Assesment of maintenance of Ziziphus spina-christi (L.) Desf. seed under cryogenic conditions

Ziziphus spina-christi (L.) Desf. Is an arboreal species which grows in hot natuarl habitats of Southern Iran. Regarding the genetic diversity of the species in the country, collection and long-term preservation of seed germplasm in order to prevent genetic erosion and risk, have a great priority. To evaluate the possibility of long-term preservation of the Ziziphus spina-christi seeds under cryogenic conditions, three pre-cryopreservation methods including PVS2, Desiccation, and 30%Glycerol were applied before incubation of the seeds under cryopreservation conditions (-196°C) or lipuid nitrogen (LN). The treated seeds were incubated in LN for periods of 1 week, 1 month and 1 year. Subsequently, the cryopreserved seeds were removed from cryogenic condition and evaluated under laboratory and greenhouse conditions. The results showed that seeds of Ziziphus spina-christi are able to tolerate cryogenic conditions. Effects of the cryopreservation pre-treatments including 30%Glycerol, Desiccation and PVS2 were significantly different on seed attributes and, Desiccation showed the best effects on survival rates and other attributes of the cryopreserved seeds. The interaction effects between cryogenic storage periods and pretreatments were significant for some of the attributes. However some of the attributes did not show different means in different incubation periods. In greenhouse conditions, the cryopreserved seeds were germinated and established well and, Desiccation method showed better results compare to those of the 30%Glycerol and PVS2.