|Authors: ||A. Senula, E.R.J. Keller|
|Keywords: ||droplet vitrification, PVS 2, regeneration, covert bacteria, antibiotics|
The genebank of the IPK contains 216 mint accessions, which are maintained in the field or in vitro.
In 2005, routine cryopreservation of seed-sterile mint was started, using axillary shoot tips from cold-acclimated nodal segments and a simple droplet-vitrification method with PVS 2 (Senula et al., 2007). At present, 35 accessions from 12 species are cryopreserved by this method.
The average regeneration rate was 65% however, there was high variation in regeneration % (between 13 to 100%), both between accessions and between two repetitions of the same accession.
This was correlated to the genotype and endophytes in the in vitro donor plants that were previously found to be free of visible infections.
After rewarming, bacterial infections often broke out of and reduced or even inhibited regeneration of plantlets.
A screening of endophytes using single donor plants prior to multiplication and cryopreservation was executed.
Since bacteria are not homogeneously distributed in the plants, the results of the screening test reflected only the given situation in the tested material proper, but not that in the whole plant.
Therefore, the use of these pre-tests alone is not conclusive.
Furthermore, some endophytes do not grow on culture media alone, which makes detection difficult.
The preventive use of antibiotics in the regeneration medium after cryopreservation resulted in higher plant regeneration, when the donor plants were infected.
The antibiotics so far tested (Cefotaxim, Ticarcillin, Vancomycin) delayed the regeneration process, but did not reduce regeneration rates.
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