Past CPWS Scholarships

June 2008 

The Sanitarium-CQU Post-graduate Scholarship for Stevia Research

Further information

The main objectives and research avenues proposed for this project:

Undertaking of plant physiology and basic management practice studies   to determine factors (including stresses) that influence or control   flowering, glycoside accumulation, ratoon performance and total yield to   optimise crop returns.  These studies will include nutrient deficiency   symptoms, irrigation and water tolerance and time of flowering and will   identify criteria to use when selecting elite plants for seed   production.

Detailed method

Basic plant physiology and management studies:

These will be conducted under controlled conditions on CQU campus   that will simulate our industry partner's target environments. Lines to   be studies will be accessed from a number of sources representing   materials currently available and under development. We will use the   analytical tools developed in parallel PhD research to quantify the   concentrations of steviol glycosides. Through trials with plants in pots   that manipulate individual environmental factors [e.g. daylength,   temperature, water availability] we will be able to de-confound the   influence of the natural environment, particularly on flowering [to   underpin the need for flowering for seed production, and the need to   obviate flowering for field production of steviol glycosides], on   spatial and temporal accumulation of steviol glycosides within stevia   plants, and on the variability between plants within populations in   terms of their steviol glycoside concentration at harvest. Environmental   ‘stresses', which could take the form of nitrogen and other mineral   excesses and deficiencies, daylength extremes, interplant-competition,   over- or under-watering, or harvesting regimes, may all condition the   propensity to flower, and each will be studied alone and in combination   to determine their importance in inducing/inhibiting flowering. We have   an in-house hydroponics system that we have developed to manage   concentrations of macro and micro-nutrients that we will apply to stevia   plants, not only for studies on flowering, but also for the general   impact of temporal variations in nutrient supply on growth and   accumulation of steviol glycosides. Such studies with pot-grown plants   can fill the gaps in our knowledge on the physiology of steviol   glycoside production.

Varietal selection and seed production:

We will access as broad a range of genetic material of Stevia   rebaudiana as is possible for the underlying development of new   varieties better suited to Australian conditions [but with potential for   overseas sales] and with desired steviol glycoside signatures. Within   these populations [200 seedlings of each] we will screen, using the   protocol developed above, the top 10% of plants based upon visual   biomass and steviol glycoside concentration. These plants will then be   isolated and allowed to inter-cross [we will need some preliminary study   on the breeding system, to determine the degree of out-crossing], and   another 200 seed progeny will likewise be screened according to   pre-determined requirements for steviol glycoside concentrations. The   seedlings from those inter-crossed plants will then be evaluated for   variability in terms of steviol glycoside concentration and if suitable   the same seed could be released to commercial seed-producers [e.g. of   vegetable seeds, one company has expressed interest -  South Pacific   Seeds] or be used by stevia farmers as basic seed for one more   multiplication before commercial planting. With a 1:1000 multiplication   rate, production quantities should easily satisfy Australian demand.

Contact: Professor David Midmore (07) 4930 9770 or via e-mail.

Applications close: 31st July 2008 for commencement before 31 August 2008

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