An efficient cryopreservation procedure for potato (Solanum tuberosum L.) utilizing the new ice blocking agent, Supercool X1000.

Cryopreservation has been recognized as a practical and efficient tool for long-term storage of vegetatively propagated plants. This study was conducted to investigate effects of modified vitrification techniques on cryopreservation of potato. In vitro plants of potato cultivars "Superior" and "Atlantic" were cold acclimated, and axillary buds were precultured, osmoprotected, exposed to PVS-2 solution, plunged into liquid nitrogen, thawed, and finally planted in the regeneration medium. In the modified vitrification technique an ice-blocking agent, Supercool X1000, was added with PVS-2 solution. Cold acclimation affected survival of cryopreserved shoot tips, and the highest survival (46.7%) was obtained after 3 weeks of acclimation at 10 degrees C. Shoot tips exposed to 2M glycerol plus 0.6M sucrose for 40 min gave 51.5% and 11.7% survival in "Atlantic" and "Superior" at 10 degrees C, respectively. Cold acclimated and osmoprotected shoot tips were dehydrated with PVS-2 containing different concentrations of Supercool X1000 prior to a plunge into liquid nitrogen. Treatments with 0.1% and 1% of Supercool X1000 significantly improved survival by 55% in "Superior" and 71.3% in "Atlantic", respectively. After cryopreservation, vitrified shoot tips resumed growth within a week in a medium (1 mg l(-1) GA(3), 0.5 mg l(-1) zeatin, and 0.1 mg l(-1) IAA) with a low level of Pluronic F-68 (0.005%) and survival was 33.7% higher in "Atlantic" and 14.7% higher in "Superior" than the control (without Pluronic F-68).

[Molecular proof of wheat transformed by total DNA of Leymus racemosus].

Four repetitive DNA sequences (pHv7161, pHv7179, pHv7191 and pHv7293) cloned from barley (Hordeum vulgare) genome were used for a molecular hybridization in the genome of Leymus racemosus (donor), Spring wheat 761 (receptor) and the wheat transformed by total DNA of Leymus racemosus (donor) through pollen tube pathway. Our results indicate that some bands are common in Leymus racemosus and the transformed wheat but absent in Spring wheat 761. The HindIII fragments which are common in Leymus racemosus and the transformed wheat have been cloned. The clone of Leymus racemosus was nominated as pLR980. pLR980 contains the homologous sequences to the four repetitive sequences of barley. The pLR980 cloned from Leymus racemosus was used as probe to study Leymus racemosus, Spring wheat 761 and the transformed wheat. This study demonstrate that pLR980 is homologous in both genome of Leymus racemosus and wheat. Common bands absent in the Spring wheat 761 were also showed in Leymus racemosus and the transformed wheat. pLR980 was proved to be associated with the transform of wheat by total DNA of Leymus racemosus through pollen tube pathway. This provides a direct witness to the exogenous DNA introduction.