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Canepa P.,Internacional Potato Center | Panta A.,Internacional Potato Center | Tay D.,Internacional Potato Center
Acta Horticulturae | Year: 2011

Using the PVS2 droplet vitrification cryopreservation technique for longterm potato conservation, it was found that some surviving shoot tips turned brown followed by necrosis during the recovery stage, suggesting that oxidation processes are involved in the viability decline. With this hypothesis, we investigated the effect of two antioxidants, ascorbic acid and glutathione, on tissue survival and plantlet recovery. Apical shoot tips from 3-week-old in vitro plantlets of S. tuberosum subsp. andigenum 'Ccompis' and 'Tacna', a multiple hybrid from cultivated and wild species, were subjected to the cryopreservation protocol using the PVS2 droplet vitrification method. One experiment was executed using three doses of ascorbic acid (50, 100 and 150 mg/L) and another with glutathione (5, 10, 15 mg/L), added to the post-thaw medium. Ascorbic acid showed a significant negative effect on the survival and recovery of shoot tips of both cultivars, without any genotype differences. In case of glutathione, 'Ccompis' plantlets showed superior survival and recovery rates compared to 'Tacna' plantlets, but the differences were not statistically significant.

Sanchez D.F.,Internacional Potato Center | Panta A.,Internacional Potato Center | Tay D.,Internacional Potato Center | Roca W.,Internacional Potato Center
Acta Horticulturae | Year: 2011

Ulluco (Ullucus tuberosus Cal.) and oca (Oxalis tuberosa Mol.) are Andean tuber crops of significant importance for the nutrition and subsistence of the Andean people. The world's largest germplasm collections of these crops, comprised of 544 and 628 accessions of ulluco and oca, respectively, are maintained at the International Potato Center (CIP). For their long-term conservation, CIP is currently developing cryopreservation techniques. Post-thaw survival and recovery resulting from shoot cryopreservation using plants cultured under different temperature regimes were investigated with 4 accessions each of ulluco and oca. Apical shoot tips from 3-week-old in vitro ulluco and oca plantlets were cryopreserved using the droplet-vitrification protocol. Shoot tips of 2 mm size were exposed to a loading solution for 20 min, dehydrated with PVS2 for 0, 15, 30, 45, 60 and 75 min, at 0°C, transferred to aluminium foil strips and plunged into liquid nitrogen. The highest recovery after cryopreservation was 35 and 15% for ulluco and oca, respectively, using 60 min of exposure to PVS2. In a second assay, in vitro donor plants of ulluco and oca were cultured at a constant temperature of 6°C, or alternating temperatures of 18°C in week 1 and 6°C in week 2. Shoot tips were cryopreserved following the protocol described above with 60 min exposition of exposure to PVS2. A constant low temperature did not increase the recovery percentage after cryopreservation. It did increase, however, with 5% in ulluco and 4% in oca plantlets when alternating temperatures were applied. These results showed that cryopreservation could be applied for long-term conservation of ulluco and oca germplasm collections.

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