ABSTRACT
BACKGROUND: Long-term in vitro cultures of Tussilago farfara (L.), a traditional medicinal plant in Austria, had been stored at 14°C for over 20 years. The cultures were vigorous and showed no visual signs of bacterial presence. The transfer from growth regulator-free culture medium to medium containing kinetin and the increase of temperature from 14°C to 25°C for fast propagation led to the emergence of latent bacteria in all twelve accessions studied. OBJECTIVE: To investigate latent infections occurring during the development of a cryopreservation protocol of genetically interesting material using droplet-vitrification. MATERIALS AND METHODS: Two protocols for droplet-vitrification were tested using plant vitrification solutions (PVS) 2 and 3. The bacteria were isolated and identified using 16S rDNA analysis. Next, non-cryopreserved in vitro plantlets were acclimatized and transferred to the glasshouse. After 6 weeks, shoot tips were harvested from the pot plants, surface-sterilized and initiated into culture. Further, newly acquired achenes of Tussilago were surface-sterilized and germinated in vitro and seedlings checked for bacteria. RESULTS: The bacteria from the long-term cultures were isolated and identified as Luteibacter. Regeneration after cryopreservation using PVS3 was successful despite the continuing presence of Luteibacter. Luteibacter could no longer be detected in the newly-initiated in vitro material in subsequent tests and it was also not detected in the seedlings. CONCLUSION: Luteibacter withstood the cryopreservation procedure. Re-initiation of infected material may be an efficient alternative to antibiotic treatment to manage bacteria in micropropagation systems.
