New Zealand is known for radiata pine (Pinus radiata) plantations, a pale coloured and non-durable timber. It is used in many agricultural and industrial sector products such as posts and poles. Wood preservatives are used to protect the non-durable timber against decay. One of the most widely used wood preservatives is the inorganic water-based preservative copper chrome arsenate (CCA). Wood preservatives give rise to environmental problems. CCA has been largely banned for most uses in the USA, Europe and Australia. There is a large demand for natural durable timbers in both the domestic market and international market. Naturally durable timbers often come from tropical forests and are frequently supplied from illegal/unsustainable sources. Such timber also has colour and is often used in the furniture industry. According to the NZ Ministry of Primary Industries’ annual forestry imports statistics (https://catalogue.data.govt.nz/dataset/annual-forestry-import-statistics), over $50 million of sawn hardwood timber and $36 million of wooden furniture were imported by New Zealand in 2017 as a result of a lacking suitable domestic resource.

Some eucalyptus species have high natural durability and colour. The natural durability makes them ideal for wide-ranging agricultural and industrial use, particularly for posts and poles. Eucalyptus bosistoana has class 1 natural durability and a fast growth rate in New Zealand’s climate. E. bosistoana can grow up to 30-40 m in height and usually has wood of excellent stiffness, high density and hardness.

The New Zealand Dryland Forests Initiative (NZDFI) was established in 2008 and aims to establish a sustainable naturally durable timber industry in New Zealand. It choose E. bosistoana as the main durable species for genetic improvement. NZDFI’s durable eucalypts will produce high value naturally durable timber to meet the future demand of durable timber and replace CCA and illegal tropical hardwood.

A successful plantation industry needs to ensure quality (i.e. natural durability of the wood). Due to differences in genetics, environment and tree age, heartwood quantity and natural durability vary significantly within a specie and tree. Breeding can be an efficient way to reduce variability.

The primary objectives of this research were:

1. Develop a method to quickly assess heartwood traits for inclusion in a large scale breeding programme.
2. Assess genetic control over heartwood traits in E. bosistoana. To achieve these objectives, this thesis also investigated: a) The distribution of extractives within a tree. b) Optimisation of the sampling technique. c) The possibility to apply the technique to other durable eucalypts species in the breeding programme.