Incorporation of Mannitol in Tissue Culture Media for Long-Term Storage of Potatoes at Moderately Low Temperature and Effect on Subsequent Micropropagation

Long-term maintenance in vitro of potato plantlets in nutrient media is necessary to preserve disease-free stocks. Since these are living plants, they eventually outgrow the containers they are in and exhaust the media, so propagation onto fresh media is required. To decrease labor and time spent in this process, it is of interest to slow plant growth to reduce turnover frequency. In this study, we investigated the effects of adding two concentrations (2 and 4%) of mannitol (a sugar alcohol that causes osmotic stress) to tissue culture media on plant growth of three potato clones at moderately low temperatures. Plantlet growth was inversely proportional to the concentration of mannitol used, but there were genotypic differences. Regeneration of the plantlets for subsequent micropropagation, after removal from the main treatments at day 64 and 121 days, was not negatively affected by the percentage of mannitol used to maintain the original stocks. Based on these results, we started using 2% mannitol as a baseline for practical long-term storage of potato breeding clones maintained in vitro. Depending on the reaction of the specific genotypes to media containing mannitol, additional adjustments might be needed.