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
Résumé
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 variabil- ity 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 loca- tions. 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. Geno- types 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.