Tate, Hanington (2015) Vegetative focused propagation of Santalum austrocaledonicum Vieillard (sandalwood) and the reproductive biology of S. lanceolatum, S. album and S. austrocaledonicum for the domestication of sandalwood. Masters (Research) thesis, James Cook University.

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Abstract

Sandalwood (Santalum spp.) is a commercially important forest product that has been traded for many centuries. The trade has been based on the exploitation of wild stands of the wood, but as supplies have dwindled interest in its cultivation has been increasing within agroforestry systems, both as an industrial crop and a small scale product. More recently, interest has increased in the domestication of the more commercially valuable species. Recent studies in Vanuatu into Santalum austrocaledonicum have identified individuals with high oil yield and quality that can form the basis of a breeding programme. A lack of appropriate knowledge of the reproductive biology within the genus and the capacity for clonal propagation has hindered progress towards genetic improvement. This situation has led to this study, which has the following objectives: (i) to determine the amenability of cuttings for propagation for S. austrocaledonicum; and (ii) elucidate key features of the reproductive biology of S. austrocaledonicum and other Santalum species that can inform their breeding and domestication.

Method To develop an effective method for the vegetative propagation of clonal sandalwood (S. austrocaledonicum), a series of four experiments were conducted. In these experiments I evaluated the effects of cutting (genotype, type of cutting, and leaf area,) and environmental (exogenous auxin, rooting media, and light intensity) treatments on adventitious root initiation and development (mean root number and length) in leafy stem cuttings using non-mist propagators. The results demonstrated that S. austrocaledonicum seedlings can be successfully propagated by cuttings.

Genotype: Cuttings taken from genotypes from the island of Erromango outperformed those from Tanna for all three measures of rooting across all experiments. In experiment 2, for instance, the level of adventitious root induction in Erromango genotypes ranged from 63 to 92% and those from Tanna 0 to 6%. Significant variation was also found among genotypes from Erromango, with genotype 'j-erro' demonstrating greater root induction compared with others across three of the four experiments.

Cutting Type: Cuttings taken from the apical and medial stem positions on the stockplant outperformed those taken from basal stems across the two clones examined. In a complementary experiment (4th), apical cuttings were found to have significantly greater rooting percentage than medial cuttings across the three clones.

Leaf area: The effect of leaf area (400 vs. 800mm²) was not significant for adventitious root induction, root number or root length. The proportion of leaves retained by the cutting during propagation positively influenced the percentage of cuttings that form adventitious roots. Significantly greater rooting percentage was found in cuttings with no leaf abscission (85%), followed by quarter (71%), half (48%), three quarters (35%) and all (21%) leaves abscised. This result indicates that the retention of some of the leaves is important in propagation by cuttings of this species.

IBA: The application of the exogenous auxin (3000, 4000 & 8000 ppm indole- 3-butyric acid) did not have a significant effect on adventitious root induction, mean root number and length when compared with the control (0 IBA).

Rooting Media: I examined the effect of three rooting media 1. Gravel-5mm (29% Air Filled Porosity AFP), 2. Vermiculite and Perlite at 1:1v/v (46% AFP) and 3. Vermiculite, Perlite and Peat 2:2:1v/v/v (42% AFP). No significant differences in percent adventitious root induction or mean root number were found between these three media. The mean length of the roots was, however, significantly shorter in the gravel medium compared with the other two media.

Light Intensity in the propagator: The effect of four different mean daily light levels (116, 86, 56 and 48 μmol m⁻² s⁻¹) in the propagator on cutting performance (mean root number and mean root length) was examined. The level of light had a significant effect on the percentage of cuttings with adventitious root induction. The influence of light on root induction was not consistent among clones, with a significant interaction found between light and clone. The greatest percentage of root induction was found for a mean daily light level of 86 μmol m⁻² s⁻¹ across all clones, which was achieved in a propagator positioned under 50% high-set shade with an additional 25% shade cloth over the top of the propagator. No significant effect of propagator light level was found for the mean number of roots or mean root length.

