Davidsonia Domestication in Far North Queensland by Tony Page and Anna Sosnin

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Davidsonia domestication in far north Queensland By Tony Page and Anna Sosnin

Davidsonia domestication in far north Queensland

By Tony Page and Anna Sosnin

May 2017

RIRDC Publication No 17/030 RIRDC Project No. PRJ-009026

ISBN 978-1-74254-953-8 ISSN 1440-6845

Davidsonia domestication in far north Queensland Publication No. 17/030 Project No. PRJ-009026

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Researcher Contact Details

Name: Tony Page Address: Verdien P/L, PO Box 1953 Innisfail, 4860 Email: [email protected]

In submitting this report, the researcher has agreed to RIRDC publishing this material in its edited form.

RIRDC Contact Details

Rural Industries Research and Development Corporation Building 007 Charles Sturt University Boorooma Street Wagga Wagga NSW 2650

C/- Charles Sturt University Locked Bag 588 Wagga Wagga NSW 2678

Phone: 02 6923 6900 Fax: 02 6923 6999 Email: [email protected]. Web: http://www.rirdc.gov.au

Electronically published by RIRDC in July 2017 Print-on-demand by Union Offset Printing, Canberra at www.rirdc.gov.au or phone 1300 634 313

Foreword

Australian native plant foods have potential for development as high value niche horticultural crops provided they can be produced competitively and meet consumer demands. Davidson plum is a unique tropical fruit with potential for development as a functional food, delivering health benefits in an intensely coloured and distinctly tart package. However, substantial variation in cultivation attributes such as fruit size and yield present challenges to viable production of Davidson plum.

This report represents an important advance in the development of Davidson plum as it provides information related to the biological features influencing its production and domestication.

The account provided of variation in fruit size and yield offers baseline information for those planning new plantings as well as assessing the performance of existing ones. The information provided in this report can help guide the next steps of the plant improvement process.

The report outlines the establishment of replicated genetic resources in partnership with Davidson plum growers, which will provide the basis of further development of the species. These resources, established with the view for production will also make a direct contribution to the production volumes of the industry. Such experimental design within commercial plantations can underpin quality of industry information. This principle is applicable across industries.

This report is an addition to RIRDC’s diverse range of over 2000 research publications and it forms part of our New and Emerging Industries R&D program, which aims to support the early stage establishment of high potential rural industries.

RIRDC’s publications are available for viewing, free downloading or purchasing online at www.rirdc.gov.au. Purchases can also be made by phoning 1300 634 313.

John Harvey Managing Director Rural Industries Research and Development Corporation

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About the Author

Tony Page and Anna Sosnin (Verdien P/L) operate a specialist nursery focusing on the improvement and silviculture of tropical tree crops. They conduct propagation and domestication work with previously wild trees as well as underutilised crop species and develop biological knowledge for their commercial production in horticultural and agroforestry systems. Tony is a Senior Researcher at the University of the Sunshine Coast and conducts research with a focus on improving the use of forest resources and developing innovative approaches to agroforestry. Acknowledgments

This research was supported by Davidsonia orchardists Margo Watkins and Peter Lawlor (Rainforest Heart / Frog Hollow), Geraldine McGuire (Rainforest Bounty) and Ken and Sue Pyke (Sunset Ridge). Initial trials on reproductive biology and propagation were conducted under Part 1 of the project, which was administered by James Cook University. John Doran provided constructive input into the experimental design and layout of the progeny trials. Additional inputs and feedback were provided by Stuart Warboys, Darren Crayn, Jonathan Cornelius, Volker Stanger, Kim Kido, Adam Wellington, Damien Settle, Daniel Keane, Kris Kupsch, Steve Stanley, Kylie Freebody, Bob Jago, Garry Sankowsky, Andrew Lilley, Helen McConnell. Definitions & Abbreviations

Etymology of Davidsonia

The type specimen for Davidsonia pruriens was registered on 12th August 1866 from a collection made from coastal lowland rainforest in Rockingham Bay (Bailey 1900), between current day Tully and Cardwell. This first scientific specimen of D. pruriens was collected by John Dallachy, who was an exceptional botanical collector from the Royal Botanic Gardens in Melbourne (Maiden 1908). As a botanist Dallachy accompanied the 1864 expedition led by George Dalrymple to establish the township of Cardwell as a port to service the rapidly developing pastoral lands further inland (Collinson 1949). The tropical rainforest so interested Dallachy that he decided to settle in Rockingham Bay until his death in 1871 (Gross 1972). The genus Davidsonia is named after John Ewen Davidson (1841-1923) (Wood 1965) who arrived in Cardwell with his business partner E.D Thomas in December 1865 with the view of establishing a sugar cane planation in Rockingham Bay. Dallachy assisted Davidson and Thomas in March 1866 to survey the Murray and Tully river areas for a suitable site to develop the plantation. Between April and June 1866 Davidson had built huts and begun cultivating and planting the first sugar cane in the area. Due to a series of events, including the departure of Davidson’s business partner (Aug 1866) due to the perceived hostility of local Aboriginal tribes, a significant flood (Dec 1866) and a cyclone (Jan 1867), Davidson abandoned the expedition, (Wood 1965). After this short venture, Davidson headed to Mackay where he formed partnership with Thomas Henry Fitzgerald (Feb 1867)(Moore 1981), which would grow to become a very significant sugar production and processing enterprise (Fox 1923).

The edible fruit from Davidsonia species are known collectively as Davidson Plum (Harden and Williams 2000). Despite assertions to Davidson’s interest in botany (Wood 1965; Mills 1981), the naming of Davidsonia probably arose from the chance meeting between Dallachy and Davidson at Rockingham Bay, during the time when Dallachy made the first herbarium collection of D. pruriens. It was more likely that this meeting, rather than any botanical, culinary or horticultural interest in the species by Davidson, resulted in it being named Davidsonia. The species name pruriens is based on the latin word prurio meaning ‘to itch’ (Lewis and Short 1879), referring to the fine hairs on the leaves and fruit, which can cause itchiness. Bailey (1900) recorded that D. pruriens was known as Ooray by Aboriginal people around the Tully River area. These people were probably those that Dallachy and Davidson first encountered during their initial activities of the Rockingham Bay Area. D. pruriens has been known as Davidson plum, Davidson’s Plum, Davidsonia Plum, Davidsonian Plum, Queensland Davidson plum (Bailey 1898; Harden and Williams 2000; Lim 2013; Hess-Buschmann 2017). In this study we use the common name Davidson plum to refer to the species D. pruriens (unless otherwise stated).

Nomenclature of variation in D. pruriens.

In this report we refer to two distinct types of D. pruriens based on their morphology (i) ‘hairy’ and (ii) ‘smooth’. The ‘hairy’ is defined by a greater abundance of hairs on the leaves and fruit compared with the ‘smooth’. Here we define them as being forms, because it is yet to be clear as whether they have formal sub-specific botanical taxonomic ranking (i.e. variety or form). It is possible that the smooth form has been generated through apomictic seed production of a single genotype and therefore probably more akin to a cultivar rather than a form or variety. Over time as more is known about the origins, diversity and stability of the smooth form then some genotypes may be classified under conventions for botanical taxonomy (McNeill et al. 2011) or cultivated plant nomenclature (Brickell et al. 2004). The two forms of D. pruriens have been referred to with several different names, so to avoid confusion they are summarized in Table 1.

Table 1: Various names used to describe the two D. pruriens forms.

Form with hairy leaves, Form with minimal hairs on Source flowers and fruits leaves, flowers and fruits

Highland Lowland (Sultanbawa et al. 2015)

Upland Coastal Anecdotal

Typical Smooth (Page and Watkins 2016)

Hairy Smooth This report

Collection and progeny trial sites

The fruit collections for the study were made from two sites known as Sunset Ridge (SR) and Rainforest Heart (FH) on the Atherton Tablelands in north Queensland. The progeny trials were established at three sites Sunset Ridge (SR), Rainforest Heart (FH) and Rainforest Bounty (RB). The Rainforest Heart site is managed by Margo Watkins and Peter Lawlor and was formerly known as Frog Hollow. The coding of the mother plants was originally denoted as Frog Hollow (FH). While the name Rainforest Heart is used throughout the report it is abbreviated as FH so that correspondence with all associated data files is maintained.

Contents

Foreword ...... iii

About the Author ...... iv

Acknowledgments ...... iv

Definitions & Abbreviations ...... iv

Etymology of Davidsonia ...... iv Nomenclature of variation in D. pruriens...... v Collection and progeny trial sites ...... v

Executive Summary...... x

Introduction ...... 1

Objectives ...... 3

Methodology ...... 4

1. Establish standardised management and yield monitoring protocols...... 4 2. Progeny trial replicated across 3 sites on the Atherton Tablelands...... 4 Plant Material ...... 4 Trial Configuration and Design ...... 5 3. Strategy to broaden genetic base of the planted population ...... 6

Results ...... 7

1. Establish standardised management and yield monitoring protocols...... 7 Reproductive phenology ...... 7 Fruit and yield variation ...... 8 Orchard Yields ...... 8 Fruit Size ...... 9 Tree Yields ...... 10 Horticultural Management...... 13 Seed Propagation ...... 13 Vegetative propagation ...... 14 Agronomy ...... 15 2. Progeny trial replicated across 3 sites on the Atherton Tablelands...... 16 Plant material ...... 16 Planting sites ...... 18 3. Source materials for the D. pruriens planted population ...... 20 Pollinators and other flower visitors ...... 20 Determination of Mating system ...... 21 Germplasm collection strategy ...... 21

Implications ...... 23

Development of D. pruriens for cultivation ...... 23 Wild variation and collection ...... 23 Breeding System ...... 23 Multispecies ...... 25 Traits of interest ...... 26 Fruit size and Yield ...... 26 Fruit Sweetness/Flavour ...... 27 Fruit nutritional Factors ...... 27 Pest Resistance ...... 28 Management of the progeny trials ...... 30

Recommendations...... 31

References ...... 31

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Tables

Table 1: Various names used to describe the two D. pruriens forms...... v

Table 2: Seed collection periods for the mother trees (genotypes) at Sunset Ridge (SR) and Rainforest Heart (FH) in 2014 and 2015...... 4

Table 3: Mean fruit yields (kg) for unselected D. pruriens for different orchard ages...... 8

Table 4: Summary of the families represented in each of the three sites. Seed were sourced from 42 mother trees from two sites (Sunset Ridge – SR and Rainforest Heart - FH) in far north Queensland. Reps represent the number of replicate 4-tree line plots. Numbers for buffers indicate the number of individuals represented within the outer buffer rows...... 17

Table 5: Sensory description of the fruit from two Davidsonia species. Extracted from (Smyth et al. 2012) and (Smyth and Sultanbawa 2016) ...... 27

Table 6: Phenolic compounds identified and levels in the fruit of D. pruriens (Dp) and D. jerseyana (Dj) across five studies...... 29

Figures

Figure 1: Seedlings of selected trees of D. pruriens that were ready for planting across three sites on the Atherton Tablelands in mid-2016 and early 2017. Seedlings were labeled with information about heritage and progeny number and planting schedule...... 5

Figure 2: Spacing and layout of the Davidsonia pruriens (red dots) genetic trials comprising an ‘offset tramline’ configuration with 2m wide tramlines, 4m between the tramlines (inter-row) and 1.5m between trees within a row...... 6

Figure 3: Monthly fruit production per tree for two D. pruriens orchards on the Atherton Tablelands in north Queensland Sunset Ridge (SR) and Rainforest Heart (FH). SR data represents four years (2008-2010 & 2016) and FH data represents two years (2015-2016)...... 9

Figure 4: Mean fruit size across 42 trees collected from two sites (FH: Rainforest Heart and SR: Sunset Ridge) during season of 2014/15. Fruit from two distinct varieties were collected ‘smooth’ FH 08 & 10 and SR14-25 and ‘hairy’ all remaining trees...... 10

Figure 5: Annual fruit yield across 42 trees collected from two sites during season of 2014/15. Fruit from two distinct varieties were collected ‘smooth’ FH 08 & 10 and SR14-25 and ‘hairy’ all remaining trees...... 11

Figure 6: Mean weekly fruit production at two orchards on the Atherton Tablelands in north Queensland Sunset Ridge (SR) and Rainforest Heart (FH). (a) 42 selected trees of two D. pruriens varieties (‘hairy’ and ‘smooth’) at SR & FH. (b) Five selected trees of the ‘smooth’ form at SR. (c) Five selected trees of the ‘hairy’ form at FH and (d) Four selected trees of the ‘hairy’ form at SR. *Note that yields of Sr24 and Sr25 in (b) are presented as 10% of actual yields to ensure the scale of the graph permits easy comparison of fruiting phenology among selections. 12

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Figure 7: Seed germination percentage 42 trees collected from two sites during season of 2014/15. Fruit from two distinct varieties were collected ‘smooth’ FH 08 & 10 and SR14-25 and ‘hairy’ all remaining trees. * Note seedlots from Sr16 to Sr25 were affected by rodent predation...... 14

Figure 8: Root development in Davidsonia pruriens marcot after 6 month (left) and stem cutting after 10 weeks (right)...... 15

Figure 9: Satellite aerial (left) and ground (right) view of the D. pruriens trial site at Rainforest Heart, Mungalli, north Queensland ...... 18

Figure 10: Satellite aerial (left) and ground (right) view of D. pruriens trial site at Rainforest Bounty, Malanda, north Queensland ...... 19

Figure 11: Satellite aerial (left) and ground (right) view of D. pruriens trial site at Sunset Ridge, Danbulla, north Queensland ...... 19

Figure 12: Areas of known D. pruriens natural populations and trees identified during reconnaissance as part of the projet ...... 22

Executive Summary

What the report is about This project developed information and resources to address the problem of variability in fruit production for Davidsonia pruriens. This was achieved through (i) evaluation of tree-to-tree and seasonal variation in fruit characters and yield, (ii) the establishment of a replicated clonal/progeny trial and (iii) development of a germplasm collection strategy to diversify the existing planted estate.

