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Rural Industries Research & Development Corporation
By J.C. Doran, G.R. Baker, E.R. Williams and I.A. Southwell March 2002
RIRDC Publication No. 02/017 RIRDC Project DAN 151A
There are some 300 producers in the industry currently with a total plantation estate of some 6000 ha.
Average plantation production of 148 kg/ha has long been recognised as below potential. This average yield was viable while prices remained high in the industry, but economic analyses showed that it would not be sustainable should the prices fall, as happened in 1999/2000. RIRDC and ATTIA recognised this and the potential of breeding to provide progressive, economically significant gains in oil yield and quality of Melaleuca alternifolia when they supported the first phase of breeding in May 1993 (three year project). They renewed their funding support for a second phase of breeding (five year project) commencing in July 1996, following the successful review of the first phase.
This is a report of the second phase of breeding (1996 to 2001) to improve M. alternifolia for oil production. The second project had as its major objectives — 1. The realisation of gains from the breeding strategy instigated during the first project. These were to come from continued management and improvement of the Coombell Seed Stand (SS) as an interim step and, concurrently, the 1994 first generation seedling seed orchard (SSO1) which was to be the principal source of seed by 1999. Time lines were defined thus– Production of improved seed lines with yields up to 17% higher than industry selections by 1997, 30% higher by 1999, and 60% higher by 2003; 2. Continued measurement and analysis of provenance/progeny trials from the first project for use in attaining Objective 1; 3. Establishment of new selection trials including a second generation seedling seed orchard (SSO2) and associated progeny trials; 4. Examination of the relative yields from improved trees and existing commercial seed lines (yield trials); 5. Production of clonal explants from the best trees in the ANU progeny trial and comparison of the relative production of clonal and seedling trees under commercial conditions; 6. Establishment of a flowering trial to compare hormone treatment and girdling as methods for inducing flowering.
The successful protocol for the first breeding project has been retained for this the second breeding project. The project involves collaboration between NSW Agriculture, the manager of the project and the major research provider, CSIRO Forestry and Forest Products, the provider of tree breeding advice and practical expertise, and several plantation owners in northern NSW who provided trial sites.
Funding support was from industry revenue through ATTIA matched by funds provided by RIRDC.
These totalled nearly $400,000 during the five years of the project and were complemented by substantial in-kind contributions from the research providers and individual growers.
The main aims of the experiments in this and the earlier tea tree breeding projects were to assess the patterns and extent of variation in commercial oil traits in M. alternifolia and estimate genetic parameters for these traits. These results have influenced decisions on selection of an appropriate breeding strategy to provide high rates of gain per generation, while remaining compatible with the limited resources available to the project. They have also determined the interim measures taken to make available to growers seed of slightly improved genetic quality while the project seed orchard matured. Other project trials have determined the realised genetic gains from use of project seed, developed techniques for controlled pollination and produced a series of full-sib crosses including hybrids with M. linariifolia, and studied the potential of cloning to boost plantation yields. In separate but closely linked projects, DNA markers have been developed for use in breeding tea tree. Major research findings that apply to M. alternifolia unless otherwise specified were – ! Very substantial variation is present at the provenance, family and individual tree levels in all of the key commercial traits assessed (i.e. survival, height growth, number of primary stems and leafiness score after up to four successive annual harvests, and oil concentration and composition).
! Certain populations in Devils Pulpit and Candole State Forests produce progeny that, on average, are superior to all other provenances in oil traits, in combination with good growth performance.
Coombell provenance which is the site of the project seed stand is amongst the poorest performing of all the provenances in project trials. M. linariifolia appears to be on a par with M. alternifolia in relation to growth and oil concentration measures but tends to err on the high side for 1,8- cineole% (i.e. >4%) and on the low side for terpinen-4-ol (i.e. <36%).
! Heritabilities (narrow sense) for oil traits were moderate to high and for growth traits low to moderate. For example, the heritabilities for oil concentration, 1,8-cineole% and terpinen-4-ol% in the Wyrallah SSO1 were 0.93, 0.43 and 0.81 respectively, while in the same trial at the same age the heritability for height growth was 0.11.
! Lack of significant genetic correlation between growth and oil traits suggests that they are independent of one another and might be improved concurrently in the one breeding population.
! Family × site interaction appears modest for growth traits and very limited for oil characteristics.
