Botany, agronomy and biotechnology of Pelargonium used for essential oil production

Pelargonium is one of the seven genera belonging to the Geraniaceae family, and includes almost 280 species mainly coming from South Africa. Some of these species have a strong rose scent mostly due to geraniol and citronellol. For a long time, hybrids between P. graveolens or P. radens and P. capitatum, have been used for essential oil (EO) production. Nowadays, EOs of Pelargonium species are produced mainly in China and Egypt. Hybrids are male sterile and propagated through cuttings. Their adaptability to different soils and climates (tropical, semi-tropical, mediterranean, or arid) is remarkable, even if cultivation parameters still have to be improved. Methods for genetic transformation of Pelargonium are available and, due to the growing knowledge of biosynthetic pathways and the cloning of terpene synthase genes in angiosperms, new strategies to improve EO yield or to modify EO composition could be imagined. For example, new crossings driven by biotechnological tools, creation of genetically modified Pelargonium with strong promoters upstream of terpene synthase genes, and batch production of Pelargonium terpenoids through recombinant yeasts or bacteria, are very promising approaches to develop EOs.