Who is the report targeted at? The audience for this research report is primary producers of Davidsonia in Australia, as well as applied researchers and technicians working in the field of horticulture and new crops.

Where are the relevant industries located in Australia? The industry has made a transition from one based largely on wild harvested fruits to a small number of modest commercial orchardist. These growers are centred around the wet tropical and subtropical areas of north Queensland and northern NSW.

Background Aims/objectives

1. To facilitate reliable commercial production by establishing standardised management and yield monitoring protocols. 2. To facilitate domestication by establishing a progeny trial comprising the most productive individuals in the planted population. 3. To facilitate domestication by broadening the genetic base of the planted population Research Beneficiaries

 Growers – The consolidation and publication of current state of knowledge in the production of Davidson plum represents a benefit for existing and future growers.  Growers, Processors & Consumers – The progeny trials were established to function as both a scientific and production resource. The 1682 selected progenies planted have an annual yield potential of around 8.9 tonnes, representing a 50% increase in industry volumes.  Researchers – the replicated progeny trial will be a highly valuable resource for future research into the genetics, heritability, breeding and agronomy of D. pruriens. Methods used

1. To facilitate reliable commercial production by establishing standardised management and yield monitoring protocols.  A grower survey, informal consultations and literature review formed the basis of publishing a book chapter on the current state of knowledge in Davidsonia production (Page and Watkins 2016).  Two growers established/reinstated yield plots on their orchards for efficient recording of yield and provided data for analysis.  The fruit size and yield in grower-selected trees was recorded from June 2014 to June 2015.

2. To facilitate domestication by establishing a progeny trial comprising the most productive individuals in the planted population.  Two D. pruriens orchardists identified candidate trees for selection based primarily on yield attributes Sunset Ridge (25 genotypes) and Rainforest Heart (17 genotypes).  Seed were collected from these selected mother trees over the 2014/15 fruiting season and grown family-identified potted seedlings.  Three replicate progeny trials were established using the seedlings of candidate mother trees in cooperation with three growers.

3. To facilitate domestication by broadening the genetic base of the planted population.  Observations of floral phenology and potential pollinators were undertaken in a D. pruriens orchard to understand the scale of potential gene transfer among planted trees.  Artificial pollinations of D. pruriens were made to ascertain the influence of pollen transfer on seed set and fruit production.  Growers and seed suppliers in north Queensland were consulted to determine the source materials used for the establishment of commercial D. pruriens orchards.  Survey of twelve natural populations was undertaken to understand the general abundance of trees located within its known distribution.

Results/key findings This project developed information of use for orchardists in understanding the scope of variation expected for fruit production in Davidson plum, and recommendations for improving productivity through domestication activities.

1. To facilitate reliable commercial production by establishing standardised management and yield monitoring protocols.  Relative fruit yield per tree increases with age with from 0.5-1.0 kg tree-1 in years 5 to 8 to 2-3kg tree-1 in years 12 to 16. These figures represent average yields and account for variation between trees within a year and between years within a tree.  Variation in fruit and yield characters were identified between the ‘hairy’ and ‘smooth’ forms with the smooth having smaller fruit, greater yield potential, earlier seasonal production, but more susceptible to fruit fly than the ‘hairy’.  Very high fruit size variation within a tree with 2- to 5- fold difference between smallest and largest fruits.  Genotype variation in yield for the grower-selected trees was significant with total fruit yield ranging from 0.55 to 32.8 kg tree-1.  Mean fruit yield for ‘hairy’ and ‘smooth’ forms was 4.7 and 5.9kg tree-1respectively. When compared with a mean fruit of 2-3kg tree-1 for unselected, the selected trees may represent a yield increase of between 50% and 300%.  The annual yield of 25 grower-selected trees had an annual fruit yield above the orchard average (3kg) including 17 ‘hairy’ and 8 ‘smooth’ forms. The mean annual yield of these 25 trees was 7.5kg.

2. To facilitate domestication by establishing a progeny trial comprising the most productive individuals in the planted population.  The progeny trials were composed of 41 D. pruriens families (26 in the replicated progeny trial and 15 as buffer trees) that were established across 3 sites (Rainforest Heart, Rainforest Bounty and Sunset Ridge) on the Atherton Tablelands.  The progeny trials were established between August 2016 and March 2017, with 93-100% survival after 3 months. All dead seedlings were replaced with seedlings from the same family.

 The study found significant scope for developing high yielding cultivars of D. pruriens, with a ‘yield potential’ of 5-15kg tree-1 season-1 for the ‘hairy’ and 20-30 kg tree-1 season-1 ‘smooth’ forms.

3. To facilitate domestication by broadening the genetic base of the planted population.  Natural insect pollinators are absent from the Davidson plum orchards in north Queensland.  Pollen grains of D. pruriens were observed to float on air currents, suggesting possible wind-mediated pollen transfer  Pollen transfer is not a limiting factor for fruit development in the Davidson plum orchards, which is probably due to the clonal (apomictic) and inbred nature of its seed as reported by Eliott et al. (2014)  The planted population of D. pruriens is most likely composed of original seed collections from Atherton Tablelands, with possibly limited representation from collections made from Kuranda, Innsifail and Tully areas. Implications for relevant stakeholders The research generated both short-term (life of project) results and long-term impacts that provide the basis for ongoing research that will permit further progress in domestication.

 The clonal and self-pollinating breeding system of Davidsonia is unusual when compared to many other tropical tree species (Ward et al. 2005). On one hand this type of breeding system permits the cost-effective proliferation of desirable genotypes without the need for specialised propagation systems for cloning. On the other hand the very limited propensity for outcrossing limits the potential for generating new generations of unique (heterozygous) populations in which to make novel selections.  Given that almost no insects are observed tending the flowers as well as the clonal and self pollinating nature of its breeding system, it is likely that pollen transfer between flowers plays only a very limited role in the breeding system of the species.  The D. pruriens germplasm collection strategy is important for diversifying germplasm available for orchardists and enabling long-term improvements. The likely clonal/inbred nature of wild populations combined with the prevalence of Atherton Tablelands D. pruriens provenances represented in the planted estate provides strong justification for undertaking further systematic collections from other provenances.  The progeny trials will serve as a key resource in determining the relative contribution of genetic and environmental variation in the variability of crop production identified by producers and other selectable traits.  The scientific utility of the trials will benefit from a consistent approach to management, further cooperation among the three growers is required to standardise the approach to managing factors such as weed control, pruning, fertilising and irrigation.

Recommendations The recommendations targeted Davidsonia industry stakeholders (growers, processors, marketers, consumers) Industry  Industry stakeholders (nationwide) to collectively determine the most important commercial characters that can be used for selection and improvement.

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 Utilise the progeny trials to quantify genetic and environmental variation on important attributes as determined above.

Growers  Standardise the approach to managing the progeny trials with respect to weed control, pruning, fertilising and irrigation.  Collect yield data from the progeny trials to determine yield consistency between years.

Research & Development  Undertake seed collections from a broad range of populations in north Queensland and establish as an ex-situ planting for conservation and breeding purposes.  Implement further nutritional research to determine the influence of genetic variation and impact of processing on key nutritional traits.  Undertake research to determine molecular genetic variation in the progeny trials to determine the proportion of clones, inbred and outcrossed individuals  Undertake research to determine molecular variation in natural populations of D. pruriens to determine the level of variation within and between populations  Clonally propagate selections from both the progeny trials and ex situ collections for establishing a seed orchard(s) and deployment to commercial growers.

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Introduction

The Australian flora contains a large number of species with edible fruit, seed, leaves and roots, which sustained Aboriginal people for generations (Gorst 2002; Isaacs 2002)(Low 1991). Many of these edible products have the potential for development as niche horticultural crops (Stynes 1997; Ahmed and Johnson 2000; Garner and Lehmann 2016) with several now being cultivated on a modest commercial scale (Clarke 2012; Foster and ABARES 2014). The commercial potential of these species is however, limited by the high cost of inputs (land, labour and freight) relative to the crop productivity of the species (Cherikoff 2016). Therefore commercial viability of native plant food production can potentially benefit from genetic improvement (Page 2004; Ryder et al. 2009; Henry 2010; Do et al. 2016) and development of appropriate methods for horticultural management (Olsen 2002; Ryder et al. 2008; Ryder et al. 2009; Ellis et al. 2010).

The benefits of domestication has been demonstrated for other Australian native genera such as Melaleuca (Doran et al. 2006), Acacia (Midgley and Turnbull 2003) and Eucalyptus (Eldridge et al. 1993) and supported their commercial development. Macadamia is well recognized as Australia’s first domesticated food crop, albeit most early domestication was conducted in Hawai’i (Hardner 2016). While there has been phenotypic (Do et al. 2016; Glover 2016; Lethbridge 2016; Mazzorana and Mazzorana 2016a; Read 2016) and genetic (Mazzorana and Mazzorana 2016b; Rennie 2016) selection in some candidate native plant food species, few have been subject to systematic domestication including genetic selection and development of crop management systems (Stynes 1997).

Davidson plums (Davidsonia species) have been identified as native fruits with considerable market potential (Clarke 2012). Wild harvested D. pruriens provided the basis for the development of a small niche industry in Australia. Over the past 15 years the supply of Davidson Plum has made an almost complete transition from wild harvest to plantations and is now used as a principal flavouring ingredient in a variety of products, particularly preserves, yoghurts, and beverages (Netzel et al. 2006; Page and Watkins 2016). Given the fruit is used primarily in processed food, it must be price competitive with processing-grade fruits of other species (Hotson 2008).

Recent research has highlighted the health properties of D. pruriens including its high potential as a functional food (food containing factors to ensure or enhance human health) (Netzel et al. 2006; Lim 2013; Williams and Chaliha 2016), with particular reference to the high levels of total phenolics, antioxidants (Konczak 2009; Konczak et al. 2010; Konczak et al. 2012; Sakulnarmrat et al. 2014; Chuen et al. 2016). Fruit extracts from D. pruriens have also demonstrated inhibitory action against some cancer cells (Sakulnarmrat et al. 2015; Chuen et al. 2016) and are effective antimicrobials (Sultanbawa et al. 2015). This research information has the potential to raise the fruit’s market profile as a health product and increase demand. This positive market outlook has led to several growers expanding their orchards and mechanise their processing to meet the demands of large-scale food manufacturers. Production estimates therefore increased from 10 tons in 2012 (Clarke 2012) to a projected 12 to 15 tonnes in 2016 (ANFIL and RIRDC 2014).

Efficiencies in production are an important component for maintaining market competitiveness. A particular problem identified by growers on the Atherton Tablelands is that of seasonal, orchard-to- orchard, and tree-to-tree variability in fruit production. This variability can reduce harvest efficiency as well as fluctuations in supply volumes. These productivity problems need to be resolved as soon as

possible to improve the competitiveness of producers and avoid potential constraints on future growth. In north Queensland the size of plantings ranges from the very small (50-200 trees) to more modest plantings (1,000-5,000 trees). As with many newly cultivated species, the industry face challenges in all segments of the supply chain, from production through marketing and consumption. High variability in fruit production can be caused by a number of interacting issues such as (a) environmental and genetic variation within and between orchards (b) history and management of the orchards and (c) mating systems and pollination.

The proposed research is important in both the context of orchard management and domestication. Like many other native plant food species, D. pruriens is essentially wild. This means (a) that the genetic material currently in cultivation is likely to be less than optimal both in terms of variability and overall performance and (b) that little is currently known about best approaches to management. Davidson plum growers are most probably aware of different and desirable phenotypes that are of value for further development (Eliott et al. 2016). Therefore the aim of this project is to improve reliability and consistency of production in Davidson plum orchards in collaboration with industry partners. The project will address this aim by determining the scale of variation in fruit and yield characters and establishing genetic resources to identify the factors contributing to the variation and provide a repository for future selection and experiments.