This finding lends support to the strategy adopted for this project of one centre for tree improvement (i.e. northern NSW) serving all tea tree growing regions.
! Selection based on rankings one year after first harvest (c. 2 years-of-age) should prove reliable and allow rapid progress in the breeding program.
! Controlled pollination (without emasculation) was applied successfully to produce a small elite ‘nucleus’ population. The degree of selfing in one female that received four separate pollens was higher than anticipated (6% to 28%) and this aspect is receiving further study.
! Clonal plantations were demonstrated to be a viable option economically in a desk study but two attempts to establish a practical demonstration of the benefits of clones failed due to site factors.
! Microsatellite and primer sequences for DNA fingerprinting project breeding lines and quality control were developed in a separate but linked project.
Two interim measures were instigated to provide growers with seed capable of producing some slight improvement in oil characteristics, while the first generation seedling seed orchard matured and produced the first highly improved seed. The first of the interim measures, involving the development of a seed stand (SS) in a patch of native forest at Coombell, produced seed from selected trees but this seed was unable to be released due the the poor general performance of this provenance in project trials. The second interim measure, release of seed from the best natural provenances identified in project progeny trials (i.e. selected populations in Devils Pulpit and Candole State Forests), has been the major output from the project so far and an outstanding success. The project yield trial has demonstrated that this seed gives 21% greater yield than industry standards acquired in 1994 at the start of breeding and 9% greater yield than contemporary (1998) industry standards. Seed totalling 6.5 kg was released to growers from these sources during 1997 to 1999. A further 55 g was released to industry in 2000-01, from SSO1 and a clonal breeding arboretum. Seed quantities were sufficient for establishment of 1000 ha of plantation. Sales of project seed have generated $229,700 for tea tree research.
The first generation seedling seed orchard (SSO1) at Wyrallah, now over seven years old (est. 1994), has been developed to a stage where, potentially, progeny from a good overall flowering will give 60% more yield than the industry standards at the commencement of breeding. If 2001 proves a good flowering year, this seed will become available in 2003. Seed (c. 1 kg) from the partial flowering of orchard trees in 1997 and 1998 (45% flowering and 35% respectively) of 30% gain potential was released to growers in 2000-01 but little interest has been shown in it to date due to the industry slowdown.
A second generation seedling seed orchard was planted at Wollongbar Agricultural Institute in April 2001. This orchard contains the best ranked trees from SSO1 that have seeded, the elite ‘nucleus’ families from controlled pollination, the best ranked trees from the clonal arboretum of ANU progeny trial selections, a few of the best seed stand trees and infusions from best natural provenances. Tea tree is known to flower early and well in most years on this site and should remain relatively free of substantial pyrgo attack, as it is isolated from commercial plantations of the species. In addition, a smaller, partial SSO2 is to be established in spring of 2001 at West Wyalong, again where early and heavy flowering has been noted on tea tree. These orchards will be thinned to give a potential gain of 90% in yield in the first instance with the prospect that this seed could be available as early as 2004.
A very high level of adherence to the project objectives, set at the start of the project in July 1996, has been achieved by the project. The experimental results from trials and experience in managing SSO1 have led to only minor changes to the breeding strategy laid down at the start of breeding activities in 1993.
Economic indicators estimated in 1998 and expressed in 1998 $ terms for this project, including the costs of the preceeding tea tree breeding projects, were highly favourable. The NPV of the R&D investment given specified assumptions was $19 million. The Benefit-Cost ratio was 14:1 and the Internal Rate of Return was 23%. A second economic analysis was undertaken in 2001, after the economic slowdown in the industry following oversupply of oil.
The conclusions of the 2001 economic analysis which focussed on evaluating the ecomonics of continuing to a third phase of breeding (2001 to 2006) were – a third phase of breeding is likely to yield significant benefits, uptake of new material that will become available in the third phase is still likely to occur at oil prices ranging from $22/kg to $16/kg, compared with the uptake of current material requiring a price of $27/kg; higher yielding material (i.e. 60% or >) will be required to keep producers in business, or attract new investors, if the price is below $27/kg and; the higher yields from cloning more than offsets the additional costs.
A proposal for a third phase of breeding has been submitted to the funding bodies for consideration. It builds on the success of earlier projects and concentrates on work needed in developing orchards and exploring cloning to deliver the highly improved germplasm that may be essential to the future economic viability of the industry in Australia.
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