Crop and Steviol Glycoside Improvement in Stevia by Breeding

Worldwide demand for purified steviol glycosides (SVglys) from Stevia rebaudiana Bertoni leaves is steadily increasing. In the future, it is expected that the agricultural production capacity will be lower than the market demand. To improve the competitiveness of stevia production it is important to produce higher-performing crops in terms of yield and quality, resource use efficiency, greater resistance and resilience against drought stress, extreme weather conditions and a range of biotic stresses. Therefore, the development of new varieties/cultivars of S. rebaudiana with higher leaf and SVglys yields with greater resistance to abiotic and biotic stresses is the topmost priority and the primary aim for plant breeders. Since genotypic and phenotypic variation in the characters, in which we are interested, was reportedly quite high, researchers have attempted to enhance knowledge about this variability, and to develop breeding strategies, starting to study the feasibility and relevance of the characters being measured under different environmental and agro-climatic conditions. The chapter, aims to provide up-to-date scientific information regarding the breeding and selection programs carried out on stevia, describing both conventional plant breeding approaches and new biotechnological approaches, in order to provide new varieties/cultivars with improving quality traits.