|Authors: ||E.R.J. Keller, A. Senula, C. Zanke|
|Keywords: ||Allium, vitrification, explant types, storage safety, endophytes, wild alliums|
The family Alliaceae contains several crop species.
Some of them do not form seeds (garlic, A. hookeri, top onions, other primary hybrids) or are, for other reasons, multiplied as clones (shallot, ornamental alliums, Tulbaghia). Furthermore, the outbreeding character causes complications in management of large collections.
As field maintenance is labour-intensive and risky and in vitro storage suffers from accumulation of endophytes, cryopreservation is the only safe method for long-term storage of Alliaceae germplasm.
Several methods help to improve the cryopreservation success.
Thus, preculture of in vitro plantlets at alternating temperatures (25/-1°C) increased the regeneration percentages in garlic from such source organs up to 80%. Using such preculture now regularly, the number of cryopreserved accessions increased to 64 considering the statistical model of Dussert and coworkers for safety storage.
Several clones of wild species, A. obliquum and A. hookeri, as well as hybrids were cryopreserved.
Two methods were used: vitrification and droplet vitrification using PVS3. The latter method resulted in 24% regeneration in A. obliquum. Preculture of donor plantlets of the hybrid A. cepa x saxatile on higher sucrose (8 vs. 3%) resulted in better regeneration (11.8 vs. 6.7%). Covert endophytes are a problem in Allium cryopreservation.
They lead sometimes to unexpected bacteria outbreaks.
Although the safety conditions require larger samples of clonal material, storing of populations consisting of smaller clones might be sensible in case of emergency rescue actions.
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