Objectives

1. To facilitate reliable commercial production by establishing standardised management and yield monitoring protocols.

Current crop management is based on grower experience within their own orchards. Consequently various methods of managing the crop exist, which is likely to contribute to the variation in yields observed between orchards. In this objective growers will be surveyed for their management practices, which will then be summarized and compared with management of other similar horticultural crops. This summary will then be presented to the participating growers with the aim of refining a standardised management protocol. This protocol will be used in both the progeny trial plots and the proposed yield plots (see below). One of the most effective ways to quantify variation in crop yields is through accurate records over multiple sites and seasons. A total of 3-4 yield plots will be established in existing grower orchards and monitored by growers for the life of the project. Weather stations will be reinstated to ensure accurate data collection for each site. Data will be collated for each season and provide a basis for understanding yield variation within and between sites. This approach will be extended to the progeny trial plot once they attain reproductive maturity.

2. To facilitate domestication by establishing a progeny trial comprising the most productive individuals in the planted population.

The development of a replicated progeny trial is important for two reasons. First, it is likely that variation between trees of an individual orchard in a given year will be at least partly caused by genetic factors. Second, because it will allow us to assess the consistency of the productive individuals within and between sites. Although results from the progeny trial will not be available during project lifetime, the trial will constitute a valuable resource that in the future will permit more precise elucidation of factors causing variation in fruit production, particularly the relative importance of genetic and environmental factors.

3. To facilitate domestication by broadening the genetic base of the planted population

Given the discovery of the clonal/inbred nature of the Davidsonia pruriens breeding system it is likely that the genetic basis of the planted population is relatively narrow. This is because seed collectors are likely to have made repeated collections from accessible populations for sale to prospective growers. It is important to determine the populations, which were most heavily collected and develop a collection strategy that focuses collection efforts towards other populations/regions. Broadening the base is important to enable future efforts towards improving the species amenability to cultivation. This project will establish the genetic resource for future development of the species as a commercial crop.

Methodology

1. Establish standardised management and yield monitoring protocols.

A grower survey, which included a questionnaire and interview was developed and finalized in January 2015. Growers in north Queensland were sent the survey in February 2015 and interviews were conducted in March 2015. The results of this survey informed the drafting of current management regimes for Davidson plum production in north Queensland that then provided the basis of a book chapter. The book chapter was sent for comment to all relevant stakeholders in north Queensland as well as some prominent growers in northern NSW. Feedback from stakeholders was incorporated into the published version outlining the current state of knowledge in Davidson plum production (Page and Watkins 2016).

To determine baseline data for the basis of monitoring yield quantification of fruit production patterns during 2014/15. Trees were identified by growers as those that demonstrated a unique feature that would be of interest for production and selection. Growers typically selected trees based on having one or combinations of large fruit, high yield and frequent producer. Growers identified two distinct forms known as ‘smooth’ (minimum hairs on leaves and fruit) and ‘hairy’ (abundance of fine hairs produced on leaves and fruit). Fruits were collected from June 2014 to June 2015. During consultations with growers about the establishment of yield plots, different approaches to consistently recording yield were proposed based on existing harvesting protocols. These included establishing a standard yield plot to monitoring of yields from existing paddocks to records over the entire planting for the smaller site. Basic morphological traits were recorded for each tree during the collection period including fruit weight (g), yield (kg), seed number, germination percent). The coefficient of variation in fruit weight was based on those producing over 50 fruits. This number was selected based on other studies to determine the minimum sample size needed to calculate fruit characters such as pulp yield in Passiflora caerulea (wild passionfruit - 52 fruits) (Bandeira et al. 2016) and fruit mass in Carya illinoinensis (pecan - 50 fruits) (Cargnelutti et al. 2015).

2. Progeny trial replicated across 3 sites on the Atherton Tablelands.

Plant Material

Seed were collected from selected mother trees from Sunset Ridge (SR) (25 genotypes) and Rainforest Heart (FH) (17 genotypes) from June 2014 to June 2015. The mother trees were selected on the basis of grower observations for large fruit size and high fruit production. Seed collection was conducted over two separate periods (Table 2). At Sunset Ridge the genotypes Sr1-13 comprised ‘hairy’ forms, whereas Sr 14-25 comprised the ‘smooth’ forms. The two collection periods for FH were almost continuous with only a brief hiatus in fruit production during December 2014. All 17 FH genotypes were collected in each of the two periods, and all but Fh08 and Fh10 (smooth) composed of the ‘hairy’ form.

Table 2: Seed collection periods for the mother trees (genotypes) at Sunset Ridge (SR) and Rainforest Heart (FH) in 2014 and 2015.

Genotypes Period Period Start Period End

Sr 1-13 1 27th Jun 2014 5th Sep 2014

Fh 1-17 1 27th Jun 2014 5th Dec 2014

Fh 1-17 2 16th Jan 2015 8th Jun 2015

Sr 14-25 (‘smooth’) 2 11th Mar 2015 1st Jun 2015

Trial Configuration and Design

Standardisation of trial layout across the three sites was important to limit potential site variation due to plant spacing. The layout should also reflect an agreed configuration that reflects a typical production situation so families can be evaluated on their horticultural performance. Based on a growers meeting on Friday 8th April 2016, and subsequent individual consultations the final agreed layout comprised a ‘tramline’ configuration with 2m b/w lines with 2.5m diagonal between trees, and 4 inter-tramlines (Figure 2). This configuration results in a stocking of 1111 trees ha-1.

Following proven methods in the breeding and improvement of woody perennials (Williams et al. 2002) the trials were established as a complete randomised block design with 23, 19 and 20 family treatments for Sunset Ridge (SR), Rainforest Bounty (RB) and Rainforest Heart (RH) sites respectively. Plot size across all three sites was 4- tree line plots with four replicates at SR and RB and eight replicates at RH.

3. Strategy to broaden genetic base of the planted population

Growers in north Queensland were consulted to determine the source materials and/or seed suppliers used for the establishment of commercial D. pruriens orchards. Growers sourced seedlings from a limited number of nurseries and seed suppliers, and consultation with six seed collectors and/or seedling suppliers was undertaken. Some of these suppliers agreed to provide information if their identity was kept confidential. All suppliers were operating during the 1990s and/or 2000s with one specifically involved in supplying commercial growers and five involved in supplying seed/seedlings for the purposes of rainforest restoration.

Results

1. Establish standardised management and yield monitoring protocols.

Reproductive phenology

Based on detailed measurements of 20 trees at the Sunset Ridge orchard we recorded a fruit to flower ratio of 0.0013. The fruit production rate of the three trees that produced fruit was around 1.1% with one tree attaining 2.5%. While the trees produce a mass of flower buds, they open gradually over a period of months, with no more than 10 flowers open on any inflorescence at any time. This type of flowering phenology may be described as opportunistic where a small number of flowers are available for pollination at any given time and only set fruit when the environmental conditions are conducive for pollination and/or fruit set.

A sample of 20 trees was marked and reproductive phenology measures were recorded across the 6 orchards during January-February 2012. The trees at the Sunset Ridge orchard were recorded to have an average of 10-12 inflorescences with approximately 80-90 buds/flowers each, bringing the total buds/flowers per tree to approximately 800-1000. This number of inflorescences and buds/flowers was substantially greater than that found at 4 other orchards surveyed (Rainforest Heart, Long Weed, Oak Grove, Peevers) where the average number of inflorescences was around 4-5, with each bearing approximately 50 buds/flowers, bringing the approximate number of buds/flowers per tree to 200-250. The Tarzali site was sampled at least a month earlier (30th November 2011) than all other sites (January-February 2012), which is evident through the difference in reproductive phenology with a substantial number of buds (99.4/inflorescnce) but fewer flowers (0.125/inflorescence), together with a reduced number of inflorescences (0.2/tree) relative to the remaining sites.

Follow up measures were undertaken at Sunset Ridge in mid-April 2012 on the 20 trees recorded in February 2012. In April the average number of inflorescences was 16.5 per tree each with an average of approximately 5 buds/flowers. While the number of inflorescences increased since February the number of buds/flowers was significantly lower. This suggests that the initial measure in February was near the commencement of a floral ‘flush’ or event and the latter measure was at the end of this event. We therefore assume that the numbers of fruit recorded in the April measure reflect the fertilisation success and fruit development of flowers measured in February. Based on these assumptions only three of the 20 trees measured developed fruit, to give a fruit to flower ratio of 0.0013 of flowers resulted in a mature fruit. If we also include immature fruit recorded in April 2012 then this brings the ratio up to 0.0059. The fruit production rate of the three trees that produced fruit was around 1.1% with one tree attaining 2.5%. Even these values would be considered to be very low, with Sutherland (1986) reporting from a review of 447 species, the fruit to flower ratios for species with bisexual flowers was 0.206 in self-incompatible and 0.723 in self-compatible species. Therein they found that self-compatible plants have up to 3 times greater fruit set values than self-incompatible plants for those with bisexual flowers.

At Sunset Ridge the mean number of flowers that were open on an inflorescence was 3.4 and 2.1 for February and April respectively. While the trees typically produce a large number of flower buds during a reproductive event, the flowers are only opened gradually so that the event is extended for months. It is common to locate less than ten open flowers on an individual inflorescence. This sort of

strategy may not be consistent with insect pollinated plants that flower en masse to attract small generalised vectors (Monteiro and Ramalho 2010) such as the beetles, flies, small bees and thrips that are typical pollinators of Australian tropical vegetation (Gross 2005).

Fruit and yield variation

Two broad forms of D. pruriens are recognised in cultivation (i) ‘hairy’ or ‘hairy’ form and the (ii) ‘smooth’ or ‘coastal’ form which has less hairy fruit and leaves, softer fruit skin, smaller fruit size but a higher yield, and a lighter crown than the ‘hairy’ form (Cornelius 2011).

Orchard Yields

Two growers provided fruit yield records for orchards aged 6, 7, 8, 13 and 14 years and represents yield expected across all trees. Some additional data for younger trees was also collected. Trees begin producing commercial fruit yields from the age of 4 years. Relative fruit yield per tree increases with age with from 0.5-1.0 kg tree-1 in years 5 to 8 to 2-3kg tree-1 in years 12 to 16 (Table 3). These figures represent average yields and account for variation between trees within a year and between years within a tree. The calculation of 2-3kg tree-1 aligns with figures of expected yields (1-3kg tree-1) estimated by Hotson (2008). The timing of fruit production within a year varied between the two orchards with a more clearly defined single season at Sunset Ridge (SR), which peaked during the months of June and July. In contrast the orchard at Rainforest Heart (RH) had two peaks during the season with a high peak in April and May and another lesser peak in August and September (Figure 3).

Table 3: Mean fruit yields (kg) for unselected D. pruriens for different orchard ages.

Orchard Age (yrs) Mean Fruit tree-1 (kg) 1-5 0.1 - 0.3 5-8 0.5 - 1.0 8-10 1.0 - 1.5 10-12 1.5 - 2.0 12-16 2.0 - 3.0

Fruit Size

To quantify fruit production and variation for individual trees, individual fruits (total of 4662) were collected from 42 selected trees. Trees were selected across two properties (SR and FH) on the Atherton Tablelands based on their relative high fruit productivity. Fruits were collected on a weekly basis during the peak production (March to September) and fortnightly during off-season (October to February). All fruits were weighed before seed extraction. Average fruit weight for individual trees ranges from 17 to 70g with most individuals between 40 and 60g. A very high variation in fruit size/weight within a tree was recorded where an average of a 2- to 5-fold difference in the weight has been recorded between the smallest and largest fruit. To calculate the coefficient of variation (CV) for fruit weight we restricted the analysis to those producing at least 50 fruit.The coefficient of variation (CV) in fruit weight for Davidson Plum selections (N=28) ranged from 25 to 86%. This scale of variation was expressed in both the ‘smooth’ and ‘hairy’ forms (mean CV 48 and 29% respectively).

Tree Yields

Genotype variation in yield was significant during the 2014 and 2015 seasons with total fruit yield ranging from 548 grams to 32.8 kg tree-1. Mean fruit yield for ‘hairy’ and ‘smooth’ forms was 4.7 and 5.9kg tree-1respectively. When compared with a mean fruit of 2-3kg tree-1 for unselected trees (Table 3), the 42 selected trees may represent a yield increase of between 50% and 300%. Twenty-five of the selected trees had an annual fruit yield of above 3kg including 17 ‘hairy’ from both sites (Fh02, 03, 04, 05, 12, 16, 17 and Sr0, 02, 03, 04, 06, 07, 08, 11, 12 & 13) and 8 ‘smooth’ forms from Sunset Ridge (Sr14, 15, 19, 20, 22, 23, 24 & 25). The mean annual yield of these 25 trees was 7.5kg. The three replicated trials established with the progeny of these 42 trees will provide scientific evidence of the effect of genotype and environment on fruit yields. Here we suggest that the ‘yield potential’ of the two forms as 5-15kg tree-1 season-1 for ‘hairy’ (Fh 02, 05, 16, 17 and Sr 01, 02, 03, 08 & 13) and 20-30 kg tree-1 season-1 for ‘smooth’ (Sr 24, 25).

