The influence of chilling, freezing, and dry-ing preservation methods on morphological properties and viability of four yeast cultures, isolated Saccharomyces boulardii (SB1 and SB2), Saccharomyces cerevisiae (SC), and Kluyveromyces lactis (KL), was studied. chilling preservation had no effect on yeast colony morphology parameters till the end of the preservation period in contrast with freez-ing and drying preservation methods. Drying preservation resulted in the highest viability decrement % of yeast cultures ranged between 59.38 to 40.21% as compared with other preservation methods. There is a noticeable re-duction in D values of preserved yeast cultures by drying, which varied from (33 to 26 day) in comparison to chilling and freezing preserva-tion that recorded (119 to 83 and 180 to 57 day), respectively. The obtained results re-vealed that chilling preservation under proper conditions, as well as freezing, is more prefer-able for the preservation of studied yeast cul-tures than that preserved yeast by the drying method.

The present work aimed to establish a protocol to minimize the potential effect of in-vitro preservation for 8 months of the two olive cultivars i.e Koronaiki and Kalamata. Three culture conditions (treatments) were chosen to investigate the most suitable one for minimizing somaclonal variations after the process of in vitro preservation. The conditions include MS medium plus mannitol, MS medium plus low temperature and MS medium plus naphthaline acetic acid. RAPD-based finger-printing was employed to determine the effects of the different chemical constituents and other culture conditions on the extent of somaclonal variations after 8 months of in vitro preservation at the DNA level. Four arbitrary primers (OPA-04, -07, -14 and -16) were successfully utilized to achieve such goal. The obtained results showed that Mannitol has more pronounced effect than the other investigated preservation culture and conditions for decreasing DNA alterations.