄球菌之前将有十多年的时间，大概是20年左右。经过精心计划和精心设计的试验性种植的个人，有足够的心材发育能力，可以进行油性状评估。建立这样的审判是当务之急。除了这项长期活动外，我们还建议采用一种简单的临时策略，以促进基于苗种的种植种群的高度遗传多样性。可以结合使用基因保护林，可以选育到种子园的后代试验以及遗传多样性的社区种子林来实施。该战略将为防止多样性进一步丧失提供保障，并促进广泛的跨界交流。从近亲衰退中释放零散的人口，有望增强人们的活力。