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Gisela 5 consists one of the most promising new cherry rootstocks in Greece. However, there is a gap in the knowledge related to the propagation of this rootstock by using cuttings. The first aim of this study was to investigate different methods to propagate the cherry rootstocks Gisela 5. The results showed that, this rootstock can be propagated by using hardwood cuttings with a moderate percentage of rooting (about 60%). More investigation is required in testing the frequency of irrigations on the rooting of cuttings in different rooting media. In addition, ·more work should be done to examine the possibly effect of endogenous hormones, carbohydrates and mineral elements in rooting of cuttings. It could help to understand better how the external factors affect the percentage of rooting of Gisela 5 cuttings. Propagation of Gisela 5 by using semi-hardwood cuttings is also possible, but the percentage of rooting is relatively low (about 35%). Improvement of the rooting could be achieved if the effect of some other external factors, such as etiolating, age of mother trees etc is examined. In cases of which propagation of Gisela 5 cherry rootstock with hardwood and semi-hardwood cuttings is impossible, the use of root cuttings could be another way to propagate this rootstock with high percentage of sprouting (67%) and rooting (90%) of achievement. More investigations should be conducted to evaluate the effect of higher concentrations of BOP on improvement of sprouting. This study also gives data for the use of micrografting as a quick grafting method. The percentage of achievement of micro grafted plants can be improved in a percentage of 55-60% if parafilm is used as wrapping material and covering of plants after micrografting. A method to produce inter-stocked trees with the micrografting method was evaluated although the percentage of achievement is low (10%). In this study, using micrografting in combination to thermotherapy was not an effective method to produce virus-free, probably because of inappropriate method of thermotherapy. More investigation should be done by using different method of thermotherapy so that vims-free plants will be able produced. In this study, experiments were conducted to i.mprove the tissue culture propagation of Gisela 5 , cherry rootstock additionally to the previous works. The results showed that shoot apices possibly are appropriate explants for the tissue culture propagation of this rootstock. Adding 5 ~lM lBA in combination to 0.15 glucose in medium improved the rooting of Gisela 5 explants. Supplement of medium with BA at concentrations as low as 0.5 ~M in'creased the sprouting of explants. Considering the importance of the diseases Phytophthora crown rot, Crown gall and Bacterial canker for the cultivation of cherry trees, it is essential for growers to know the level of susceptibility of Gisela 5 to these diseases. In this study, the susceptibility of cherry rootstock Gisela 5 to infection by Phytophthora Crown Rot (P. cactorum, P. citrophthora, P. parasitica, and P. citricola), Crown Gall (Agrobacterillm tllmejaciens) and Bacterial Canker (Pselldonwnas syringae) was evaluated. The results showed that Gisela 5 is susceptible to all pathogens tested. The susceptibility of Gisela 5 in natural infections by the pathogens used in this study should also be evaluated. Before that, caution should be taken when Gisela 5 is used in locations where these diseases are endemic and this may limit its commercial potential.

A range of Ribes cultivars of different geographical orlgm find recognised horticultural 'hardiness', have been investigated with respect to foliar and winter responses to freezing. Differences were observed in the freezing responses of actively-growing foliar material given cold pretreatments but no significant effects persisted below -10°C, suggesting that the selected cultivars possess little in the way of genetically determined cold response that might be exploited in ultra-low temperature cryopreservation. Differences were observed between cultivars in their ability to cold harden, and a rootstock with high cold hardening ability was able to significantly increase the foliar hardiness of a scion with lesser cold hardening ability. This improvement did not extend beyond performance -10°C. The natural cold hardiness of overwintering buds was exploited in a simple and effective cryopreservation protocol that used field material directly with a -20°C pretreatment in a conventional freezer, did not require cryoprotectants and needed only a single passage of in vitro culture. Geographical origin did not appear to be related to survival following freezing at 20° C and -196°C (LN). The biochemical responses of in vitro material of selected cultivars to the various stages of cryopreservation showed some significant differences, largely with respect to protein changes, but there was no clear pattern of response for any of the selected criteria. However, both before and after low temperature treatment, reproducible biochemical differences were seen between two accessions of the cultivar Ojebyn from different, accredited sources. This material has shown stable, phenotypic differences over several subsequent field seasons suggesting the possibility of genetic or epigenetic change as a consequence of in vitro maintenance. The field material has subsequently been transferred to the University of Copenhagen where DNA fingerprinting will be carried out on material from 2007.

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