It has been suggested that rainfall is a predictor of fruit development, particularly during the fruiting period. Reliable rainfall data associated with one of the orchards revealed no correlation with yield over a two-year period. Correlation analaysis was undertaken to determine if rainfall 2-, 4-, 6- and 8- weeks prior to fruit set was influential but no significant associations were detected.

Variation in the timing of fruit production between the ‘hairy’ and the ‘smooth’ forms occurred at Sunset Ridge with the ‘smooth’ yielding fruit earlier (Mar-Apr) than the ‘hairy’ (Jul-Aug) (Figure 6a) and the orchard as a whole (Jun-Jul) (Figure 3). The Sunset Ridge orchard comprises primarily ‘hairy’ forms and therefore they make a greater contribution of the seasonality of the orchard than the ‘smooth’ forms. Peak yield period for the selected trees at Rainforest Heart was May-Jun (Figure 6a), which occurred towards the end of the first ‘flush’ of fruit in the orchard (Figure 3). The selected trees were a subset of the orchards and the apparent variation in peak between selected trees and the orchards may indicate genetic variation in the timing of fruit production. Seed collectors on the Atherton tablelands mentioned that remnant and mature (+50 years) D. pruriens can yield fruit twice a year around the months of May and October, with anecdotal yields over 100kg. A Davidson plum grower from northern NSW suggested that the ‘hairy’ form will produce fruit all year, while the ‘smooth’ form produces fruit from Mar-Aug.

Potential variation in seasonality of fruit production between selected trees within a site was assessed. At Sunset Ridge the ‘smooth’ forms generally produced fruit in a single flush with slight variation between genotypes for the timing of the peak. Peak fruit production for selections Sr14 and Sr15 occurred in mid to late March, while Sr24 and Sr25 peaked about 4 weeks later in late April (Figure 6b). This contrasted with the fruiting phenology of the ‘hairy’ forms at Sunset Ridge, which had a more prolonged (11 weeks) flush with 2-3 apparent monthly peaks (Figure 6d). The selected trees of the ‘hairy’ form growing at Rainforest Heart produced most fruit as a single peak, which varied between genotype by 1-3 weeks.

(a) (b)*

Horticultural Management

Seed Propagation

D. pruriens generally produce fruit with two fan-shaped seed. In 80% of fruits only one of these seeds will be filled (potentially viable) and the remaining 20% of fruits having two filled seeds. It is relatively simple to identify filled seed when extracting from the fruit by hand, as they have a more substantial size and weight compared with unfilled seed. Seed can be stored for short periods (2-3 weeks) in a plastic bag under refrigeration, but cannot be dried as they will lose viability. Seeds can be sown in a standard soil-less germination medium and most can be expected to begin germination within 4 weeks and ready for potting on after 3 months. Some seeds can take longer to germinate and so a second phase of potting can occur at about 6 months after sowing.

The main issue with germinating D. pruriens seed is predation by rodents, which have an insatiable appetite for the seeds. Seed will need to be protected from rodents by completely covering the seed trays with a mesh cage. In the field, the seeds are also an attractive food source for cockatoos, which represent a significant pest problem for orchardists and can cause substantial economic loss. In this project seed germination in seedlots not affected by rodents ranged from 32-92% (mean 55%) across the different seedlots (Figure 7). Rodents began to consume ten seedlots (Sr16 to Sr 25) before they were protected by mesh and therefore the germination rate (21%) was substantially lower than those unaffected. Approximately 10% of seeds were polyembryonic and produced two seedlings from a single seed, although no instances of three seedlings arising from one seed were recorded. The seedlings developing from polyembryonic seed typically had notable growth differences between them, with one demonstrating stronger growth than the other. This observation confirms the existence of polyembryony in D. pruriens with Eliott et al. (2014) demonstrating at least 25% of seed containing two or three embyros, with higher survival and greater growth in earlier germinating seedlings.

The nursery phase for D. pruriens is considerably long (~18-24 months), because seedlings need to have developed a stem with a minimum basal diameter of 10-15mm before outplanting. Good survival can be achieved by using seedlings of such maturity, while considerable losses can be expected for less developed seedlings with a stem diameter of <10mm. Some growers will produce in large polybags (2.8L), in this project seedlings were produced in 90mm plastic polytubes (0.8L).

Vegetative propagation

A series of vegetative propagation trials were conducted with D. pruriens from 2012 to 2015 These included (i) cutting, (ii) marcoting and (iii) grafting, using mature and seedling stock plants sourced from the orchards. This initial research demonstrated that while mature D. pruriens may be difficult to propagate clonally, both marcoting and cutting propagation offer the best opportunity for bulking up ramets for use in clonal tests.

Marcotting A total of 18 marcots were taken in April 2012 with 5 (28%) developing adventitious roots (Figure 8), 8 (44%) developing callus, 4 (22%) alive without callus and 1 (6%) dead. Given the low number of replicates the results are indicative of the effects of the treatments. It is evident that the best results were obtained from marcots set on current season’s growth (physiologically young or semi-hard wood) with application of 0.5% IBA. Root induction and growth was greatest in Young/IBA (22.2 %) followed by Mature/IBA (5.6 %), with no root development in both ‘Young’ and ‘Mature’ stems without IBA application. Marcots were evaluated six months after setting (April-October 2012), another inspection of these grafts is recommended to give a more accurate indication of ultimate success.

Figure 8: Root development in Davidsonia pruriens marcot after 6 month (left) and stem cutting after 10 weeks (right).

Grafting None of the grafting attempts were successful in striking grafts after 5 weeks and with these numbers no statistical test is applicable. No relevant data could be obtained from the experiment. It is likely that the poor results from grafting are related to the action of the ‘Omega’ grafting tool used. The action of this tool did not prepare a suitable surface for good contact between scion and rootstock. Further work using a standard top wedge graft, prepared with a sharp grafting knife is required to determine the feasibility of grafting Davidson plum.

Cuttings Cutting experiments were conducted in 2012 using both mature trees and seedlings (1-2 years). Adventitious root induction and development (Figure 8) in cuttings collected from mature trees ranged from 6 (control) to 16% (IBA). Greater success was achieved with cuttings collected from seedlings ranging from 18% (IBA) to 40% (control). The apparent interaction between hormone (IBA) and juvenility requires further investigation. The position of the cutting along the stem (apical vs. basal) had no effect on the percentage cuttings developing adventitious roots.

Cutting propagation using seedlings from selected trees was conducted in 2015 to determine the propensity for cloning. Cuttings were collected from juvenile seedlings (<1 year old) and set in a standard soil-less potting mix, under greenhouse conditions without exogenous auxin. Root induction was recorded in 60-80% of cuttings over a period of 3 months. The evaluations undertaken in the project suggest cutting propagation from juvenile seedlings could be an option for bulking up an individual progeny as a clone

Agronomy

The agronomy of D. pruriens is not well documented, although the importance of maintaining adequate soil moisture throughout the growing and fruiting season is gaining wide acceptance among growers. Irrigating the crop is essential for many sites to mitigate variability in rainfall, particularly during the period of fruit set and development. Much benefit is also gained in the general health and vigour of the tree by maintaining high soil organic matter, and protecting the soil from high temperatures. Regular applications of small amounts of fertiliser (either organic or inorganic) over the

entire growing season is important for increasing overall tree vigour, which supports higher flower and fruit production.

Canopy structure is an important modifying factor affecting fruit yields, where multi-stemmed trees have higher yields than single stemmed trees. Trees with multiple stems have a greater number of sites where inflorescences can be formed (particularly in leaf axils for D. pruriens), which has an overall positive effect on fruit numbers and thus yield. Much of the multi-stemmed trees in north Queensland have come about after natural wind damage, particularly the weather events of Cyclone Larry (2006) and Yasi (2011). A multi-stemmed habit can also be promoted by pruning the central leader during the first years after establishment. (Hotson 2008) suggests that Davidsonia trees respond well to pollarding at ‘harvestable height’ every 2-3 years. The crowns of most cultivated trees are upright and erect, which contrasts to the spreading canopies of much older remnant trees observed in pasture areas of the Atherton Tablelands. It is not yet clear whether the difference in canopy structure between wild and cultivated trees is due to higher tree density of plantations, or the difference in age between the plantations and remnant trees.

Protecting the crop from prevailing winds through the use of planted or natural windbreaks will reduce leaf-to-air vapour pressure deficit allowing leaf stomata to remain open and tree growth to continue. This protection combined with ensuring adequate soil moisture will contribute to improved growth and reproduction. The reduction in wind velocity that windbreaks afford may also promote efficient transfer of pollen between trees to affect successful fertilization and subsequent fruit set.

D. pruriens trees typically attain sexual maturity at around 3 years of age, although consistent production of commercial quantities of fruits occurs at around 5 to 8 years of age. Following cyclone damage, mature trees can take a further 2-3 years to recover condition and begin producing commercial volumes. In north Queensland the timing of fruiting varies between sites, but typically occurs between March and October. At some sites a low-level of fruit set occurs continuously over most of the season, whereas other sites can experience a more intense season lasting around 2 months. The species produces a mass of flower buds that open gradually over a period of months. During the season, flowering is promoted by rain events followed by warm sunny conditions. Flowers open at a rate of 1-2 per day with generally no more than 10 flowers open at a given time on an inflorescence with up to 200 flower buds. This type of flowering phenology may be described as opportunistic where a small number of flowers are available for pollination at any given time and only set fruit when the environmental conditions are conducive for pollination and/or fruit set.

The rate of flower development is positively associated with temperature and flower opening and pollen shed occurs primarily in the mid-afternoon particularly during periods of warmer temperature and lower humidity. Flowers can open over a period of approximately 12-hours, followed by pollen shed for up to 24-hours, but under warm and dry conditions may occur within 6-8 hours. Flowers can be abscised (shed) immediately after pollen shed, or later after the anthers too have been abscised.

2. Progeny trial replicated across 3 sites on the Atherton Tablelands.

Plant material

Seedlings were grown in 90mm poly-tubes with soil-less bark-based potting media and fertilised using slow release fertiliser for a period of 18-24 months. Larger seedlings were tip pruned eight weeks prior to planting to reduce overall leaf area and increase root:shoot ratio. Seed were sourced from

collections during 2014/15 from Sunset Ridge and Rainforest Heart. Resulting seedlings represented 41 families, 26 of which were represented in the replicated progeny trial and the remaining 15 represented in the buffer trees only (those which surround the trial trees) (Table 4). 48 seedlings per family were required for full representation of four replicates across each of the three sites and 17 families met this requirement. Five families were represented at two sites and four families were represented at a single site. The three trials were established between August 2016 and March 2017. All trees were fertilised with ~75g of Katek fertiliser at the time of planting. Good rains followed the planting of all plantings with good survival (93 to 100%) recorded across the three sites 2 months after planting

Sunset Ridge Rainforest Bounty Rainforest Heart Family Reps Buffers Reps Buffers Reps Buffers

Fh01 4 4

Fh02 4 4 6 4

Fh03 4 4 4 4

Fh04 4 4 4

Fh05 8 8 4 1

Fh06 3 3 3

Fh07 4 2

Fh08 2 2 2

Fh09 4

Fh10 3 2 2

Fh11 6 8 4

Fh12 4 1 4

Fh13 2 2

Fh14 4 4 4

Fh15 4 4 4

Fh16 8 8 5 29 4 12

Fh17 4 2 5 13 4

Sr01 4 6 9 4 2 Sr02 4 11 9 9 4 16

Sr03 4 13 8 4 3

Sr04 3 4 2 4 4

Sr05 4 2 2

Sr06 4 4 5

Sr07 4 4 2 4 Sr08 4 16 8 1 4 10

Sr09 4 6 15

Sr10 8 9

Sr11 4 4 2 4 3

Sr12 4 4 4

Sr13 4 7 4 4 4

Sr14 4 7 2

Sr15 9 8

Sr16 7

Sr18 10

Sr19 4 4 4

Sr20 4 7

Sr21 8

Sr22 3 4 4

Sr23 4 2 2

Sr24 8 13 10 23 4 7

Sr25 8 8 4 4 Total 23 20 20 Families Planting sites

Rainforest Heart This site is located on Brooks Rd., Mungalli (S 17 32’ 31”, E 145 42’ 36”) at an elevation of ~452m ASL (Figure 9). The aspect is north with a variable grade of between 7 and 8%. Existing vegetation is pasture grass, with some planted orchard trees (Lemon Aspen & Syzygium), some of which were retained in the trial area. Site length is 132 m and the width is 40 m at the northern end which narrows to 22 m at the southern end (0.48 ha). The soil type is Utchee Association (UtS + UtVS) (Laffan 1988). Twenty families were established in the progeny trial at Rainforest Heart (Table 4) representing 354 trial plants with an additional 127 buffers (481 D. pruriens planted in total). The trial was established over two separate plantings, on 8th August 2016 and 3rd March 2017. Families established at each planting were generally unique except for two families (Sr24 and Sr25) that were established at both these times. A drip irrigation system was installed at the time of the first planting. All trees were watered on demand as determined using soil tensiometer. A loss of 3.5% of seedlings was recorded in May 2017 with refills provided on 11th May 2017.

