PREPARATION OF SHOOT TIPS BY SUCROSE AND DEHYDRATION PRE-TREATMENT OF ULLUCUS TUBEROSUS CAL. FOR CRYOPRESERVATION
Ullucus tuberosus (ulluco) is a vegetatively propagated tuber crop of the Andean region. An method for cryopreservation of ulluco was tested with the aim of long term storage of U. tuberosus genetic resources. The excess of water, resulting in lethal ice formation, was removed from shoot tips by two methods; (i) by desiccation over silica gel and (ii) by osmotic dehydration using plant vitrification solution (PVS3). Plant shoot tips were not able to recover from water stress caused by the removal of up to 82% of water. The effect of a sucrose pre-treatment improved the tolerance of shoot tips towards PVS3 dehydration. Shoot tips lose their water at a rate of 1.4 g H2O.g-1 DW during first hour and reach 22% of their initial water content. After two hours of desiccation over silicagel, the regeneration of thawed shoot tips from liquid nitrogen reached only 10%. This desiccation decreased the ice nucleation (taking place at -36°C) by 6°C which could help to narrow down the time that lethal ice nucleation can take place before glass formation. PVS3 pre-treatment decreases the percentage of crystallizable water to less than 2% of water. The combination of sucrose pre-treatment and 2 h desiccation over silica gel allowed 10% of the shoot tips to survive and regrow following cryopreservation. In the case where shoot tips were treated with PVS3 for 1.5 h, regeneration percentage reached 52.5%. According to our results, the theoretical potential for improvement of regeneration after LN is 21% which makes it a promising method for cryopreservation of ulluco.
Zamecnikova, J., Fernandez, E., Viehmannova, I., Zamecnik, J. and Faltus, M. (2011). PREPARATION OF SHOOT TIPS BY SUCROSE AND DEHYDRATION PRE-TREATMENT OF ULLUCUS TUBEROSUS CAL. FOR CRYOPRESERVATION . Acta Hortic. 908, 331-338
ulluco, in vitro, PVS3, dehydration, desiccation, water content, differential scanning calorimetry, cryopreservation