| Research Abstract |
Long-term storage of fruit-tree pollen by freeze-drying method has been studied. Pollen storage is important for pollination, cross breeding, and for preservation of plant genetic resources. Freeze-drying seems to be a promising method for the storage.
Material & Methods : Pollen of several fruit species, mainly of Pyrus pyrifolia N.(Japanse pear), were used. Pollen was freeze-dried for 15 min. at 25-150mmHg, sealed in ampules under vacuum, and stored at -20ﾟC in a deep-freezer.
Effects of Conditions : Over-drying to less than 3% resulted poor survival. Storage temperature of -20ﾟC or lower is necessary for long-term storage. One hour or more rehumidification after seal-opening is necessary for good germination.
Survival and Viability of Pollen Stored for 20-25 Years : The viability of long-term stored pollen of pear, treated as above and preserved at -20ﾟC since 1973, was evaluated by germination test and by cross pollination between 1993-1998.
Germination rate of the long-term stored pollen attained 51-75%, and growth of pollen tube was as normal as fresh one. Fertilization ability, evaluated by fruit set rate (44-51%) was a liitle lower than by fresh pollen, but seed number per fruit was as same as with fresh pollen, and presented no problems for cross-pollination. In 1998, after 25 years, the pollen still germinated normally.
Conclusion : Viability of pear pollen can be maintained for more than 25 years if the pollen was freeze-dried and stored in deep-freezer. This method seems valuable and reliable for long-term storage of fruit-tree pollen, and promising to develop a method for semi-eternal preservation of genetic resources of horticultural crops and other plants.
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