Figure 9: Satellite aerial (left) and ground (right) view of the D. pruriens trial site at Rainforest Heart, Mungalli, north Queensland

Rainforest Bounty This site is located on Lindsay Rd, Malanda (S 17 21’ 15”, E 145 38’ 00”) at an elevation of ~694m ASL (Figure 10). The aspect is undulating with a variable, but low grade, slope, a slight depression exists towards the northern end of the plot, although it was reported to be very rarely inundated. Existing vegetation was pasture grass with a few emergent Acacia. Site length is 140 m and the width is 44 m at the northern end which narrows to 26 m at the southern end (0.54 ha). The soil type is a Tranters Association graduating to Pin Gin Umala complex (Laffan 1988). Twenty families were

established in the progeny trial at Rainforest Bounty (Table 4) representing 456 trial plants with an additional 179 buffers (635 D. pruriens planted in total). The trial was established on 27-28th February 2017. Trees were watered manually for the first 4 weeks before installation of a drip irrigation system. A loss of 7% of seedlings was recorded 2-months after planting with refills provided on 11th May 2017.

Figure 10: Satellite aerial (left) and ground (right) view of D. pruriens trial site at Rainforest Bounty, Malanda, north Queensland

Sunset Ridge This site is located on Eastern Connection Rd in Danbulla (S 17 12’ 37”, E 145 39’ 16”) at an elevation of ~770m ASL (Figure 11). The aspect is south-west with a consistent grade of ~6.5%. Existing vegetation is pasture grass, which was grazed by cattle. The site measured 62 x 75m (0.47 ha). The soil type is a Pin Gin Galmara complex (Laffan 1988). The site is bordered to the east by an existing Davidson plum orchard of about 15 years of age. The trial site is rain-fed with manual irrigation carried out during extended dry periods. Twenty-three families were established in the progeny trial at Sunset Ridge (Table 4) representing 432 trial plants with an additional 134 buffers (566 D. pruriens planted in total). The trial was established on 27-28th February 2017. The site does not have irrigation installed and trees are watered when required manually. No seedling losses were recorded 2-months after planting.

Figure 11: Satellite aerial (left) and ground (right) view of D. pruriens trial site at Sunset Ridge, Danbulla, north Queensland

3. Source materials for the D. pruriens planted population

Pollinators and other flower visitors

Given that each Davidson plum produces two seeds it is assumed that fruit development is dependant upon successful fertilisation. This in turn is dependant upon successful transfer of pollen to the female parts (stigma) of the flowers either within- (self compatible) or between- (outcrossing) trees. (Eliott et al. 2016) reported that the flowers of Davidsonia species present traits which are consistent with a generalized insect pollination syndrome (entomophily). While some growers have described the vectors of Davidsonia pollen as a black fly, thrips or small wasps (Cornelius 2011; Kupsch pers. comm. 2012), most growers in north Queensland are yet to observe insects tending the flowers. Department of Environment and Conservation (NSW) (2004) reported that flies and native bees are likely pollinators of D. pruriens in north Queensland. During the phenology observations, controlled pollinations, cutting collection and marcot setting associated with this project, none of the six personnel (Cornelius, Gazoul, Kido, Page, Settle and Stanger) observed an insect tending a D. pruriens flower, and very few flying insects were observed within the orchards. Despite Eliott et al. (2016) suggesting Davidsonia spp. having the floral morphology traits of being insect pollinated, they also reported very few potential pollinators have been observed in the flowers of either D. jerseyana or D. pruriens.

To develop methods for controlled pollinations and determine the nature of the mating system of D. pruriens, initial observations of flower phenology were undertaken over a 24-hour period (April 2012). It is evident that the rate of flower development is positively associated with temperature, although these observations are yet to be quantified. Flower opening and pollen shed occurred primarily in the mid-afternoon during a period of warmer temperature and lower humidity. Flowers can open over a period of approximately 12-hours, followed by pollen shed for up to 24-hours, but under warm and dry conditions may occur within 6-8 hours. Flowers can be abscised (shed) immediately after pollen shed, or later after the anthers too have been abscised. Pollen is shed from longitudinal slits along the length of the anther, which can be facilitated by agitation with forceps. The pollen is minute in size and clearly observed to drift on air currents. This observation combined with a consistent lack of flower- tending insects across the orchards suggests wind pollination may be operating in this species. Wind pollination in the tropics may be considered unusual, with Ollerton (2009) reporting 96% of tropical species worldwide being animal pollinated; primarily insects, birds and bats. In Australia the frequency of wind pollinated species in tropical lowlands of Australia is also low with levels recorded between 0.3 and 7.9% (Irvine and Armstrong 1990). Bullock (1994) stressed however that the importance of wind pollination in tropical flora may not be fully recognised since identifying specific cases of wind facilitated pollen transfer can be problematic. Furthermore he described wind-pollinated flowers as ‘simple and undistinctive’, which is a vague feature when compared with distinct floral ornamentation associated with specialist insect vectors.

Pollen shedding is inhibited during periods of rain when the anthers are wet, which may reduce flower pollination and subsequent fruit set. Further work on description of the pollen morphology is suggested to determine if these features are also indicative of wind pollination. When flowers persist beyond anther filament shedding, the two styles are prominent and sometimes change colour to red. Given the lack of a distinct stigma it was assumed that the length of each style is pollen receptive, but further detailed analysis would be required to confirm this. No nectar was observed in any of the flowers, however closer examination with micro-capillaries is required to confirm this observation.

Determination of Mating system

Our observation of pollen that float on air-currents and the obvious lack of any insects tending flowers during all experiments, lead us to consider that wind pollination may be possible for D. pruriens. The controlled pollination of 104 and 42 flowers with ‘cross’- and ‘self’- pollen respectively, and a subsequent lack of fruit set in any of these, may mean that pollination is not a limiting factor for fruit set in these orchards, and it is possibly more dependent on environmental conditions that are conducive to fruit development. It is recognised however, that these findings are based on a small number of samples and additional controlled pollination work is required to confirm this.

The mating system influences the level of fertilisation in an orchard and in turn fruit yields. Given the lack of general knowledge on the mating system of D. pruriens, we undertook controlled pollination across 10 trees in the Sunset Ridge orchard. Individual inflorescences on each of these trees were designated as being either self- (6 of the 10 trees) or cross-pollinated (7 of the 10 trees). All open flowers were removed from these inflorescences and they were bagged to prevent open pollination. Flowers were emasculated in the morning on each day from 6-11th May 2012, and opened at a rate of 1.0-1.8 per day. Further pollinations were also made on the 15th and 18th May 2012. Emasculated flowers were pollinated immediately after emasculation with the appropriate pollen treatment. Pollination was undertaken by applying to the stigma, an anther that was shedding pollen. ‘Cross’ anthers were collected from a range of different trees, while ‘self’ anthers were collected from other flowers on the same tree as pollination.

A total of 104 cross- and 42 self-pollinations were made between 6-18th May 2012, with no fruit set recorded for any of these treatments. With 343 and 492 flowers remaining on the cross- and self- pollinated inflorescences respectively, the bags were left in place to determine the rate of possible spontaneous self-pollination. It is evident that while greater numbers of controlled pollinations are required to elucidate the true nature of the mating system (particularly given the very low fruit/flower ratio), this small trial demonstrates that pollination may not be the limiting factor in fruit production. Our results contrast with some pollinator exclusion experiments reported by The Department of Conservation and Environment (NSW) (2004) which demonstrated fruit containing viable seed can be produced in Davidson plum (possibly D. jerseyana) without cross-pollination. This report did not reveal the method used for excluding pollinators. In our study the flowers may have been adversely affected by the bagging of the inflorescences, and further examination of isolating whole plants (possibly grafted or marcoted potted plants) is recommended to determine the effect of bags on flower health.

Germplasm collection strategy

Planting of D. pruriens on the Atherton Tablelands commenced during the late 1980s as one of a suite of trees that were planted as part of ecological restoration projects. Two plant nurseries have been prominent in this effort including TREAT (Parks and Wildlife) and Eacham Nursery (Tablelands Regional Council). Seed collectors supplying these nurseries reported that most collections were made from Tablelands populations, particularly from many of the ‘paddock trees’ and those occurring on the margins of remnant rainforest and within national parks and reserves. A great diversity of trees from the Tableland were collected to supply these nurseries. Seed collections were also made from D. pruriens from localities such as Kuranda and Mission Beach / Tully but represented only a small proportion of the total seeds collected over a 10-20 year period. Collections were often targeted so

that the regional ecosystem of the source seed trees matched that of the target plantings. The market for the seedlings included private landowners that were establishing mixed species plantings as part of landscape restoration efforts and small-scale Davidson plum plantings.

The larger D. pruriens orchards used in this project sourced their seed/seedlings from a limited number of suppliers able to provide larger quantities and generally did not source their seedlings from the TREAT or Eacham Nursery. These suppliers sourced seed from exclusively around the Tablelands including ‘paddock trees’ that produced an abundance of fruits. The paddock trees are those that were retained by settlers during the period of land clearing, who may have known about their edibility (Page and Watkins 2016). These paddock trees represent an important resource for D. pruriens seed collectors. In the mid-2000s one grower produced approximately 11,000 D. pruriens germinants from their planted trees of Tablelands origin. These germinants were sold for further potting and sale by a large commercial nursery in the Atherton tablelands. These seedlings possibly comprise a significant proportion of the trees planted over the last 10 years.

Surveys of twelve natural populations of D. pruriens was undertaken during the project. The trees were found to be relatively common, but widely dispersed, with no observations of clumps of trees. Very few fruits were observed on the trees during exploration of wild populations, although inspection of leaves revealed that all were of the ‘hairy’ form. None of the seed collectors, botanists or naturalists consulted in this project could confirm the existence of a wild ‘smooth’ population or individual. One grower has reported the possibility of less hairy forms growing in natural vegetation around Mungalli.

The nature of the smooth form is unclear. It could be any of the following:  a distinct geographic type (e.g. ecotype or even subspecies);  one extreme of a continuous range of variation (and not necessarily from one particular location);  progeny or descendants of a particular individual tree, perhaps the bearer of a major gene mutation with dominant inheritance. (Cornelius 2011)  Figure 12: Areas of known D. pruriens natural populations and trees identified during reconnaissance as part of the projet

Area Population Reconnaissance Bloomfield Wujal Wujal Inspection Required

Mossman Area Daintree and Cape Tribulation Inspection Required Port Douglas Inspection Required Julatten Very few trees located Mt Lewis / Mt Windsor Inspection Required Kuranda Kuranda Trees easily located Speewah Trees easily located Black Mountain Rd, 2 trees located Cairns Lake Morris Road Trees easily located Mt Whitfield 3-4 trees located Crystal Cascades No trees located Lake Placid No trees located Innisfail Palmerston Hwy Trees identified Babinda Boulders No trees located Etty Bay Inspection Required Bramston Beach Inspection Required Silkwood/Japoonvale Trees Identified Koombooloomba Koombaloomba Dam? Inspection Required Tully Falls Inspection Required

Tully Mission Beach Trees Identified Hull River Inspection Required Tully River Inspection Required Murray River Inspection Required Kirrama Range Inspection Required north west of Cardwell

Implications

Development of D. pruriens for cultivation

Plant species may be considered to be semi-domesticated when they are being cultivated and under a degree of human selection but remains morphologically or genetically similar to wild populations (Meyer et al. 2012). While no specific evidence exists for the domestication of D. pruriens, Eliott et al. (2016) suggested that Davidsonia species may be considered semi-domesticated according to Meyer’s (2012) definition. The successful domestication of a new crop will depend on a program of development that has clear goals for improvement. This in turn will depend on clear definitions of traits to be improved, understanding of genetic variation within available germplasm and the heritability of these traits (Fehr 1987). This project set out to make basic evaluation of phenotypic variation and establish genetic resources for help support domestication of Davidson plum. It is recognized however that future attention to goal setting is required to support Davidson plum development. In this section we examine existing knowledge of D. pruriens as it relates to its domestication and development as a new fruit crop.

Wild variation and collection

The clonal and self-pollinating breeding system of D. pruriens is not typical of many other tropical tree species (Ward et al. 2005). For the domestication of Davidson plum further seed collections need to be made from wild populations to avoid the early development of ‘genetic bottle neck’ (narrowing of genetic diversity) as demonstrated in other domesticated crops (Doebley et al. 2006). Genetic bottlenecks are more acute in crops that have been based on only limited sampling of the genetic variation across the genome (Olsen and Gross 2008). This is particularly important for D. pruriens for two reasons (a) evidence suggests the cultivated populations in north Queensland were based on collections from a limited number of populations confined to the Atherton tablelands and (b) genetic diversity within a Davidsonia population is limited by its clonal and inbred breeding system. The optimum strategy for collecting D. pruriens germplasm would be to sample a small number of trees at any given site, but from many different populations (Eliott et al. 2016). This approach would maximise genetic variation in the ex situ population and provide opportunity for identifying unique genotypes for use in Davidson plum plant improvement. The benefit of the clonal and self-pollinating breeding system of D. pruriens is that seedlings arising from wild mother trees in wild populations should have a very similar morphology between them. This improves the efficiency of capturing interesting forms growing in the wild.

