Leptospermum for bioactive honey production in South Australia: selection, genetic diversity and propagation
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(Thesis)
Date
2022
Authors
Hancox, Tate Jason James
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Delaporte, Kate
Burton, Rachel
Binks, Rachel
Burton, Rachel
Binks, Rachel
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Abstract
Antibiotic-resistant bacteria are becoming more prevalent, and so it is vital that alternate 166 antibacterial sources are investigated; one crucial source is bioactive honey. The most well-167 known bioactive honey is Manuka honey, which is produced in Australia and New Zealand 168 from Leptospermum scoparium J.R.Forst. & G.Forst.; however, in Australia, there are a number 169 of Leptospermum species with the potential to produce highly bioactive honey. Currently, the 170 South Australian honey industry is investing in a plant improvement program to improve the 171 quality of bioactive honey produced. 172 The first step in this process is species selection. This project focused on L. scoparium, which 173 already has an established industry, and Leptospermum continentale Joy Thomps., as a native 174 Leptospermum from South Australia. The next step in the plant improvement program is 175 within species selection. 176 The success of plant improvement programs can be improved by ensuring that plants initially 177 selected for improvement and cultivation represent a wide range of genetic diversity. To do 178 this, plant material of L. scoparium was sourced from the Grampians, Victoria and material 179 from L. continentale was collected from across the natural distribution in South Australia. After 180 genomic deoxyribonucleic acid (DNA) extraction, both species were sequenced using Diversity 181 Array Technology sequencing (DArTseq). The data were analysed using multivariate ordination 182 methods, Bayesian STRUCTURE analysis and F-statistics to assess genetic diversity and 183 differentiation for each species. The study identified a moderate level of diversity across the 184 populations surveyed for L. scoparium from the Grampians and significant differences in the 185 genetic diversity for L. continentale across the natural distribution in South Australia. The 186 analysis suggested sufficient diversity and material existed within the cultivated L. scoparium to initiate a breeding program and identified regions to focus on for future nectar collection 188 and sampling for L. continentale. 189 In addition, improvement programs require genotypes to be readily clonally propagated. 190 Detailed methodology for tissue culture has been published but is expensive and requires 191 specialist facilities. An alternative is cutting propagation, which is cost-effective, scalable and 192 more readily accessible. Detailed cutting propagation methodology for L. scoparium and L. 193 continentale was lacking in the literature. Thus, a series of experiments were undertaken to 194 identify the effect of auxin and genotype on propagation and transplant survival for each 195 species. For L. continentale, the length of time cuttings spent in a mist propagation tent was 196 investigated as this species proved challenging to propagate. 197 These experiments culminated in a refined methodology for L. scoparium and L. continentale 198 propagation. For L. scoparium and L. continentale, cuttings should be treated with 3 g/L indole 199 butyric acid (IBA), planted into a free draining media, watered, and placed onto a heat mat in 200 a mist propagation tent. Cuttings of L. scoparium should be transplanted at six weeks from 201 planting, whereas L. continentale cuttings should be transplanted at nine weeks. Cuttings 202 should be transplanted into premium quality potting mix. Using these methods, plants were 203 produced from four genotypes of L. scoparium and seven genotypes of L. continentale.
School/Discipline
School of Agriculture, Food and Wine
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2022
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