Methods for in vitro propagation of Pelargonium x Hortorum and others: from meristems to protoplasts.

Geraniums (Pelargonium spp.) are among the most popular bedding and pot plants (25% of the French domestic market). On one hand, as vegetatively propagated plants, Pelargonium are submitted to pathogen pressure. On the other hand, innovation via interspecific hybridisation faces some difficulties. In this chapter, the two first protocols (from seeds and meristems) explain how in vitro plants free of virus could be obtained. The development of this technique is the long-term preservation of genetic resources via meristem cryopreservation. The third protocol describes propagation of Pelargonium with limited risks of variation. This technique also allows the constitution and the maintenance of a plant-stock from which explants can be taken for other studies. The two last protocols describe plant regenerations from leaf discs and mesophyll protoplasts, used for gene transfer and somatic hybridisation. These protocols were established mainly with Pelargonium x hortorum cultivars, but we propose possible solutions for the other species: P. x peltatum, P. x domesticum, P. capitatum and P. graveolens.