Breeding System

The work of (Eliott et al. 2013; Eliott et al. 2014; Eliott et al. 2016) on the reproductive biology of D. pruriens, D. jersyana and D. johnsonii makes a very important contribution to the understanding of

genetic structure and natural gene flow within Davidsonia populations. The same features of Davidsonia reproductive biology also impacts on the approach for its domestication. Here we summarise the main features of the breeding system as outlined by the two Eliott et al. (2014 and 2016) studies as it relates to the domestication of Davidsonia, readers seeking more information would be encouraged to source these important publications.

 D. pruriens is predominantly clonal (89% of progeny genetically identical to the maternal parent) with some self-fertilisation (9% progeny resulting from inbreeding) and somatic mutation of clonal progeny (2% of progeny).  D. jerseyana is predominantly (if not entirely) self-fertilising with high fecundity, and no evidence of inbreeding depression.  D. johnsonii is exclusively clonal (producing only seedless fruits) and propagating entirely through root suckers

Williams and Adam (2010) and Eliott et al. (2016) proposed that the flowers of D. pruriens and D. jerseyana species have features that are typical of one pollinated by insects. These features include an actinomorphic (radially symmetric) structure with fused sepals forming a tube that contains nectaries as well as a flower opening crowded with pollen shedding anthers. The flowers of D. pruriens are however covered in the same stiff and irritable hairs that adorn the fruits and leaves. Williams and Adam (2010) further suggest that these hairs can deter insects that may destroy the flower, but they also limit potential pollinators. Any insect attempting to tend the flowers of D. pruriens would, in their words, ‘. . . need to be able, in flight, to avoid the outer surface of the calyx whorl as it attempted to land on the flower.’ The hairy nature of the D. pruriens flower that limits potential pollinators may contribute to the lack of observations of insects tending flowers in this study and reported by Eliott et al. (2016). The flowers of D. johnsonii contrast with flowers both lacking hairs and being tended by a large number of insects Eliott et al. (2016). While purely speculative, the flowers of D. pruriens and D. jerseyana may be adapted to pollination by a very rare or extinct insect vector and in the absence of the vector has evolved the capacity for clonality and self-pollination. However, the observation in this study of pollen grains floating on air currents after agitation of a dehiscing anther may suggest the possibility that D. pruriens may be adapted for wind pollination. It is obvious that the pollination ecology of Davidsonia is enigmatic and requires further investigations to elucidate the mechanisms of pollen transfer between individuals.

Many tropical fruit trees are naturally polyembryonic including Citrus spp., mango (Mangifera indica), Mangosteen (Garcinia mangostana), Langsat (Lansium domesticum), jaboticaba (Myrciaria califlora) and several species of edible Syzygium (Litz 1985; Sedgley and Griffin 1989). In Mango (Mangifera indica) the classification of different cultivars is based on their mode of reproduction and centre of origin with two types: monoembryonic (Indian type) and polyembryonic (south east Asian type) (Mukherjee 1997). Monoembryonic mangoes produce a single sexual embryo, while polyembryonic produce multiple embryos with most being clonal and one being sexual (Aron et al. 1998). Mango is a predominantly outcrossing crop with high rates of self-incompatibility, so the sexually produced embryos in both types of mango will be outcrossed. In mango plant improvement has relied on classical breeding techniques (Iyer and Degani 1997; Bally et al. 2009). Mangosteen trees are dioecious (male and female trees) and produce polyembryonic seed that are obligate (always) apomictic (clonal) with male trees almost always absent and no evidence of sexual reproduction (Traub 1939; Richards 1990). The breeding and domestication of mangosteen has been severely limited by the lack of genetic variation in the crop (putatively a single clone) and clonal (apomictic

seed) method of natural reproduction (Ray 2002). While D. pruriens produces bisexual flowers, its breeding system more closely resembles that of mangosteen rather than mango, with predominantly clonal apomictic seed and limited (9%) sexual reproduction that is derived almost exclusively from self-pollination.

Eliott et al. (2016) reports that many of the features of the Davidsonia breeding system (apomixis, polyembryony, putative polyploidy, parthenocarpy, self-compatibility and clonal propagation) are potentially useful for domestication purposes. Henry (2010) suggested that domestication of Davidsonia may feature hybrid formation and wider use of the seedless trait. While in isolation these traits can be used to produce stable cultivars with desirable economic traits, when they feature so prominently in the breeding system of the genus, it can present challenges for long-term and sustainable improvements. The parthenocarpy in D. johnsonii, the primarily apomictic seed production of D. pruriens and obligate inbreeding system of D. jerseyana all limit the ease in which desirable traits can be transferred between genotypes within and between species. While there are biotechnologies that can be used to overcome these barriers their uptake may be restricted in an industry with limited resources to devote to research and development. The immediate strategy should therefore be to screen and collect from as many potential natural populations to locate and conserve novel genotypes that can be used for direct selection and propagation. The development of more sophisticated techniques for generating heterozygous progeny can be undertaken as the industry develops further and the economics of the industry can justify such an investment.

Multispecies

Davidsonia is comprised three species used in commercial production (D. pruriens D. jerseyana and D. johnsonii) and while growers in north Queenland have trialled production of all three, they have settled on production of D. pruriens. The reason for this is its adaptability to the local environment, larger fruit and greater resilience to fruit fly relative to other species of Davidson plum. In northern NSW, all three species are produced commercially. Given the limited genetic diversity across all three species and each having the potential to contribute commercial traits to improvement, consideration should be given for including the genomes of all three species in domestication. The breeding programmes of commercial fruit tree species typically use genetic variation from multiple species. For instance the main progenitors of the modern apple (M. domestica) appear to be M. pumila and M. sylvestris with genetic contributions of up to five other Malus species. (Watkins 1976; Hancock 1992). The mango originated in the Indo-Burma region and grows wild in the forest of northeast India, cultivated forms are identified as the species Mangifera indica although there is evidence of earlier hybridization with other species (Bally et al. 2009). In blueberries, which is a more recently domesticated fruit crop, the genetic makeup of the domesticated form comprises contributions from Vaccinium corymbosum, V. ashei (rabbiteye blueberry) and to a lesser extent V. angustifolium (Galletta and Ballington 1996). In Davidsonia three taxa D. pruriens, D. jerseyana and D. johnsonii could potentially contribute to the domestication of Davidson plum. Each of these species may offer traits in the development of cultivars adapted to local conditions. For instance D. pruriens has large fruit, D. jerseyana has a ‘juicy’ fruit and D. johnsonii has fruits with no or insignificant seeds.

Traits of interest

Fruit size and Yield

This project has demonstrated significant variation in both fruit size and yield that could be used to improve these traits. A very high variation in fruit weight within a tree was recorded, where the coefficient of variation (CV) in fruit weight ranged from 25 to 86%. This range would be considered high, where it has been suggested that a CV of between 10 and 30% is desirable for characteristics such as fruit size (Ferreira et al. 2016; Do et al. 2017). The CV for berry weight in Vaccinium corrymbosum (highbush blueberry) was ~26% (Litwinczuk et al. 2005). In clonal selections of Punica granatum (pomegranate) the CV for fruit weight was 9.3% (Zaouay and Mars 2014). The CV for fruit weight in selected genotypes of the tropical fruit species Spondias genotypes was 14.5% (de Lima et al. 2015). (Kaushik et al. 2016) noted however that more variation in eggplant fruit weight was found in the wild species S. insanum (CV 111%), compared with cultivated eggplant accessions (S. melongena)(36%). The CV for nut weight in Prunus scoparia (wild almond in Iran) was 32% (Khadivi-Khub et al. 2016). Prunus nepaulensis is an edible fruit species that is locally cultivated in the temperate Himalayan regions of India, the CV for fruit weight in this species is 21.6% (Shankar and Synrem 2012). In the Australian native fruit species Kunzea pomifera (muntries) Do et al. (2017) found the coefficient of variation in 100-berry weight was 20.5%, which is lower than recorded for individual fruit weight for D. pruriens.

Fruit weight (both mean value and range of variation) in the Vitus genus is influenced by multiple interactions between genotype, environmental factors, and cultural practice (Dai et al. 2011). The relative influence of these factors on the variation in fruit weight variation in D. pruriens in this study was not evaluated. The three D. pruriens replicated progeny trials established during this project will provide a useful resource for determining the genetic influence of these traits including heritability. The progeny trials can also be used to determine the variation within families and individuals in consistency of yield between seasons. In Davidson plum the demand for pureed and processed fruit is developing more strongly than for fresh product. Therefore the large size variation in Davidson plum trees may not necessarily influence perceived fruit quality and therefore market development. The variation may however, present challenges for mechanised harvesting and processing protocols, with fruit possibly requiring size grading before processing.

Fruit yield in other fruit crop species is under the influence of many genes and therefore has quantitative inheritance (Cantin et al. 2010; Kumar and Wehner 2013). Given that yield is not generally controlled by few genes it is therefore reasonable to consider that low genetic variation among D. pruriens would result in relatively consistent yields between trees. The reality is much different from this with individuals producing very low (0.55 kg tree-1) to very high yields (32 kg tree- 1).

There would be considerable benefit for breeding Davidsonia to extend the harvesting period, which would be achievable through exploitation of the variation recorded for peak fruiting times. Growers have already managed to extend the fruiting season in north Queensland by growing the earlier yielding ‘smooth’ and later yielding ‘hairy’ forms. Further expansion of the season could be achieved by targeting high yielding individuals and families with early or late yield profile.

Fruit Sweetness/Flavour

Characters such as fruit flavour and sweetness have been identified as traits in Davidsonia that might be considered for improvement (Eliott et al. 2016). This is not surprising because fruit sugar content is one of the most important quality traits perceived by consumers (Cirilli et al. 2016). The °brix level for the fruit of D. pruriens has been recorded at 4.5 to 6.5, which is well below the 8-12 °brix recommended for determining good quality in many fruit and vegetables (Harrill 1998). Mean °brix levels across 24 genotypes of Australian native food muntries (Kunzea pomifera) varied from 7.8 to 16.0. (Henry 2010) described the fruit of Davidsonia as edible, ‘but not generally attractive to human tastes without the addition of significant amounts of sugar’. While it is probable that there will be significant variation between genotypes for fruit sugar content, it is unlikely that the extent would be sufficient for rapid improvement in sweetness comparable to other sweet edible fruits. It is therefore probably not a trait worth considering as an immediate selection criteria. Flavour descriptors for the fruit of Davidsonia reveal that they are intensely tart and astringent (Table 5), and as such are not generally consumed fresh but in a processed or prepared state. Given that processing is obligatory for this fruit with the flavour modified before consumption, the importance of including flavour as a selectable trait would need to be determined through wider consultation with processors and consumers. The deeply saturated crimson colour of Davidson plum is an important culinary characteristic that is valued in the market.

Table 5: Sensory description of the fruit from two Davidsonia species. Extracted from (Smyth et al. 2012) and (Smyth and Sultanbawa 2016)

Davidson species Fruit Flavour Descriptors D. jerseyana Aroma is earthy like fresh beetroot with slight pickled and chemical notes. Flavour is intensely tart and astringent. D. pruriens Frozen fruit aroma of rosella and stewed rhubarb, some musk and candy notes. Flavour is intensely tart and astringent.

Fruit nutritional Factors

Cherikoff (2016) suggests native Australian plant foods need not be mere alternatives to other food products currently on the market. One of the points of differentiation for native food is their often elevated levels of certain nutritional components. Davidson plum (all species) has the potential to be marketed as a functional food (food containing factors to ensure or enhance human health) (Netzel et al. 2006; Lim 2013; Williams and Chaliha 2016). Davidson plum has been identified has having particularly high total phenolics and antioxidants (Konczak et al. 2009; Konczak et al. 2010; Konczak et al. 2012; Sakulnarmrat et al. 2014; Chuen et al. 2016). Fruit extracts from D. pruriens have also demonstrated inhibitory action against some cancer cells (Sakulnarmrat et al. 2015; Chuen et al. 2016) and are effective antimicrobials (Sultanbawa et al. 2015) . Variation in the levels of phenolics and antioxidants has been found for Davidsonia in the literature (Table 6). While extraction methods can play a role in this variation (Chuen et al. 2015; Chuen et al. 2016), more consideration of the market significance of this variation is required.

If the nutritional factors are going to be an important consideration in the development of D. pruriens then more research would be required to (i) determine the factors contributing to the variation in particular factors/nutrients (genetic, environmental/production, processing and storage) (ii) decide

which factors are going to be of commercial significance and therefore monitored/selected during domestication, cultivation and processing and (iii) standardisation of methods for extraction and analysis because they have significant impact on results (Chuen et al. 2015; Chuen et al. 2016).

