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Domesticating Lebeckia ambigua: Solving the rhizobia issues.

Harrison, Robert (2017) Domesticating Lebeckia ambigua: Solving the rhizobia issues. Honours thesis, Murdoch University.

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Permanent dryland pastures are under-utilised in southern Australia (Angus and Peoples 2012), possibly due to the lack of well adapted perennial legume species that can fit into current farming systems. Lebeckia ambigua has been proposed as a candidate to fill this void with its adaptability to drought, acidic and infertile soils in low rainfall areas (Howieson et al. 2013). The research on L. ambigua has so far focussed on deep, sandy soils where cropping is problematic. Increasing the soil fertility in these previously low-profitable regions could provide mixed farming production with a comparative advantage over continuous cropping (Angus and Peoples 2012). However, the successful incorporation of L. ambigua into an agricultural system will require an understanding of its symbiont, Burkholderia species. Although L. ambigua and Burkholderia spp. have only recently been identified for domestication into agriculture (Howieson et al. 2013), researchers have had success with cultivating them throughout southern Western Australia (WA), except with inoculation.

There is a challenge to keep the inoculant B. spp. alive, in a peat carrier, when coated onto L. ambigua seed for sowing in a drying environment. Clay granules, as an alternative carrier, have previously been shown to be unable to carry high numbers of cells of B. spp. (Howieson et al. 2013). Field experiments with amended clay granules carrying B. spp. produced nodules on L. ambigua, albeit not in large number. Attempts at quantifying the numbers of cells in the amended granules, by resuscitating B. spp. from them using antibiotic media and plant infection techniques, were unsuccessful. However, antibiotic profiling of B. spp. strains identified chloramphenicol (20μg/ml) in YMA as an excellent media to suppress contaminants in the clay to facilitate enumeration.

Recently recovered strains of B. spp. were assessed alongside previous strains for tolerance to desiccation, which gave rise to a set of possible strains that could surpass the commonly used strain in this regard (WSM4204). Although clay granules were indicated to hold B. spp. cells sufficient for nodulation in the field, further studies must focus on the optimisation of a suitable inoculant technology for L. ambigua. The B. spp. and strain differences in tolerance to desiccation identified in this work may assist this target.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Howieson, John and Yates, Ron
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