The annual variability of dry leaves and steviol glycosides production in Stevia rebaudiana (Bertoni) genotypes grown in two regions of Morocco

Abstract

Stevia rebaudiana is a perennial shrub native to Paraguay. Its leaves naturally accumulate steviol glycoside (SVglys) sweeteners. Currently, the demand for calorie-free sweeteners has prompted researchers to study other "natural" sweeteners that can replace sugar in the global market. Optimization of stevia perennial cultivation in Morocco 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 be used as genitors for new varieties. This study investigates the dry leaves production and the variability in total SVglys, rebaudioside A (RebA) and stevioside (STV) contents in stevia genotypes cultivated in two distinct regions of Morocco, Agadir and Marrakech, over four years. The analysis reveal significant year-to-year variability in dry leaf yields and SVglys content, with notable increases observed in the second year, indicating that specific climatic conditions were highly favorable during Y2. In addition, the results showed significant difference of SVglys, STV and RebA yields across the 4-harvest years. The STV represented the major SVglys in the both studied regions over the four harvest years with an amount reaching up to 12.63 %, followed by the RebA. In Agadir, the mean cumulative production per plant over four years was 518.57 g of dry leaves, 18.79 g of RebA, 51.37 g of STV and 80.87 g of SVglys. While in Marrakech, the cumulative dry leaves production was 529.9 g, 22.93 g of RebA, 41.99 g of STV and 77.95 g of SVglys. These findings highlight the influence of genotype and environment on SVglys production, emphasizing Morocco's potential as a competitive region for stevia cultivation.