Sultanbawa et al. (2015) reported that the highland or ‘hairy’ variety of D. pruriens had significantly higher total phenolics level and antioxidant capacity than the lowland or ‘smooth’ variety. The total phenolic levels and FRAP values of the lowland (smooth) fruits from both NSW and QLD orchards were similar, which indicates that the variation between the lowland and the highland varieties might be genetic, rather than agronomic. Depending on the target market, this is another factor that perhaps should be considered in any evaluation of the best cultivars to propagate.

Pest Resistance

Hotson (2008) identified a range of pests for Davidsonia with the following having the potential to cause economic damage: native budworm (Heliothis spp.), light brown apple moth (Epiphyas postvittana), orange fruit borer moth (Isotenes mierana) and fruit fly (Dacus spp). Page and Watkins (2016) identified three pests of economic significance: stem-boring jewel beetle (Cyriodes cincta), sulphur-crested cockatoos (Cacatua galerita) and giant white-tailed rats (Uromys spp.). The progeny trials established in this project have the potential to be used to assess genetic tolerance or resistance to these pests. It is probably not expected that genetic tolerance could be found for the seed consuming sulphur-crested cockatoos or giant white-tailed rats, although the seedless trait in D. johnsonii could offer some prospect for countering these pests.

Table 6: Phenolic compounds identified and levels in the fruit of D. pruriens (Dp) and D. jerseyana (Dj) across five studies.

Compound Measure Dp Dj Dp? Dp Dp Dp

Reference (Konczak 2009) (Konczak 2009) (Konczak et al. 2010) (Sakulnarmrat et al. (Chuen et al. 2015) (Chuen et al. 2016) 2014)

Extract Type Crude Extract Crude Extract Crude Extract Phenolic-Rich Extract Phenolic-Rich Extract Crude Extract

Total phenolics (FC) (umol GA E/gFW) 48.60 ± 2.48 50.25 ± 6.34 14.1 to 15.9 949 ± 239a 45.14 ± 6.74

Phenolic compounds (HPLC identified) 280 nm (umol GA E/gFW) 13.9 to 15.4

Phenolic compounds (HPLC identified) 326 nm (umo lCHA E/gFW) -

Phenolic compounds (HPLC identified) 370 nm (umol R E/gFW) Traces

Phenolic compounds (HPLC identified) 520 nm (umol C3G E/gFW) 0.76 to 0.85

Total Reducing Capacity (FRAP) (μmol Fe+2/g DW) 670.7 ± 49.3 599.8 ± 20.7 53.9 ± 4.0 9258 ± 926

ORAC (μmol TE./gDW) 8792 ± 370

ORAC-H (μmol TEq/gDW) 982.41 ± 129.30 686.24 ± 109.83 83.1 ± 10.9

ORAC-L (μmol TEq/gDW) 210.38 ± 2.06 214.04 ± 0.64

ORAC-T (μmol TEq/gDW) 1192.79 900.28

Total Anthocyanins (mg C 3G Eq/g DW) 47.80 ± 1.2 98.65 ± 6.5 383 ±10

Total Flavonoids (mg Cat E.b/g DW) 353 ±3.1

Flavonoids (mg RUE/g) 22.33 ± 2.08 18.33 - 78.33

Proanthocyanins (mg CAE/g) 3.20 ± 0.43 3.2 - 5.94

Anthocyanins (mg CGE/g) 2.02 ± 0.41 1.5 - 4.79

ABTS (100 μg/mL) 7.01-36.3

DPPH (100 μg/mL) 13.48-18.22

FRAP (100 μg/mL) 0.05-0.13

CUPRAC (100 μg/mL) 0.19-0.44

TPC (mg GAE/g) 35.17 - 94.13

Management of the progeny trials

The three progeny trials established as part of this study represent a resource for determining the practical implications of the breeding system on orchard productivity and plant improvement. The planted estate for D. pruriens is likely based on a collection from a limited number of trees from the Tablelands population(s). Given the clonal/inbred nature of its breeding system, it should be expected that the planted estate to be composed of closely related clones. The very high variation in fruit size and yields within and between plantations recorded in this study does not necessarily reflect the related nature of the germplasm. The progeny trials will permit for the first time quantification of the yield variation as it relates to genetic structure of the trees. This will give a much clearer idea of the contribution that genotype and environment has on important commercial characters. The scientific utility of the trials would benefit from a consistent approach to management between growers. One of the growers had an obligate organic approach to management, while the others use organic methods but are not restricted in their targeted use of pesticides. This difference in approach to managing the orchards need not affect the differences between the site provided all have consistent weed management during establishment years. The timing and method of pruning, fertiliser application/rate, and irrigation regimes are probably the main areas for further standardisation. While the methods of irrigation are different, the on-demand strategy is consistent between the sites. Discussion of the critical measures for on-demand is something that requires further clarification.

The progeny trials were established to function as both a scientific and production resource and therefore represent a commercial benefit for the orchardists. As the trials mature they will increase the available Davidson plum product on the market benefiting both processors and consumers. Given the likely clonal structure of the progeny trial, the expected yields may reflect the yields of the selected mother trees. The average yield of the mother trees was 5.3kg tree-1 season-1 (4.7 and 5.9kg tree-1 for ‘hairy’ and ‘smooth’ respectively). A total of 1682 trees were established across all the progeny trials, which can potentially produce an annual crop of around 8.9 tonnes. While the total industry Davidson plum yields have not been quantified for 2017, in 2014 they were projected to be around 12 to 15 tonnes by 2016 (ANFIL and RIRDC 2014). So the production potential of the progeny trials established in this project may represent a 50% increase in industry volumes.

Given the progeny trials are an important commercial resource for the growers they were not intended to be converted to become a seedling seed orchard, but as a source for identifying and propagating outstanding families or individuals. The line-plot experimental design was chosen for the following reasons (a) it will permit easier identification of the trial design in the future as the sites inevitably change (tree death, removal or degradation of permanent markers etc) (b) the clonal and inbred nature of the species breeding system cancels out any effect of a trial design to maximize cross pollination between single tree plots, (c) it offers the potential for undertaking future sub-experiments (pruning, fertilizing) on an individual tree or plot basis (d) if required it can be converted into a seedling seed orchard by removal of any underperforming trees and families. It was intended that further selection will come through the clonal propagation of selected individuals and/or families by either apomictic seed or other vegetative means.

Recommendations

Industry  Industry stakeholders to collectively determine the most important commercial characters that can be used for selection and improvement.  Utilise the progeny trials to quantify genetic and environmental variation on important attributes as determined above.

Research & Development  Undertake seed collections from a broad range of populations in north Queensland and establish as an ex-situ planting for conservation and breeding purposes.  Undertake research to determine molecular genetic variation in the progeny trials to determine the proportion of clones, inbred and outcrossed individuals  Undertake research to determine molecular variation in natural populations of D. pruriens to determine the level of variation within and between populations  Clonally propagate selections from both the progeny trials and ex situ collections for establishing a seed orchard(s) and deployment to commercial growers.

References

(NSW) DoEaC (2004) Recovery Plan for the Davidson’s Plum (Davidsonia jerseyana). Department of Environment and Conservation (NSW), Hurstville. Ahmed AK, Johnson KA (2000) Turner Review No.3: Horticultural development of Australian native edible plants. Australian Journal of Botany 48:417-426. ANFIL, RIRDC (2014) Focus on Davidson plum: Davidsonia jerseyana, Davidsonia pruriens. RIRDC publication 14-112. Rural Industries Research and Development Corporation, Canberra. Aron Y, Czosnek H, Gazit S, Degani C (1998) Polyembryony in Mango (Mangifera indica L.) is controlled by a single dominant gene HortScience 33:1241-1242. Bailey FM (1898) Edible fruits indigenous to Queensland No. 1. Davidsonian Plum. Queensland Agricultural Journal 2:471. Bailey FM (1900) Davidsonia, F.v.M. In: The Queensland Flora Vol 2. Queensland Government, Brisbane. Bally ISE, Lu P, Johnson PR (2009) Mango Breeding. In: Jain SM, Priyadarshan PM (eds) Breeding Plantation Tree Crops: Tropical Species. p51-82. Springer New York, New York, NY. http://dx.doi.org/10.1007/978-0-387-71201-7_2. Bandeira CT, Fortes SKG, Toebe M, Saifert L, Giacobbo CL, Welter LJ (2016) Sample size for estimate the average of Passiflora caerulea fruits traits. Ciencia Rural 46:1729-1736. Brickell CD, Baum BR, Hetterscheid WLA, Leslie AC, McNeill J, Trehane P, Vrugtman F, Wiersema JH (eds) (2004) International Code of Nomenclature for Cultivated Plants. Acta Horticulturae 647, 7th Edition edn, Edinburgh (UK), Toronto (Canada)

Bullock SH (1994) Wind pollination of neotropical dioecious trees. Biotropica 26:172-179. Cantin CM, Gogorcena Y, Moreno MA (2010) Phenotypic diversity and relationships of fruit quality traits in peach and nectarine Prunus persica (L.) Batsch breeding progenies. Euphytica 171:211-226. Cargnelutti A, Poletto T, Muniz MFB, Baggiotto C, Poletto I (2015) Sample size for evaluating the weight and diameter of pecan fruits. Ciencia Rural 45:794-798. Cherikoff V (2016) New Market Opportunities for Australian Indigenous Food Plants. In: Australian Native Plants: Cultivation and Uses in the Health and Food Industries. p339-348, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-29. Chuen TLK, Vuong QV, Hirun S, Bowyer MC, Goldsmith CD, Scarlett CJ (2015) Optimum aqueous extraction conditions for preparation of a phenolic-enriched Davidson's plum (Davidsonia pruriens F. Muell) extract. International Journal of Food Science and Technology 50:2475- 2482. Chuen TLK, Vuong QV, Hirun S, Bowyer MC, Predebon MJ, Goldsmith CD, Sakoff JA, Scarlett CJ (2016) Antioxidant and anti-proliferative properties of Davidson's plum (Davidsonia pruriens F. Muell) phenolic-enriched extracts as affected by different extraction solvents. Journal of Herbal Medicine 6:187-192. Cirilli M, Bassi D, Ciacciulli A (2016) Sugars in peach fruit: a breeding perspective. Horticulture Research 3:12. Clarke M (2012) Australian Native Food Industry Stocktake. RIRDC publication 12/066. Rural Industries Research and Development Corporation, Canberra. Collinson JW (1949) Cardwell, A Gateway to the West. The Historical Society of Queensland Inc. Cornelius J (2011) Davidsonia cultivation: summary and synthesis of FNQ grower responses to question on productivity, germplasm, and research priorities. RIRDC-funded project - 'Davidsonia domestication: productivity constraints in Far North Queensland'. James Cook University, Cairns. Dai ZW, Ollat N, Gomes E, Decroocq S, Tandonnet JP, Bordenave L, Pieri P, Hilbert G, Kappel C, van Leeuwen C, Vivin P, Delrot S (2011) Ecophysiological, Genetic, and Molecular Causes of Variation in Grape Berry Weight and Composition: A Review. American Journal of Enology and Viticulture 62:413-425. de Lima MSS, Dantas A, Fonseca AAO, Barroso JP (2015) Characterization of fruits from selected umbu-cajazeira (Spondias sp.) genotypes. Interciencia 40:311-316. Do CM, Delaporte KL, Schultz CJ (2017) Benchmarking study of quality parameters of Rivoli Bay selection of Kunzea pomifera (muntries): A new Indigenous crop from Australia. Scientia Horticulturae 219:287-293. Do CM, Panakera-Thorpe LL, Delaporte K, Schultz CJ (2016) Kunzea pomifera (muntries): selection validation and evaluation of important horticultural traits. Acta Horticulturae 1117:31-37. Doebley JF, Gaut BS, Smith BD (2006) The Molecular Genetics of Crop Domestication. Cell 127:1309-1321. Doran JC, Baker GR, Williams ER, Southwell IA (2006) Genetic gains in oil yields after nine years of breeding Melaleuca alternifolia ( Myrtaceae). Australian Journal of Experimental Agriculture 46:1521-1527. Eldridge KG, Davidson J, Harwood J, Van Wyk G (1993) Eucalypt Domestication and Breeding, Vol Ch. 6. Clarendon Press, Oxford. Eliott F, Shepherd M, Rossetto M, Henry R (2016) The Reproductive Systems of Davidson's Plum (Davidsonia jerseyana, Davidsonia pruriens and Davidsonia johnsonii) and the Potential for Domestication. In: Australian Native Plants. p49-67, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-7. Eliott FG, Connelly C, Rossetto M, Shepherd M, Rice N, Henry RJ (2013) Novel microsatellite markers for the endangered Australian rainforest tree Davidsonia jerseyana (Cunoniaceae) and cross-species amplification in the Davidsonia genus. Conservation Genetics Resources 5:161- 164. Eliott FG, Shepherd M, Rossetto M, Bundock P, Rice N, Henry RJ (2014) Contrasting breeding systems revealed in the rainforest genus Davidsonia (Cunoniaceae): can polyembryony turn the tables on rarity? Australian Journal of Botany 62:451-464.

