Micropropagation and in vitro conservation of virus-free rose germplasm

Today, the propagation and the production of roses should be in accordance with the EU regulations, mainly concerning the commercialization of plants free from "quality pathogens", i.e., ApMV, ArMV and PNRSV viruses. Hence, the possibility of recovering virus-free material by means of thermotherapy and shoot-tip culture, as well as propagating and preserving high-quality shoot cultures in vitro, should be considered of strategic importance. Here, effective protocols of micropropagation, in vitro thermotherapy, synthetic seed preparation and slow growth storage are reported for an ancient hybrid tea rose, the 'Rosa Sant' Antonio di Padova', and a selection of Rosa City Flor (R) the 'Domenica'. Virus-free shoot culture lines were obtained by the treatment of single shoots at 37 degrees C for 2 weeks, followed by shoot-tip excision and culturing in gelled BA-containing MS medium. Synthetic seeds of 'Rosa di Sant' Antonio di Padova' were produced by hardening 3% Na-alginate beads, containing apical buds, in 100 mM CaCl2 center dot 2H(2)O solution for 30 min. All the synseeds were then able to "germinate" in 10- 11 days, independently from the presence of sucrose in the "artificial endosperm" of the bead. As for slow growth storage, both the cultivars could be successfully conserved at 4 degrees C in the dark inside glass jars for up to 6 months, while the conservation inside plastic cylinders and gas-permeable plastic bags was less effective. In addition, promising results were achieved with the cryopreservation of 'Domenica' by means of the treatment of shoot tips with a vitrification solution (PVS2) for 60 min, followed by their direct immersion in liquid nitrogen.