Stevia or Stevia rebaudiana Bertoni are two of the numerous names of this subtropical plant with a sweetening power as much as 300 times higher than in case of sucrose. Stevia is a plant with a very interesting, but up to this date not very utilised potential. The fields of its application, processing, cultivation and wintering options have not been explored very extensively, and therefore I have decided to elaborate this topic related to the impact of the environmental conditions for growing of Stevia rebaudiana. The resources for the text of the diploma thesis were formed by available specialised publications and the Internet. The first part of the thesis represents a brief overview of the whole issue concerning the topic of Stevia rebaudiana. The objectives, hypotheses and methodology of the conducted research, including the findings based on the plant growing as well, and the evaluation of the experiment results have been included in the second part. The purpose of the thesis was to expand the knowledge regarding cultivation, reproduction methods and wintering options of the stevia plants. A field and a greenhouse experiments were staged with a focus on temperature indicators during the growing season and their impact on the total number of wintered plants. Simultaneously, an evaluation of the dry matter yield of the plants per an area unit and statistical processing and evaluation of the experiment results have been performed. Further, a determination of seed germination for Stevia rebaudiana in laboratory conditions has been conducted. The research results have shown that the plants obtained vegetatively are more suitable for cultivation due to a higher yield of the dry matter in both greenhouse as well as field conditions. The only pests invading stevia were the whiteflies appearing only in the greenhouse environment. Variable conditions were arranged for the wintering of the Stevia rebaudiana plants within the experiment; and in spite of the various materials and thermal insulation layers, the plants have not successfully wintered in an unheated environment. On the contrary, in the heated greenhouse space, most of the plants have successfully wintered. The stevia seed germination was low and proves the opinion of the majority of authors. The dry matter yields also matched the yields mentioned in the specialised literature.

Stevia rebaudiana Bertoni, une herbe vivace de la famille des Asteraceae originaire du Paraguay, est d'un intérêt croissant en tant que source d’édulcorants naturels acoloriques, les glycosides de steviol (SVglys). Ces diterpénoïdes sont organisés autour d’un noyau de steviol et diffèrent par le nombre et la nature d’unités de sucre liées à ce noyau. Ils sont accumulés à des concentrations allant de 4 à 20% de la masse sèche des feuilles, selon le génotype, le stade phénologique et les conditions de croissance. S. rebaudiana apparaît comme une espèce alternative prometteuse en Europe, mais nécessite au préalable une évaluation de ses besoins en culture et un travail de sélection variétale afin d’optimiser la teneur et la composition en SVglys en milieu tempéré. L'objectif de ce travail était d'étudier les sources de variabilité génotypique et environnementale pour l’accumulation en SVglys et la production de biomasse foliaire. Une forte variabilité génotypique a été observée pour la composition en SVglys et, à un degré moindre, pour la teneur en SVglys ainsi que pour des critères morphologiques et de précocité. L’environnement (fertilisation, durée du jour, stade phénologique, âge de la plante) a également eu un effet sur l’élaboration de la biomasse foliaire et sur la teneur en SVglys, alors que la composition en SVglys a été moins affectée par ces facteurs. Ces résultats suggèrent des mécanismes biochimiques et génétiques complexes régissant la voie de biosynthèse des SVglys. Ils laissent également entrevoir des possibilités de sélection variétale et donnent des indications sur les exigences de S. rebaudiana pour sa culture sous nos climats. / Stevia rebaudiana Bertoni, a perennial shrub of the Asteraceae family originating from Paraguay, is of increasing interest as a source of zero-calorie natural sweeteners: the steviol glycosides (SVglys). These diterpenoids differ in the number and the nature of sugar units bound to a steviol skeleton. They accumulate in leaves at concentrations ranging from 4 to 20%, according to genotype, phenological stage, and growth conditions. S. rebaudiana appears as a promising alternative culture in Europe, but requires investigations to assess its cultivation plant requirements and a breeding effort to optimize SVgly content and composition under temperate climate. The objective of this work was to explore the sources of genotypic and environmental variability for SVglys accumulation and leaf biomass production. High genotypic variability has been observed for SVgly composition and, to a lesser extent, for SVgly content as well as for morphological criteria and precocity. Leaf biomass and SVgly content varied also with the environment (fertilization, daylength, phenological stage) and over the years in perennial culture, while SVgly composition was less affected by these factors. These results suggested complex biochemical and genetic mechanisms regulating SVglys biosynthetic pathway. In parallel they revealed breeding potentialities and gave indications on S. rebaudiana requirements for its cultivation under temperate climate.