Towards a semi-perennial culture of Stevia rebaudiana (Bertoni) Bertoni under temperate climate: effects of genotype, environment and plant age on steviol glycoside content and composition

Abstract

Stevia rebaudiana (Bertoni) Bertoni is a perennial shrub native to Paraguay whose leaves accumulate sweetening compounds of high value: steviol glycosides (SVglys). These diterpenoids differ in the number (1-4) and the nature of sugar units bound to a steviol skeleton: mainly glucose but also rhamnose and xylose. The two main SVglys are stevioside (ST; 3 glucose units) and rebaudioside A (RA, 4 glucose units). Along with an evaluation of genotypic variability for SVglys content and composition, this study investigates the winter survival and the effect of perennial cultivation on S. rebaudiana genotypes through a 2-year experiment conducted on two locations. The first year, a population of 96 genotypes was examined in a nursery field (site A) and a subset of five genotypes was grown in a field trial (site B). The winter surviving genotypes (16 on site A and 5 on site B) were studied the following year, alongside new plantings of the same lines (8 on site A and 5 on site B). The genotypes showed a high variability in SVgly content (from 45.7 to 186.2 mg g -1 DM) and composition along four distinct clusters. There was no correlation between total SVglys content and composition. Genotypes without RA had no other SVglys with more than three conjugated sugars. SVgly content varied among environments and generally increased between 1-and 2-year-old plants, while SVgly composition remained stable. This study showed that breeding for winter survival in temperate conditions would allow an increase in SVgly productivity in a semi-perennial stevia production.

Development of screening methods for functional characterization of UGTs from Stevia rebaudiana

“…The method developed in vitro showed that UGT76G1 contained in a crude extract of N. benthamiana catalyzes the β-1,3 glucosylation of Dulc A to form Reb C, from Genotype E's extract. The crude extract containing UGT76G1 also produces Reb F from the S. rebaudiana extract, confirming the assumption previously made 8 , although the precursor of this SVgly was not identified on the chromatograms. Usually, methods to test activity in vitro require purification of the recombinant protein.…”

“…In our case, part of the GFP fluorescence in the nucleus may also come from fusions degradation. Many chemical phenotypes have been observed in our S. rebaudiana collection 8 . The diversity of SVglys profiles thus makes it possible to produce numerous extracts directly obtained from the plant, with different combinations of substrates.…”

Genetic diversity and population structure of the sweet leaf herb, Stevia rebaudiana B., cultivated and landraces germplasm assessed by EST-SSRs genotyping and steviol glycosides phenotyping

“…No available public collection exists and only private companies own collections that are not available. The phenotypic study of a limited number of genotypes have been conducted in different countries [8–10]. Since many years, the use of molecular markers has improved significantly the management and utilization of crop genetic diversity [11].…”

Cultivation of Stevia rebaudiana Bertoni and Associated Challenges

“…At the same time, a better understanding of the genotypic control of SVglys composition would be of interest for plant breeding. Plant breeding efforts in stevia have been largely focused on improving leaf yield and Reb A concentration in the leaves [75,78,[80][81][82][83][84][85][86][87][88].…”