Callus culture as a new approach for the production of high added value compounds in Ilex paraguariensis: genotype influence, medium optimization and compounds identification.

Ilex paraguariensis (yerba mate) is a native species from South America and is a rich source of bioactive compounds. There is a lack of research efforts on the phytochemical investigation of callus culture from this species. In the present study, an effort was made to optimize callus culture conditions and to identify secondary compounds. Calli were induced from 10 genotypes using leaf explants and the best genotype was selected to evaluate the effects of cytokinin types and concentrations on callus induction and biomass accumulation. The best genotype and cytokinin treatment were used to conduct one last experiment with sucrose concentrations in culture media and its effects on calli biomass, antioxidant activity and secondary compounds accumulation. Callus initiation was genotype dependent, and the 6-156-6 line had the best response. Zeatin supplemented medium showed higher callus induction rate (82%) and higher biomass accumulation after 120 days (328.2 mg). Higher biomass and secondary compounds accumulation were observed for calli on 3% sucrose medium. Antioxidant activity was not affected by sucrose concentrations. Yerba mate callus culture allowed the accumulation of chlorogenic acid, cryptochlorogenic acid, neochlorogenic acid, 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, 4,5-dicaffeoylquinic acid, theobromine and caffeine.

Plant densities and harvesting times on productive and physiological aspects of Stevia rebaudiana Bertoni grown in southern Brazil.

Stevia (stevia rebaudiana Bertoni) is a species characterized by producing non-caloric substances with high sweetening potential. Among these substances, rebaudioside A and stevioside are produced in greater quantity. Plant density and harvesting time are factors that affects biomass and sweetening compounds yield in this species. The objective of this research was to evaluate the effect of plant densities and harvesting times on the productive and physiological characteristics of stevia in southern Brazil. The experimental design was in randomized blocks, in a split-plot scheme, with 9 treatments comparing the effect of three planting densities (166 667, 83 333 and 33 333 plants ha-1) in the plots and three harvesting periods (before, in the beginning and in full flowering) in the subplots. Harvesting at the beginning of flowering promoted higher dry leaf biomass yield and, when associated with the lowest planting density, promoted higher levels of rebaudioside A and stevioside. The lowest planting density resulted in greater leaves biomass accumulation, whereas the highest density promoted higher yields per area. Interaction between density of 166 667 plants ha-1 and the harvest at the onset of flowering promoted higher yields of rebaudioside A (43.22 kg ha-1) as well as higher rebaudioside A/stevioside ratio (0.60).