Ellis G, Oliver G, Vincent A, Raghu S (2010) The Effect of Irrigation and Weed Competition on Yield of a Commercial Scale Solanum centrale (Bush Tomato) Production System: a Preliminary Investigation. Desert Knowledge Cooperative Research Centre, Alice Springs. Fehr WR (1987) Principles of Cultivar Development: Theory and Technique. Macmillan, New York. Ferreira JP, Schmildt ER, Schmildt O, Cattaneo LF, Alexandre RS, Cruz CD (2016) Comparison of methods for classification of the coefficient of variation in papaya. Revista Ceres 63:138-144. Foster M, ABARES (2014) Emerging animal and plant industries their value to Australia. RIRDC Publication No 14/069, RIRDC Project No PRJ-008496. Rural Industries Research and Development Corporation (RIRDC), Canberra. Fox MJ (1923) The Sugar Industry. Sugar Growing Countries. In: History of Queensland: Its People and Industries. States Publishing Company, Brisbane. Garner A, Lehmann L (2016) Overview of Australian Native Plants. In: Australian Native Plants. p1- 4, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-2. Glover R (2016) Cultivation of Riberry (Syzygium luehmannii). In: Australian Native Plants. p155- 163, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-16. Gorst JR (2002) Indigenous fruits of Australia. In. International Society for Horticultural Science (ISHS), Leuven, Belgium, p555-561. Gross A (1972) Dallachy, John (1808–1871). In: Australian Dictionary of Biography, Vol 4. National Centre of Biography, Australian National University. http://adb.anu.edu.au/biography/dallachy-john-3355/text5055, . Gross CL (2005) A comparison of the sexual systems in the trees from the Australian tropics with other tropical biomes - More monoecy but why? American Journal of Botany 92:907-919. Harden GJ, Williams JB (2000) A revision of Davidsonia (Cunoniaceae). Telopea 8:413-428. Hardner C (2016) Macadamia domestication in Hawai'i. Genetic Resources and Crop Evolution 63:1411-1430. Harrill R (1998) Using a Refractometer to Test the Quality of Fruits & Vegetable. Pineknoll Publishing, Keedysville, Maryland, USA. Henry RJ (2010) Plant Resources for Food, Fuel, and Conservation. Earthscan, London. Hess-Buschmann S (2017) Davidson Plum. In: Glover R, Read C (eds) Australian Native Food & Botanicals. Rural Industries Research and Development Corporation (RIRDC). http://anfab.org.au/main.asp?_=Davidson Plum. Hotson A (2008) The Davidson Plum. In: The new crop industries handbook. Native Foods. p40-47. RIRDC, Canberra. Irvine AK, Armstrong JE (1990) Beetle pollination in tropical forests of Australia. In: Bawa KS, Hadley M (eds) Reproductive ecology of tropical forest plants. p135–148. Unesco, Parthenon, Carnforth. Isaacs J (2002) Bush Food: Aboriginal Food and Herbal Medicine. New Holland Publishers, Sydney. Iyer CPA, Degani C (1997) Classical Breeding and Genetics. In: Litz RE (ed) The Mango: Botany, Production and Uses. p49-68. CAB International, Oxon. Kaushik P, Prohens J, Vilanova S, Gramazio P, Plazas M (2016) Phenotyping of Eggplant Wild Relatives and Interspecific Hybrids with Conventional and Phenomics Descriptors Provides Insight for Their Potential Utilization in Breeding. Frontiers in Plant Science 7:16. Khadivi-Khub A, Sarooghi F, Abbasi F (2016) Phenotypic variation of Prunus scoparia germplasm: Implications for breeding. Scientia Horticulturae 207:193-202. Konczak, I, Zabaras D, Dunstan M, Aguas P, Roulfe P, Pavan A (2009) Health Benefits of Australian Native Foods - An evaluation of health-enhancing compounds. . RIRDC publication 09-133 Rural Industries Research and Development Corporation, Canberra. Konczak, I., Sakulnarmrat K, Bull M (2012) Potential Physiological Activities of Selected Australian Herbs and Fruits. . RIRDC publication 11-097. Rural Industries Research and Development Corporation, Canberra. Konczak I (2009) Health Benef its of Australian Native Foods – An evaluation of health-enhancing compounds. RIRDC Publication No. 09/133. Rural Industries Research and Development Corporation, Canberra.

Konczak I, Zabaras D, Dunstan M, Aguas P (2010) Antioxidant capacity and hydrophilic phytochemicals in commercially grown native Australian fruits. Food Chemistry 123:1048- 1054. Kumar R, Wehner TC (2013) Quantitative Analysis of Generations for Inheritance of Fruit Yield in Watermelon. HortScience 48:844-847. Laffan MD (1988) Soils and land ues on the Atherton Tableland, North Queensland, Vol 61. CSIRO Australian Soils and Land Use Series. CSIRO Australia, Division of Soils. Lethbridge B (2016) Cultivation of Quandong (Santalum acuminatum). In: Australian Native Plants: Cultivation and Uses in the Health and Food Industries. p147-153, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-15. Lewis CT, Short C (1879) A Latin Dictionary. Clarendon Press, Oxford. Lim TK (2013) Davidsonia pruriens. In: Edible Medicinal And Non-Medicinal Plants: Volume 5, Fruits. p132-135. Springer Netherlands, Dordrecht. http://dx.doi.org/10.1007/978-94-007- 5653-3_9. Litwinczuk W, Szczerba G, Wrona D (2005) Field performance of highbush blueberries (Vaccinium x corymbosum L.) cv. 'Herbert' propagated by cuttings and tissue culture. Scientia Horticulturae 106:162-169. Litz RE (1985) Somatic Embryogenesis in Tropical Fruit Trees. In: Tissue Culture in Forestry and Agriculture. p179-193. Maiden JH (1908) Records of Victorian Botanists. Victorian Naturalist 25:101-120. Mazzorana G, Mazzorana M (2016a) Cultivation of Anise Myrtle (Syzygium anisatum). In: Australian Native Plants: Cultivation and Uses in the Health and Food Industries. p7-18, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-4. Mazzorana G, Mazzorana M (2016b) Cultivation of Lemon Myrtle (Backhousia citriodora). In: Australian Native Plants: Cultivation and Uses in the Health and Food Industries. p113-126, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-12. McNeill J, Barrie FR, Buck WR, Demoulin V, Greuter W, Hawksworth DL, Herendeen PS, Knapp S, Marhold K, Prado J, Reine WFPHv, Smith GF, Wiersema H, Turland NJ (eds) (2011) International Code of Nomenclature for algae, fungi, and plants. Eighteenth International Botanical Congress, July 2011, ISBN 978-3-87429-425-6. Koeltz Scientific Books, Melbourne, Australia. Meyer RS, DuVal AE, Jensen HR (2012) Patterns and processes in crop domestication: an historical review and quantitative analysis of 203 global food crops. New Phytologist 196:29-48. Midgley SJ, Turnbull JW (2003) Domestication and use of Australian acacias: case studies of five important species. Australian Systematic Botany 16:89-102. Mills JA (1981) Davidson, John Ewen (1841–1923). Australian Dictionary of Biography 8: Australian Dictionary of Biography, National Centre of Biography, Australian National University. URL: http://adb.anu.edu.au/biography/davidson-john-ewen-5902/text10051. Monteiro D, Ramalho M (2010) Generalist bees (Meliponina) and the reproductive success of the mass flowering tree Stryphnodendron pulcherrimum (Fabales: Mimosaceae) in the Atlantic Rainforest, Bahia. Neotropical Entomology 39:519-526. Moore C (1981) Kanaka Maratta: a history of Melanesian Mackay. . James Cook University., Mukherjee SK (1997) Introduction: botany and importance. In: Litz RE (ed) The Mango: Botany, Production and Uses. p69-146. CAB International, Oxon. Netzel M, Netzel G, Tian QG, Schwartz S, Konczak I (2006) Sources of antioxidant activity in Australian native fruits. Identification and quantification of anthocyanins. Journal of Agricultural and Food Chemistry 54:9820-9826. Ollerton J, Alarcon R, Waser NM, Price MV, Watts S, Cranmer L, Hingston A, Peter CI, Rotenberry J (2009) A global test of the pollination syndrome hypothesis. Annals of Botany 103:1471- 1480. Olsen G (2002) Broadscale production of wattle seed to address salinity. Conservation Science Western Australia Journal 4:185–191.

Olsen KM, Gross BL (2008) Detecting multiple origins of domesticated crops. Proceedings of the National Academy of Sciences 105:13701-13702. Page T (2004) Muntries: The domestication and improvement of Kunzea pomifera. Rural Industries Research and Development Corporation, Canberra. Page T, Watkins M (2016) Cultivation of Davidson's Plum (Davidsonia spp.). In: Sultanbawa Y, Sultanbawa F (eds) Australian Native Plants: Cultivation and Uses in the Health and Food Industries. p33-48, Traditional Herbal Medicines for Modern Times. CRC Press, Boca Raton. http://dx.doi.org/10.1201/b20635-6. Ray PK (2002) Mangosteen. In: Breeding Tropical and Subtropical Fruits. p300-306. Springer-Verlag and Naroosa Publishing House, New Delhi, India. Read CD (2016) Cultivation of Native Pepper (Tasmannia lanceolata). In: Australian Native Plants: Cultivation and Uses in the Health and Food Industries. p133-145, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-14. Rennie S (2016) Cultivation of Australian Finger Lime (Citrus australasica). In: Australian Native Plants: Cultivation and Uses in the Health and Food Industries. p81-87, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-9. Richards AJ (1990) Studies in Garcinia, dioecious tropical forest trees: agamospermy. Botanical Journal of the Linnean Society 103:233-250. Ryder M, Latham Y, Hawke B (2008) Cultivation and Harvest Quality of Native Food Crops. Rural Industries Research and Development Corporation, Canberra. Ryder M, Walsh F, Douglas J, Waycott M, Robson H, Singh Z, de Sousa Majer M, Collins T, White J, Cheers B (2009) Sustainable Bush Produce Systems – Progress Report 2004–2006. Desert Knowledge Cooperative Research Centre, Alice Springs. Sakulnarmrat K, Srzednicki G, Konczak I (2014) Composition and inhibitory activities towards digestive enzymes of polyphenolic-rich fractions of Davidson's plum and quandong. Lwt-Food Science and Technology 57:366-375. Sakulnarmrat K, Srzednicki G, Konczak I (2015) Bioprospecting Davidson's plum and quandong: Cytoprotective and proapoptotic activities. Lwt-Food Science and Technology 61:622-629. Sedgley M, Griffin AR (1989) Sexual reproduction of tree crops. Academic Press, London. Shankar U, Synrem IL (2012) Variation in morphometric traits of fruits and seeds of Prunus nepaulensis Steud. in Meghalaya, India. Tropical Ecology 53:273-286. Smyth H, Sultanbawa Y (2016) Unique Flavours from Australian Native Plants. In: Australian Native Plants: Cultivation and Uses in the Health and Food Industries. p265-274, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-23. Smyth HE, Sanderson JE, Sultanbawa Y (2012) Lexicon for the sensory description of Australian native plant foods and ingredients. Journal of Sensory Studies 27:471-481. Stynes B (1997) Opportunities for contributing to the development of Aboriginal food plants. Tropical Grasslands 31:311-314. Sultanbawa Y, Williams D, Chaliha M, Konczak I, Smyth H (2015) Changes in Quality and Bioactivity of Native Foods during Storage. RIRDC publication 15-010. Rural Industries Research and Development Corporation, Canberra. Sutherland S (1986) Patterns of fruit set: what controls fruit-flower ratios in plants. Evolution 40:117- 128. Traub H (1939) Polyembryony in Myrciaria cauliflora. Botanical Gazette 101:233-234. Ward M, Dick CW, Gribel R, Lowe AJ (2005) To self, or not to self. . . A review of outcrossing and pollen-mediated gene flow in neotropical trees. Heredity 95:246-254. Williams DJ, Chaliha M (2016) Nutritional Characteristics and Bioactive Compounds in Australian Native Plants: A Review. In: Australian Native Plants: Cultivation and Uses in the Health and Food Industries. p223-236, Traditional Herbal Medicines for Modern Times. CRC Press. http://dx.doi.org/10.1201/b20635-20. Williams E, Matheson A, Harwood C (2002) Experimental Design and Analysis for Tree Improvement. Second Edition edn. CSIRO Publishing, Collingwood, Australia. Williams G, Adam P (2010) The flowering of Australia’s rainforests: a plant and pollination miscellany. CSIRO Publishing, Melbourne.

Wood CT (1965) The Queensland Sugar Industry: As Depicted in the Whish and Davidson Diaries. Delivered at a meeting of the Society on 22 April 1965). Zaouay F, Mars M (2014) Phenotypic variation and estimation of genetic parameters to improve fruit quality in Tunisian pomegranate (Punica granatum L.) accessions. Journal of Horticultural Science & Biotechnology 89:221-228.

37 Davidsonia domestication in far north Queensland

By Tony Page and Anna Sosnin

RIRDC Publication No 17/030 RIRDC Project No PRJ-009026

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