Reproductive Biology: To understand the breeding system in sandalwood (Santalum species), two experiments were undertaken. In these experiments I evaluated floral phenology in five species (S. lanceolatum, S. austrocaledonicum, S. album, S. macgregorii and S. yasi), and controlled hybridisation between three species (S. lanceolatum, S. austrocaledonicum and S. album) of sandalwood.

Floral Phenology: Systematic investigation of S. lanceolatum, S. austrocaledonicum, S. album, S. macgregorii and S. yasi has found that flowers in all species open rapidly (over 3-4 hrs), primarily in the morning. Flower life of an unpollinated flower varies significantly among the species, with mean days of flower life ranging from 24 hours (S. macgregorii) to 8.7 days (S. album). Full closing of flowers after opening was displayed among some of the species. S. lanceolatum (12-24 hrs), S. austrocaledonicum (12-36 hrs) and S. macgregorii (up to 12 hrs) closed after opening, while S. album and S yasi remained open. A change in colour of the tepals was observed in S. album S. yasi and S. magregorii. The tepals changed from white to pink after opening in S. album (19-24 hrs) and S. yasi (4-12hrs), and then changed progressively to dark red/purple. In S. macgregorii, the flower bud turned pink just before opening, and changed colour to red/purple after flower opening.

Breeding system of Santalum lanceolatum: Self- and intraspecific crosscompatibility was examined in 13 genotypes of S. lanceolatum, and interspecific crosscompatibility between S. lanceolatum with each of S. austrocaledonicum and S. album. A total of 20% of genotypes formed seed after self-pollination. Conversely, a total of 62% of genotypes pollinated with outcross (intraspecific) pollen set seed. S. lanceolatum was found to be cross compatible with both S. austrocaledonicum or S. album. However, although the percentage of seed set was similar between intra- (7.5%) and interspecific (7.6%) crosses, the germination of seeds produced through interspecific pollination was greater (S. album = 114% (some seeds producing 2 seedlings), and S. austrocaledonicum = 70%) than those produced through intraspecific (41%) pollinations. The implications of this breeding system on both the domestication of sandalwood as well as the genetic conservation issues surrounding introduction of a foreign species into a natural population are discussed.

Item ID:	46663
Item Type:	Thesis (Masters (Research))
Keywords:	breeding, cuttings, domestication, floral phenology, genetic improvement, hybridization, leafy stem cuttings, light intensity, mating system, rooting media, sandalwood, Santalum album, Santalum austrocaledonicum Vieillard, Santalum austrocaledonicum, Santalum lanceolatum, Santalum, vegetative propagation
Related URLs:	http://researchonline.jcu.edu.au/20127/
Additional Information:	Publications arising from this thesis are available from the Related URLs field. The publications are: Chapter 4: Tamla, H.T., Cornelius, J.P., and Page, T. (2012) Reproductive biology of three commercially valuable Santalum species: development of flowers and inflorescences, breeding systems, and interspecific crossability. Euphytica, 184 (3). pp. 323-333.
Date Deposited:	14 Dec 2016 00:06
FoR Codes:	07 AGRICULTURAL AND VETERINARY SCIENCES > 0705 Forestry Sciences > 070505 Forestry Pests, Health and Diseases @ 20% 07 AGRICULTURAL AND VETERINARY SCIENCES > 0705 Forestry Sciences > 070501 Agroforestry @ 80%
SEO Codes:	82 PLANT PRODUCTION AND PLANT PRIMARY PRODUCTS > 8201 Forestry > 820199 Forestry not elsewhere classified @ 40% 82 PLANT PRODUCTION AND PLANT PRIMARY PRODUCTS > 8203 Industrial Crops > 820302 Essential Oil Crops (e.g. Tea Tree, Eucalyptus, Lavender, Peppermint, Boronia, Sandalwood) @ 60%
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