Establishment of embryo suspension cultures of grapevines (Vitis L.)

Somatic embryos of Seyval blanc, Dornfelder, Re- gent, Riesling, Müller-Thurgau and Rupestris du Lot originating from leaf discs or anther culture were checked with regard to their ability to be cultivated in suspensions for an induction of secondary embryo- genesis. Culture parameters like carbohydrates, phytohormones, pH, intervals of media change, the anti-oxidant dithioerythritol (DTE), and the size of embryos were tested to optimize the suspension cul- ture conditions. In liquid culture, glucose was better utilized than sucrose or maltose. The pH (5.8 - 5.0) and the embryo size mainly influenced the quality of em- bryogenic suspensions. Medium change proved to be necessary at a pH <4.5 or after a culture period >4 weeks. Browning of media was avoided by addition of 3 or 6 mM DTE. Homogeneous suspension cultures were maintained by fragmentation of embryos accord- ing to their developmental stage. From suspensions containing embryos of globulary- and heart-stage (0.5-2.0 mm) 50 % new somatic embryos were ob- tained whereas further developed embryos (torpedo- stage, >2.0 mm) were not suitable for cultivation in suspension. Best induction of secondary embryos was obtained from Seyval blanc, Dornfelder, Müller-Thurgau and Rupestris du Lot. After transfer to a LS- medium the seedlings of Dornfelder and Müller-Thurgau regenerated to rooted in vitro plantlets