Deciphering performances of fifteen genotypes of Stevia rebaudiana in southwestern France through dry biomass and steviol glycoside evaluation

Stevia rebaudiana (Bertoni) is a perennial shrub native of Paraguay whose leaves naturally accumulate steviol glycoside (SG) sweeteners. Optimization of S. rebaudiana semi-perennial cultivation in Europe is based upon breeding adapted high-value genotypes. The basis of a pre-breeding program is to evaluate in field conditions the performances of a large set of genotypes that could then be used as genitors for new varieties. This study investigates the performances of fifteen clones gathered from different origins in the second year of production under the environmental conditions of southwestern France. The performances were evaluated in terms of SG yield on the basis of dry leaf biomass yield, SG content and composition. The fifteen genotypes showed a very wide range of performances, expressing ratios of 15, 3.5 and 4 between the worst and best genotypes for SG yield, dry leaf biomass yield and SG content respectively. The sweetest SG (RebA) could represent 72% of total SG content in the best genotype. We confirmed the major role of dry leaf weight in SG yield. Five canopy descriptors out of ten, number of principal stems, stem density (number of stems/m² of canopy area), canopy volume (m3), Harvest Index (HI) and Specific Stem Mass (g/m2), were relevant to describe aerial biomass variability and classify the genotypes. This study thus provides biomass descriptors as tools for future breeding purposes and highlights the urgent need to evaluate the great genetic diversity of S. rebaudiana as a prerequisite for breeding purposes.