Improvement of Stevia rebaudiana Biomass Production and Steviol Glycoside Synthesis, Poster Board #423

Stevia rebaudiana (stevia) is an herbaceous perennial native to Paraguay that produces high concentrations of non-toxic, non-nutritive ent-kaurene diterpenoid glycosides, some of which are approximately 300 times sweeter than sucrose.  Stevia is an obligate outcrossing species, thus likely maintaining a high degree of heterozygosity and subject to improvement through breeding.  Important breeding objectives for stevia improvement include an increased rate of biomass production, inhibition of flowering during the growing season, and high concentrations of steviol glycosides such as rebaudioside A (reb A).  Approximately 700 plants from an open-pollinated stevia population from China were evaluated in a field plot at Michigan State University for phenotypic and steviol glycoside analysis.  The population exhibited considerable variability for many traits, including steviol glycoside concentration.  For example, reb A concentration ranged from less than 5 mg/g dry tissue to over 125 mg/g dry tissue.  Total steviol glycoside content was correlated positively with plant vigor and not correlated with development rate (node appearance rate) or branching, indicating that breeding for high rates of biomass accumulation should not have negative effects on sweetener production.  Ten individuals were selected based on steviol glycoside profile and used to generate a series of half-sib families.  Several traits, including flowering date and  leaf size, varied in a family-specific manner and will be discussed.