Genetic control of rebaudioside A and C concentration in leaves of the sweet herb, Stevia rebaudiana

Abstract

Stevia rebaudiana Bertoni produces steviol glycoside sweeteners in its leaves that are up to 240 times sweeter than sugar. Understanding the genetic basis of glycoside proportions will aid in their manipulation through plant breeding. The experiments conducted in this study were focused on the genetic control of the proportions of two of those glycosides, rebaudioside A and rebaudioside C. The study was conducted using F2 population from crosses between two sets of parents with divergent glycoside profiles. Segregation in the first set of F2s showed that the presence/absence of rebaudioside A is controlled by a single dominant gene, but that the actual proportions of rebaudioside A may be controlled by multiple loci or alleles. In a second cross, proportions of rebaudioside A and rebaudioside C were found to co-segregate and were shown to be controlled by a single additive gene. This result suggests that both rebaudioside A and C are synthesized by the same enzyme. The results were used to propose a model for glycosylation of steviol glycosides. Key words: Diterpene glycoside, genetic analysis, glycosylation, biosynthetic model